Asian Cardiovasc Thorac Ann 2007;15:102-105
© 2007 Asia Publishing EXchange Ltd
Evaluation of Bioprosthetic Valve for Small Aortic Root in Elderly Patients
Noritsugu Shiono, MD,
Yoshinori Watanabe, MD,
Muneyasu Kawasaki, MD,
Hiroki Yokomuro, MD,
Takeshirou Fujii, MD,
Nobuya Koyama, MD
Division of Cardiovascular Surgery, Faculty of Medicine, Toho University, Tokyo, Japan
For reprint information contact: Noritsugu Shiono, MD Tel: 81 3 3762 4151 Ext. 6540 Fax: 81 3 3766 7810 Email: shiono{at}med.toho-u.ac.jp, Division of Cardiovascular Surgery, Department of Surgery (Omori), School of Medicine, Faculty of Medicine, Toho University, 6-11-1 Omorinishi, Otaku, Tokyo, Japan 143-8541.
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ABSTRACT
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The hemodynamics of stentless bioprostheses are superior to those of mechanical valves, especially for patients with a small aortic root. Between March 1999 and July 2001, we implanted 18 Freestyle stentless porcine valves using our technique of repeated division of the space by halving the distance. Seven patients received 19–21-mm valves and 11 received 23–25-mm valves. Clinical data and early and midterm outcomes of both groups were compared. The mean preoperative echocardiography gradient of the small valve group was 84.7 mm Hg, and when discharged from hospital, the mean gradient was 14.8 mm Hg. One operative death was encountered due to arrhythmia. This stentless porcine prosthesis has excellent hemodynamics and can be implanted safely and easily, even in elderly patients with a small aortic root, using our suture technique.
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INTRODUCTION
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Aortic valve replacement (AVR) with a small prosthetic valve is technically straightforward and frequently performed, but it may result in patient-prosthesis mismatch and a high residual outflow gradient. The use of stentless valves results in lower residual postoperative gradients but the implant procedures are technically more demanding, thereby increasing the total ischemic time. Annular enlargement allows insertion of a larger aortic prosthesis, but this may also increase the surgical risk. At Toho University Omori Hospital, we have recently been implanting a bioprosthetic stentless valve (Freestyle; Medtronic, Irvine, CA, USA) in elderly patients, using our subcoronary technique of repeated division of the space by halving the distance. To determine the outcome and safety of bioprosthetic valve insertion using our suturing technique in small aortic roots, we compared operative, early, and midterm outcomes after AVR in patients with a small aortic root (19–21 mm) and those with a large aortic root (23–25 mm).
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PATIENTS AND METHODS
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Between March 1999 and July 2001, 18 Freestyle stentless porcine valves were implanted for AVR using our modified subcoronary technique. The methods of exposure and sizing were identical to those described in previous reports.1–5 The aortic incision was located approximately 2 cm above the sinotubular junction and included three quarters of the circumference of the ascending aorta. The native valve was excised and the annulus size determined. Two stay sutures were placed at each commissure, each cusp annulus was divided in half and another suture was placed, each cusp was divided in half again 3 more times (Figure 1
). A total of 27 interrupted 3/0 polyester (Nespolene; Aswell, Inc., Osaka, Japan) stitches were thus placed for the prosthesis inflow. The defining concept of this technique is the use of an equal balance and tension to maintain the round shape of the stentless valve (Figure 1). A single stitch forms no rumples at the prosthesis inflow. We used 27 valve inflow stitches regardless of valve size. Seven patients had small aortic roots; one received a 19-mm valve and 6 received 21-mm valves. Eleven patients received 23–25-mm valves. The stitch distance was 2.2 mm for 19-mm valves, 2.3 mm for 21-mm valves, 2.6 mm for 23-mm valves, and 2.9 mm for 25-mm valves. Concomitant operations comprised coronary artery bypass grafting in one patient, and carotid endarterectomy in one. Echocardiographic measurements were taken before surgery, at discharge, and every 6 months after surgery (range, 6–36 months). The left ventricular (LV) mass was calculated from 2-dimensional M-mode measurements taken according to the recommendations of the American Society of Echocardiography.6 The relevant clinical data and early and midterm outcomes in both groups were compared.
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Figure 1. The implant method: repeated division of the space by halving the distance. Two stitches are placed at the commissure, each cusp annulus is divided in half and a suture is placed (2), each cusp is divided in half again three times (3).
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RESULTS
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The characteristics of both groups are given in Table 1. Males outnumbered females in the large valve group. The small valve group was significantly shorter in height than the large valve group. The pressure gradient in the small valve group was somewhat higher than that in the large valve group before AVR (Table 2). However, after AVR, the pressure gradient in the small valve group was significantly less (Figure 2). Before AVR, the LV mass index of the large valve group was greater than the small valve group (Figure 3). After AVR, the difference in LV mass index between groups was not significant. There was one operative death due to arrhythmia in a 68-year-old woman. She had been treated for coronary disease by percutaneous coronary intervention before AVR. Postoperative complications included atrioventricular block in one patient, and re-exploration in another. The postoperative pressure gradient rapidly decreased in all surviving patients. Left ventricular mass index decreased immediately and reached normal levels approximately 12 months after surgery.
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DISCUSSION
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Stentless xenograft valves offer better hemodynamic function and are used predominantly in elderly patients with aortic valve disease. The implant techniques are more complex than for stented valves, as reflected by the longer ischemic and cardiopulmonary bypass times. However, thanks to advances in modern myocardial preservation techniques, the extended ischemic time has shown little effect on patient outcomes. Krause1 described a technique requiring 15–21 vertical sutures of 3/0 Ti-Cron. We used a pair of 3/0 Nespolene stay sutures, thus eliminating the possibility of cutting the myocardium with traction sutures. The commissure traction sutures were placed at the subcommissural level to keep the inflow on a single plane. Every cusp had 7 interrupted sutures, regardless of the valve size; all valve sizes required 27 inflow sutures, which was fewer than the number required in the technique described by Krause.1 The critical concept in our technique is the equal balance of the inflow sutures. The left and right coronary sinus portions of the Freestyle valve are excised, leaving a 3–4-mm rim of tissue next to the cusp, and the noncoronary sinus portion is left intact. This method allows for simple suturing of stentless valves, even in a surgeon’s first-time implant. The distal suture line (for securing the Freestyle valve beneath the patient’s coronary orifice) is completed using continuous 4/0 Prolene sutures. The Freestyle valve was easily implanted using our technique.
Postoperative hemodynamic function was excellent with no significant regurgitation and a rapid resolution of LV hypertrophy. The pressure gradients in patients receiving 19–21-mm valves decreased to approximately 15 mm Hg at discharge. The pressure gradients in the patients with 23–25-mm valves decreased to a similar level after 6 months. Thirty-six months of echocardiographic follow-up showed no significant difference in the pressure gradients of patients with small or large valves. This stentless prosthesis improved the hemodynamics in elderly patients with a small aortic root in the early and midterm follow-up. The ventricular mass index had decreased by 20% at discharge (Figure 3
). In addition, very low pressure gradients resulted in a rapid resolution of LV hypertrophy. Westaby and colleagues2 investigated the mechanisms of Freestyle valve improvements. At the ventricular level, hypertrophy regresses and the relative wall thickness decreases. At the outflow tract level, the physical dimensions remain constant, however, increased stroke volume is associated with a wider flow jet and thus a greater effective orifice area. The overall results therefore demonstrate progressive functional improvement at both the ventricular and valvular level, which optimizes the degree of coupling between the heart and the systemic circulation.
This study confirms that the stentless porcine prosthesis has excellent hemodynamics in smaller valve sizes, and it can be implanted safely and easily, even in the elderly, using our modified subcoronary suture technique.
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REFERENCES
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- Krause AH Jr. Technique for complete subcoronary implantation of the Medtronic Freestyle porcine bioprosthesis. Ann Thorac Surg 1997;64:1495–8.[Abstract/Free Full Text]
- Westaby S, Amarasena N, Long V, Prothero A, Amarasena GA, Banning AP, et al. Time-related hemodynamic changes after aortic replacement with the freestyle stentless xenograft. Ann Thorac Surg 1995;60:1633–9.[Abstract/Free Full Text]
- Westaby S, Jin XY, Katsumata T, Arifi A, Braidley P. Valve replacement with a stentless bioprosthesis: versatility of the porcine aortic root. J Thorac Cardiovasc Surg 1998;116:477–84.[Abstract/Free Full Text]
- Sintek CF, Fletcher AD, Khonsari S. Small aortic root in the elderly: use of stentless bioprosthesis. J Heart Valve Dis 1996;5 Suppl 3:S308–13.
- Kon ND, Westaby S, Amarasena N, Pillai R, Cordell AR. Comparison of implantation techniques using freestyle stentless porcine aortic valve. Ann Thorac Surg 1995;59:857–62.[Abstract/Free Full Text]
- Devereux RB, Reichek N. Echocardiographic determination of left ventricular mass in man. Anatomic validation of the method. Circulation 1977;55:613–8.
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ABSTRACT
INTRODUCTION
