Comparative Rest and Exercise Hemodynamics of 23-mm Stentless Versus 23-mm Stented Aortic Bioprostheses

Comparative Rest and Exercise Hemodynamics of 23-mm Stentless Versus 23-mm Stented Aortic Bioprostheses Roland Fries, MD, Olaf Wendler, MD, Hermann Schieffer, MD, and Hans-Joachim Schäfers, MD, PhD Departments of Cardiology and Angiology, and Thoracic and Cardiovascular Surgery, University Hospitals Homburg, Homburg/ Saar, Germany Background. The hemodynamic superiority of stentless valves at rest has been generally accepted, but there is a lack of studies on exercise hemodynamics. Methods. We assessed aortic valve hemodynamics at rest and during exercise in 10 patients with a 23-mm stentless aortic bioprosthesis (Medtronic Freestyle; Medtronic Europe SA/NV, St. Stevens Woluwe, Belgium), in 10 patients with a 23-mm stented aortic bioprosthesis (Carpentier-Edwards, SAV, model 2650; Baxter Edwards AG, Horw, Switzerland), and in 10 healthy volunteers (control group) by means of Doppler echocardiography. Results. Gradients at rest and gradients on comparable maximum exercise levels were significantly lower in patients with stentless valves compared to those with stented valves (rest: 6 2/11 4 mm Hg [mean/peak] versus 12 3/21 10 mm Hg; exercise: 9 3/18 6 mm Hg [mean/peak] versus 22 8/40 11 mm Hg). Patients with stentless valves revealed, in comparison to healthy young men, significantly higher gradients, but the small gradient difference of 3/7 mm Hg (mean/peak) at rest remained nearly unchanged throughout the exercise protocol (4/8 mm Hg [mean/peak] at 25 W, 4/9 mm Hg at 50 W and 4/9 mm Hg at 75 W). In contrast, the gradient difference between patients with stented and stentless valves increased significantly from one exercise level to the next (6/12 mm Hg [mean/peak] at rest, 8/14 mm Hg at 25 W, 12/17 mm Hg at 50 W, and 15/25 mm Hg at 75 W). Conclusions. A stentless aortic bioprosthesis seems to be an appropriate aortic valve substitute, especially in patients who perform regular physical exercise. (Ann Thorac Surg 2000;69:817 22) 2000 by The Society of Thoracic Surgeons Limited durability has remained a major drawback of stent-mounted porcine bioprostheses, mainly due to primary tissue failure. It has been shown that the stent of a bioprosthesis is a major factor governing stress on the tissue component [1, 2]. Thus, stentless bioprostheses, first used by Binet and associates in the early 1960s [3], represent a potentially more durable alternative to stented xenografts. Lack of availability and a more complex operation technique has restricted the use of stentless valves until now. Recent hemodynamic studies at rest have shown that stentless porcine xenografts in the aortic position are superior to conventional stented bioprostheses [4 7]. However, hemodynamic performance at rest is not truly representative of a patient s daily activities. The exercise hemodynamics of stentless bioprostheses may essentially contribute to the excellent left ventricular remodeling, which has been demonstrated after stentless aortic valve replacement [8 11]. In order to elucidate these issues, we compared the hemodynamic performance of a 23-mm stentless aortic bioprosthesis to a stented 23-mm Accepted for publication Aug 31, 1999. Address reprint requests to Dr Fries, Medical Clinic III, Department of Cardiology and Angiology, University Hospitals Homburg, 66421 Homburg/Saar, Germany; e-mail: fries@med-in.uni-sb.de. counterpart, at rest and during exercise, by means of Doppler echocardiography. Patients and Methods We assessed aortic valve hemodynamics at rest and during exercise in 3 groups of individuals. Group 1 was the control group and consisted of 10 healthy volunteers. We chose young people in order to ensure optimum transaortic flow conditions in the control group. Group 2 consisted of 10 patients who had aortic valve replacement with a stentless aortic bioprosthesis (Medtronic Freestyle; Medtronic Europe SA/NV, St. Stevens Woluwe, Belgium), while group 3 consisted of 10 patients with a stented aortic bioprosthesis (Carpentier-Edwards, SAV, model 2650; Baxter Edwards AG, Horw, Switzerland). Consecutive patients who had received a 23-mm valve at least 3 months before the investigation were included in the study. Written informed consent was obtained from all patients and none refused to participate. The decision to compare the 23-mm Carpentier- Edwards valve to the 23-mm Medtronic Freestyle valve was not taken because of the identical manufacturer s labeled size, which may differ significantly from measured internal and external diameters [12]. The selection 2000 by The Society of Thoracic Surgeons 0003-4975/00/$20.00 Published by Elsevier Science Inc PII S0003-4975(99)01409-5

818 FRIES ET AL Ann Thorac Surg STENTLESS VS STENTED AORTIC BIOPROSTHESES 2000;69:817 22 of our study groups was taken as a consequence of the clinical setting in which an aortic bioprosthesis should be implanted, and where one may chose between a stentless and a stented valve. Intraoperatively we used an independent valve sizer and found a 23-mm supraannular porcine Carpentier-Edwards valve suitable in cases in which a 23-mm Medtronic Freestyle valve could be implanted by the full root replacement technique. Operative Procedures In all patients, St. Thomas solution was used for cardioplegia. Carpentier-Edwards valves were inserted using standard operating techniques. A transverse aortotomy was performed, the diseased aortic valve completely excised, and the stented bioprosthesis inserted in a supraannular position using interrupted Teflon supported mattress sutures. The Medtronic Freestyle valve was inserted using a total root replacement technique [13]. The aorta was transected just above the sinotubular ridge, both coronary ostia were mobilized with buttons of aortic wall, and the diseased aortic valve was removed. The stentless bioprosthesis was connected to the left ventricular outflow tract with a continuous suture (Prolene; Ethicon, Hamburg, Germany) incorporating a strip of pericardium as a basal external reinforcement of the annulus. Using continuous Prolene sutures, the coronary arteries were then implanted into the corresponding sinuses of Valsalva of the bioprosthesis. Finally the distal porcine root was anastomosed to the ascending aorta. Echocardiography The Ultramark 9 (Advanced Technology Laboratories, Bothell, WA) was used for all measurements. Left ventricular end-systolic and end-diastolic dimensions and thickness of left ventricular posterior wall and interventricular septum were assessed in the short axis of a parasternal view by multiple M-mode measurements with calculation of fractional shortening. Left ventricular mass was calculated as ASE-cube using the formula of Troy [14]. Aortic valve maximum Doppler velocity was measured with a continuous-wave transducer (ATL 2.00 MHz CW, PN 4000-0307-03; Advanced Technology Laboratories). Particular care was taken to obtain the highest possible velocity by variation of the acoustic window and transducer orientation. The modified Bernoulli equation was used to calculate peak gradients (p 4V 2, where V peak transvalvular flow velocity), and mean pressure gradients were obtained by averaging the cardiac cycle measurement which resulted in the highest peak gradient. Table 1. Demographics of the Study Patients Variable Medtronic Freestyle Carpentier- Edwards Control p Value n 10 10 10 NS Age (years) 70 9 a 72 3 a 27 4 NS a Body surface area (m 2 ) 1.73 1.4 a 1.76 1.4 a 1.94 0.1 NS a Follow-up (months) 9 3 7 2... NS Preoperative aortic lesion: AS 5 6 AS AR 4 4... NS AR 1 0 Additional CABG (n) 5 5... NS LVEDD (mm) 45 5 49 6 49 6 NS Fractional shortening 40 10 35 7 36 4 NS (%) LVM preoperative (g) 314 61 325 54... NS LVM postoperative (g) 211 60 289 89 213 32 0.01 AR aortic regurgitation; AS aortic stenosis; CABG coronary artery bypass grafting; LVEDD left ventricular end-diastolic diameter; LVM left ventricular mass. Exercise Protocol During bicycle exercise, patients sat on a seat reclined in a 50 position (Ergo-Metrics 900 L; Ergoline, Bitz, Germany). The starting workload was 25 W, and then was increased by 25 W every 3 minutes until symptomatic termination of the test occurred (dyspnea, muscular fatigue). To facilitate Doppler measurements during exercise, the chest site where optimum Doppler waveforms were recorded was marked before starting exercise. In case of unsatisfactory Doppler signal, the whole bicycle unit was tilted slightly to the left side until optimal measurements were obtained. Measurements were performed during the last minute of each 3-minute workload level. Blood pressure and heart rate were measured noninvasively every minute using a sphygmomanometer cuff fixed on the right arm. Statistical Methods Results were expressed as mean standard deviation. A Mann-Whitney U-test was used for comparative analysis of continuous variables in 2 groups of patients. Analysis of variance was used for comparison of all 3 patient groups. Statistical significance was established at p less than or equal to 0.05. Results Clinical Patient Characteristics Demographics of the patients and controls are shown in Table 1. There were no significant differences between the 2 groups of patients with stentless and stented valve replacement, except for left ventricular mass at time of the investigation. Trivial aortic regurgitation was postoperatively detected in 1 of 10 patients with Medtronic Freestyle valves, and in 2 of 10 patients with the Carpentier-Edwards valves. Minimal mitral reflux was present in 4 patients of each group with bioprosthetic valves and in 2 individuals of the control group. Rest and Exercise Hemodynamics Rest and maximum exercise hemodynamics of patients with stentless valves compared to those with stented valves are shown in Table 2. All patients reached a 50 W

Ann Thorac Surg FRIES ET AL 2000;69:817 22 STENTLESS VS STENTED AORTIC BIOPROSTHESES 819 Table 2. Hemodynamic Data of Patients with Bioprostheses Medtronic Freestyle Carpentier-Edwards Variable a Rest b Maximum Exercise a Rest b Maximum Exercise p Workload (W) 63 18 70 23 NS Heart rate (bpm) 76 14 105 18 73 14 107 15 NS a NS b Diastolic BP (mm Hg) 78 11 81 12 80 15 84 19 Systolic BP (mm Hg) 128 18 177 38 133 24 178 33 Mean gradient (mm Hg) 6 2 9 3 12 3 22 8 Peak gradient (mm Hg) 11 4 18 6 21 10 40 11 BP blood pressure. NS a NS b NS a NS b 0.009 a 0.0004 b 0.02 a 0.0004 b workload. The 75 W exercise level was reached by 5 of 10 patients with Carpentier-Edwards valves, and by 4 of 10 patients with the Freestyle valve. Focusing on the differences in maximum peak and mean transvalvular gradients at rest, as well as during exercise, superiority of the stentless valve is clearly evident. Comparing the course of peak and mean pressure gradients during exercise, gradients were consistently highest in patients with Carpentier-Edwards valves and lowest in healthy volunteers (Figs 1 and 2). The differences between the 3 study groups were statistically significant at rest (before and after exercise) and on each exercise level (ANOVA p 0.0001). Average Gradient Differences Between Study Groups Differences of average mean and peak gradients between patients with stented and stentless valves, and between patients with stentless valves and healthy subjects are displayed in Figure 3. Between patients with stentless valves and healthy subjects, differences remained stable throughout the exercise protocol, while the gradient differences between patients with stented and stentless valves increased significantly from one exercise level to the next. Comment Although stentless bioprostheses have been in use since the early 1960s [3], until now lack of availability and the more complex operation technique required for replacement of the aortic root (instead of the degenerated valve only) has restricted the use of stentless valves to a minority of patients. Hemodynamic superiority of stentless bioprostheses at rest has been confirmed by recent studies [4 7]. By contrast there is lack of comparative hemodynamic exercise studies. Methodology Simultaneous Doppler and catheterization studies have shown that continuous-wave Doppler ultrasound can accurately predict pressure gradients across prosthetic valves in the aortic position [15]. By use of the short form of the Bernouli equation gradients are estimated 3 to 5 mm Hg higher than after correction for left ventricular outflow tract (LVOT) velocity. This overestimation occurs to the same extent in resting and exercise gradients [16, 17]. As we focused on Doppler gradient differences between patient groups such systematic overestimation is not of great importance and does not impair the clinical Fig 1. Average peak gradients ( standard deviation) of the study patients at rest (before and 5 minutes after exercise) and during exercise. Fig 2. Average mean gradients ( standard deviation) of the study patients at rest (before and 5 minutes after exercise) and during exercise.

820 FRIES ET AL Ann Thorac Surg STENTLESS VS STENTED AORTIC BIOPROSTHESES 2000;69:817 22 Fig 3. Difference of average peak and mean gradients between patients with Freestyle valves and the control group, and between patients with Carpentier-Edwards valves and those with Freestyle valves. significance of our results. Correcting the Bernoulli equation for LVOT velocity requires repeated PW-Doppler measurements after exact positioning of the measure volume of the LVOT by means of B-mode echocardiography (2-dimensional picture). Taking into account the increasing patient movements during exercise, and the short time window for measurements at each exercise level (1 minute), in our experience, this cannot be performed reliably. For the same reason, we did not try to calculate further LVOT flow dependent variables, such as effective orifice area, stroke volume, and cardiac output. Rest Hemodynamics We found a resting peak gradient of 21 10 mm Hg (mean gradient 12 3 mm Hg) in 10 patients with 23-mm Carpentier-Edwards valves. Previously reported peak gradients for normally functioning Carpentier-Edwards valves are comparable to our findings (8 to 23 mm Hg) [16, 18 21]. The relatively wide range of measured values in these studies may be explained by inclusion of patients with different valve sizes and partly by differences in methodology. In 10 patients with 23-mm Medtronic Freestyle valves we determined a peak gradient of 11 4mmHganda mean gradient of 6 2 mm Hg. These are almost exactly the same values as reported by Westaby and colleagues [11] in a series of 17 patients with the same valve and valve diameter (peak gradient: 12 7 mm Hg, mean gradient: 5 2 mm Hg). Data are confirmed by Sintek and colleagues [6] and Jin and associates [9] for the Medtronic Freestyle valve, and by other investigaters for a comparable type of stentless porcine valve, such as the Toronto SPV [4, 8, 22, 23] and the Biocor valve [17, 24]. Exercise Hemodynamics The mean exercise gradient in our patients with Carpentier-Edwards valves (22 8 mm Hg) is confirmed in the few studies including exercise measurements in patients with stented bioprostheses. Craver and colleagues [25] reported in 10 patients with a 23-mm modified orifice Hancock valve, a mean pressure gradient during exercise of 28 16 mm Hg, and in 6 patients with 23-mm Carpentier-Edwards valves, Chaitman and colleagues [18] reported a mean gradient of 29 5 mm Hg. Jaffe and coworkers [26] found a mean transvalvular gradient of 28 8 mm Hg in 7 patients with 23-mm Medtronic Intact valves. By contrast, there are no data published concerning transvalvular gradients during bicycle exercise in the Medtronic Freestyle valve. We measured mean gradients of 9 3 mm Hg and peak gradients of 18 6mmHgat a workload of 70 23 W. In comparison to healthy young men, gradients were only slightly higher (3/7 mm Hg (mean/peak) at rest and 4/9 mm Hg during exercise, Figs 1 and 2). These differences were statistically significant, but may be physiologically negligible. Taking into account natural aortic valve degeneration with age (elasticity loss and sclerosis), it can be speculated that there would be insignificant or no gradient differences when comparing our patients with Freestyle valves to healthy subjects of comparable age. Our results with the Freestyle valve are comparable to findings in a different type of stentless aortic bioprosthesis (Biocor valve). Eriksson and colleagues [17] reported 26 patients with 19 to 25-mm extended Biocor valves with gradients of 8 3/12 4 mm Hg (mean/peak) at rest and 15 6/24 8 mm Hg (mean/peak) during bicycle exercise (median 60 W) 15 months postoperatively. Donatelli and coworkers [24] studied 7 patients with 23 to 27-mm Biocor valves and measured gradients of 6 2/11 3 mm Hg (mean/peak) at rest and 9 2/15 5 mm Hg (mean/peak) after exercise (modified Bruce protocol), 6 months postoperatively. Difference of Average Gradients Between Study Groups As in previous studies, gradients were usually measured immediately after and not during exercise. Our data provide new information concerning transaortic gradients in different types of aortic valves, on different exercise levels. Interestingly, the difference of average gradients between patients with Freestyle valves and healthy subjects remained almost unchanged when comparing values at rest (3/7 mm Hg [mean/peak]) and during exercise (4/8 mm Hg [mean/peak] at 25 W, 4/9 mm Hg at 50 W and 4/9 mm Hg at 75 W). By contrast the difference of average gradients between patients with Carpentier- Edwards valves and those with Freestyle valves increased significantly from one exercise level to the next (6/12 mm Hg [mean/peak] at rest, 8/14 mm Hg at 25 W, 12/17 mm Hg at 50 W and 15/25 mm Hg at 75 W). This finding means that resting hemodynamics may be representative for exercise hemodynamics in stentless but not in stented bioprostheses. In the latter, hemodynamic performance significantly decreases with increasing activity. In our series the average gradient difference between patients with Carpentier-Edwards and those with Medtronic Freestyle valves was at a workload of 75

Ann Thorac Surg FRIES ET AL 2000;69:817 22 STENTLESS VS STENTED AORTIC BIOPROSTHESES 821 W, more than twice as high as at rest (Fig 3). This may explain why left ventricular remodeling is so much better in patients with stentless valves, as compared to those with stented valves [8 11]. Better regression of left ventricular hypertrophy is confirmed in our patients. When comparing left ventricular mass measurements preoperatively and at time of the exercise test, it is evident that left ventricular mass decreased significantly better in patients with stentless valves (Table 1). The reason for the significantly sharper increase of transprosthetic gradients in patients with Carpentier- Edwards valves remains unclear. We cannot suppose that there were any differences in the increase of cardiac output or stroke volume in the study groups. Each individual patient had a normally sized and normally functioning left ventricle, had either no coronary artery disease or were completely revascularized, and showed adequately increasing heart rate and blood pressure during exercise. Furthermore, the symptom limiting exercise was muscular fatigue (and not angina or dyspnea) in all patients. Thus we can expect comparable increase in cardiac output during exercise in all 3 study groups. Differences in geometrical orifice area cannot explain better hemodynamic performance of the Freestyle valve as the internal diameter (at the valve base) of a 23-mm Carpentier-Edwards porcine valve (21-mm) is even larger than the internal diameter of a 23-mm Freestyle valve (20-mm). By contrast, according to lower gradients and reflecting a less impaired transprosthetic blood flow, in vivo and in vitro measurements of effective orifice area reveal significantly smaller values in stented valves [4 6, 22]. Variables influencing transprosthetic flow in favor of the stentless valve design may be valve shape and surface, as well as distensibility of the aortic root. During exercise a possible increase of effective orifice area may also be of importance, but data concerning this issue are conflicting and methodologically problematic, as formulas for calculation of effective orifice area are flow dependent [27]. As different implantation techniques may influence transaortic flow characteristics, our results might be slightly different if we had used the root inclusion or subcoronary technique. However, taking into account that many surgeons use stentless valves up to two sizes larger as stented valves in the same patient, we could have compared the 23-mm Carpentier-Edwards valve with a 25 or 27-mm Medtronic Freestyle, and our results in favor of the stentless valve would have been even more impressive. The hemodynamic performance of stentless aortic bioprostheses implanted in elderly patients, by the full root replacement technique, is slightly inferior to that of natural valves in healthy young men. The small, and probably physiologically insignificant, gradient difference between stentless valves and natural valves at rest remains unchanged during exercise. By contrast, the already significant gradient difference between patients with stented bioprostheses and those with stentless grafts increases even further during exercise. Our data strongly support the suggestion that, from the hemodynamic point of view, a stentless aortic bioprosthesis is an appropriate aortic valve substitute, especially in patients with a smaller aortic root and in those performing regular physical activity. References 1. Angell WW, Pupelloo DF, Bessone LN, Hiro SP, Brock JC. Effect of stent mounting on tissue valves for aortic replacement. J Cardiac Surg 1991;6(Suppl 4):595 9. 2. Broom ND. Fatigue induced damage in gluteraldehyde preserved heart valve tissues. J Thorac Cardiovasc Surg 1978;76: 202 11. 3. Binet JP, Duran CG, Carpentier A, Langlois J. Heterologous aortic valve transplantation. Lancet 1965;2:1275. 4. David TE, Bos J, Rakowski A. Aortic valve replacement with the Toronto SPV bioprosthesis. J Heart Valve Dis 1992;1: 244 8. 5. Hvass U. O Brien-Angell stentless valve. Early results in 120 implants. In: Piwnica A, Westaby S, eds. Stentless bioprosthesis. Oxford: Isis Medical Media, 1995:182 9. 6. Sintek CF, Fletcher AD, Khonsari S. Stentless porcine aortic root: valve of choice for the elderly patient with small aortic root? J Thorac Cardiovasc Surg 1995;109:871 6. 7. Westaby S, Huysmans HA, David TE. Stentless aortic bioprostheses: compelling data from the second international symposium. Ann Thorac Surg 1998;65:235 40. 8. David TE, Feindel CM, Bos J, Sun Z, Scully HE, Rakowski H. Aortic valve replacement with a stentless porcine aortic valve. A six year experience. J Thorac Cardiovasc Surg 1994; 108:1030 6. 9. Jin XY, Westaby S, Gibson DG, Pillai R, Taggart DP. Left ventricular remodelling and improvement in Freestyle stentless valve hemodynamics. Eur J Cardiothorac Surg 1997;12: 63 9. 10. Jin XY, Zhang ZM, Gibson DG, Yacoub MH, Pepper JR. Effects of valve substitute on changes in left ventricular function and hypertrophy after aortic valve replacement. Ann Thorac Surg 1996;62:683 90. 11. Westaby S, Amarasena N, Long V, et al. Time related hemodynamic changes after aortic replacement with the Freestyle stentless xenograft. Ann Thorac Surg 1995;60: 1633 9. 12. Christakis GT, Buth KJ, Goldman BS, et al. Inaccurate and misleading valve sizing: a proposed standard for valve size nomenclature. Ann Thorac Surg 1998;66:1198 203. 13. Kon ND, Westaby S, Amarasena N, Pillai R, Cordell AR. Comparison of implantation techniques using freestyle stentless porcine aortic valves. Ann Thorac Surg 1995;59: 857 62. 14. Troy BL, Pombo J, Rackley CE. Measurement of left ventricular wall thickness and mass by echocardiography. Circulation 1972;45:602 11. 15. Burstow DJ, Nishimure RA, Bailey KR, et al. Continuous Doppler echocardiographic measurements of prosthetic valve gradient. A simultaneous Doppler catheter correlative study. Circulation 1989;80:504 14. 16. Wiseth R, Levang OW, Tangen G, Rein KA, Skjaerpe T, Hatle L. Exercise hemodynamics in small ( 21-mm) aortic valve prostheses assessed by Doppler echocardiography. Am Heart J 1993;125:138 46. 17. Eriksson MJ, Brodin LA, Dellgren GN, Radegran K. Rest and exercise hemodynamics of an extended stentless aortic bioprosthesis. J Heart Valve Dis 1997;6:653 60. 18. Chaitman BR, Bonan R, Lepage G, et al. Late hemodynamic evaluation of the Carpentier-Edwards porcine xenograft. Circulation 1979;60:1170 82.

822 FRIES ET AL Ann Thorac Surg STENTLESS VS STENTED AORTIC BIOPROSTHESES 2000;69:817 22 19. Levine FH, Carter JE, Buckley MJ, Daggett WM, Akins CW, Austen WG. Hemodynamic evaluation of Hancock and Carpentier-Edwards bioprostheses. Circulation 1981;64 (Suppl):II192 5. 20. Rothkopf M, Davidson T, Lipscomb K, et al. Hemodynamic evaluation of the Carpentier-Edwards bioprosthesis in the aortic position. Am J Cardiol 1979;44:209 14. 21. Williams GA, Labovitz AJ. Doppler hemodynamic evaluation of prosthetic (Starr-Edwards and Björk-Shiley) and bioprosthetic (Hancock and Carpentier-Edwards) cardiac valves. Am J Cardiol 1985;56:325 32. 22. Del Rizzo DF, Goldman BS, Joyner CP, Sever J, Fremes SE, Christakis GT. Initial experience with the Toronto stentless porcine valve. J Cardiac Surg 1994;9:379 85. 23. Walther T, Falk V, Autschbach R, et al. Hemodynamic assessment of the stentless Toronto SPV bioprosthesis by echocardiology. J Heart Valve Dis 1994;3:657 65. 24. Donatelli F, Triggiani M, Mariani MA, et al. Rest and exercise hemodynamics of stentless porcine bioprostheses in aortic position. Cardiologia 1994;39:41 7. 25. Craver JM, King SB III, Douglas JS, et al. Late hemodynamic evaluation of Hancock modified orifice aortic bioprosthesis. Circulation 1979;60(Suppl):I93 7. 26. Jaffe WM, Coverdale A, Roche AHG, Whitlock RML, Neutze JM, Barratt-Boyes BG. Rest and exercise hemodynamics of 20 to 23 mm allograft, Medtronic Intact (porcine), and St. Jude Medical valves in the aortic position. J Thorac Cardiovasc Surg 1990;100:167 74. 27. Schwammenthal E, Vered Z, Rabinowitz B, Kaplinsky E, Feinberg S. Stress echocardiography beyond coronary artery disease. Eur Heart J 1997;18(Suppl D):130 7. The Thoracic Surgery Foundation for Research and Education Don t Forget Your Foundation Gift Your Foundation is making a difference in cardiothoracic surgery. This is possible only because of your support. Please consider an annual gift to The Foundation of appreciated stocks, bonds or mutual funds. You avoid capital gains tax and earn an income tax deduction by donating rather than selling these assets. This may be better for you than a gift of cash. This is also a good time to review your estate plans. Do you know if the IRS will take 75 85 percent of your qualified retirement plan? Did you know that a gift to your Foundation can reduce this? Did you know that you can increase your net income through a gift to The Foundation? If you have been thinking of making a charitable contribution to The Thoracic Surgery Foundation for Research and Education, this may be the time to consider a planned gift. Often, this type of giving enables an individual to give a larger gift at a cost that is actually lower than if the gift were to be made outright. You may also find that planned giving enables you to meet other personal financial goals while making significant charitable gifts. You may give to The Foundation through a revocable instrument, such as a bequest in your will, or through an irrevocable agreement like a charitable lead trust or a charitable remainder trust. You may also give through a life insurance policy or your retirement plan. For more information about your annual gift or a deferred gift, contact Frank Kurtz, TSFRE Executive Director, telephone: (312) 644-6610; fax: (312) 527-6635; e-mail: frank_kurtz@sba.com. 2000 2001 Research Award Applications Applications for The Thoracic Surgery Foundation s 2000 2001 program of Research Grants, Fellowships and Career Development Awards will be available in August 2000. To request an application, please contact Lainie Castle at the Foundation office at telephone: (312) 464-6100, extension 4798. Applications can also be downloaded from The Foundation s home page, www.tsfre. org, after August 1, 2000. 2000 by The Society of Thoracic Surgeons Ann Thorac Surg 2000;69:822 0003-4975/00/$20.00 Published by Elsevier Science Inc