Aortic Arch Replacement for Dissection
1999; Elsevier BV; Volume: 4; Issue: 1 Linguagem: Inglês
10.1016/s1522-2942(07)70103-4
ISSN1532-8627
AutoresMarc R. Moon, D. Craig Miller,
Tópico(s)Cardiac Structural Anomalies and Repair
ResumoAortic dissections that involve the aortic arch are usually type A, but can be retrograde extensions of type B dissections. Chronic arch dissections can remain asymptomatic for years, requiring only careful long-term surveillance and blood pressure control to minimize the likelihood of expansion; however, when aneurysmal dilatation occurs, surgical intervention becomes necessary. Aneurysmal dilatation of a dissected arch is not necessarily the result of neglect or medical treatment failure, as it can potentially complicate successful medical or surgical treatment of patients with either type A or type B dissections. Type A dissections include all of those that involve the ascending aorta, irrespective of the site of the primary tear or distal extension of the dissection. In the acute setting, operative intervention is carried out to prevent the expected sequelae of rupture with cardiac tamponade, acute aortic regurgitation caused by loss of commissural suspension, or myocardial infarction caused by coronary artery involvement. In these patients, the operative mortality risk is 10% to 25% compared with a 90% mortality rate at 3 months for nonoperative management (approximately 1% per hour for the first 48 hours).1Hirst AE Johns VJ Kime SW Dissecting aneurysm of the aorta: A review of 505 cases.Medicine. 1958; 37: 217-279Crossref PubMed Scopus (1126) Google Scholar, 2DeBakey ME McCollum CH Crawford ES et al.Dissection and dissecting aneurysms of the aorta: Twenty-year follow-up of five hundred twenty-seven patients treated surgically.Surgery. 1982; 92: 1118-1134PubMed Google Scholar, 3Miller DC Mitchell RS Oyer PE et al.Independent determinants of operative mortality for patients with aortic dissections.Circulation. 1984; 70: 153-164PubMed Google Scholar, 4Haverich A Miller DC Scott WC et al.Acute and chronic aortic dissections: Determinants of long-term outcome for operative survivors.Circulation. 1985; 72: 22-34Google Scholar, 5Lansman SL Raissi S Ergin MA et al.Urgent operation for acute transverse aortic arch dissection.J Thorac Cardiovasc Surg. 1989; 97: 334-341PubMed Google Scholar, 6Crawford ES Svensson LG Coselli JS et al.Surgical treatment of aneurysm and/or dissection of the ascending aorta, transverse aortic arch, and ascending aorta and transverse aortic arch: Factors influencing survival in 717 patients.J Thorac Cardiovasc Surg. 1989; 98: 659-674PubMed Google Scholar, 7Svensson LG Crawford ES Hess KR et al.Dissection of the aorta and dissecting aortic aneurysms: Improving early and long-term surgical results.Circulation. 1990; 82: 24-38Google Scholar, 8Kouchoukos NT Wareing TH Murphy SF et al.Sixteen-year experience with aortic root replacement: Results of 172 operations.Ann Surg. 1991; 214: 308-320Crossref PubMed Scopus (384) Google Scholar, 9Galloway AC Colvin SB Grossi EA et al.Surgical repair of type A aortic dissection by the circulatory arrest-graft inclusion technique in sixty-six patients.J Thorac Cardiovasc Surg. 1993; 105: 781-790PubMed Google Scholar, 10Fann JI Smith JA Miller DC et al.Surgical management of aortic dissection during a 30-year period.Circulation. 1995; 92: 113-121Crossref Google Scholar Type B dissections do not involve the ascending aorta, and can be treated successfully with either medical or surgical therapy.11Glower DD Fann JI Speier RH et al.Comparison of medical and surgical therapy for uncomplicated descending aortic dissection.Circulation. 1990; 82: 39-46Google Scholar, 12Miller DC The continuing dilemma concerning medical versus surgical management of patients' with acute type B dissections.Semin Thorac Cardiovasc Surg. 1993; 5: 33-46PubMed Google Scholar Both types, however, can involve the aortic arch, either as the location of the primary intimal tear or after distal or proximal extension. Controversy exists as to the best treatment for acute dissections that originate or involve the transverse arch. Acute type A dissection. In patients with acute type A dissections, surgical treatment of the arch, whether or not it is the site of the primary tear, can include “simple” ascending aortic replacement, “hemi-arch” replacement with a beveled, open distal aortic anastomosis under profound hypothermic circulatory arrest (PHCA) and ascending replacement, or complete transverse arch replacement with reimplantation of the arch vessels. We have moved away from simple ascending aortic replacement on the basis that circulatory arrest allows a more sound distal anastomosis, enables direct inspection of the arch and proximal descending thoracic aorta (with repair or resection of distal fenestrations, when appropriate), allows antegrade true lumen arterial reperfusion and rewarming after recannulation of the proximal arch graft, and avoids potential clamp injuries to the distal ascending aorta. The latter two options are distinctly different in that hemi-arch replacement requires only 15 to 30 minutes of circulatory arrest at 20°C to 22°C, whereas total arch replacement requires a substantially longer period of circulatory arrest time and lower core temperatures, both of which prolong cardiopulmonary bypass (CPB) and impair coagulation homeostasis. The Mount Sinai group reported circulatory arrest times ranging from 45 to 67 minutes for patients with acute and subacute arch dissections in which an aggressive approach to resecting arch tears was employed (total arch replacement was necessary in 11 of 19 patients); this appears to have been associated with increased bleeding, as evidenced by the need for a Cabrol shunt between the periprosthetic space and the venous circulation (the older wrap inclusion techniques were used then) in 40% of patients.4Haverich A Miller DC Scott WC et al.Acute and chronic aortic dissections: Determinants of long-term outcome for operative survivors.Circulation. 1985; 72: 22-34Google Scholar In their hands, however, this approach was associated with an acceptable early mortality rate of 21% for these complicated, high risk patients. Series from Japan13Kazui T Kimura N Yamada O et al.Total arch graft replacement in patients with acute type A aortic dissection.Ann Thorac Surg. 1994; 58: 1462-1468Abstract Full Text PDF PubMed Scopus (58) Google Scholar, 14Okita Y Takamoto S Ando M et al.Mortality and cerebral outcome in patients who underwent aortic arch operations using deep hypothermic circulatory arrest with retrograde cerebral perfusion: No relation of early death, stroke, and delirium to the duration of circulator)' arrest.J Thorac Cardiovasc Surg. 1998; 115: 129-138Abstract Full Text Full Text PDF PubMed Scopus (156) Google Scholar and France15Bachet J Goudot B Dreyfus G et al.The proper use of glue: A 20-year experience with the GFR glue in acute aortic dissection.J Card Surg. 1997; 12: 243-255Crossref PubMed Scopus (3) Google Scholar also advocated total arch replacement for such patients with dissections that involved the arch, reporting mortality rates of 11% to 23%. On the other hand, Crawford et al16Crawford ES Kirklin JW Naftel DC et al.Surgery for acute dissection of ascending aorta: Should the arch be included?.J Thorac Cardiovasc Surg. 1992; 104: 46-59PubMed Google Scholar and Borst et al17Borst HG Buhner B Jurmann M Tactics and techniques of aortic arch replacement.J Card Surg. 1994; 9: 538-547Crossref PubMed Scopus (37) Google Scholar were more cautious, reporting that the probability of operative death more than doubled in certain individuals if arch replacement was carried out for patients with acute type A aortic dissections. Borst et al reported the Hannover series of partial (open-distal) versus total arch replacement for patients with aneurysms (n = 58) or dissections (n = 92, acute; n = 54, chronic). Their reported circulatory arrest times were remarkably low for both partial and total arch replacements (17 ± 6 minutes and 34 ± 13 minutes, respectively), but the mortality rate increased substantially with total arch replacement for patients with aneurysms (3% partial arch v 19% total arch), acute dissections (12% partial arch v 36% total arch), or chronic dissections (6% partial arch v 20% total arch). In Crawford's series at Baylor, among 82 patients with acute type A dissections, one third of patients underwent combined ascending and arch replacement, whereas the procedure was limited to the ascending aorta in two thirds.16Crawford ES Kirklin JW Naftel DC et al.Surgery for acute dissection of ascending aorta: Should the arch be included?.J Thorac Cardiovasc Surg. 1992; 104: 46-59PubMed Google Scholar The operative death rate increased from 17% for ascending aortic replacement alone to 31% for patients in whom the procedure included at least the proximal arch (hemi-arch replacement). Arch repair was an independent predictor of operative mortality, although it seemed to reduce the need for late reoperations on the distal aorta. Additionally, advanced New York Heart Association functional class, diabetes, and the need for concomitant coronary artery bypass grafting appreciably increased the risk if the procedure was extended into the arch, whereas their impact after isolated ascending aortic replacement was minimal. In the combined Stanford-Duke series of patients with aortic dissections due to arch tears (n = 47 patients), advanced age, number and severity of dissection related complications, and coexistent medical illnesses adversely influenced the already high operative risk.18Yun KL Glower DD Miller DC et al.Aortic dissection resulting from tear of transverse arch: Is concomitant arch repair warranted?.J Thorac Cardiovasc Surg. 1991; 102: 355-370PubMed Google Scholar We currently prefer the hemi-arch, open distal technique for patients with acute type A dissections to allow for assessment of the extent of intimal disruption and the condition of the arch vessels and to ensure a more sound distal anastomosis (this technique has been previously published in this journal).19Yun KL Miller DC Technique of aortic valve preservation in acute type A aortic dissection.Op Tech Card Thorac Surg. 1996; 1: 68-81Abstract Full Text Full Text PDF Google Scholar We resect the tear if practical, but do not perform complete arch replacement in this setting unless there is rupture or impending rupture of the arch itself, especially if other risk factors are present. Inherent in this approach is the known potential for dilatation of the distal false channel requiring subsequent reoperation. Close follow-up is essential to monitor the progression of false lumen dilatation and to decide when the appropriate time for surgical intervention is necessary. Follow-up of patients with aortic dissection, whether treated medically or surgically, should include a computed tomographic or magnetic resonance imaging scan before hospital discharge and at 3 months. Scans can then be obtained at 6 month intervals for 1 to 2 years, then annually throughout the patient's life if there are no major pathoanatomical changes detected over time. Strict blood pressure control and negative inotropic therapy are also essential; DeBakey et al2DeBakey ME McCollum CH Crawford ES et al.Dissection and dissecting aneurysms of the aorta: Twenty-year follow-up of five hundred twenty-seven patients treated surgically.Surgery. 1982; 92: 1118-1134PubMed Google Scholar found that aneurysms subsequently developed in 46% of patients with uncontrolled hypertension, but only in 17% with controlled blood pressure. Acute type B dissection. In patients with acute type B dissections, we currently treat most individuals with medical therapy; in general, surgical intervention is undertaken for those with complications, eg, acute rupture or leak, the presence of a large false aneurysm, ischemia of distal end-organs, or progression of the dissection during medical therapy manifested by persistent or recurrent pain. We take a more aggressive surgical approach, however, in younger, healthy patients and those with the Marfan syndrome. The advent of endovascular stent-grafting for patients with acute type B dissections has also changed the decision-making process, but this experimental treatment modality is confined to just a few centers around the world. In the Stanford-Duke series of patients with type B dissections, the 30-day mortality rate for patients with no compelling indication for emergency operation was 10% with medical therapy and 19% with surgical therapy.11Glower DD Fann JI Speier RH et al.Comparison of medical and surgical therapy for uncomplicated descending aortic dissection.Circulation. 1990; 82: 39-46Google Scholar Patients who develop ischemic complications due to distal aortic branch compromise undergo angiographic investigation and stenting of branch vessels or the aorta itself, with or without fenestration of the dissection flap.20Moon MR Dake MD Pelc LR et al.Intravascular stenting of acute experimental type B dissections.J Surg Res. 1993; 54: 381-388Abstract Full Text PDF PubMed Scopus (61) Google Scholar, 21Slonim SM Nyman U Semba CP et al.Aortic dissection: Percutaneous management of ischemic complications with endovascular stents and balloon fenestration.J Vase Surg. 1996; 23: 241-253Abstract Full Text Full Text PDF PubMed Scopus (206) Google Scholar, 22Slonim SM Nyman UR Semba CP et al.True lumen obliteration in complicated aortic dissection: Endovascular treatment.Radiology. 1996; 201: 161-166PubMed Google Scholar We have always considered early operation (proximal descending aorta replacement, or, currently, a stent-graft to cover the primary intimal tear) in younger, low-risk patients in an attempt to prevent the adverse late sequelae of the disease; although this aggressive approach is intuitively logical and today is endorsed by the Mount Sinai and Yale groups, its use and effectiveness compared with medical therapy alone remains unknown at this time.12Miller DC The continuing dilemma concerning medical versus surgical management of patients' with acute type B dissections.Semin Thorac Cardiovasc Surg. 1993; 5: 33-46PubMed Google Scholar, 22Slonim SM Nyman UR Semba CP et al.True lumen obliteration in complicated aortic dissection: Endovascular treatment.Radiology. 1996; 201: 161-166PubMed Google Scholar We do, however, avoid manipulation and clamping of the arch during operations in patients with acute type B dissections by using circulatory arrest and constructing an “open proximal” aortic anastomosis. In the early Stanford surgical series, the operative mortality rate for patients with an acute type B dissection caused by an arch tear was 75%, compared with 32% if the tear was in the descending aorta.3Miller DC Mitchell RS Oyer PE et al.Independent determinants of operative mortality for patients with aortic dissections.Circulation. 1984; 70: 153-164PubMed Google Scholar In the Stanford-Duke series of patients with primary intimal tears located in the arch, none of the four patients who underwent arch repair at the time of descending thoracic replacement survived, and only one of three patients without concomitant arch repair survived.18Yun KL Glower DD Miller DC et al.Aortic dissection resulting from tear of transverse arch: Is concomitant arch repair warranted?.J Thorac Cardiovasc Surg. 1991; 102: 355-370PubMed Google Scholar After 2 years, 75% ± 22% of medically-treated patients were alive compared with only 14% ± 13% of the surgically-treated group; however, by 3 years, all the medical patients had died. Clearly, these historical data from the 1970s indicate that substantial room for improvement existed in dealing with patients with type B dissections originating from an arch tear, including newer surgical techniques that rely on profound hypothermic arrest.7Svensson LG Crawford ES Hess KR et al.Dissection of the aorta and dissecting aortic aneurysms: Improving early and long-term surgical results.Circulation. 1990; 82: 24-38Google Scholar, 23Crawford ES Coselli JS Safi HJ Partial cardiopulmonary bypass, hypothermic circulatory arrest, and posterolateral exposure for thoracic aortic aneurysm operation.J Thorac Cardiovasc Surg. 1987; 94: 824-827PubMed Google Scholar, 24Caramutti VM Dantur JR Favaloro MR et al.Deep hypothermia and circulatory arrest as an elective technique in the treatment of type B dissecting aneurysm of the aorta.J Card Surg. 1989; 4: 206-215Crossref PubMed Scopus (24) Google Scholar, 25Stone CD Greene PS Gott VL et al.Single-stage repair of distal aortic arch and thoracoabdominal dissecting aneurysms using aortic tailoring and circulatory arrest.Ann Thorac Surg. 1994; 57: 580-587Abstract Full Text PDF PubMed Scopus (16) Google Scholar, 26Miller DC Surgical management of acute aortic dissection: New data.Semin Thorac Cardiovasc Surg. 1991; 3: 225-237PubMed Google Scholar Radiographic studies have shown that the distal false lumen remains patent in the majority of patients (85%) after proximal thoracic aortic repair, but the persistence of the false channel does not portend a catastrophic late outcome; in fact, it may be the only source of blood flow to major organs in some patients.27Guthaner DF Miller DC Silverman JF et al.Fate of the false lumen following surgical repair of aortic dissections: An angiographic study.Radiology. 1979; 133: 1-8PubMed Google Scholar In the Mount Sinai series, persistence of the false lumen was associated with the development of late thoracic aortic false aneurysms, but the incidence was relatively low and long-term survival was not substantially different between patients with a closed versus patent distal false lumen.28Ergin MA Phillips RA Galla JD et al.Significance of distal false lumen after type A dissection repair.Ann Thorac Surg. 1994; 57: 820-825Abstract Full Text PDF PubMed Scopus (163) Google Scholar Two of 18 (11%) patients with a persistently patent distal false lumen required late reoperations. Event-free survival at 5 years was 84% for patients with a thrombosed false lumen, versus 63% for those with a patent false lumen (P = not significant [NS]). Resection of a primary arch intimal tear did not necessarily obliterate the distal false lumen; 23% of patients who underwent partial or total arch replacement for an arch tear had a patent false lumen. Persistence of the false channel, therefore, does not appear to correlate with successful exclusion of the primary intimal tear, but depends more on the presence of distal fenestrations between the true and false lumens.27Guthaner DF Miller DC Silverman JF et al.Fate of the false lumen following surgical repair of aortic dissections: An angiographic study.Radiology. 1979; 133: 1-8PubMed Google Scholar More intensive long-term medical follow-up is necessary to decrease the death rate from late aortic rupture by prompting earlier reoperation in patients whose chronic dissections become aneurysmal. Of all late deaths in the early Stanford series, at least 15% were caused by late aortic rupture, and in DeBakey et al's 20-year series, 29% of late deaths were caused by aortic rupture.2DeBakey ME McCollum CH Crawford ES et al.Dissection and dissecting aneurysms of the aorta: Twenty-year follow-up of five hundred twenty-seven patients treated surgically.Surgery. 1982; 92: 1118-1134PubMed Google Scholar, 4Haverich A Miller DC Scott WC et al.Acute and chronic aortic dissections: Determinants of long-term outcome for operative survivors.Circulation. 1985; 72: 22-34Google Scholar Subsequent aneurysmal formation occurred more often with dissections that involved the entire descending and abdominal aorta (35%) compared with dissections limited to either the ascending (14%) or proximal descending (16%) aorta.2DeBakey ME McCollum CH Crawford ES et al.Dissection and dissecting aneurysms of the aorta: Twenty-year follow-up of five hundred twenty-seven patients treated surgically.Surgery. 1982; 92: 1118-1134PubMed Google Scholar Overall, late aneurysms developed in 29% of patients after successful initial surgical treatment of patients with acute dissections. Reoperation in this setting should not be considered a treatment failure, but rather a timely and prudent treatment of the late aortic sequelae of aortic dissections. In the Stanford series, the linearized rate of reoperation was 3.4% per patient year; or, in actuarial erms, 13% ± 4% of patients at 5 years and 23% ± 6% at 10 years had required an aortic reoperation, postoperatively.4Haverich A Miller DC Scott WC et al.Acute and chronic aortic dissections: Determinants of long-term outcome for operative survivors.Circulation. 1985; 72: 22-34Google Scholar The reoperative rate was similar in patients with type A or type B dissections, but higher in younger patients and in those with primary tears in the arch (27% ± 13% at 1 year); however, even in patients with primary arch tears, the site of reoperation rarely included the arch itself. Among the 21 reoperations required in 135 hospital survivors, 8 were on the proximal aorta and 13 were for distal aortic replacement. Arch replacement was performed in three patients with type A dissections and in two patients with type B dissections. Aneurysmal dilatation of chronic dissections involving the aortic arch is uncommon, but its surgical treatment can be quite challenging; this is the subject of this current review. Consideration of surgical intervention should probably be more aggressive in patients with arch false aneurysms caused by chronic dissection than in those caused by degenerative aneurysms. In Pressler and McNamara's29Pressler V McNamara JJ Thoracic aortic aneurysm: Natural history and treatment.J Thorac Cardiovasc Surg. 1980; 79: 489-498PubMed Google Scholar series, aortic rupture was the cause of death in 77% of patients with thoracic aortic aneurysms due to dissection compared with only 44% of degenerative aneurysms; however, this disparity is due in part to the fact that the diagnosis of aortic dissection was made during the acute phase shortly before fatal rupture in many patients with dissections in this historical retrospective study. Hirose et al30Hirose Y Hamada S Takamiya M et al.Aortic aneurysms: Growth rates measured with CT.Radiology. 1992; 185: 249-252PubMed Google Scholar reported that the growth rate of aneurysms was greater in the arch (0.56 cm/ year) than in the descending thoracic (0.42 cm/year) or abdominal aorta (0.28 cm/year). The Mount Sinai group found that once an aneurysm reached 5 cm, its growth rate increased substantially; aneurysm expansion rate was also higher in smokers.31Dapunt OE Galla JD Sadeghi AM et al.The natural history of thoracic aortic aneurysms.J Thorac Cardiovasc Surg. 1994; 107: 1323-1333Abstract Full Text PDF PubMed Scopus (233) Google Scholar Juvonen et al32Juvonen T Ergin MA Galla JD et al.Prospective study of the natural history of thoracic aortic aneurysms.Ann Thorac Surg. 1997; 63: 1533-1545Abstract Full Text Full Text PDF PubMed Scopus (242) Google Scholar also developed a model to predict the risk of rupture in patients with thoracic aneurysms based on aneurysm size, age, and the presence of pain or chronic obstructive pulmonary disease; unfortunately, these data did not include aortic dissections. The Yale group found that the growth rate increased with aneurysm size and was higher in the presence of a dissection; furthermore, descending aneurysms expanded faster than more proximal thoracic aortic aneurysms (Fig I).33Coady MA Rizzo JA Hammond GL et al.What is the appropriate size criterion for resection of thoracic aortic aneurysms?.J Thorac Cardiovasc Surg. 1997; 113: 476-491Abstract Full Text Full Text PDF PubMed Scopus (474) Google Scholar Indications for resection of a chronic dissection involving the aortic arch include: (1) Arch diameter (true and false lumens combined) greater than 6 to 7 cm or greater than twice the size of the normal thoracic aorta for that individual; (2) enlargement of more than 7 to 10 mm in 1 year; (3) symptoms attributable to the dissection such as pain, hoarseness, swallowing or respiratory difficulties, caval obstruction; or (4) localized saccular protrusion of the false lumen, which might put the patient at a higher risk of rupture. Patients with the Marfan syndrome are generally younger and are more likely to experience rapid progressive aortic dilatation33Coady MA Rizzo JA Hammond GL et al.What is the appropriate size criterion for resection of thoracic aortic aneurysms?.J Thorac Cardiovasc Surg. 1997; 113: 476-491Abstract Full Text Full Text PDF PubMed Scopus (474) Google Scholar, 34Pyeritz RE Marfan syndrome: Current and future clinical and genetic management of cardiovascular manifestations.Semin Thorac Cardiovasc Surg. 1993; 5: 11-16PubMed Google Scholar, 35Hwa J Richards JG Huang H et al.The natural history of aortic dilatation in Marfan syndrome.Med J Aust. 1993; 158: 558-562PubMed Google Scholar; therefore, arch replacement should generally be considered when expansion exceeds 3 to 5 mm per year or when the aortic diameter exceeds 5 cm in healthy individuals. Aortic pathology that is superior to the left mainstem bronchus on computed tomographic scan can be addressed effectively via a median sternotomy. If surgical access is required beyond the left mainstem bronchus, a left thoracotomy or bilateral anterior thoracotomy is required. In this review, we only describe our techniques for arch replacement in patients with chronic dissections via the anterior approach. For arch replacement in chronic dissections, the “elephant trunk” methods, in which a free segment of graft is left dangling distally in the descending aorta, is ideal to simplify future aortic operations.36Borst HG Frank G Schaps D Treatment of extensive aortic aneurysms by a new multiple-stage approach.J Thorac Cardiovasc Surg. 1988; 95: 11-13PubMed Google Scholar, 37Crawford ES Coselli JS Svensson LG et al.Diffuse aneurysmal disease (chronic aortic dissection, Marfan, and mega aorta syndromes) and multiple aneurysm: Treatment by subtotal and total aortic replacement emphasizing the elephant trunk operation.Ann Surg. 1990; 211: 521-537Crossref PubMed Scopus (196) Google Scholar The dissection most often extends far distally, and although the descending aorta may not yet be aneurysmal at the time of arch replacement, the distal graft is available for either a later planned procedure or when dilatation of the descending thoracic aorta becomes sufficient to warrant further replacement. CPB. If previous ascending aortic replacement has been performed and redo sternotomy can be accomplished safely, the arterial perfusion cannula may be inserted into the previous graft to provide antegrade flow during the period of cooling. Otherwise, CPB (Fig II) is commenced initially using either a subclavian or femoral arterial cannula, and the arterial line is “Y-ed” to allow subsequent recannulation of the arch graft for antegrade CPB flow after arch reconstruction. Over time, we have been using the subclavian artery more often, following the lead of Sabik et al38Sabik JF Lytle BW McCarthy PM et al.Axillary artery: An alternative site of arterial cannulation for patients with extensive aortic and peripheral vascular disease.J Thorac Cardiovasc Surg. 1995; 109: 885-891Abstract Full Text Full Text PDF PubMed Scopus (315) Google Scholar from the Cleveland Clinic, hoping that this will minimize the incidence of CPB malperfusion of vital end-organs. When femoral arterial cannulation is performed in a patient with a chronic dissection, bilateral tympanic membrane temperature (and/or bilateral radial artery pressure) monitoring is used to ensure equal cerebral cooling rates, myocardial temperature is measured, and the descending aorta is interrogated with transesophageal echocardiography to make sure that neither the false nor true lumen becomes obliterated at the onset of retrograde CPB perfusion. Malperfusion of important aortic arch branches or abdominal aortic tributaries at this point can be a catastrophic complication. We cannulate the femoral or subclavian artery with the stronger pulse (contrary to our policy in patients with acute dissections), which usually communicates directly with the aortic true lumen above, but prefer the right side if femoral vein cannulation should become necessary. If a venous cannula needs to be passed into the right atrium, using the right femoral vein affords the most reliable direct access route to the inferior vena cava (IVC) by minimizing problems navigating the guidewire or cannula across the IVC bifrucation. In complicated cases where ascending aortic false aneurysms have eroded into the posterior table of the sternum, CPB can be instituted and the patient cooled to 22°C using femoral-femoral cannulation before the sternotomy is completed under PHCA; a 28F multifenes-trated venous cannula (DLP Medical Products, Medtronic, Inc, Grand Rapids, MI) is placed at the right atrial-superior vena cava (SVC) junction under echocardiography guidance and a centrifugal (suction) pump system is used to augment venous drainage. Otherwise, standard bicaval venous cannulation is employed with tourniquets around both the SVC and the IVC. Once the chest is open and CPB is initiated, a 14F sump vent can be placed into the pulmonary artery to reduce bronchial return to the left heart. Alternatively, if severe aortic valvular regurgitation is present or a false aneurysm of the ascending aorta has eroded into the left atrium or left ventricle creating a fistula or the ventricle cannot be kept adequately decompressed by manual massage, we prefer using a large (20F) apical left ventricular (LV) sump vent. The CPB circuit also includes an arteriovenous shunt for retrograde cerebral perfusion (RCP) during periods of circulatory arrest. Preparation for circulatory arrest. Because of previous ascending aortic operations or extensive aneurysms, it commonly is not possible to clamp the ascending aorta safely before turning off the pump. For total arch replacement, the patient is cooled to 15°C (bladder temper
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