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J Thorac Cardiovasc Surg 2007;133:1455-1463
© 2007 The American Association for Thoracic Surgery
Surgery for Acquired Cardiovascular Disease |
a Department of Cardiothoracic Surgery, Mount Sinai School of Medicine, New York, NY
b Department of Anesthesiology, Mount Sinai School of Medicine, New York, NY.
Poster Presentation at the Western Thoracic Surgical Association meeting, Sun Valley Idaho, June 21-24, 2006.
Received for publication July 13, 2006; revisions received December 31, 2006; accepted for publication January 31, 2007. * Address for reprints: Christian D. Etz, MD, Mount Sinai School of Medicine, Department of Cardiothoracic Surgery, One Gustave L. Levy Place, PO Box 1028, New York, NY 10029. (Email: christian.etz{at}mountsinai.org).
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Abstract |
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Methods: A review was conducted of 275 patients (202 were male, mean age 69 ± 11 years, range 17–88 years) who underwent aortic root replacement using conduits constructed intraoperatively from pericardial valves and impregnated Dacron grafts between September 1993 and February 2005. There were 151 patients with degenerative aneurysms and 63 patients with atherosclerotic aneurysms; 43 patients had dissections (9 acute type A), 13 patients had endocarditis, and 5 patients had other pathologic conditions. The ascending aorta alone was replaced in 154 patients, a hemiarch reconstruction was performed in 105 patients, and extensive arch reconstruction was performed in 16 patients. Hypothermic circulatory arrest and an open distal anastomosis were used in 95% of patients.
Results: Hospital mortality was 17 of 275 patients (6.2%). Four additional patients (1.5%) sustained permanent strokes. Among surviving patients, the rate of stroke was estimated as 0.85 per 100 patient-years and the rate of significant hemorrhage was estimated as 0.3 per 100 patient-years. Reoperation for valve failure occurred in only 1 patient 12 years postoperatively. Long-term survival in men was similar to that of a normal matched control population, but was significantly lower in women (P = .002).
Conclusions: Men who recover satisfactorily after reconstruction of the aortic root with a stented bioprosthetic valved conduit (6-month survivors) enjoy long-term outcomes equivalent to that of a normal matched population; the postoperative mortality rate in women is twice that of a normal population.
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Introduction |
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Aortic root reconstruction is warranted when a diseased aortic valve is associated with a dilated or dissected aortic root or ascending aorta. Elective surgery is also indicated in the presence of significant dilatation of the sinuses of Valsalva, the sinotubular junction, or the ascending aorta. In addition, elective root replacement may be advisable in a minimally dilated aortic root and ascending aorta if aortic valve disease is associated with a genetic predisposition to aneurysm formation or dissection.
Since Bentall and De Bono introduced the surgical technique involving composite mechanical valved conduits in 1968, various adaptations of the original concept have been the standard therapy for patients with an aortic root aneurysm.3,4 Because a mechanical valved conduit mandates lifelong anticoagulation, alternative strategies have been sought. Valve-sparing operations have become an increasingly appealing alternative in younger patients requiring aortic root surgery whose life expectancy exceeds the anticipated durability of an implanted biological valve. For elderly patients, in whom biological valves generally last longer, the use of a conduit constructed in the operating room by sewing a bioprosthetic valve to a vascular graft is the most attractive option.
The objective of this study was to evaluate patients who have undergone what we will refer to as a biological Bentall operation to determine whether the benefit of avoiding anticoagulation by using a biological valve in the aortic conduit is offset by the need for reoperation because of valve deterioration.
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Materials and Methods |
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Indications
The principal indication for aortic root reconstruction (Table 1) was a degenerative aortic aneurysm in 151 patients (55%): of these, 9 had annuloaortic ectasia, 7 had a bicuspid valve, and 3 had Marfan syndrome. An atherosclerotic aortic aneurysm was present in 63 patients (23%); 43 patients (16%) had dissections, one quarter of which (9) were acute type A; 13 patients (5%) had aortic valve endocarditis affecting the root; and 5 patients had other pathologic conditions.
Fourteen patients underwent emergency root reconstructions (including 9 for acute type A dissection and 4 with root endocarditis). Twenty-one patients had urgent procedures because of shortness of breath, anginal pain, or syncope. The remaining 240 patients (87%) underwent elective procedures.
A total of 48 patients (18%) had undergone previous cardioaortic procedures; 27 patients (10%) had received oral anticoagulants before the root reconstruction, and 50 patients (18%) had received platelet inhibitors. At hospital admission, 85 patients (31%) were being treated for hypertension with ß-adrenergic blocking agents, and 49 patients (18%) were being treated with angiotensin-converting enzyme inhibitors.
Surgical Technique
Cannulation and myocardial protection
Arterial cannulation was carried out through the femoral artery (19%), the ascending aorta (18%), and, more recently, the right axillary artery (61%; Figure 1) as previously described by our group5; the left axillary artery or the aortic arch was cannulated in 6 cases (2%). Venous cannulation was usually through a 2-stage catheter in the right atrium, but in some patients in whom the heart was not fully exposed, the right atrium was accessed through a wire-directed catheter placed through the femoral vein. Myocardial protection was provided with cold antegrade blood cardioplegia, systemic perfusion at 20°C, and, in patients with severe coronary disease, retrograde blood cardioplegia. Cardioplegia was administered every 20 to 30 minutes during periods of myocardial ischemia.
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Perfusion warming was performed at the end of the procedure with the gradient between the esophageal and blood temperature maintained at less than 10°C. Warming was maintained until the esophageal temperature reached 35°C and bladder temperature was greater than 32°C. Downward drift, however, resulted in most patients leaving the operating room with esophageal and bladder temperatures of 32°C. Warming was usually accomplished in 1 hour of perfusion; during the last 15 or 20 minutes, partial bypass was frequently used to take advantage of improved warming with pulsatile perfusion.
Selective cerebral perfusion
Perfusion of all 3 head vessels was achieved with SCP when arch replacement was planned or cerebral protection time was expected to exceed 30 minutes. Once the use of the trifurcation graft was introduced for arch repair, SCP was provided by inflow to the trifurcation graft through the right axillary artery. SCP was performed at a blood temperature of 15°C to 20°C and flow sufficient to maintain a pressure of 50 to 60 mm Hg. This usually required a flow of 800 to 1200 mL/min.
Aortic root reconstruction
A button Bentall procedure was used in 93% of patients, a Cabrol procedure was used in 4% of patients, and a classic Bentall procedure was used in 3% of patients (Table 2). No valvuloplasty or valve-sparing procedures were included in this series; in all 275 patients, a stented pericardial valve (Carpentier-Edwards Perimount series in most cases; Edwards Lifesciences, Irvine, Calif) was used. The Dacron graft was oversized 5 to 7 mm larger than the valve diameter.
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All graft material was albumin-impregnated woven Dacron.
Extent of Operation
Only the ascending aorta was replaced in 152 patients (55%); a hemiarch reconstruction was performed in 102 patients (37%); and extensive arch reconstruction was performed in 21 patients (8%), with an elephant trunk stage I in 13 cases. Overall cardiopulmonary bypass time was 260 ± 57 minutes. The distal anastomosis was performed open in more than 95% of the cases (n = 262). Detailed operative data are shown in Table 2.
One third of the patients had coronary artery disease requiring concomitant bypass grafting (n = 101); 15 patients underwent a concomitant mitral valve procedure (Table 2).
Follow-up
All patients were followed by the referring cardiologist and contacted periodically by our research personnel. The follow-up questionnaire included cardiac reoperations (paravalvular leakage, prosthetic valve endocarditis), myocardial infarction, cerebral, visceral or peripheral thromboembolic events, hemorrhage, endocarditis, and anticoagulant intake, and was completed in all cases by the patients themselves, their cardiologists, or close family members.
Annual computed tomography scans were scheduled in all patients and attained in 61% of patients. Postoperative events were compiled and analyzed according to the Guidelines for Reporting Morbidity and Mortality after Cardiac Valvular Operations7 and our institutional checklist. For this study, follow-up was closed on December 31, 2005, and extended to 11 years.
Statistical Methods
Data were entered in an Excel spreadsheet (Microsoft Corp, Redmond, Wash) and transferred to an SAS file (SAS Institute Inc, Cary, NC) for data description and analysis. Patient characteristics are described as percentages, and groups were compared using chi-square tests. Early death is defined as death within 30 days after the procedure or death before discharge, if beyond 30 days. Logistic regression analysis was used to study independent factors associated with adverse outcome, early death, or permanent stroke. For patients who did not experience early death, long-term follow-up commences 30 days after the procedure and continues until the date of death, or December 31, 2005, for patients with no death information. Kaplan–Meier life tables were calculated to describe early and long-term survival. The Cox proportional hazards model was used to identify independent risk factors for long-term survival, controlling for age and gender. Long-term survival of male and female patients was compared with New York State death rates from 2001 for corresponding ages and person-years of exposure, and the differences were tested by methods for Poisson regression.
The risk factors considered for analysis were age, gender, history of hypertension, chronic obstructive pulmonary disease (COPD), coronary artery disease, history of neurologic dysfunction, aortic regurgitation, urgency of the procedure, pathologic condition for which the procedure was indicated, cannulation site, extent of procedure, presence of clot or atheroma, open distal anastomosis, and concomitant procedures (mitral valve replacement/repair, concomitant coronary artery bypass grafting, and other concomitant procedures such as tricuspid valve replacement). For long-term analysis, anticoagulant and ß-adrenergic blocking agent intakes were also considered.
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Results |
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All known preoperative risk factors were entered in a stepwise logistic regression analysis to identify those that were independent predictors of adverse outcome. Three factors were identified: clot or atheroma (P = .0004), coronary artery disease (P = .01), and nonelective procedure (P = .03).
Postoperative Complications
Severe postoperative complications after bioprosthetic root reconstruction occurred in 68 patients (24.7%) (Table 3). The most common serious complications were respiratory and cardiac. Twenty-one percent of patients had transient neurologic dysfunction, but only 7 patients had strokes, 3 of whom died. Six patients required dialysis, which was permanent in 2 patients; 4 patients had only transient postoperative renal failure.
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Late Mortality
Long-term survival among patients who did not die before discharge or within 30 days of the procedure was compared with New York State 2001 death rates (Figure 3). The median duration of follow-up was 3.6 years (range 0–10.7 years).
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For the group as a whole, multivariate analysis indicated that the long-term outcome after a biological valved conduit reconstruction of the aortic root among female patients was significantly worse than that for male patients, and that their risk factors differed. For female patients, multiregression analysis revealed the presence of clot or atheroma as an independent predictor of late death. Open distal anastomosis and prescription of ß-blocking drugs at hospital discharge were protective factors for long-term survival in women. In male patients, the presence of COPD and performance of any concomitant procedure were independent predictors of late death.
Aortic Reoperation
Two patients required early revision for mediastinitis after primary aortic root reconstruction with a bioprosthetic valved conduit. No reoperation for early failure of the biological Bentall procedure or for anastomotic pseudoaneurysm occurred.
Structural Valve Deterioration
Reoperation for structural valve dysfunction was required in only 1 patient, 12 years after root replacement with a biological valved composite graft.
Thromboembolic Events
Seven of the 125 patients who were alive at study time reported having a permanent stroke during follow-up. One was undergoing long-term anticoagulation for an indication unrelated to the Bentall procedure. One additional patient who died in follow-up is known to have had a stroke, making a total of 8 documented strokes among hospital survivors, a rate of 0.85 per 100 patient-years of follow-up. However, we could not update information about strokes for 39 of the 55 patients who died in follow-up. If they had experienced strokes at the same rate as the 16 deceased patients with known stroke information, the linearized stroke rate would be estimated as 1.2 per 100 patient-years.
Hemorrhage
After hospital discharge, 3 patients had a significant hemorrhage as defined by the Society of Thoracic Surgeons guidelines. All 3 were alive at study time. Two of them were being treated with anticoagulants for indications unrelated to the biological Bentall procedure. The linearized incidence of significant hemorrhage during follow-up was estimated as 0.3 per 100 patient-years. The median time to hemorrhage was 503 days (498–2016 days).
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Discussion |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionConclusionsReferences |
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Because the main advantage of implanting a biological valved conduit compared with a mechanical valve is to avoid anticoagulation, we were startled to see that so many of our patients, especially in the earlier years of this experience, were discharged with anticoagulants. Postoperative patient care in our referral practice is largely the province of cardiologists, who generally think that a 3-month interval of anticoagulation postoperatively is a good idea to guard against thromboembolism until the conduit endothelializes fully. Only a small minority of patients remained on anticoagulation long term for reasons unrelated to the conduit (chiefly atrial fibrillation), but the levels of anticoagulation needed for this indication are lower than those considered mandatory to prevent thrombosis of a mechanical valve. Only 18% of the population received platelet inhibitors, perhaps because only 23% of the patients had atherosclerotic aneurysms and were therefore deemed likely to benefit from antiplatelet therapy. We were gratified to see a low rate of embolic, thrombotic, and hemorrhagic complications and an absence of early biological valve failure during long-term follow-up.
Long experience has indicated that tissue valves undergo accelerated degeneration in young individuals, but it may be that newer techniques of valve preservation make a biological prosthesis a reasonable option beginning in early middle age. The greater ease of operation compared with valve-sparing procedures, the absence of early valve failure even when preoperative aortic insufficiency has been moderate or severe, and the lack of worry about early degeneration when a connective tissue disorder is present make biological valved graft replacement appealing.
The importance of clot or atheroma observed intraoperatively underlines the importance of embolization in determining both short- and long-term adverse outcomes after aortic root replacement regardless of method. One of the results we anticipated was that axillary cannulation would emerge as a factor reducing the risk of embolization (and therefore of adverse outcome) in these patients, many of whom have a high risk of stroke because of underlying atherosclerosis. During the last 5 years of the study, axillary cannulation was used predominantly because the axillary artery is rarely—in contrast with the ascending aorta or femoral artery—affected by severe atherosclerosis. Although the low rate of adverse outcome in the relatively small number of patients with different cannulation techniques did not permit the identification of axillary artery cannulation as a significant factor contributing to long-term survival, we did observe that the rate of adverse outcome during the last 5 years of the series, when axillary artery cannulation was the technique of choice, decreased to 5.1%. In addition to its perceived advantage in preventing embolization, the axillary artery also provides an excellent route for SCP, which may be required in high-risk cases for cerebral protection. Axillary artery cannulation also diminishes the risk of reentry into a previously operated chest by allowing rapid initiation of cardiopulmonary bypass.
Another potentially important but somewhat unexpected finding of this study is that the long-term outcome of female patients who survive root replacement with a biological valved conduit is different—and worse—than the outlook for male patients, if compared with an age-matched population. As noted in Table 4, Zehr and colleagues8 found female gender to be a univariate predictor of late death in a significantly younger population with the same male:female (25%) ratio. Male patients who recover satisfactorily after reconstruction of the aortic root with a biological valved conduit enjoy long-term outcome equivalent to that of a normal age-matched population, but women who survive the biological Bentall procedure are twice as likely to die during follow-up than their age-matched normal peers. This finding is in accord with similar observations after combined valve and coronary artery bypass surgery, after which morbidity and mortality are less favorable for women than for men.9–11 The difference in the prognosis for men and women after aortic root operation may represent a difference in the pathophysiology leading to surgery in men and women: Only 31% of the male patients had an atherosclerotic aneurysm (n = 35; 17%) or dissection (n = 27; 13%), in contrast with 60% of female patients with atherosclerotic aneurysm (n = 28; 38%) or dissection (n = 16; 22%).
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Although degenerative disease can affect the entire vascular system (as in Marfan syndrome), localized degenerative aortic aneurysm disease (eg, bicuspid valve disease) may be considered cured once the aortic root has been resected and is therefore unlikely to affect long-term survival. The relatively high mean age and the low percentage of Marfan disease may reflect an unusually high proportion of localized degenerative disease in the men in this series. In contrast, an atherosclerotic root aneurysm, or a dissection—which accounted for a much higher proportion of the cases in women—may reflect more severe and widespread disease. In the majority of the female patients, although resection of the root aneurysm eliminated the risk of localized rupture or dissection, a propensity for dissection or widespread atherosclerotic disease likely continued to be a threat in other segments of the vascular system. This theory to explain our results is supported by the finding that the presence of clot and atheroma in the aortic root was the most significant predictor of late death in female patients. The fact that an open distal anastomosis enhanced long-term outcome is consistent with the known risks of crossclamping the aorta in the presence of atherosclerosis or dissection. Similarly, that the use of ß-adrenergic blocking agents improved long-term survival in women makes sense if many of them had ongoing serious cardiovascular pathologic conditions. It is also likely that women are referred later for aneurysm surgery, because the major indication for elective operation is the extent of aortic dilatation, which is usually measured in absolute terms rather than being indexed to the size of the patient. It seems plausible that a 6-cm aorta reflects more advanced disease in a petite woman than in an average (much larger) man.
In men, COPD and any concomitant procedures independently predicted late death after the biological Bentall procedure. Nevertheless, longevity for male survivors did not differ from the expected mortality rate in an elderly age-matched control population.14,15
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Conclusions |
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References |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionConclusionsReferences |
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