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Stentless or stented aortic valve implants in elderly patients?

Stentless or stented aortic valve implants in elderly patients? Abstract Objective: To assess differences in indication and mid-term results between stentless and stented procedures in elderly patients, we followed aortic valve patients over a period of 5 years. Methods: In a consecutive series of 154 elderly aortic patients in regular sinus rhythm from 1992 to 1997, we inserted 103 stentless (Toronto SPVTM, St Jude Medical Inc., St Paul, Minneapolis, MN) and 51 stented (Carpentier–Edwards supra annular porcine, Baxter Inc., Irvine, CA) bioprostheses in the aortic position. Results: All 154 patients seemed preoperatively eligible for a stentless procedure. Mean age was 74.8 years (range 67–86 years) with a majority of female patients. The surgeon’s (in)experience, major dilatation or calcifications of the ascending aorta and aberrant coronary anatomy were the most common reasons for drawback from the stentless procedure (51/154 patients). Aortic clamp time was significantly higher in the stentless vs. stented group (70 vs. 57 min, P<0.0001). The large average 25.3 mm size of the stentless prostheses (vs. 23.7 mm stented) stands in full contrast with the low mean body surface area of 1.68 m2 (vs. 1.70 m2) of the patients. We encountered. respectively. 5 and 2 hospital-deaths (P=n.s.). The follow-up period ranged from 6 to 66 months and was 97% complete, yielding, respectively, 302 and 139 patient-years. Survival (Kaplan–Meier method) was statistically higher in favor of the stentless procedures (log rank: P=0.03). All survivors progressed markedly to a mean postoperative NYHA class 1.3 respectively, 1.4 (vs. preop. 3.3 and 3.2). Echocardiographic transvalvular gradients compared favorable for the stentless group in the small under 25 mm valves (P=0.02 for 23 mm sized valves between groups) with improved left ventricular function and a significant decrease of left ventricular end diastolic diameter (LVEDD 48.0 vs. 56.5 mm) at 1 year follow-up. Cusp calcifications on control echocardiography were detected earlier (beyond 3 years) in the stented group, without signs of early significant regurgitation or dysfunction in both groups, except for one patient necessitating re-operation. Conclusion: Although the implantation technique is much more demanding for stentless procedures, reflected by a longer aortic clamp-time, and remains impossible in some cases, elderly, small sized patients take full benefit of their large, non-obstructive prostheses. Toronto SPVTM stentless prostheses, Stented, Technicality, Survival Introduction Our indications for bioprosthesis in the aortic position are: age above 70 or less than approx. 10 years life-expectancy, contraindications for lifelong anticoagulation, severe gastro-intestinal antecedents and the patient’s own request. Smaller stented porcine prosthesis (<23 mm) often present in unacceptably high gradients, increasing over time, particularly in the elderly and therefore often smaller patients [1]. The Toronto SPVTM valve is a non-stented porcine xenograft developed by David and co-workers in Toronto and manufactured by St Jude Medical (St. Paul, Minneapolis, MN), bearing in mind that the native aortic wall is the best stent for any prosthesis. The implantation technique is quite similar to the freehand homograft originally described by Ross [2], and thus technically more elaborated than any standard stented aortic valve procedure. To prevent the occurrence of paravalvular leakage by resorption of the muscle bar, the outer surface of the porcine aorta is covered with Dacron tissue, which might be responsible for a transient graft-to-host reaction over a period of several months. Taking care to avoid aortic valve incompetence during diastole, David [3] advocates insertion of stentless valves, one or two sizes larger than the aortic annulus, according to the native aortic sinotubular junction, which is often dilated in longstanding aortic disease, described as the ‘oversizing’ technique. This report evaluates 103 Toronto SPVTM stentless aortic heterografts in a series of 154 consecutive elderly patients. During the same period, the remaining 51 patients had Carpentier–Edwards supra annular porcine prostheses (Baxter Inc., Irvine, CA) implanted in the aortic position. In order to assess differences in indication and mid-term results between stentless and stented procedures in elderly patients, we compared both series retrospectively over a period of 5.5 years. Materials and methods From July 1992 to December 1997, 103 Toronto SPVTM aortic valves were implanted, out of 154 consecutive potential candidates for stentless procedure. The other 51 patients underwent classic stented porcine Carpentier–Edwards insertion. Their mean age was around 75 years (range 67–86 years), while the study comprises a majority of female patients. As expected, those most elderly patients were small with a mean body surface area below 1.70 m2. Only few patients (all isolated aortic) were preoperatively in NYHA functional class II, the average NYHA class score was 3.3 and 3.2. Calcified stenosis was the most frequently encountered etiology with preoperative mean transvalvular gradients ranging from 41 to 136 mmHg. Additional coronary artery disease was frequently present, with an approximately equal 10% incidence of concomitant vascular pathology (carotid artery stenosis, renal artery stenosis, peripheral artery disease) (Table 1 ). Table 1 Open in new tabDownload slide Preoperative data Table 1 Open in new tabDownload slide Preoperative data Operative technique Standard cardiopulmonary bypass was used in all cases. Myocardial protection was accomplished with mild (32°C) systemic hypothermia, topical cooling and anterograde or retrograde crystalloid cardioplegia, the latter in all cases of significant aortic regurgitation. In the absence of dilatation of the ascending aorta, the sizing of the sino-tubular junction at the top of the aortic conus corresponds closely to the implanted stentless valve size in our experience [3],[7]. The inflow part of the aortic valve is inserted in the supra-annular position at the nadir of the sinuses by simple interrupted sutures. This can be exaggerated at the non-coronary sinus level, so that the valve creeps up the ascending aortic wall, without obstructing the valve opening, given the use of the right porcine sinus containing the muscle bar at the human non-coronary site. In contrast, at the commisural level, the ventricular side remain infra-annular, thus creating a single plain of insertion at the inflow side. After correct fixation of the three commisures, the outflow part is secured by a smooth running suture [4], carefully avoiding any obstruction or damage to the coronary ostia. Echocardiographic data All valve replacements were evaluated by postoperative transesophagal or transthoracic echocardiography. Mean and peak transvalvular gradients were calculated by using two-dimensionally guided continuous and pulsed Doppler. Transvalvular pressure P was calculated using the simplified Bernoulli equation: P=4v2 as advocated by Waggoner [5]. Definitions The definition of complications was in accordance with published guidelines for reporting valve-related morbidity and mortality [6]. Statistical analysis was performed by SPSS 7.5 software (Chicago, IL). Discrete variables were analyzed using χ2 or Fisher exact tests. Unpaired Student’s t-test was used for continuous variables with Gaussian distribution. For continuous variables with non-Gaussian distribution, a Mann–Whitney test was used. Survival curves were generated using Kaplan–Meier analysis (log rank). Significance was assumed for P-values less than 0.05. Follow up Seventy-nine percent (124) of our patients were followed at our institution. Seven weeks, 6 months and every following year after discharge, patients were interviewed, before clinical examination, by staff-members on general health, medication and incidences of thrombo-embolism, hemorrhage or complications. The remainder (31) were followed by their referring cardiologist and/or physician, and data were acquired by mail, fax or phone. During follow-up, echocardiographic control in house or by outside cardiologists was further obtained after 6 months and every year (78% complete for 124 patients). Procedures Operative data are shown in Table 2 . The hundred and three patients who underwent stentless valve replacement, include one standard re-operation and one emergency re-operation for blocked St Jude bileaflet mechanical valve. Concomitant coronary artery grafting (CABG) was frequently performed in 48% and 49% of patients (mean 2.3 and 2.2 anastomoses). Mean aortic cross-clamp time was 76 min (range 45–114) for all stentless procedures, and 81 min in addition of CABG (range 58–128). It decreased to 56 min for isolated valve replacement after the inevitable learning curve for the first 20 procedures. It increased again after the start of the minimally invasive valve technique to an average of 75 min. This gives a highly significant difference in aortic clamp time between the isolated stentless and stented procedures (76 vs. 67 min. P<0.0001). For several reasons, 51 patients underwent stented valve replacement during the same period. In nearly half the cases (25 patients), particularly during the early learning phase, it was the (often less experienced) surgeon’s decision to switch to a stented implantation, whereas heavily calcified ascending aorta and unfavorable coronary artery anatomy with both ostia originating at proximity of the commissures accounted for approximately 20% of the dropouts each (respectively, 12 vs. 10 patients), while in the remaining cases the exact indication for stented implantation remains unknown (4). Table 2 Open in new tabDownload slide Operative data Table 2 Open in new tabDownload slide Operative data Results Thirty-day mortality There were five and two operative deaths in each series. Three stentless patients necessitating intra-aortic balloon pumping for pre-operative low cardiac output syndrome died because of their poor condition. One patient expired of respiratory problems, another of arrhythmia induced by a low potassium level. The two stented patients died of low cardiac output syndrome and myocardial infarction. All those events were believed to be unrelated to the valve condition and post-mortem examination (5 out of 7) excluded valve dysfunction. Morbidity Nine (vs. 2) patients necessitated intra-aortic counterpulsation for postoperative low cardiac output, and the survivors were successfully weaned in a stable condition between 2 and 9 days following the initial operation. Two patients presented cerebro-vascular accidents (CVA) immediately post-operatively, one of them believed to be a massive air embolus. One transient ischemic attack (TIA) occurred 7 days after uneventful aortic valve operation, with temporary right hemiparesis and complete neurologic recuperation, in a patient with severe vascular antecedents. All those incidents occurred in the stentless group. Other complications included atrial fibrillation (respectively, 9 and 3 patients), pneumothorax (2 and 0), temporary atrio-ventricular bloc (1 and 1), bronchopneumonia (3 and 1), postpericardiotomy syndrome (2 and 1), revision for bleeding (2 and 1) and acute tubular necrosis (1 each). The mean hospitalisation time was 13 days (vs. 12 days, P=n.s.) for isolated stentless valve replacement, and 14 days (14) days for the combined procedures. Overall morbidity was calculated 32 and 20%, respectively, for the stentless and stented group. Follow-up Follow-up was 97 and 100% complete and ranged from 6 to 66 (average 34–32) months, yielding, respectively, 302 and 139 patient-years. We maintained all our patients on an oral Coumadin anticoagulation regime for 3 months (INR 2.5 and 3.5), except in 3 stentless patients where the anticoagulation was stopped after a few weeks for, respectively, persistent gastric bleeding (twice) and severe non-cardiac bleeding problems. There were, respectively, 6 and 12 late deaths, 4 were non-cardiac and 2 cardiac in the stentless group, whereas in the stented group 7 were non-cardiac and 5 cardiac, including the only valve-related due to a recurrent valve endocarditis 31 months after successful valve replacement for endocarditis. Survival (Kaplan–Meier method) depicted in Fig. 1 showed a statistically significant difference (log rank P=0.03) in favor of the stentless procedures. Mean follow-up time was 61.63 months for the stentless (95% CL=57.2–66.05 months) vs. 52.29 months (95% CL=44.05–60.51). All surviving stentless patients progressed to NYHA functional class I or II on most recent follow-up (average 1.3). One stented patient remained in class III, the remaining advanced to I or II (average 1.4: P=n.s.). No episodes of endocarditis nor paravalvular leakage were diagnosed on clinical and echocardiographic examination of all surviving patients. The freedom of thrombo-embolism at 5 years was, respectively, 83 and 94% (Fig. 2 ), with a statistically significant difference (log rank: P=0.02). in favor of the stented group. Two bleeding episodes occurred, one in each group, after 23 and 40 months. One stented valve was removed after 4 years for extensive calcification, accounting for the sole re-operation. Fig. 1 Open in new tabDownload slide Survival curve (Kaplan–Meier method). Bottom: number of patients at risk. C.E., Carpentier–Edwards. Fig. 1 Open in new tabDownload slide Survival curve (Kaplan–Meier method). Bottom: number of patients at risk. C.E., Carpentier–Edwards. Fig. 2 Open in new tabDownload slide Freedom from thrombo-embolism. Bottom: number of patients at risk. C.E., Carpentier–Edwards. Fig. 2 Open in new tabDownload slide Freedom from thrombo-embolism. Bottom: number of patients at risk. C.E., Carpentier–Edwards. Echocardiography Echocardiographic data are summarized in Table 3 . The mean transvalvular pressure gradient on discharge over the most common used 23 mm and 25 mm stentless valves were measured 9.4 mmHg and 7.7 mmHg (peak 9–25 and 8–24 mmHg), whereas the small 21 mm aortic valves presented acceptable 12.5 mmHg mean gradients (peak 11–24 mmHg) at discharge. The transvalvular gradients of the stented bioprostheses implanted over the same period were comparable for the larger sizes and definitely more elevated in the smaller sizes on follow-up (P=0.02 for the 23 mm and P=n.s. for the 25 mm size at 1 year). Due to lack of numbers in the other groups, only the 23 and 25 mm stented and stentless groups were statistically comparable. One 29 mm stentless valve presented mild regurgitation, while 8 large valves (size over 25 mm) trivial echocardiographic regurgitation, all stented valves were judged competent. Leaflet calcifications and/or loss of mobility were rarely observed in the stentless group (overall 4 patients), whereas more than half of the controlled stented bioprostheses (5 patients) presented marked calcifications after 4 years. Most stentless valves retained their flexibility even years after implantation. Left ventricular end diastolic diameters (LVEDD) decreased over the years, more pronounced in the smaller valve sizes of the stentless group conform Table 4 . Table 3 Open in new tabDownload slide Transvalvular mean echocardiographic gradients Table 3 Open in new tabDownload slide Transvalvular mean echocardiographic gradients Table 4 Open in new tabDownload slide Left ventricular end diastolic diameter (mm) Table 4 Open in new tabDownload slide Left ventricular end diastolic diameter (mm) Discussion and conclusions We reviewed retrospectively the results of our elderly aortic bioprosthesis patients eligible for stentless procedures. The mid-term clinical results (5.5 years) of the Toronto SPVTM stentless valve were compared with the data of other biological valves which we routinely use in our institution. One-third of the potential candidates underwent stented implantation, half of them for obvious anatomical reasons, the others because of an anticipated time-loss by the surgeon in case of a more complex procedure. The ‘oversizing’ technique enforced us to implant larger (stentless) valves, in rather small elderly patients which possibly contributes to the good results we obtained in this high-risk group [2],[7]. The higher technicality of stentless insertion is reflected by a significant longer aortic clamp-time (for isolated aortic replacement 70 vs. 58 min: P<0.0001). Nevertheless, in-hospital mortality was equal in both series. In contrast, survival was significantly better in the stentless group compared with the stented (log rank: P=0.02), whereas functional class of the survivors was reported equivocal in both series on most recent follow-up. Transvalvular echocardiographic gradients in the smaller stentless sizes appear to compare favorably with the data of the standard Carpentier–Edwards supra-annular stented prosthesis, whereas those gradients can be unacceptable high in some prosthesis and increase in time [8]. Nevertheless, we did not measured a consistent decrease in transvalvular stentless gradients over time as reported by some authors [9]. Although consistent, the reduction of left ventricular end diastolic diameter was not that spectacular compared to the regression of ventricular mass in other series, except for the smaller sizes less than 25 mm [2],[10]. Since the majority of our patients presented calcified aortic stenosis with hypertrophic, through often good contractile ventricles, the reduction of the ventricular diameter occurred rather gradually. Repeated echocardiographic control ruled out any major valvular regurgitation or dysfunction to date in the stentless group. The stentless valves seem to remain mobile and flexible on echocardiography, many years after implantation, which definitively reduces the stresses on the leaflets [11],[12]. Although there is actually no proof of prolonged durability in the stentless group, the persistent mobility of the valvular apparatus at follow-up seems promising for the future, and hopefully delays calcification [13],[14]. For that matter, our only explantation for premature calcification was performed in the stented group. Notwithstanding the fact that we cannot explain why survival was significant better in the stentless group, this could create a large group of re-operations for primary valve failure at an advanced age [15]. Rather unexpected, the rate of occurrence of thromboembolism was high in our cohort of (stentless) patients off anticoagulation, perhaps due to an advanced age and high survival rate, associated with important vascular or coronary pathology in the majority of patients. In conclusion, we actually prefer stentless implantation, in older, active patients in sinus rhythm, especially in the smaller sized, often female, patients. Further close follow-up, especially in regard to primary valve failure and durability remains mandatory. References [1] Ramirez M.H. , Wong M. , Sadler N. , Sah P.M. . Doppler evaluation of bioprosthetic and mechanical aortic valves: data from four models in 107 stable, ambulatory patients , Am Heart J , 1988 , vol. 115 (pg. 418 - 425 ) Google Scholar Crossref Search ADS PubMed WorldCat [2] Ross D.N. . Homograft replacement of the aortic valve , Lancet , 1962 , vol. 2 pg. 487 Google Scholar Crossref Search ADS PubMed WorldCat [3] David TE. Implantation technique for the Toronto SPV bioprosthesis. In: Piwnica A, Westaby S (eds). Surgery for acquired aortic valve disease. Oxford: Isis Medical Media, 1997;102–109. [4] Vesely I. , Boughner D. , Song T. . Tissue buckling as a mechanism of bioprosthetic valve failure , Ann Thorac Surg , 1988 , vol. 46 (pg. 302 - 308 ) Google Scholar Crossref Search ADS PubMed WorldCat [5] Waggoner A.D. , Perez J.E. . Principles and physics of Doppler , Cardiol Clin , 1990 , vol. 8 (pg. 173 - 190 ) Google Scholar PubMed WorldCat [6] Edmunds L.H. , Clark L.H. , Cohn L.A. , Grunkemeier G.L. , Miller D.C. , Weisel R.D. . Guidelines for reporting morbidity and mortality after cardiac valvular operations , Ann Thorac Surg , 1996 , vol. 62 (pg. 932 - 935 ) Google Scholar Crossref Search ADS PubMed WorldCat [7] Van Nooten G.J. , Caes F. , François K. , Van Belleghem Y. . Early experience with the Toronto SPV stentless aortic valve , Cardiovasc J South Africa , 1996 , vol. 86 2 (pg. 69 - 73 ) WorldCat [8] Reisner S.A. , Meltzer R.S. . Normal values of prosthetic valve Doppler echocardiographic parameters: a review , J Am Soc Echocardiol , 1988 , vol. 1 (pg. 201 - 210 ) Google Scholar Crossref Search ADS WorldCat [9] David T.E. , Feindel C.M. , Scully H. , Bos J. , Rakowski H. . Aortic valve replacement with stentless porcine aortic valve; a ten-years experience , J Heart Valve Dis , 1998 , vol. 7 (pg. 250 - 254 ) Google Scholar PubMed WorldCat [10] Del Rizzo, Goldman BS, Christakis GT, David TE. Hemodynamic benefits of the Toronto stentless valve. J Thorac Cardiovasc Surg 1996;112:1431–1438. [11] Cristie G.W. , Barrat-Boyes B.G. . Stress reduction in bioprosthetic heart valve leaflets by the use of a flexible stent , J Cardiac Surg , 1992 , vol. 6 (pg. 476 - 481 ) Google Scholar Crossref Search ADS WorldCat [12] Sabbah H.N. , Hamid M.S. , Stein P.D. . Mechanical stresses on closed cusp of porcine bioprosthetic valves: correlation with sites of calcification , Ann Thorac Surg , 1986 , vol. 42 (pg. 92 - 96 ) Google Scholar Crossref Search ADS WorldCat [13] Jamiesom W.R. , Rosado L.J. , Munro A.L. , et al. Carpentier–Edwards standard porcine bioprosthesis: primary valve failure by age group , Ann Thorac Surg , 1988 , vol. 46 (pg. 155 - 156 ) Google Scholar Crossref Search ADS PubMed WorldCat [14] Milano A. , Bortolotti U. , Talenti E. , et al. Calcification as the main cause of porcine bioprosthetic dysfunction , Am J Cardiol , 1984 , vol. 53 (pg. 1006 - 1070 ) Google Scholar Crossref Search ADS WorldCat [15] Gross C.H. , Harringer W. , Mair R. , et al. Aortic valve replacement: is the stentless xenograft an alternative to the homograft? Early results of a randomized study , Ann Thorac Surg , 1995 , vol. 60 (pg. 418 - 421 ) Google Scholar Crossref Search ADS WorldCat Author notes Presented at the 12th Annual Meeting of the European Association for Cardio-thoracic Surgery, Brussels, Belgium, September 20–23, 1998. © 1999 Elsevier Science B.V. Elsevier Science B.V. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png European Journal of Cardio-Thoracic Surgery Oxford University Press

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Oxford University Press
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© 1999 Elsevier Science B.V.
Subject
Articles
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1010-7940
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DOI
10.1016/S1010-7940(98)00288-7
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Abstract

Abstract Objective: To assess differences in indication and mid-term results between stentless and stented procedures in elderly patients, we followed aortic valve patients over a period of 5 years. Methods: In a consecutive series of 154 elderly aortic patients in regular sinus rhythm from 1992 to 1997, we inserted 103 stentless (Toronto SPVTM, St Jude Medical Inc., St Paul, Minneapolis, MN) and 51 stented (Carpentier–Edwards supra annular porcine, Baxter Inc., Irvine, CA) bioprostheses in the aortic position. Results: All 154 patients seemed preoperatively eligible for a stentless procedure. Mean age was 74.8 years (range 67–86 years) with a majority of female patients. The surgeon’s (in)experience, major dilatation or calcifications of the ascending aorta and aberrant coronary anatomy were the most common reasons for drawback from the stentless procedure (51/154 patients). Aortic clamp time was significantly higher in the stentless vs. stented group (70 vs. 57 min, P<0.0001). The large average 25.3 mm size of the stentless prostheses (vs. 23.7 mm stented) stands in full contrast with the low mean body surface area of 1.68 m2 (vs. 1.70 m2) of the patients. We encountered. respectively. 5 and 2 hospital-deaths (P=n.s.). The follow-up period ranged from 6 to 66 months and was 97% complete, yielding, respectively, 302 and 139 patient-years. Survival (Kaplan–Meier method) was statistically higher in favor of the stentless procedures (log rank: P=0.03). All survivors progressed markedly to a mean postoperative NYHA class 1.3 respectively, 1.4 (vs. preop. 3.3 and 3.2). Echocardiographic transvalvular gradients compared favorable for the stentless group in the small under 25 mm valves (P=0.02 for 23 mm sized valves between groups) with improved left ventricular function and a significant decrease of left ventricular end diastolic diameter (LVEDD 48.0 vs. 56.5 mm) at 1 year follow-up. Cusp calcifications on control echocardiography were detected earlier (beyond 3 years) in the stented group, without signs of early significant regurgitation or dysfunction in both groups, except for one patient necessitating re-operation. Conclusion: Although the implantation technique is much more demanding for stentless procedures, reflected by a longer aortic clamp-time, and remains impossible in some cases, elderly, small sized patients take full benefit of their large, non-obstructive prostheses. Toronto SPVTM stentless prostheses, Stented, Technicality, Survival Introduction Our indications for bioprosthesis in the aortic position are: age above 70 or less than approx. 10 years life-expectancy, contraindications for lifelong anticoagulation, severe gastro-intestinal antecedents and the patient’s own request. Smaller stented porcine prosthesis (<23 mm) often present in unacceptably high gradients, increasing over time, particularly in the elderly and therefore often smaller patients [1]. The Toronto SPVTM valve is a non-stented porcine xenograft developed by David and co-workers in Toronto and manufactured by St Jude Medical (St. Paul, Minneapolis, MN), bearing in mind that the native aortic wall is the best stent for any prosthesis. The implantation technique is quite similar to the freehand homograft originally described by Ross [2], and thus technically more elaborated than any standard stented aortic valve procedure. To prevent the occurrence of paravalvular leakage by resorption of the muscle bar, the outer surface of the porcine aorta is covered with Dacron tissue, which might be responsible for a transient graft-to-host reaction over a period of several months. Taking care to avoid aortic valve incompetence during diastole, David [3] advocates insertion of stentless valves, one or two sizes larger than the aortic annulus, according to the native aortic sinotubular junction, which is often dilated in longstanding aortic disease, described as the ‘oversizing’ technique. This report evaluates 103 Toronto SPVTM stentless aortic heterografts in a series of 154 consecutive elderly patients. During the same period, the remaining 51 patients had Carpentier–Edwards supra annular porcine prostheses (Baxter Inc., Irvine, CA) implanted in the aortic position. In order to assess differences in indication and mid-term results between stentless and stented procedures in elderly patients, we compared both series retrospectively over a period of 5.5 years. Materials and methods From July 1992 to December 1997, 103 Toronto SPVTM aortic valves were implanted, out of 154 consecutive potential candidates for stentless procedure. The other 51 patients underwent classic stented porcine Carpentier–Edwards insertion. Their mean age was around 75 years (range 67–86 years), while the study comprises a majority of female patients. As expected, those most elderly patients were small with a mean body surface area below 1.70 m2. Only few patients (all isolated aortic) were preoperatively in NYHA functional class II, the average NYHA class score was 3.3 and 3.2. Calcified stenosis was the most frequently encountered etiology with preoperative mean transvalvular gradients ranging from 41 to 136 mmHg. Additional coronary artery disease was frequently present, with an approximately equal 10% incidence of concomitant vascular pathology (carotid artery stenosis, renal artery stenosis, peripheral artery disease) (Table 1 ). Table 1 Open in new tabDownload slide Preoperative data Table 1 Open in new tabDownload slide Preoperative data Operative technique Standard cardiopulmonary bypass was used in all cases. Myocardial protection was accomplished with mild (32°C) systemic hypothermia, topical cooling and anterograde or retrograde crystalloid cardioplegia, the latter in all cases of significant aortic regurgitation. In the absence of dilatation of the ascending aorta, the sizing of the sino-tubular junction at the top of the aortic conus corresponds closely to the implanted stentless valve size in our experience [3],[7]. The inflow part of the aortic valve is inserted in the supra-annular position at the nadir of the sinuses by simple interrupted sutures. This can be exaggerated at the non-coronary sinus level, so that the valve creeps up the ascending aortic wall, without obstructing the valve opening, given the use of the right porcine sinus containing the muscle bar at the human non-coronary site. In contrast, at the commisural level, the ventricular side remain infra-annular, thus creating a single plain of insertion at the inflow side. After correct fixation of the three commisures, the outflow part is secured by a smooth running suture [4], carefully avoiding any obstruction or damage to the coronary ostia. Echocardiographic data All valve replacements were evaluated by postoperative transesophagal or transthoracic echocardiography. Mean and peak transvalvular gradients were calculated by using two-dimensionally guided continuous and pulsed Doppler. Transvalvular pressure P was calculated using the simplified Bernoulli equation: P=4v2 as advocated by Waggoner [5]. Definitions The definition of complications was in accordance with published guidelines for reporting valve-related morbidity and mortality [6]. Statistical analysis was performed by SPSS 7.5 software (Chicago, IL). Discrete variables were analyzed using χ2 or Fisher exact tests. Unpaired Student’s t-test was used for continuous variables with Gaussian distribution. For continuous variables with non-Gaussian distribution, a Mann–Whitney test was used. Survival curves were generated using Kaplan–Meier analysis (log rank). Significance was assumed for P-values less than 0.05. Follow up Seventy-nine percent (124) of our patients were followed at our institution. Seven weeks, 6 months and every following year after discharge, patients were interviewed, before clinical examination, by staff-members on general health, medication and incidences of thrombo-embolism, hemorrhage or complications. The remainder (31) were followed by their referring cardiologist and/or physician, and data were acquired by mail, fax or phone. During follow-up, echocardiographic control in house or by outside cardiologists was further obtained after 6 months and every year (78% complete for 124 patients). Procedures Operative data are shown in Table 2 . The hundred and three patients who underwent stentless valve replacement, include one standard re-operation and one emergency re-operation for blocked St Jude bileaflet mechanical valve. Concomitant coronary artery grafting (CABG) was frequently performed in 48% and 49% of patients (mean 2.3 and 2.2 anastomoses). Mean aortic cross-clamp time was 76 min (range 45–114) for all stentless procedures, and 81 min in addition of CABG (range 58–128). It decreased to 56 min for isolated valve replacement after the inevitable learning curve for the first 20 procedures. It increased again after the start of the minimally invasive valve technique to an average of 75 min. This gives a highly significant difference in aortic clamp time between the isolated stentless and stented procedures (76 vs. 67 min. P<0.0001). For several reasons, 51 patients underwent stented valve replacement during the same period. In nearly half the cases (25 patients), particularly during the early learning phase, it was the (often less experienced) surgeon’s decision to switch to a stented implantation, whereas heavily calcified ascending aorta and unfavorable coronary artery anatomy with both ostia originating at proximity of the commissures accounted for approximately 20% of the dropouts each (respectively, 12 vs. 10 patients), while in the remaining cases the exact indication for stented implantation remains unknown (4). Table 2 Open in new tabDownload slide Operative data Table 2 Open in new tabDownload slide Operative data Results Thirty-day mortality There were five and two operative deaths in each series. Three stentless patients necessitating intra-aortic balloon pumping for pre-operative low cardiac output syndrome died because of their poor condition. One patient expired of respiratory problems, another of arrhythmia induced by a low potassium level. The two stented patients died of low cardiac output syndrome and myocardial infarction. All those events were believed to be unrelated to the valve condition and post-mortem examination (5 out of 7) excluded valve dysfunction. Morbidity Nine (vs. 2) patients necessitated intra-aortic counterpulsation for postoperative low cardiac output, and the survivors were successfully weaned in a stable condition between 2 and 9 days following the initial operation. Two patients presented cerebro-vascular accidents (CVA) immediately post-operatively, one of them believed to be a massive air embolus. One transient ischemic attack (TIA) occurred 7 days after uneventful aortic valve operation, with temporary right hemiparesis and complete neurologic recuperation, in a patient with severe vascular antecedents. All those incidents occurred in the stentless group. Other complications included atrial fibrillation (respectively, 9 and 3 patients), pneumothorax (2 and 0), temporary atrio-ventricular bloc (1 and 1), bronchopneumonia (3 and 1), postpericardiotomy syndrome (2 and 1), revision for bleeding (2 and 1) and acute tubular necrosis (1 each). The mean hospitalisation time was 13 days (vs. 12 days, P=n.s.) for isolated stentless valve replacement, and 14 days (14) days for the combined procedures. Overall morbidity was calculated 32 and 20%, respectively, for the stentless and stented group. Follow-up Follow-up was 97 and 100% complete and ranged from 6 to 66 (average 34–32) months, yielding, respectively, 302 and 139 patient-years. We maintained all our patients on an oral Coumadin anticoagulation regime for 3 months (INR 2.5 and 3.5), except in 3 stentless patients where the anticoagulation was stopped after a few weeks for, respectively, persistent gastric bleeding (twice) and severe non-cardiac bleeding problems. There were, respectively, 6 and 12 late deaths, 4 were non-cardiac and 2 cardiac in the stentless group, whereas in the stented group 7 were non-cardiac and 5 cardiac, including the only valve-related due to a recurrent valve endocarditis 31 months after successful valve replacement for endocarditis. Survival (Kaplan–Meier method) depicted in Fig. 1 showed a statistically significant difference (log rank P=0.03) in favor of the stentless procedures. Mean follow-up time was 61.63 months for the stentless (95% CL=57.2–66.05 months) vs. 52.29 months (95% CL=44.05–60.51). All surviving stentless patients progressed to NYHA functional class I or II on most recent follow-up (average 1.3). One stented patient remained in class III, the remaining advanced to I or II (average 1.4: P=n.s.). No episodes of endocarditis nor paravalvular leakage were diagnosed on clinical and echocardiographic examination of all surviving patients. The freedom of thrombo-embolism at 5 years was, respectively, 83 and 94% (Fig. 2 ), with a statistically significant difference (log rank: P=0.02). in favor of the stented group. Two bleeding episodes occurred, one in each group, after 23 and 40 months. One stented valve was removed after 4 years for extensive calcification, accounting for the sole re-operation. Fig. 1 Open in new tabDownload slide Survival curve (Kaplan–Meier method). Bottom: number of patients at risk. C.E., Carpentier–Edwards. Fig. 1 Open in new tabDownload slide Survival curve (Kaplan–Meier method). Bottom: number of patients at risk. C.E., Carpentier–Edwards. Fig. 2 Open in new tabDownload slide Freedom from thrombo-embolism. Bottom: number of patients at risk. C.E., Carpentier–Edwards. Fig. 2 Open in new tabDownload slide Freedom from thrombo-embolism. Bottom: number of patients at risk. C.E., Carpentier–Edwards. Echocardiography Echocardiographic data are summarized in Table 3 . The mean transvalvular pressure gradient on discharge over the most common used 23 mm and 25 mm stentless valves were measured 9.4 mmHg and 7.7 mmHg (peak 9–25 and 8–24 mmHg), whereas the small 21 mm aortic valves presented acceptable 12.5 mmHg mean gradients (peak 11–24 mmHg) at discharge. The transvalvular gradients of the stented bioprostheses implanted over the same period were comparable for the larger sizes and definitely more elevated in the smaller sizes on follow-up (P=0.02 for the 23 mm and P=n.s. for the 25 mm size at 1 year). Due to lack of numbers in the other groups, only the 23 and 25 mm stented and stentless groups were statistically comparable. One 29 mm stentless valve presented mild regurgitation, while 8 large valves (size over 25 mm) trivial echocardiographic regurgitation, all stented valves were judged competent. Leaflet calcifications and/or loss of mobility were rarely observed in the stentless group (overall 4 patients), whereas more than half of the controlled stented bioprostheses (5 patients) presented marked calcifications after 4 years. Most stentless valves retained their flexibility even years after implantation. Left ventricular end diastolic diameters (LVEDD) decreased over the years, more pronounced in the smaller valve sizes of the stentless group conform Table 4 . Table 3 Open in new tabDownload slide Transvalvular mean echocardiographic gradients Table 3 Open in new tabDownload slide Transvalvular mean echocardiographic gradients Table 4 Open in new tabDownload slide Left ventricular end diastolic diameter (mm) Table 4 Open in new tabDownload slide Left ventricular end diastolic diameter (mm) Discussion and conclusions We reviewed retrospectively the results of our elderly aortic bioprosthesis patients eligible for stentless procedures. The mid-term clinical results (5.5 years) of the Toronto SPVTM stentless valve were compared with the data of other biological valves which we routinely use in our institution. One-third of the potential candidates underwent stented implantation, half of them for obvious anatomical reasons, the others because of an anticipated time-loss by the surgeon in case of a more complex procedure. The ‘oversizing’ technique enforced us to implant larger (stentless) valves, in rather small elderly patients which possibly contributes to the good results we obtained in this high-risk group [2],[7]. The higher technicality of stentless insertion is reflected by a significant longer aortic clamp-time (for isolated aortic replacement 70 vs. 58 min: P<0.0001). Nevertheless, in-hospital mortality was equal in both series. In contrast, survival was significantly better in the stentless group compared with the stented (log rank: P=0.02), whereas functional class of the survivors was reported equivocal in both series on most recent follow-up. Transvalvular echocardiographic gradients in the smaller stentless sizes appear to compare favorably with the data of the standard Carpentier–Edwards supra-annular stented prosthesis, whereas those gradients can be unacceptable high in some prosthesis and increase in time [8]. Nevertheless, we did not measured a consistent decrease in transvalvular stentless gradients over time as reported by some authors [9]. Although consistent, the reduction of left ventricular end diastolic diameter was not that spectacular compared to the regression of ventricular mass in other series, except for the smaller sizes less than 25 mm [2],[10]. Since the majority of our patients presented calcified aortic stenosis with hypertrophic, through often good contractile ventricles, the reduction of the ventricular diameter occurred rather gradually. Repeated echocardiographic control ruled out any major valvular regurgitation or dysfunction to date in the stentless group. The stentless valves seem to remain mobile and flexible on echocardiography, many years after implantation, which definitively reduces the stresses on the leaflets [11],[12]. Although there is actually no proof of prolonged durability in the stentless group, the persistent mobility of the valvular apparatus at follow-up seems promising for the future, and hopefully delays calcification [13],[14]. For that matter, our only explantation for premature calcification was performed in the stented group. Notwithstanding the fact that we cannot explain why survival was significant better in the stentless group, this could create a large group of re-operations for primary valve failure at an advanced age [15]. Rather unexpected, the rate of occurrence of thromboembolism was high in our cohort of (stentless) patients off anticoagulation, perhaps due to an advanced age and high survival rate, associated with important vascular or coronary pathology in the majority of patients. In conclusion, we actually prefer stentless implantation, in older, active patients in sinus rhythm, especially in the smaller sized, often female, patients. Further close follow-up, especially in regard to primary valve failure and durability remains mandatory. References [1] Ramirez M.H. , Wong M. , Sadler N. , Sah P.M. . Doppler evaluation of bioprosthetic and mechanical aortic valves: data from four models in 107 stable, ambulatory patients , Am Heart J , 1988 , vol. 115 (pg. 418 - 425 ) Google Scholar Crossref Search ADS PubMed WorldCat [2] Ross D.N. . Homograft replacement of the aortic valve , Lancet , 1962 , vol. 2 pg. 487 Google Scholar Crossref Search ADS PubMed WorldCat [3] David TE. Implantation technique for the Toronto SPV bioprosthesis. In: Piwnica A, Westaby S (eds). Surgery for acquired aortic valve disease. Oxford: Isis Medical Media, 1997;102–109. [4] Vesely I. , Boughner D. , Song T. . Tissue buckling as a mechanism of bioprosthetic valve failure , Ann Thorac Surg , 1988 , vol. 46 (pg. 302 - 308 ) Google Scholar Crossref Search ADS PubMed WorldCat [5] Waggoner A.D. , Perez J.E. . Principles and physics of Doppler , Cardiol Clin , 1990 , vol. 8 (pg. 173 - 190 ) Google Scholar PubMed WorldCat [6] Edmunds L.H. , Clark L.H. , Cohn L.A. , Grunkemeier G.L. , Miller D.C. , Weisel R.D. . Guidelines for reporting morbidity and mortality after cardiac valvular operations , Ann Thorac Surg , 1996 , vol. 62 (pg. 932 - 935 ) Google Scholar Crossref Search ADS PubMed WorldCat [7] Van Nooten G.J. , Caes F. , François K. , Van Belleghem Y. . Early experience with the Toronto SPV stentless aortic valve , Cardiovasc J South Africa , 1996 , vol. 86 2 (pg. 69 - 73 ) WorldCat [8] Reisner S.A. , Meltzer R.S. . Normal values of prosthetic valve Doppler echocardiographic parameters: a review , J Am Soc Echocardiol , 1988 , vol. 1 (pg. 201 - 210 ) Google Scholar Crossref Search ADS WorldCat [9] David T.E. , Feindel C.M. , Scully H. , Bos J. , Rakowski H. . Aortic valve replacement with stentless porcine aortic valve; a ten-years experience , J Heart Valve Dis , 1998 , vol. 7 (pg. 250 - 254 ) Google Scholar PubMed WorldCat [10] Del Rizzo, Goldman BS, Christakis GT, David TE. Hemodynamic benefits of the Toronto stentless valve. J Thorac Cardiovasc Surg 1996;112:1431–1438. [11] Cristie G.W. , Barrat-Boyes B.G. . Stress reduction in bioprosthetic heart valve leaflets by the use of a flexible stent , J Cardiac Surg , 1992 , vol. 6 (pg. 476 - 481 ) Google Scholar Crossref Search ADS WorldCat [12] Sabbah H.N. , Hamid M.S. , Stein P.D. . Mechanical stresses on closed cusp of porcine bioprosthetic valves: correlation with sites of calcification , Ann Thorac Surg , 1986 , vol. 42 (pg. 92 - 96 ) Google Scholar Crossref Search ADS WorldCat [13] Jamiesom W.R. , Rosado L.J. , Munro A.L. , et al. Carpentier–Edwards standard porcine bioprosthesis: primary valve failure by age group , Ann Thorac Surg , 1988 , vol. 46 (pg. 155 - 156 ) Google Scholar Crossref Search ADS PubMed WorldCat [14] Milano A. , Bortolotti U. , Talenti E. , et al. Calcification as the main cause of porcine bioprosthetic dysfunction , Am J Cardiol , 1984 , vol. 53 (pg. 1006 - 1070 ) Google Scholar Crossref Search ADS WorldCat [15] Gross C.H. , Harringer W. , Mair R. , et al. Aortic valve replacement: is the stentless xenograft an alternative to the homograft? Early results of a randomized study , Ann Thorac Surg , 1995 , vol. 60 (pg. 418 - 421 ) Google Scholar Crossref Search ADS WorldCat Author notes Presented at the 12th Annual Meeting of the European Association for Cardio-thoracic Surgery, Brussels, Belgium, September 20–23, 1998. © 1999 Elsevier Science B.V. Elsevier Science B.V.

Journal

European Journal of Cardio-Thoracic SurgeryOxford University Press

Published: Jan 1, 1999

Keywords: Toronto SPVTM stentless prostheses Stented Technicality Survival

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