Chapter 19 Aortic Aneurysm

CHAPTER 19 - Thoracic Aneurysms and Aortic Dissection Aubrey C. Galloway e!!rey ". #iller $ran% C. "&encer "te&hen '. Col(in TH)RAC*C A+E,R-"#" General Considerations #odern sur.ical treatment o! arterial aneurysms was introduced nearly a century a.o by Rudol! #atas/ who described a method o! internal re&air o! aneurysms termed reconstructi(e endoaneurysmorrha&hy. +early !i!ty years later/ in 1901/ notable wor% by Cooley and De'a%ey demonstrated the !easibility o! re&airin. aneurysms in(ol(in. the thoracic aorta. "ubse2uently/ e3cisional thera&y became the mainstay o! the modern sur.ical a&&roach to aneurysm disease/ with resection o! the aneurysmal aortic se.ment !ollowed by restoration o! blood !low throu.h the &lacement o! an inter&osition Dacron .ra!t. #ore recently e3cisional thera&y and endoaneurysmorrha&hy with internal .ra!t &lacement ha(e been used !or re&air o! thoracic aortic aneurysms. 4hen the aneurysm is well locali5ed/ total e3cision o! the diseased aorta usually is !easible/ and the in(ol(ed area is re&laced with an end-to-end Dacron .ra!t 6.ra!t inter&osition techni2ue7. #any sur.eons &re!er this techni2ue !or aneurysms in(ol(in. the aortic root or the ascendin. aorta/ because the e3cisional method is associated with a lower ris% o! subse2uent reo&eration !or &seudoaneurysm. 'y contrast/ in &atients with more e3tensi(e aneurysmal disease/ i.e./ aneurysms that in(ol(e a lon. se.ment o! aorta or in(ade ad8acent structures/ e3cisional thera&y is unnecessary and may be ha5ardous. *n these &atients a sim&ler and e2ually e!!ecti(e method is re&lacement o! the diseased se.ment o! aorta !rom within by &lacin. a Dacron .ra!t/ without e3cisin. the aorta itsel!. An end-to-end anastomosis between the .ra!t and the aorta is &er!ormed/ wor%in. !rom within the o&en aneurysm. The wall o! the aneurysm subse2uently is wra&&ed around the .ra!t !or tissue co(era.e. This techni2ue/ termed the .ra!t inclusion method/ has the ad(anta.e o! limited o&erati(e dissection and is associated with less ris% o! bleedin. or in8ury to ad8acent structures. Etiolo.y and Patho.enesis An aortic aneurysm can be de!ined as a locali5ed or di!!use aortic dilatation/ usually e3ceedin. 0 to 9 cm in diameter. Aneurysms de(elo& !rom a wea%ness or de!ect in the aortic wall/ which has a tendency to dilate &ro.ressi(ely. This is to some e3tent a sel!&er&etuatin. &rocess/ because the lateral wall tension o! a (ascular tube is related to the radius by :a&lace;s law 6tension < &ressure = radius7. The lar.er the aneurysm/ the .reater the wall tension. Past conce&ts o! the &atho.enesis o! aneurysm !ormation were o(ersim&li!ied and inaccurate. Aneurysms do not !orm sim&ly !rom tension related to &assi(e dilation but are a result o! a com&le3 remodelin. &rocess in(ol(in. the (essel wall/ as was recently outlined in a re(iew by Halloran and 'a3ter. This remodelin. &rocess in(ol(es a chan.e in the structure o! colla.en and elastin within the (essel wall with an increased &roteolytic en5yme acti(ity that chan.es the balance between &roteases and &rotease inhibitors 6Table 19-17. "erine &rotease/ metallo&rotease/ and neutro&hil elastase acti(ity are increased in the aneurysmal (essel/ resultin. in a net de.radation o! elastin and colla.en. Protease inhibitor acti(ity is simultaneously decreased/ leadin. to an additional imbalance in the ratio o!

&rotease to &rotease inhibitor. These biochemical chan.es &roduce &ro.ressi(e dilation o! the (essel wall. *n!lammatory mediators also are acti(ated/ es&ecially in &atients with atherosclerotic/ in!ectious/ or autoimmune diseases/ additionally enhancin. the &roteolytic &rocess. The net e!!ect is (ascular remodelin. with dilation o! the (essel wall. *nitially there is a loss o! elastin in the media with com&ensatory thic%enin. o! the ad(entitia/ which maintains (essel wall inte.rity des&ite increased wall tension. :ater in the &rocess/ increased colla.enase acti(ity leads to de.radation o! the ad(entitial layer with additional dilation or ru&ture o! the aneurysm. The main causati(e !actors associated with aortic aneurysms are a.e/ hy&ertension/ smo%in./ atherosclerosis/ aortic dissection/ and connecti(e tissue disorders. Althou.h atherosclerosis has lon. been thou.ht to be a &rimary cause o! aneurysmal !ormation/ this may be an o(ersim&li!ication. 4hile atherosclerosis is associated with aneurysmal disease/ the &resence o! atherosclerosis alone &robably is not su!!icient !or an aneurysm to de(elo&. Chronic atherosclerosis results more o!ten in a &roli!erati(e/ obstructi(e (ascular disease/ with aneurysmal dilatation occurrin. in a minority o! indi(iduals. The a(ailable data su..est that other !actors/ such as in!lammation or a .enetic tendency !or increased &roteolytic acti(ity/ also must be &resent !or an aneurysm to de(elo& in atherosclerotic &atients. Aortic dissection may result in acute or chronic aneurysmal dilatation. This is discussed in detail later in this cha&ter. The most common connecti(e tissue disorder associated with aneurysm !ormation is Erdheim;s cystic medial necrosis/ in which the underlyin. de!ect is idio&athic de.eneration o! the media with &ro.ressi(e aneurysmal dilation. #ar!an syndrome and Ehlers-Danlos syndrome/ both with identi!iable .enetic de!ects/ are well- de!ined connecti(e tissue diseases associated with aortic aneurysms. *n #ar!an syndrome/ the de!ect is in the .ene codin. !or !ibrillin/ which is a ma8or structural com&onent o! the micro!ibrils in connecti(e tissue. #ar!an syndrome &atients ha(e a well-described &henoty&e that includes a tall stature/ hi.h &alate/ 8oint hy&ermobility/ lens disorders/ mitral (al(e &rola&se/ and aneurysms in(ol(in. the aortic root or other &arts o! the aorta. Patients with #ar!an syndrome ha(e a si.ni!icantly increased ris% o! aortic (al(ular insu!!iciency/ aortic ru&ture/ and aortic dissection. A similar but less common de!ect is Ehlers-Danlos syndrome/ which is a conse2uence o! a .rou& o! .enetic mutations leadin. to de!ecti(e colla.en synthesis/ resultin. in aneurysm !ormation in multi&le locations throu.hout the body. "imilar to #ar!an &atients/ these &atients de(elo& aneurysms o! the aortic root with an increased ris% o! s&ontaneous aortic ru&ture. The sur.eon should be !amiliar with the (arious .enetic de!ects associated with aneurysmal disease/ because identi!ication o! a .enetic disorder can lead to earlier and more e!!ecti(e o&erati(e treatment o! these hi.h-ris% &atients. :ess common causes o! thoracic aneurysms include trauma/ in!ection 6sy&hilitic or other mycotic7/ in!lammatory diseases 6.ranulomatous and Ta%ayasu;s arteritis7/ and autoimmune diseases. Classi!ication Aneurysms o! the thoracic aorta are best classi!ied in terms o! anatomic location> the clinical si.ni!icance and the sur.ical a&&roach (ary widely with the location o! the aneurysm. The !our ma8or locations are 617 the aortic root and ascendin. aorta/ 617 the trans(erse aortic arch/ 6?7 the descendin. thoracic aorta/ and 6@7 the thoracoabdominal

aorta. Aneurysms o! the aortic root or ascendin. aorta are the most common/ re&resentin. o(er @A &ercent o! thoracic aneurysms in a lar.e series. The descendin. aorta is in(ol(ed in about ?0 &ercent o! thoracic aneurysms/ and the trans(erse arch and the thoracoabdominal aorta are in(ol(ed in 1A to 10 &ercent each. :ocali5in. aneurysms to a s&eci!ic location may be misleadin./ because the entire aorta may be diseased and the most ob(ious location mi.ht be only a &ortion o! a more di!!use disease &rocess. )ther descri&ti(e terms ha(e been hel&!ul in identi!yin. s&eci!ic areas o! aortic in(ol(ement. Aortoannular ectasia is a descri&ti(e term !or a de.enerati(e dilatation o! the aortic annulus and the sinuses o! Balsal(a/ &roducin. aortic insu!!iciency and a locali5ed aneurysm in(ol(in. the aortic root. This lesion o!ten is associated with connecti(e tissue diseases such as #ar!an syndrome or Ehlers-Danlos syndrome. Traumatic aneurysms may occur a!ter blunt trauma to the chest. They are located 8ust distal to the subcla(ian artery at the site o! insertion o! the li.amentum arteriosum. 4hile the mana.ement o! acute traumatic aortic transection is discussed in Cha& 9 6Trauma7/ the sur.ical mana.ement o! electi(e re&air o! a traumatic aneurysm is similar to that o! all other descendin. thoracic aneurysms. The term dissectin. aneurysm is a misnomer/ usually meanin. aortic dissection/ which results !rom an intimal tear in the aortic wall with subse2uent disru&tion o! the media/ &roducin. a true and a !alse lumen throu.hout the dissected aorta. 4hen a dissected aorta dilates to o(er 0 to 9 cm in diameter/ it is a&&ro&riately termed an aortic aneurysm secondary to aortic dissection. These may be acute or chronic. Clinical #ani!estations The classic sym&tom associated with a lar.e or an e3&andin. aneurysm is &ain/ which may be e3cruciatin. and se(ere. 4ith chronic aneurysms the sym&toms may be more subtle/ such as chronic &ressure or a low-.rade achin. &ain. 'ecause sym&tomatic &atients ha(e an increased ris% o! ru&ture/ &ain &ossibly related to aneurysmal e3&ansion must be thorou.hly in(esti.ated. +ew onset o! &ain in a &atient with a %nown aneurysm is hi.hly si.ni!icant and may indicate ra&id e3&ansion/ lea%a.e/ or im&endin. ru&ture. :ar.e aneurysms may &roduce sym&toms !rom com&ression o! ad8acent structures/ such as the trachea/ mainstem bronchus/ su&erior (ena ca(a/ &ulmonary artery/ recurrent laryn.eal ner(e/ or (ertebral bodies. "y&hilitic aneurysms/ seen less now than in the &ast/ were %nown !or their tendency to in(ade bone/ &roducin. bac% &ain !rom erosion o! the thoracic s&ine/ which occurs less !re2uently with other aneurysms. The most common sym&toms in &atients with thoracic aneurysms are/ in decreasin. order o! !re2uency/ &ain/ &ulmonary sym&toms/ and hoarseness. The ma8ority o! &atients with moderate-si5ed thoracic aneurysms are asym&tomatic unless si.ni!icant enlar.ement has occurred. These aneurysms usually are disco(ered incidentally in a routine chest radio.ra&h or durin. catheteri5ation or ima.in. studies &er!ormed !or other reasons. ,sually there are no &hysical abnormalities or hemodynamic disturbances/ e3ce&t in aneurysms o! the aortic root/ which may be associated with aortic (al(ular insu!!iciency. Dia.nostic "tudies

)nce an abnormal shadow has been identi!ied on chest 3-ray/ an attem&t to establish the dia.nosis o! an aneurysm is made with ma.netic resonance ima.in. 6#R*7/ com&uted tomo.ra&hy 6CT7/ or echocardio.ra&hy. Aorto.ra&hy/ &re(iously the &rimary dia.nostic tool/ is seldom necessary because o! newer ima.in. techni2ues. The !ull e3tent o! aneurysmal in(ol(ement can be well demonstrated with #R*/ CT/ or #R an.io.ra&hy. Echocardio.ra&hy is used to determine the si5e o! the ascendin. aorta and aortic root and is es&ecially hel&!ul in detectin. any associated (al(ular insu!!iciency. 4hen sur.ery in(ol(in. the aortic root is necessary/ cardiac catheteri5ation usually is indicated to additionally de!ine the de.ree o! aortoannular ectasia and the de.ree o! coronary artery dis&lacement. An aortic root an.io.ram with runo!! ima.es o! the aortic arch is recommended/ e(aluatin. the in(ol(ement o! the sinuses o! Balsal(a/ the de.ree o! aortic insu!!iciency/ the amount o! coronary artery dis&lacement/ and the de.ree o! aneurysmal in(ol(ement o! the aortic arch distally. Patients with thoracic aneurysms ha(e a hi.h incidence o! associated coronary artery disease. These &atients should ha(e screenin. studies or coronary an.io.ra&hy be!ore aneurysm re&air. +atural History and )&erati(e *ndications The natural history o! aortic aneurysms is one o! &ro.ressi(e enlar.ement with e(entual ru&ture. $actors related to the ris% o! ru&ture include aneurysmal si5e/ chan.e in si5e/ a.e o! the &atient/ &ain/ sym&toms o! aneurysmal e3&ansion/ smo%in./ and chronic obstructi(e &ulmonary disease 6C)PD7. u(onen and associates analy5ed multi&le ris% !actors to de(elo& a multi(ariate e2uation to calculate the &robability o! ru&ture !or thoracic aneurysms. Patients with lar.e aneurysms 6more than 9 to C cm in diameter7 with ra&id aneurysm e3&ansion or with &ain .enerally underwent electi(e re&air/ while others with aneurysms o! moderate si5e were monitored with serial CT scans o(er a&&ro3imately 0 years. The ris% o! ru&ture !or aneurysms o! (arious si5es was as !ollowsD less than ? cm/ A &ercent> ?E@ cm/ 9 &ercent> @E0 cm/ 11 &ercent> 0E9 cm/ ?9 &ercent> 9EC cm/ 0A &ercent> and CEF cm/ 1AA &ercent. A.e and C)PD were !actors other than aneurysm si5e that inde&endently increased the ris% o! ru&ture. The a&&ro3imate ris% o! ru&ture !or an indi(idual &atient with a thoracic aneurysm can be estimated on the basis o! clinical (ariables and com&ared with the estimated o&erati(e ris%. Althou.h the ma8ority o! aortic aneurysms steadily enlar.e and electi(e sur.ery can be &lanned/ sudden ru&ture occurs in a small &ro&ortion o! &atients with smaller aneurysms that were not &ro.ressi(ely enlar.in.. Patients treated nono&erati(ely should be warned o! this &ossibility. )ther clinical trials ha(e demonstrated a similar ris% o! ru&ture !or thoracic aneurysms. *n a lar.e series re&orted by 'ic%ersta!! and associates in which &atients were treated nono&erati(ely/ the 1-year sur(i(al rate was 9A &ercent/ and the 0-year sur(i(al rate was 1? &ercent. )(er CA &ercent o! the deaths were caused by ru&ture o! the aneurysm. Pressler and #c+amara re&orted obser(ations in 19A &atients with thoracic aneurysms/ 119 o! whom were treated sur.ically. The 0-year sur(i(al rate in the &atients treated nono&erati(ely was only 11 &ercent/ with hi.h ru&ture rates noted !or atherosclerotic and dissectin. aneurysms. "imilarly/ $in%elmeier demonstrated that @1 &ercent o! &atients with chronic traumatic thoracic aneurysms died or de(elo&ed sym&toms !rom the aneurysm within 0 years.

Data su&&ort electi(e o&erati(e treatment !or most thoracic aneurysms lar.er than 0 to 9 cm in diameter/ because o! the si.ni!icant ris% o! ru&ture and death within 0 years. )&eration should be stron.ly considered in &atients with saccular aneurysms or connecti(e tissue diseases once the aneurysm e3ceeds @.0 to 0 cm/ de&endin. on the estimated o&erati(e ris%/ because the ru&ture rate is hi.her in these &atients. Aortic Root and Ascendin. Aortic Aneurysms General Considerations Aneurysms locali5ed to the aortic root are o!ten a result o! cystic medial necrosis or connecti(e tissue disease in(ol(in. the aortic wall. Atherosclerotic aneurysms occur in the ascendin. aorta but are seldom limited to this area. Aortic dissection/ in!lammatory diseases 6sy&hilis/ autoimmune diseases/ and aortitis7/ and con.enital de!ects 6bicus&id aortic (al(e and aortic coarctation7 are other causes o! ascendin. aortic aneurysms. *n a series o! 190 ascendin. aortic and aortic arch aneurysms re&orted !rom +ew -or% ,ni(ersity 6+-,7/ 19 &ercent were !rom aortic dissection/ 11 &ercent !rom atherosclerosis/ 11 &ercent !rom cystic medial necrosis or connecti(e tissue diseases/ and 1C &ercent !rom other causes. Aneurysms in(ol(in. the ascendin. aorta 6$i.. 19-17 may be isolated to the su&racoronary &osition/ may e3tend distally to in(ol(e the aortic arch/ or may e3tend &ro3imally with in(ol(ement o! the aortic root and sinuses o! Balsal(a. 4ith aneurysms ori.inatin. in the su&racoronary &art o! the ascendin. aorta 6i.e./ not in(ol(in. the sinuses o! Balsal(a7/ the aortic (al(e usually is normal and unin(ol(ed/ unless se&arate &atholo.y such as con.enital aortic stenosis is &resent. *n contrast/ aneurysms ori.inatin. in the aortic root by de!inition in(ol(e the sinuses o! Balsal(a/ causin. distortion o! the sinotubular rid.e 6the &oint where the commissures o! the aortic (al(e attach to the ascendin. aorta7. The &rocess o! aortoannular ectasia stretches and distorts the (al(ular commissures and cus&s/ &roducin. central aortic insu!!iciency. *n these &atients the annulus/ the sinuses o! Balsal(a/ and the sinotubular 8unction are all dilated/ and the coronary ostia usually are dis&laced su&eriorly by 1 to ? cm. *n some &atients aortic insu!!iciency is se(ere/ and cardiac !ailure may be the initial clinical !indin.. Chronic ascendin. aneurysms !rom aortic dissection o!ten &roduce a similar !indin./ because the dissection &rocess may distort the commissural attachments o! the aortic (al(e at the sinotubular rid.e/ &roducin. aortic insu!!iciency. 'e!ore sur.ical thera&y was a(ailable/ most &atients with #ar!an syndrome died in the third decade o! li!e !rom aortic dissections or ru&ture. Early sur.ical inter(ention !or aortic root aneurysms is there!ore recommended in &atients with #ar!an syndrome or Ehlers-Danlos syndrome/ usually when the diameter o! the aortic root e3ceeds @.0 to 0 cm. )&erati(e Treatment The standard o&erati(e a&&roach !or aneurysms in(ol(in. the aortic root or ascendin. aorta is throu.h a median sternotomy incision/ usin. cardio&ulmonary by&ass and cardio&le.ia. 4hen the aneurysm is con!ined to the ascendin. aorta without in(ol(ement o! the aortic root/ the ascendin. aorta is re&laced with a wo(en Dacron .ra!t/ be.innin. 8ust distal to the sinotubular rid.e and endin. &ro3imal to the innominate artery 6$i.. 19-17. Concomitant (al(e re&lacement is &er!ormed i! aortic (al(e disease is &resent.

Re&lacement o! the aortic root is &er!ormed when the aortic root is aneurysmal 6aortoannular ectasia7. The o&eration most commonly used !or root re&lacement is the com&osite (al(e .ra!t &rocedure/ which in(ol(es re&lacement o! the aortic (al(e and aortic root with an aortic (al(eEDacron .ra!t conduit/ &laced !rom the aortic annulus to the distal aorta beyond the aneurysm. This techni2ue necessitates reim&lantation o! the coronary arteries into the com&osite .ra!t. The need !or aortic root re&lacement o!ten can be determined &reo&erati(ely by #R*/ CT/ or echocardio.ra&hic studies/ or by an an.io.ram o! the aortic root durin. cardiac catheteri5ation. The !inal decision o!ten is made at o&eration> i! the sinuses o! Balsal(a and the aortic annulus are dilated and the ostia o! the coronary arteries are dis&laced more than 1 cm !rom the annulus/ then the aortic root should be re&laced. The techni2ue !or aortic root re&lacement initially was described by 'entall and Debono. 4ith the 'entall method/ the com&osite (al(e .ra!t is &laced !rom within the aorta without cuttin. out the aneurysm/ reim&lantin. the coronary arteries into the .ra!t. The aneurysmal sac is closed around the com&osite .ra!t as &art o! a .ra!t inclusion techni2ue 6$i.. 19-?7. This classic 'entall method is used less !re2uently today because o! a si.ni!icant incidence o! late !alse aneurysm !ormation within the aneurysmal wra&. The most widely used techni2ue !or root re&lacement is a modi!ication o! the 'entall &rocedure in which the aortic root is totally e3cised/ lea(in. GbuttonsH o! aortic tissue around each coronary ostium !or subse2uent direct reim&lantation into the com&osite .ra!t 6$i.. 19-@7. Cabrol described an alternati(e method !or coronary artery reim&lantation durin. aortic root re&lacement usin. a Dacron tube 1A mm in diameter to connect the le!t and ri.ht coronary arteries/ subse2uently &er!ormin. a side-to-side anastomosis between the small tube .ra!t and the com&osite (al(e .ra!t to reestablish coronary !low 6$i.. 19-07. Aortic root re&lacement also can be &er!ormed usin. a cryo&reser(ed homo.ra!t or a &ulmonary auto.ra!t. Results Aortic root re&lacement with a com&osite .ra!t can be sa!ely &er!ormed/ with e3cellent lon.-term results. The o&erati(e mortality rate is 1 to 0 &ercent/ de&endin. on the number o! associated ris% !actors/ such as coronary artery disease/ reo&eration/ +ew -or% Heart Association 6+-HA7 class *B !unctional status/ #ar!an or EhlersDanlos syndrome/ aneurysm ru&ture/ or su&erim&osed acute aortic dissection. The o&erati(e ris% is less !or isolated ascendin. aneurysm re&air without root in(ol(ement. 'ecause the o&erati(e ris% is mar%edly increased once ru&ture or dissection has occurred/ electi(e o&eration should be recommended whene(er an aneurysm lar.er than @.0 to 0.0 cm in diameter is identi!ied. Aortic Arch Aneurysms Aortic arch aneurysms may be isolated or may be &art o! a continuous aneurysmal &rocess in(ol(in. the ascendin. and descendin. aorta. The most common causes are atherosclerosis/ aortic dissection/ and connecti(e tissue disorders. The dia.nosis usually is sus&ected a!ter identi!ication o! an abnormality on a chest radio.ra&h and con!irmed by #R*/ CT/ or aorto.ra&hy. The innominate/ carotid/ or subcla(ian arteries also may be aneurysmal. The &ro3imal and distal e3tent o! disease and the de.ree o! .reat-(essel in(ol(ement should be clearly de!ined &reo&erati(ely/ because these characteristics stron.ly in!luence the o&erati(e a&&roach.

Treatment The o&erati(e &rocedure !or arch re&lacement is com&le3/ in(ol(in. issues o! sur.ical techni2ue and cerebral &rotection. De&endin. on the e3tent o! arch in(ol(ement/ it may be necessary to &er!orm total arch re&lacement 6$i.. 19-97 with reim&lantation o! the arch (essels into the .ra!t/ or &artial hemi-arch re&lacement 6$i.. 19-C7/ with &lacement o! a be(eled .ra!t lea(in. the arch (essels to arise !rom the nati(e aortic arch su&eriorly. The hemi-arch re&air has been used with increasin. !re2uency at +-, o(er the &ast se(eral years. This techni2ue/ initially described by Cooley/ is sim&ler to &er!orm and allows the sur.eon the !reedom to tailor the re&air as necessary/ re&lacin. anywhere !rom 10 to F0 &ercent o! the aortic arch. A third techni2ue o! arch re&lacement/ the ele&hant trun% techni2ue described by 'orst and associates/ is used in a small number o! &atients who will re2uire a subse2uent o&eration !or a descendin. aneurysm. The ele&hant trun% techni2ue is similar to standard total arch re&lacement/ but the distal .ra!t is in(a.inated into itsel! while the anastomosis is constructed/ and the in(a.inated &ortion is subse2uently un!olded so that it lies !ree in the descendin. aorta. This allows the sur.eon easier access to the distal .ra!t/ or ele&hant trun%/ durin. the subse2uent descendin. aneurysm re&air/ which usually is &er!ormed se(eral wee%s later (ia a le!t thoracotomy. *n (arious lar.e clinical trials re&orted by Coselli/ "(ensson/ Er.in/ and Galloway the o(erall o&erati(e ris% !or arch aneurysm sur.ery has ran.ed !rom 9 to 10 &ercent/ de&endin. on the number o! ris% !actors &resent. The ris% !actors !or &oor outcome ha(e been identi!ied as ad(anced a.e/ emer.ency sur.ery/ acute dissection/ aneurysm ru&ture/ cardiac tam&onade/ #ar!an syndrome or other connecti(e tissue diseases/ &re(ious aortic sur.ery/ and &resence o! a second aneurysm in the descendin. thoracic aorta. )ther o&erati(e (ariables in!luencin. sur(i(al include cardio&ulmonary by&ass time/ o&erati(e bleedin./ renal !ailure/ and stro%e. 'e!ore the introduction o! dee& hy&othermia and circulatory arrest/ arch aneurysm re&air had one o! the hi.hest o&erati(e ris%s o! any sur.ical &rocedure/ with mortality rates e3ceedin. C0 &ercent. The demonstration that the brain could sa!ely tolerate circulatory arrest !or &eriods o! u& to @0 min i! the tem&erature was care!ully lowered to 10 to 1CIC !ormed the basis !or an im&ro(ed sur.ical a&&roach. This techni2ue/ termed dee& hy&othermia and circulatory arrest/ was !irst a&&lied by Grie&& and associates in 19C0. The hy&othermic circulatory arrest techni2ue in(ol(es core coolin. o! the blood to 1A to 10IC while the head is &ac%ed in ice and the body is cooled e3ternally with a coolin. blan%et. The &atient is cooled until the tym&anic membrane tem&erature is 10 to 1CIC or until electroence&halo.ram 6EEG7 silence is achie(ed/ a!ter which cardio&ulmonary by&ass is sto&&ed. ,se o! hy&othermic circulatory arrest !or cerebral &rotection allows the sur.eon to sto& all blood !low durin. arch re&air so that a &recise/ sound technical arch anastomosis can be &er!ormed. The techni2ue has the added ad(anta.e o! a(oidin. clam&in. and mani&ulation o! the diseased aorta/ which lessens the ris% o! aortic in8ury or emboli5ation. The circulatory arrest techni2ue has resulted in a dramatically lower mortality rate. The incidence o! &ermanent neurolo.ic in8ury 6stro%e7 a!ter circulatory arrest is low i! the cerebral ischemic time does not e3ceed @0 min. A re&ort by Galloway in 19F9 described re&air o! 190 arch aneurysms o(er 1A years usin. hy&othermia and

circulatory arrest in the ma8ority o! cases> F0 &ercent o! the arch re&airs had circulatory arrest times o! less than @0 min. The o&erati(e mortality rate was a&&ro3imately 1A &ercent/ and the !re2uency o! stro%e was less than 1 &ercent. Er.in and associates analy5ed neurolo.ic outcome in &atients under.oin. hy&othermic circulatory arrest !or arch re&air and demonstrated a correlation between the ris% o! tem&orary neurolo.ic dys!unction 6transient con!usion/ a.itation/ or obtundation7 and the circulatory arrest inter(al. Tem&orary neurolo.ic dys!unction occurred in 1A to ?A &ercent o! the &atients in whom the circulatory arrest inter(al had e3ceeded 0A min. The most common cause o! &ermanent neurolo.ic in8ury in the &atients was embolic e(ents/ not ischemia !rom the circulatory arrest. The incidence o! neurolo.ic in8ury a!ter aortic arch re&air (aries !rom A to 10 &ercent in di!!erent series. The ris% !actors !or stro%e are a.e/ com&le3ity o! the arch re&air/ circulatory arrest time/ and the amount o! clot or atheromatous debris in the arch. A new techni2ue o! cerebral &rotection in(ol(in. retro.rade cerebral &er!usion 6throu.h the su&erior (ena ca(a7 has been used to minimi5e the ris% o! cerebral ischemia durin. arch aneurysm sur.ery. Retro.rade &er!usion uses (enous &er!usion o! the brain with blood that has been cooled to C to 11IC. $low rates usually are 1AA to 0AA m:Jmin durin. the &eriod o! systemic circulatory arrest/ maintainin. a cerebral (enous &er!usion &ressure at ?A to @A mmH.. Re&orts by 'a(aria/ Er.in/ :ytle/ and Coselli ha(e shown a diminished ris% o! stro%e with the use o! retro.rade cerebral &er!usion. The techni2ue is o! most im&ortance in cases in which the circulatory arrest time is e3&ected to e3ceed @0 min. Descendin. Thoracic Aortic Aneurysms General Considerations Descendin. aneurysms may result !rom atherosclerosis/ cystic medial necrosis/ connecti(e tissue diseases/ aortic dissection/ in!ection/ in!lammation/ or &rior trauma. Atherosclerosis and de.enerati(e diseases &robably are the most common causes o! descendin. aneurysms. The ma8ority o! aneurysms be.in in the &ro3imal descendin. aorta and e3tend !or (aryin. distances/ o!ten in(ol(in. the entire descendin. thoracic aorta. Atherosclerotic aneurysms .enerally are !usi!orm/ but some are locali5ed and saccular. Concomitant abdominal aortic aneurysms occur in 10 to ?A &ercent o! the &atients/ and the entire thoracoabdominal aorta may be in(ol(ed in 1A &ercent. The aneurysmal disease may e3tend &ro3imally to in(ol(e the aortic arch. Traumatic aneurysms arise !rom &rior aortic transection a!ter blunt trauma to the chest/ de(elo&in. in those !ew &atients who sur(i(ed the initial in8ury. 4hile acute traumatic aortic transection usually !ollows trauma/ a chronic aneurysm can de(elo& a!ter acute traumatic aortic in8ury/ usually occurrin. immediately distal to the le!t subcla(ian artery/ where the aorta is !i3ed by the li.amentum arteriosum. A chronic traumatic aneurysm o! the descendin. aorta .enerally is re&aired with a &rosthetic .ra!t and reconstruction techni2ues identical to those used !or other !orms o! chronic descendin. aortic aneurysms. Clinical #ani!estations #ost &atients with descendin. aortic aneurysms are asym&tomatic/ and the dia.nosis is made a!ter a chest radio.ra&h/ usually &er!ormed !or other reasons. "ym&toms/ when &resent/ usually result !rom aneurysmal enlar.ement or com&ression o! ad8acent

structures. :ar.e aneurysms may com&ress the le!t main bronchus/ resultin. in cou.h and dys&nea/ or erode into the lun. &arenchyma/ &roducin. hemo&tysis. Enlar.in. aneurysms near the le!t recurrent laryn.eal ner(e may &roduce (ocal cord &aralysis and hoarseness. Pain is the most common and concernin. sym&tom/ because it usually su..ests si.ni!icant com&ression o! an ad8acent (ital structure or aneurysmal e3&ansion with im&endin. ru&ture. The &hysical e3amination usually is normal. Rarely a bruit is audible in the le!t &ara(ertebral area. Peri&heral &ulses usually are normal/ althou.h a lar.e aneurysm com&ressin. the le!t subcla(ian artery may result in diminished &ulses in the le!t arm. A chronic dissection may shear o!! the ori.in o! the subcla(ian or iliac (essels/ resultin. in diminished or une2ual &ulses in the arms or le.s. Dia.nostic "tudies The dia.nosis o! a thoracic aneurysm usually is sus&ected a!ter identi!ication o! a mass in the re.ion o! the descendin. aorta on a chest radio.ra&h. The di!!erential dia.nosis includes broncho.enic carcinoma/ metastatic carcinoma/ or mediastinal tumors. :aminar calci!ications may be (isible in the wall o! the aorta. The dia.nosis is con!irmed by standard CT or #R* 6$i.. 19-F7/ which readily demonstrate the si5e and e3tent o! aortic aneurysmal in(ol(ement. These studies also are es&ecially use!ul to e(aluate aneurysms &eriodically !or &ro.ressi(e enlar.ement so that the &ro&er timin. o! sur.ery can be determined. Aorto.ra&hy may be used to con!irm the dia.nosis and !urther delineate the &recise e3tent o! the aneurysmal in(ol(ement be!ore sur.ery. Today standard aorto.ra&hy is seldom necessary/ howe(er/ because newer !orms o! enhanced #R or CT an.io.ra&hy are a(ailable. These ima.in. studies allow three-dimensional reconstruction o! the aorta with scan times o! less than ? min and ha(e lar.ely re&laced con(entional aorto.ra&hy in the e(aluation o! thoracic aortic aneurysms. 'ecause concomitant atherosclerosis o!ten is &resent in the coronary/ renal/ or carotid arteries/ a thorou.h &reo&erati(e e(aluation should be underta%en. Pro(ocati(e stress testin./ coronary arterio.ra&hy/ and carotid studies should be &er!ormed as indicated to determine whether concomitant cardio(ascular disease re2uires treatment be!ore thoracic aneurysm re&air. Patients with sym&tomatic coronary artery disease or with a &ositi(e stress test should under.o cardiac catheteri5ation and re(asculari5ation be!ore aneurysm re&air. )&erati(e *ndications *n &atients with descendin. aneurysms lar.er than 0 to 9 cm in diameter electi(e o&erati(e re&air is recommended. This is es&ecially im&ortant because o! the hi.h ris% o! subse2uent ru&ture in these &atients and because emer.ency sur.ery has mortality rates !our to !i(e times hi.her than electi(e sur.ery. *n &atients with aneurysms less than 0 cm in diameter/ a &olicy o! obser(ation may be used/ but these &atients re2uire !re2uent !ollow-u& ima.in. studies/ and o&eration is indicated i! the aneurysm e3&ands or i! the &atient becomes sym&tomatic. )&erati(e Techni2ue A (ariety o! techni2ues ha(e been used !or re&air o! descendin. aortic aneurysms/ with technical ad(ances resultin. in a mar%ed reduction in the o&erati(e mortality

o(er the &ast 1A to 10 years. Two ma8or o&erati(e techni2ues are in use. ,n&rotected cross-clam&in. is &er!ormed with cross-clam&s &laced &ro3imally and distally without distal &er!usion/ or with a sin.le &ro3imal cross-clam& with controlled distal e3san.uination. *n &er!usion or shuntin. techni2ues by&ass or &assi(e shunts are used to maintain distal aortic &er!usion durin. the cross-clam& time. Per!usion may be done with le!t atrio!emoral by&ass/ with !emoralE!emoral by&ass with an o3y.enator/ or with a Gott shunt !rom the &ro3imal to the distal aorta. Per!usion and shuntin. techni2ues were introduced to limit s&inal cord ischemia durin. the cross-clam& time. )&erati(e e3&osure is achie(ed with a le!t &osterolateral thoracotomy throu.h an a&&ro&riate inters&ace/ usually the !ourth/ !i!th/ or si3th. $or most midEdescendin. aortic aneurysms a !i!th inters&ace incision is used/ althou.h the si3th rib may be resected i! more e3tensi(e e3&osure is re2uired. *nitially the aorta is mobili5ed and encircled &ro3imal and distal to the aneurysm. *n some cases the aorta is controlled &ro3imally between the le!t carotid and le!t subcla(ian arteries> a&&ro3imately 10 &ercent o! descendin. aneurysms re2uire &lacement o! the cross-clam& &ro3imal to the le!t subcla(ian artery. )&erati(e dissection in this area is !acilitated by o&enin. the &ericardium to e3&ose the intra&ericardial &ortion o! the trans(erse aortic arch. The (a.us ner(e and recurrent laryn.eal ner(e should be mobili5ed and &rotected. The techni2ue !or .ra!t &lacement is standard. An initial dissection is &er!ormed to isolate the aorta &ro3imally and distally. The aorta must be su!!iciently mobili5ed to allow &recise &lacement o! the cross-clam&s/ with &ro3imal control usually obtained !irst. The sur.eon must then decide whether a sim&le cross-clam& techni2ue or a &er!usion techni2ue is to be used. 4hen the aorta is clam&ed and o&ened widely/ thrombus is remo(ed !rom the lumen. )stia o! intercostal (essels are o(ersewn !rom within the aneurysm unless they are to be reim&lanted into the side o! the .ra!t. *n most &atients with descendin. aortic aneurysms the aneurysm is not resected/ but rather the .ra!t is &laced internally a!ter the aneurysmal contents are e(acuated. A wo(en Dacron .ra!t is inserted/ and end-toend anastomoses are &er!ormed &ro3imally and distally with continuous (ascular suture. Rarely/ an interru&ted or !elt-rein!orced suture techni2ue is used i! the aorta is es&ecially !riable. A!ter the .ra!t is &laced the clam&s are tem&orarily o&ened to remo(e air or thrombus/ a!ter which the suture lines are securely tied. The crossclam&s are remo(ed slowly/ and the distal body is &er!used throu.h the .ra!t. Re&er!usion o!ten is accom&anied by transient hy&otension/ which is corrected by (olume in!usion and sodium bicarbonate to correct re&er!usion-related acidosis. )nce hemostasis is obtained the aneurysmal sac usually is wra&&ed around the .ra!t to &ro(ide additional hemostasis and tissue co(era.e. The most dreaded com&lication a!ter re&air o! descendin. thoracic aneurysms is &ara&le.ia/ which continues to occur in a small &ro&ortion o! &atients des&ite numerous technical e!!orts to minimi5e the ris%. "im&le cross-clam&in. without distal &er!usion can be &er!ormed relati(ely sa!ely i! occlusion lasts less than 1A min/ but lon.er un&rotected cross-clam& &eriods are associated with an increased ris% o! &ara&le.ia. *! the cross- clam& &eriod e3ceeds @A to @0 min/ the ris% o! &ara&le.ia is o(er 1A &ercent/ and it a&&roaches 1AA &ercent once the cross-clam& time e3ceeds 9A min. Research su..ests that when the cross-clam& time e3ceeds ?A to @A min/ &er!usion o! the distal aorta reduces the ris% o! &ara&le.ia/ renal insu!!iciency/

intestinal ischemia/ and re&er!usion-related white blood cell acti(ation with multior.an dys!unction. Per!usion Techni2ue with "&inal Cord #onitorin. $or o(er 10 years at +-,/ a distal &er!usion by&ass techni2ue with !emoralE!emoral or atrio!emoral by&ass 6$i.. 19-97 has been used !or most &atients under.oin. electi(e re&air o! descendin. aneurysms. The techni2ue initially was &ro&osed by Cunnin.ham and associates in 19F1. Per!usion o&tions include usin. !emoral (einE !emoral artery &er!usion with an o3y.enator/ or le!t atrio!emoral artery by&ass usin. he&arin-bonded circuits/ no o3y.enator/ minimal he&arin/ and a cell-sa(erEra&id in!user. The le!t atrio!emoral by&ass techni2ue minimi5es the use o! he&arin and allows better control o! the &ro3imal blood &ressure/ because the le!t heart is unloaded by the le!t heart by&ass/ minimi5in. the need !or nitro&russide. :e!t atrio!emoral by&ass is &re!erred !or most &atients. *n addition to distal &er!usion/ a %ey com&onent o! this a&&roach has been the use o! somatosensory e(o%ed &otential 6"EP7 monitorin. to e(aluate s&inal cord ischemia or the ade2uacy o! &er!usion while the aorta is occluded. Research indicates that &ara&le.ia usually results !rom s&inal cord ischemia because o! low aortic &er!usion &ressure or !rom the direct interru&tion o! critical se.mental blood su&&ly to the s&inal cord. Diminution o! s&inal cord "EPs durin. the cross-clam& time su..ests that s&inal cord &er!usion &ressure is inade2uate or critical intercostal arteries ha(e been interru&ted. *! the distal &er!usion &ressure is low and the "EPs become abnormal/ the !low rate is increased until the distal &ressure e3ceeds 00 mmH.. This o!ten results in a return o! the "EP am&litude to normal. *n &atients with re!ractory shoc% it is o!ten im&ossible to achie(e an ade2uate distal &er!usion &ressure. *n a small number o! &atients the "EPs are lost des&ite an ade2uate distal &er!usion &ressure. *n this situation intercostal arteries arisin. !rom the aneurysmal se.ment o! aorta should be reim&lanted into the Dacron .ra!t. *n these &atients the loss o! "EPs su..ests that the blood su&&ly to the distal s&inal cord is de&endent on critical intercostal arteries arisin. !rom the aneurysmal se.ment o! aorta. *n a&&ro3imately one-third o! the &o&ulation the anterior s&inal artery is inade2uate to su&&ly the distal s&inal cord/ which recei(es its ma8or blood su&&ly !rom se.mental arteries arisin. between TF and :1. 4hether this is because o! a true arteria radicularis ma.na 6artery o! Adam%iewic57/ or whether the se.mental blood su&&ly is !rom a cluster o! intercostal arteries is debatable. The ma8ority o! a(ailable data su&&ort the idea that se(eral se.mental arteries usually are &resent. The +-, e3&erience with CF &atients under.oin. descendin. aneurysm re&air was re&orted by Galloway and associates in 1999. A selecti(e o&erati(e a&&roach was used in these &atients/ usin. by&ass with distal &er!usion and "EP monitorin. !or most electi(e cases and sim&le cross- clam& with controlled distal e3san.uination !or others. 4ith this techni2ue/ the incidence o! &ara&le.ia was low/ and it was 5ero in &atients under.oin. electi(e re&air. *n &er!used &atients/ &ara&le.ia did not occur as lon. as the &er!usion &ressure was abo(e 00 mmH. and the "EPs remained intact. The !low rate re2uired to maintain an ade2uate distal &ressure and s&inal cord &er!usion (aried !rom ? :Jmin to as hi.h as 9 :Jmin. #any sur.ical .rou&s recommend the use o! a distal &er!usion method routinely/ es&ecially when the cross-clam& time is e3&ected to e3ceed ?A to @A min. 'orst

recommended the routine use o! le!t atrio!emoral by&ass !or descendin. aneurysm re&air to minimi5e the ris% o! &ara&le.ia/ renal insu!!iciency/ and death. :awrie and collea.ues re(iewed 909 &atients who underwent descendin. thoracic aortic aneurysm resection !rom 190? to 199? at 'aylor Colle.e o! #edicine. The incidence o! neurolo.ic in8ury was reduced by the use o! a by&ass techni2ue/ which they recommend whene(er the cross-clam& time is li%ely to e3ceed ?A min. The routine use o! distal &er!usion and "EP monitorin. is contro(ersial. Craw!ord and associates re&orted no di!!erence in the incidence o! &ara&le.ia when usin. distal &er!usion and "EP monitorin. com&ared to the sim&le cross-clam& method. "in.le Cross-clam&in. with Controlled Distal E3san.uination The techni2ue o! sin.le &ro3imal cross-clam&in. with controlled distal e3san.uination 6$i.. 19-1A7 was &o&ulari5ed by Cooley and Craw!ord. Theoretically/ controlled distal e3san.uination reduces (enous distention and lowers cerebros&inal !luid &ressure/ im&ro(in. cord &er!usion durin. the cross-clam& &eriod and limitin. s&inal cord ischemia and edema. E3&erimentally this has been shown to &ro(ide some measure o! s&inal cord &rotection and to len.then the amount o! time that crossclam&in. can be maintained sa!ely/ without neurolo.ic in8ury. Published clinical data are encoura.in./ showin. an acce&tably low ris% o! &ara&le.ia with this a&&roach as lon. as the cross-clam& &eriod does not e3ceed ?A to @A min. *n re&orts !rom Galloway/ Coselli/ Craw!ord/ and Cooley the ris% o! &ara&le.ia was less than 1 &ercent in selected &atients under.oin. isolated descendin. aneurysm re&air with use o! the sim&le cross-clam& with controlled distal e3san.uination method. "ince no by&ass circuit !or distal &er!usion is re2uired and no he&arin is used/ the ris% o! bleedin. and coa.ulo&athy may be lower. Results #ortality rates are ? to 9 &ercent !or electi(e descendin. aneurysm re&air/ and 1A &ercent !or emer.ency sur.ery in &atients with ru&ture/ hy&otension/ or shoc%. Bariables associated with an increased ris% o! death include emer.ent o&eration/ acute ru&ture/ shoc%/ a.e/ and untreated concomitant coronary artery disease. The most common &erio&erati(e com&lications in descendin. aneurysm re&air are bleedin./ renal !ailure/ stro%e/ myocardial in!arction/ res&iratory !ailure/ and &ara&le.ia. *n the +-, analysis o! descendin. thoracic aortic aneurysm re&air/ the !actors most hi.hly associated with an increased ris% o! &ara&le.ia were emer.ency &resentation and &reo&erati(e shoc%. *n &atients in whom a re&air techni2ue usin. distal &er!usion and "EP monitorin. was &er!ormed/ &ara&le.ia was related to the inability to maintain an ade2uate distal &er!usion &ressure abo(e 00 mmH. and to the loss o! "EPs. *n &atients under.oin. re&air with a non&er!used sin.le- cross-clam& techni2ue/ &ara&le.ia was &rimarily related to the len.th o! the cross-clam& time. 'oth &er!usion techni2ues and sin.le-cross-clam&in. methods are (iable o&tions !or descendin. aortic aneurysm re&air. The authors recommend usin. a selecti(e o&erati(e strate.y that includes both o&tions but &re!er a by&ass techni2ue with distal &er!usion !or most &atients under.oin. electi(e re&air. The ris% o! &ara&le.ia is e3ceedin.ly low with this a&&roach as lon. as distal &er!usion is ade2uate 6abo(e 00 to 9A mmH.7 and the "EPs remain intact. The sin.le-cross-clam& techni2ue is &articularly use!ul in selected &atients with acute ru&ture/ bleedin./ aneurysmal erosion into the lun./ or anatomically com&licated aneurysms.

The lon.-term &ro.nosis a!ter aneurysm re&air de&ends on the &resence o! concomitant coronary artery or cerebro(ascular disease and on the &resence o! aneurysmal disease in other &arts o! the aorta. A&&ro3imately ?A &ercent o! &atients with descendin. thoracic aneurysms de(elo& aneurysmal disease elsewhere/ so !ollow-u& ima.in. studies on a yearly basis are stron.ly recommended. +ew De(elo&ments A techni2ue usin. endo(ascular stented .ra!ts !or the treatment o! descendin. thoracic aortic aneurysms has been described. A re&ort by #itchell and associates !rom "tan!ord ,ni(ersity demonstrated success!ul results in @@ &atients with three deaths 6C &ercent7. E3&andable stented .ra!ts are &laced &ercutaneously to e3clude the aneurysmal se.ment o! aorta. $urther lon.-term !ollow-u& is necessary to e(aluate the e!!ecti(eness o! this &rocedure. Thoracoabdominal Aneurysms Etiolo.y and Classi!ication Thoracoabdominal aneurysms usually are associated with atherosclerosis/ connecti(e tissue disease/ or aortic dissection. Craw!ord classi!ied thoracoabdominal aneurysms on the basis o! the anatomic e3tent o! aortic in(ol(ement as !ollowsD Ty&e *K&ro3imal descendin. to u&&er abdominal aorta Ty&e **K&ro3imal descendin. aorta to below the renal arteries Ty&e ***Kdistal descendin. and abdominal aorta Ty&e *BKsu&rarenal and in!rarenal abdominal aorta Physiolo.y o! Re&air Thoracoabdominal aneurysms ty&ically in(ol(e the se.ment o! aorta where the celiac a3is/ su&erior mesenteric artery/ and renal arteries arise. "ur.ical re&air o! these aneurysms is challen.in. and may result in transient s&inal cord/ renal/ and (isceral or.an ischemia/ with subse2uent ischemic re&er!usion-related white blood cell acti(ation/ leadin. to multior.an in8ury. The ris%s o! &osto&erati(e renal insu!!iciency and multi&le or.an !ailure are hi.her in re&air o! thoracoabdominal aortic aneurysms than o! other aneurysms. Coa.ulo&athy and bleedin. may be si.ni!icant in these &atients. *! massi(e trans!usion is re2uired/ the ris% o! multi&le or.an !ailure is increased. The blood su&&ly to the lower s&inal cord is se.mental and arises !rom the aorta between TF and :1 in a&&ro3imately one-third o! the &o&ulation. ,nderstandin. s&inal cord ischemia durin. aortic cross-clam&in. is &articularly im&ortant in &atients with thoracoabdominal aneurysms/ because these aneurysms in(ol(e the aortic se.ment in which the blood su&&ly to the lower s&inal cord most commonly arises. Re&lacement o! the thoracoabdominal aorta is associated with the hi.hest ris% o! &ara&le.ia o! any aneurysmal sur.ery/ with a ris% ran.in. !rom 0 to @A &ercent/ de&endin. on the e3tent o! aortic in(ol(ement and the cross-clam& time. )&erati(e Treatment

Ethered.e and De'a%ey described the !irst sur.ical a&&roach !or thoracoabdominal aneurysms in 1900/ which in(ol(ed re&lacement o! the aorta with a homo.ra!t. The De'a%ey techni2ue subse2uently e(ol(ed into reconstruction o! the aorta with a lon. tube .ra!t/ !rom which smaller .ra!ts were indi(idually attached to the celiac/ su&erior mesenteric/ and renal arteries. The o&erati(e mortality was hi.h/ e3ceedin. 0A &ercent !or many years. *n 1990 Craw!ord described the basic re&air techni2ue !or thoracoabdominal aortic aneurysms that is still used today. This techni2ue uses the .ra!t inclusion method/ with reim&lantation o! the ostia o! the (isceral (essels as an island into the side o! the aortic Dacron .ra!t 6$i.. 19-117. Craw!ord summari5ed a 1A-year e3&erience with 9A0 such o&erations in 19F9/ with an o&erati(e mortality o! a&&ro3imately 9 &ercent. The o&erati(e e3&osure re2uires a lar.e thoracoabdominal incision. The si3th or se(enth intercostal s&ace o! the le!t chest is entered/ the costal cartila.e is di(ided/ and the incision is e3tended below the umbilicus. The dia&hra.m is di(ided circum!erentially alon. the &eri&hery/ &reser(in. the central inner(ation. *n the le!t chest the descendin. thoracic aorta is isolated &ro3imal to the aneurysm. The s&leen/ le!t colon/ and %idney are re!lected medially/ and the retro&eritoneum is entered to e3&ose the aorta distally to the bi!urcation. The retro&eritoneal lym&hatics o!ten are tied in continuity. )nce the aneurysm has been e3&osed the aorta is clam&ed &ro3imally. Distally the aorta is le!t o&en or clam&ed and &er!used. The aneurysm is incised/ and an anastomosis is &er!ormed between the .ra!t and &ro3imal aorta. "e.mental intercostal arteries or clusters o! arteries abo(e and below the dia&hra.m are reim&lanted into the .ra!t. The cross-clam& is se2uentially mo(ed distally beyond the reim&lanted intercostal arteries. The (isceral (essels are reim&lanted and re&er!used in a similar !ashion. A!ter reim&lantation o! the (isceral (essels an anastomosis between the .ra!t and the distal aorta is &er!ormed. This may be done immediately ad8acent to the su&erior mesenteric and renal arteries/ immediately below the renal arteries/ or at the aortic bi!urcation. Craw!ord !ound that the ris% o! &ara&le.ia could be si.ni!icantly reduced by reim&lantin. lar.e intercostal (essels/ or clusters o! (essels/ into the aortic .ra!t. 4ith Craw!ord;s techni2ue intercostal arteries are reim&lanted and re&er!used within 1A to ?A min. Additional techni2ues !or s&inal cord &rotection include se2uential reim&lantation o! intercostal arteries/ by&ass methods to increase s&inal cord blood !low/ the use o! intrathecal (asodilators such as &a&a(erine/ systemic steroids/ intra(enous lidocaine !or membrane stabili5ation/ systemic hy&othermia/ barbiturate administration to lower neurometabolism/ calcium-channel bloc%ers and o3y.en radical sca(en.ers to minimi5e re&er!usion in8ury/ and cerebros&inal !luid 6C"$7 draina.e to decrease s&inal cord &ressure. The by&ass techni2ues and the sin.le-cross-clam& techni2ue with controlled distal e3san.uination ha(e been used to minimi5e the ris% o! &ara&le.ia. Distal &er!usion methods/ howe(er/ are used less !re2uently with thoracoabdominal aneurysms. The techni2ue is cumbersome because the aorta is clam&ed abo(e and below the area !rom

which the cord se.mental blood su&&ly arises. "e&arate &er!usion must be &ro(ided to the (isceral (essels/ or the cross-clam& must be se2uentially mo(ed so that the intercostal (essels are intermittently &er!used be!ore reim&lantation. +e(ertheless/ some sur.eons ad(ocate &er!usion o! the aorta whene(er !easible. The sin.le cross-clam& with controlled distal e3san.uination is used more commonly. 'y em&tyin. blood !rom the lower body 6distal e3san.uination7/ the C"$ &ressure is lowered si.ni!icantly/ which ma3imi5es cord &er!usion and increases the sa!e ischemic inter(al. $or thoracoabdominal aneurysm re&air the controlled distal e3san.uination method is o!ten combined with the techni2ues o! C"$ draina.e to lower C"$ &ressure and administration o! intrathecal &a&a(erine to increase blood su&&ly to the s&inal cord by a !actor o! !i(e. 4ith sin.le cross-clam&in. and controlled distal e3san.uination/ C"$ draina.e/ and intrathecal &a&a(erine/ the incidence o! &ara&le.ia has been as low as A to 0 &ercent in some re&orts. Des&ite these ad(ances and the (ariety o! technical o&tions a(ailable/ the o&timal method o! s&inal cord &rotection durin. thoracoabdominal aneurysm re&air is contro(ersial. Results *n 199? "(ensson and associates re&orted the cumulati(e 'aylor Colle.e o! #edicine e3&erience with 1/0A9 &atients under.oin. thoracoabdominal aneurysm re&air o(er ?A years. The o&erati(e mortality rate was F &ercent/ and the incidence o! &ara&le.ia was 19 &ercent. The other ma8or com&lications included renal insu!!iciency 61F &ercent7/ .astrointestinal com&lications 6C &ercent7/ and myocardial in!arction. Bariables associated with increased o&erati(e ris% were a.e/ &reo&erati(e creatinine le(el/ concurrent &ro3imal aortic aneurysm/ concomitant coronary artery or &ulmonary disease/ and aortic cross-clam& time. Bariables associated with an increased ris% o! &ara&le.ia were cross-clam& time/ e3tent o! the aneurysmal in(ol(ement 6Craw!ord ty&es * and **7/ aortic ru&ture/ a.e/ &ro3imal aortic aneurysm/ and a history o! &reo&erati(e renal insu!!iciency. The e3tent o! aneurysmal in(ol(ement is stron.ly associated with the ris% o! &ara&le.ia. *n "(ensson;s re&ort the incidence o! &ara&le.ia was ?1 &ercent in &atients with Craw!ord ty&e ** thoracoabdominal aortic aneurysms. "imilarly/ in a re&ort by Grie&& and collea.ues the incidence o! &ara&le.ia was ?A &ercent in &atients with Craw!ord ty&e * or ty&e ** aneurysms. *n lar.e aneurysms with in(ol(ement o! more than 1A interse.mental arteries/ the ris% o! &ara&le.ia increased by a !actor o! 19. A)RT*C D*""ECT*)+ Etiolo.y Aortic dissection be.ins as a tear in the intima/ with entry o! blood and se&aration o! the media !or a (ariable distance/ resultin. in blood !low down a G!alse lumen.H A locali5ed aneurysm may de(elo& immediately/ or months or years later where the aortic wall has become wea%ened and enlar.ed !rom the ori.inal dissection. The disease is ? to @ times more common in males than in !emales and occurs &redominantly in older &atients. Dissection may occur in any a.e .rou&/ but with certain cases occurrin. in childhood/ usually secondary to coarctation o! the aorta. Aortic dissection usually results !rom a combination o! hy&ertension and de.enerati(e connecti(e tissue disease. Roberts has em&hasi5ed that a history o! hy&ertension is obtainable in 9A to C0 &ercent o! &atients/ with hy&ertro&hy o! the le!t (entricle

&resent in a&&ro3imately 9A &ercent. Roberts determined that hy&ertension !re2uently is the &reci&itatin. !actor in &atients with #ar!an syndrome who de(elo& aortic dissection and &redicted that &ro&er control o! hy&ertension would si.ni!icantly lower the ris% o! dissection in all &atients. The stron.est &redis&osin. !actor to aortic dissection is cystic medial necrosis/ which may be idio&athic 6Erdheim;s cystic medial necrosis7 or secondary to a %nown connecti(e tissue disease/ such as #ar!an syndrome or Ehlers-Danlos syndrome 6see abo(e/ Thoracic Aneurysms/ subsection Etiolo.y and Patho.enesis7. )ther !actors associated with aortic dissection include aortic coarctation and con.enital bicus&id aortic (al(e. Rarely/ an atherosclerotic &la2ue or traumatic in8ury ser(es as the initiatin. tear site !or aortic dissection. Aortic dissection usually is not caused by atherosclerosis. Atherosclerosis is a &roli!erati(e disease o! the intima and media/ occurrin. most !re2uently in the abdominal aorta. Aortic dissection is a disease o! the media/ almost always ori.inatin. in the thoracic aorta/ althou.h the dissection may continue distally to the aortic bi!urcation. Althou.h aortic dissection and atherosclerosis occur in older &atients/ they are distinctly di!!erent and uni2ue disease &rocesses. Rarely/ an atherosclerotic &la2ue ser(es as a lead site !or aortic dissection. Patholo.y The ma8or initiatin. &atholo.ic e(ent is a tear in the intima and media/ usually in(ol(in. hal! the circum!erence o! the aorta. The intimal tear &ermits blood to enter the media and dissect distally. The aortic wall &ro.ressi(ely se&arates 6GdissectsH7 with an inner lumen com&osed o! intima and an outer !alse lumen com&osed o! the media and ad(entitia. *n the classic &atholo.ic analysis &ublished by Roberts/ the intimal tear was located in the ascendin. aorta in about CA &ercent o! &atients/ in the aortic arch in 1A &ercent/ in the u&&er descendin. thoracic aorta near the li.amentum arteriosum in 1A &ercent/ and in the abdominal aorta in about 1 &ercent. *n a study by #iller and associates the intimal tear was !ound to be in the ascendin. aorta in 9A &ercent o! &atients/ in the aortic arch in 1A &ercent/ and in the descendin. aorta in ?A &ercent. )nce the dissection be.ins/ it usually e3tends ra&idly throu.h the thoracic and abdominal aorta into the &eri&heral arteries. The dissection &rocess e3tends into a &eri&heral artery in more than 0A &ercent o! &atients. Roberts has estimated that the entire aorta will dissect within minutes unless some structural abnormality that has disru&ted continuity o! the aortic wall/ such as atherosclerosis or coarctation/ halts the dissection. *! this theory is correct/ youn.er &atients with less atherosclerosis would more !re2uently ha(e dissection in(ol(in. the entire aorta. A GreentryH tear can be identi!ied in most &atients/ located in the aorta in about one-hal! o! the &atients/ and in a &eri&heral artery in the others. As the dissection &ro.resses/ branch (essels are sheared o!! and obliterated unless a communication with the !alse lumen is established. Pro3imally/ the coronary arteries may be in(ol(ed. )!ten one or more aortic (al(e commissures are detached/ creatin. aortic insu!!iciency. The commissure between the ri.ht sinus and the noncoronary sinus is most commonly in(ol(ed. Distally/ any (essel may be in(ol(ed. *nnominate or carotid artery in(ol(ement may &roduce neurolo.ic in8ury. )bstruction o! a

subcla(ian artery may &roduce arm ischemia and a di!!erential &ressure between the two arms. )cclusion o! intercostal arteries may cause s&inal cord in8ury with &ara&aresis or &ara&le.ia. Dissection o! renal arteries may &roduce renal insu!!iciency/ hematuria/ oli.uria/ or anuria. Distally/ acute obstruction o! the iliac or !emoral arteries may cause le. ischemia/ mani!ested with &ain/ sensory loss/ or e(en .an.rene. )(erall/ a&&ro3imately 0&ercent o! &atients with aortic dissection ha(e some de.ree o! (isceral ischemia/ &eri&heral neurolo.ic in8ury/ or &ara&le.ia on admission. The dissection may result in a !atal com&lication at any time. Ru&ture into the &ericardial ca(ity with cardiac tam&onade is the most common !atal com&lication/ &robably because the (elocity o! blood !low and aortic diameter are .reatest in the ascendin. aorta. Ru&ture into the le!t &leural ca(ity or the retro&eritoneum occurs less commonly. Clinical #ani!estations The abru&t onset o! e3cruciatin. &ain/ almost immediately reachin. its &ea% intensity/ is characteristic o! aortic dissection. A &atient with a myocardial in!arction/ by contrast/ may .radually de(elo& &ain o! increasin. se(erity. "utton and associates re&orted that chest &ain/ usually in the anterior chest/ occurred in nearly FA &ercent o! 11? &atients with aortic dissection. 'ac% &ain occurred in about one-third o! the &atients/ su..estin. that absence o! bac% &ain does not rule out a dissection o! the thoracic aorta. Another characteristic is the tendency !or the &ain to mi.rate into di!!erent areas as the dissection e3tends distally. #any di!!erent &ain syndromes can occur. The &ain may radiate to the nec%/ the arms/ the e&i.astrium/ or the le.s. *t mi.ht mimic myocardial in!arction or &ulmonary embolus. The dia.nosis o! aortic dissection must be considered in &atients with sus&ected myocardial in!arction o! &ulmonary embolus in order to a(oid a !atal treatment error. Pain is seldom com&letely absent in a &atient with acute aortic dissection/ althou.h "&ittell and cowor%ers re&orted that 10 &ercent o! 1?9 &atients &resented with &ainless dissection. )ther &resentin. sym&toms include con.esti(e heart !ailure/ tam&onade/ synco&e/ stro%e/ &eri&heral neurolo.ic in8ury/ le. or arm ischemia/ &ara&le.ia/ .astrointestinal hemorrha.e/ hematuria or anuria/ hoarseness/ dys&ha.ia/ su&erior (ena ca(a syndrome/ and aortic insu!!iciency. *n the "&ittell study the initial clinical im&ression was a dia.nosis other than aortic dissection in ?F &ercent o! the &atients. An awareness o! the (ariety o! sym&toms associated with aortic dissection is essential i! the dia.nosis is to be made &rom&tly. Classi!ication De'a%ey classi!ied aortic dissections into ty&es */ **/ and *** 6$i.. 19-117. *n the De'a%ey ty&e * dissection the tear site ori.inates in the ascendin. aorta/ usually 8ust abo(e the le!t main coronary artery/ and the dissection continues distally into the descendin. or abdominal aorta. *n the ty&e ** dissection the tear site is in a similar location in the ascendin. aorta/ but the dissection sto&s distally at the innominate artery. *n the ty&e *** dissection the tear site ori.inates in the u&&er descendin. thoracic aorta/ 8ust distal to the subcla(ian artery> in ty&e ***A the dissection is locali5ed in the thoracic aorta/ and in ty&e ***' the dissection &roceeds into the abdominal aorta.

The "tan!ord classi!ication &ro&osed by #iller is based on the clinical course and the sur.ical si.ni!icance o! the dissection 6see $i.. 19-117. "tan!ord ty&e A dissection includes any dissection in(ol(in. the ascendin. aorta 6De'a%ey ty&es * and **7/ and "tan!ord ty&e ' dissection in(ol(es only the descendin. aorta 6De'a%ey ty&e ***7. )(erall/ a&&ro3imately two-thirds o! &atients with acute dissection ha(e "tan!ord ty&e A/ and one-third ha(e "tan!ord ty&e '. This is si.ni!icant/ because the &ro.nosis without treatment is much worse !or "tan!ord ty&e A dissections. Dia.nostic "tudies )n the chest radio.ra&h a widened mediastinum or a le!t &leural e!!usion !rom e3tra(asation o! blood !re2uently is seen. *n some &atients the chest radio.ra&h is com&letely normal. The electrocardio.ram 6ECG7 is o! (alue in distin.uishin. a dissection !rom a myocardial in!arction/ but there are no characteristic !eatures o! aortic dissection. )ccasionally the ECG is misinter&reted because o! the &resence o! "T-se.ment ele(ation secondary to hy&ertension and (entricular strain. *! &atients are treated !or myocardial in!arction with thrombolytic thera&y on the basis o! this misinter&retation/ catastro&hic e3san.uination may occur. The most common abnormalities on the ECG are sinus tachycardia or le!t (entricular hy&ertro&hy !rom the antecedent hy&ertension. Transeso&ha.eal echocardio.ra&hy 6TEE7 is the initial dia.nostic &rocedure o! choice !or most &atients with sus&ected aortic dissection 6$i.. 19-1?7. The e3amination can be &er!ormed in the emer.ency de&artment immediately whene(er a dia.nosis o! aortic dissection is considered. TEE is sensiti(e and s&eci!ic/ establishin. the dia.nosis with a 99 &ercent accuracy. The tear site usually can be located/ and the ascendin. aorta and aortic arch can be assessed and &otential com&lications such as aortic (al(ular insu!!iciency and cardiac tam&onade identi!ied. *! the cardiolo.y team is not e2ui&&ed to ma%e the dia.nosis &rom&tly by TEE/ other (aluable tests include a ra&id-se2uence CT scan with contrast/ #R*/ or enhanced #R an.io.ra&hy 6$i.. 19-1@7. Aorto.ra&hy is hi.hly accurate/ but it is seldom necessary. #edical Treatment )nce the dia.nosis o! aortic dissection is established/ immediate dru. thera&y to control the blood &ressure and decrease the !orce!ul contractility o! the le!t (entricle 6d&Jdt7 is initiated. Antihy&ertensi(e thera&y should be started when the dia.nosis is sus&ected because lowerin. the blood &ressure may sto& the dissection &rocess and &re(ent e3san.uination. Barious &harmacolo.ic re.imens are a(ailable/ usin. combination dru. thera&y to achie(e beta-adrener.ic bloc%ade and a!terload reduction. The &rimary .oal o! medical thera&y is to reduce shear stress by reducin. le!t (entricular d&Jdt. The systolic blood &ressure should be %e&t below 11A to 11A mmH.. +atural History and )&erati(e *ndications Patients with acute "tan!ord ty&e A dissection are at ris% !or early death because o! aortic ru&ture or cardiac and neurolo.ic com&lications. These &atients ha(e an e3tremely &oor &ro.nosis with medical thera&y/ and they should be o&erated on emer.ently. *n contrast/ &atients with acute "tan!ord ty&e ' dissection ha(e a relati(ely .ood &ro.nosis/ and early o&eration in this .rou& .enerally is recommended only !or &atients with com&lications.

The hi.h mortality rate !or uno&erated &atients with "tan!ord ty&e A dissection is documented in (irtually e(ery re&ort. Thirty to 0A &ercent o! these &atients die within 1@ h/ 0A to C0 &ercent within 1 to 1 wee%s/ and 9A &ercent within ? months. *n a classic re(iew o! @10 cases by Hirst/ C@ &ercent o! &atients with ty&e A dissection died within 1 wee%s and 91 &ercent within 9months. )! the 91 &atients re&orted by :indsay and Hurst/ almost all o! the untreated ty&e A &atients died within 1 month. The sur(i(al rate !or &atients recei(in. nono&erati(e thera&y !or "tan!ord ty&e ' dissection is much better/ with a 1-month sur(i(al rate o! F0 to 9A &ercent. Conse2uently/ most &atients with ty&e ' dissections are treated medically unless a com&lication de(elo&s. Com&lications re2uirin. immediate o&erati(e treatment are ru&ture/ hemodynamic com&romise/ &rolon.ed &ain/ aneurysm e3&ansion/ (isceral or limb ischemia/ and new neurolo.ic si.ns. Close obser(ation is mandatory in &atients recei(in. medical thera&y. This includes serial hematocrit determinations/ chest 3rays/ and !ollow-u& ima.in. studies durin. the initial hos&ital stay. A&&ro3imately 1A &ercent o! &atients with acute ty&e ' dissection treated medically de(elo& a serious com&lication within 1 wee%s/ and &rom&t sur.ery is indicated !or these &atients. *n &atients who sur(i(e acute aortic dissection a chronic aneurysm may de(elo&/ usually with a double lumen in the distal aorta. 'lood !low o!ten is &resent in both lumens/ althou.h the !alse lumen clots and heals in a&&ro3imately 1A &ercent o! the &atients. 4hen !low is &resent in both aortic lumens/ the (isceral blood su&&ly may arise !rom the true lumen or the !alse lumen. $or e3am&le/ one renal artery may arise !rom the !alse lumen and the other !rom the true lumen/ or both renal arteries may arise !rom the !alse lumen while all other (essels arise !rom the true lumen. $re2uently/ the aorta .radually becomes aneurysmal/ es&ecially i! hy&ertension is &oorly controlled. $or &atients with chronic aneurysms secondary to dissection/ sur.ical inter(ention is recommended when the aorta .rows lar.er than 0 to 9 cm in diameter/ similar to the recommendations !or other &atients with chronic aneurysms. Patients with chronic aortic dissection must be monitored closely with yearly ima.in. studies> a&&ro3imately ?A to @A &ercent o! these &atients re2uire sur.ery within 0 years. )&erati(e Treatment o! "tan!ord Ty&e A Dissection #odern sur.ical treatment o! ascendin. aortic dissection e(ol(ed !rom the wor% o! De'a%ey and Cooley/ who re&orted success!ul e3cision and .ra!tin. o! a chronic ascendin. dissection in 1900. *n the early years the o&erati(e mortality e3ceeded 0A &ercent. Today the mortality rate !or re&air o! acute ty&e A dissection is less than 1A &ercent/ which com&ares !a(orably to the &oor &ro.nosis with medical thera&y. Prom&t o&eration is recommended !or almost e(ery &atient with acute "tan!ord ty&e A aortic dissection. The main ob8ecti(es o! o&eration are to remo(e the intimal tear site/ to re&lace diseased or dilated aorta as necessary/ to obliterate the !alse lumen and redirect blood !low into the true lumen/ and to correct associated (al(ular insu!!iciency or coronary ischemia. These .oals usually are best accom&lished with use o! dee& hy&othermia and circulatory arrest 6described abo(e !or arch aneurysm re&air7. ,se o! circulatory arrest allows the sur.eon to a(oid clam&in. and &otentially in8urin. the diseased aorta and allows &er!ormance o! the distal anastomosis Go&en/H under direct (ision. At

+-, a (ariation o! the hemi-arch re&lacement techni2ue 6$i.. 19- 107 is used almost e3clusi(ely !or re&air o! acute ty&e A dissections. The techni2ue includes internal re&lacement o! the dissected aortic se.ment with a Dacron .ra!t. The most !re2uent cause o! o&erati(e death is hemorrha.e. Per!ormin. the distal arch anastomosis with an Go&enH techni2ue durin. circulatory arrest &ermits &recise inclusion o! all layers o! the dissected aorta. The anastomoses usually are &er!ormed with a continuous suture o! @-A &oly&ro&ylene> e3cessi(e tension on the suture line/ which may lacerate the !riable intima/ is a(oided. )nce the distal anastomosis is com&leted/ the &rosthetic .ra!t is occluded and !low to the brain is restored while the &ro3imal anastomosis is &er!ormed. The aortic wall is closed around the .ra!t to com&lete the .ra!t inclusion techni2ue. This techni2ue limits the ris% o! o&erati(e e3san.uination. Alternati(ely/ the aorta may be e3cised totally/ with remo(al o! the tear site and any aneurysmal se.ments. The intima and ad(entitia are rea&&ro3imated &ro3imally and distally with Te!lon !elt rein!orcement/ obliteratin. the !alse lumen. An end-to-end inter&osition Dacron .ra!t is then inserted &ro3imally and distally. This method may be associated with !ewer late !alse aneurysms/ but the ris% o! early bleedin. may be increased. #iller re&orted that e3cision o! the intimal tear site does not in!luence late sur(i(al. *n contrast/ the +-, e3&erience su..ests that remo(al o! the tear site !rom the circulation is a basic &rinci&le in the treatment o! aortic dissection and should be done whene(er &ossible. 4hen the aortic (al(e is in(ol(ed with aortic dissection/ resultin. in aortic insu!!iciency/ resus&ension o! the (al(e has been hi.hly e!!ecti(e. $ann and associates re&orted satis!actory durability a!ter aortic (al(e resus&ension. *n the +-, e3&erience re&orted by Galloway/ &atients with se(ere (al(ular insu!!iciency underwent success!ul (al(e re&air usin. (al(e reconstruction techni2ues ado&ted !rom the homo.ra!t e3&erience. *! a com&etent (al(e cannot be assured/ howe(er/ aortic (al(e re&lacement should be &er!ormed> the lon.-term results are e3cellent a!ter (al(e re&lacement under these circumstances. )(erall/ the ris% in acute ty&e A aortic dissection re&air is relati(ely low/ with an o&erati(e mortality rate o! 0 to 1A &ercent in most ma8or medical centers. $actors that increase o&erati(e ris% are ru&ture/ shoc%/ and (isceral or.an ischemia. )&erati(e Treatment o! "tan!ord Ty&e ' Dissection 4ith "tan!ord ty&e ' dissections ori.inatin. in the descendin. thoracic aorta/ most .rou&s ad(ocate initial medical thera&y. *n 1A to 10 &ercent o! these &atients ur.ent o&eration is indicated !or com&lications such as recurrent &ain/ &ro.ressi(e mediastinal hematoma/ lea%a.e/ acute e3&ansion/ ru&ture/ (isceral or.an ischemia/ e3tremity ischemia/ &ro.ressi(e neurolo.ic dys!unction/ and retro.rade dissection with aortic (al(e in(ol(ement. The o&eration !or re&air o! ty&e ' dissection is &er!ormed throu.h a le!t thoracotomy. The .oals o! thera&y are to e3clude the tear site !rom the circulation/ to obliterate the !alse lumen/ and to redirect blood !low throu.h the .ra!t into the true lumen o! the aorta distally. The o&erati(e techni2ues used to re&lace the descendin. aorta !or a

"tan!ord ty&e ' dissection are identical to those described &re(iously !or aneurysms o! the descendin. thoracic aorta. The o&erati(e mortality rate !or re&air o! acute ty&e ' dissection is 1A to 10 &ercent/ &rimarily because most ty&e ' re&airs are done emer.ently. *! initial medical thera&y is success!ul and ur.ent sur.ery is not necessary/ the &atient is ree(aluated in 1 to 1 months and yearly therea!ter. Electi(e re&air is recommended i! the &atient de(elo&s sym&toms or &ro.ressi(e aneurysmal disease. Pro.nosis Aortic dissection usually occurs in &atients with chronic hy&ertension and in those with chronic de.enerati(e disease o! the aorta. A..ressi(e treatment o! hy&ertension and care!ul !ollow-u& !or the remainder o! the &atient;s li!e is mandatory. The residual !alse lumen beyond the site o! re&air may .radually enlar.e and become aneurysmal within se(eral years. *n the series re&orted by #iller and associates the 0-year and 1Ayear sur(i(al rates were C9 and ?C &ercent/ res&ecti(ely. :ate ru&ture in another se.ment o! the aorta accounted !or ?A &ercent o! the late deaths. Ti.ht control o! hy&ertension is essential. #ore than one !atal aortic ru&ture has resulted !rom inad(ertent cessation o! antihy&ertensi(e thera&y years a!ter reco(ery !rom sur.ical treatment o! aortic dissection. :ate aneurysm !ormation in another &art o! the aorta occurs in at least ?A &ercent o! &atients with aortic dissection within 0 years. There!ore/ &atients with aortic dissection must be monitored care!ully !or any si.n o! aortic enlar.ement> a yearly #R* or CT e(aluation !or the remainder o! the &atient;s li!e is recommended. 6'iblio.ra&hy omitted in Palm (ersion7