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Ann Thorac Surg 2009;87:90-94. doi:10.1016/j.athoracsur.2008.09.051
© 2009 The Society of Thoracic Surgeons
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Original Articles: Adult Cardiac

The 17-mm St. Jude Medical Regent Valve Is a Valid Option for Patients With a Small Aortic Annulus

Homare Okamura, MD*, Atsushi Yamaguchi, MD, Masashi Tanaka, MD, Kazuhiro Naito, MD, Naoyuki Kimura, MD, Chieri Kimura, MD, Toshiyuki Kobinata, MD, Takashi Ino, MD, Hideo Adachi, MD

Department of Cardiovascular Surgery, Saitama Medical Center, Jichi Medical University, Saitama, Japan

Accepted for publication September 23, 2008.

* Address correspondence to Dr Okamura, Department of Cardiovascular Surgery, Saitama Medical Center, Jichi Medical University, 1-847 Amanuma-cho Omiya-ku Saitama-shi, Saitama, 330-8503, Japan (Email: homareokamura{at}hotmail.co.jp).


   Abstract
Top
 Abstract
Introduction
 Patients and Methods
 Results
 Comment
 References
 
Background: When aortic valve replacement is performed in patients with a small aortic annulus, prosthesis–patient mismatch is of concern. Such prosthesis–patient mismatch may affect postoperative clinical status and survival. We investigated the outcomes of isolated aortic valve replacement performed with a 17-mm mechanical prosthesis in patients with aortic stenosis.

Methods: Twenty-three patients with aortic stenosis (mean age, 74.6 ± 6.3 years) underwent isolated aortic valve replacement with a 17-mm St. Jude Medical Regent prosthesis. Mean body surface area was 1.41 ± 0.13 m2. Preoperative echocardiography yielded a mean aortic valve area of 0.36 ± 0.10 cm2/m2, a mean left ventricular–aortic pressure gradient of 68.4 ± 25.3 mm Hg, and a mean left ventricular mass index of 200 ± 69 g/m2.

Results: There was no operative mortality, and there were no valve-related events. Echocardiography at 14.0 ± 10.0 months after aortic valve replacement showed a significant increase in the mean effective orifice area index (0.95 ± 0.24 cm2/m2), decrease in the mean left ventricular–aortic pressure gradient (17.4 ± 8.2 mm Hg), and decrease in the mean left ventricular mass index (124 ± 37 cm2/m2). Prosthesis–patient mismatch (effective orifice area index < 0.85 cm2/m2) was present in 8 patients at discharge. In these patients as well as in those without prosthesis–patient mismatch, the left ventricular mass index decreased remarkably during follow-up.

Conclusions: Aortic valve replacement with a 17-mm Regent prosthesis appears to provide satisfactory clinical and hemodynamic results in patients with a small aortic annulus. Remarkable left ventricular mass regression during follow-up was achieved irrespective of the effective orifice area index at discharge.


   Introduction
Top
 Abstract
 Introduction
Patients and Methods
 Results
 Comment
 References
 
Aortic valve replacement (AVR) is the standard therapy for patients with severe aortic stenosis; persistent improvement in hemodynamic status results. With the aging population, greater numbers of patients are exhibiting aortic stenosis; thus, the number of patients undergoing AVR is increasing.

As early as 1978, Rahimtoola [1] noted the problem of prosthesis–patient mismatch (PPM) after aortic valve surgery performed with a prosthetic valve. Prosthesis–patient mismatch is attributable to a difference between the area of the implanted prosthetic valve and that of the patient's native valve. Previous studies have shown that PPM, defined as an effective orifice area index (EOAI; ie, effective orifice area divided by body surface area) of less than 0.85 cm2/m2, may affect postoperative clinical status and survival [2, 3]. Thus, to prevent PPM, surgeons performing AVR need to be careful in choosing both the prosthesis and the operative method.

The average effective orifice area reported by the manufacturer for the 17-mm St. Jude Medical Regent valve is 24% less than that for the 19-mm Regent valve, ie, 1.3 cm2 versus 1.7 cm2. The 17-mm Regent prosthesis may be considered an alternative in patients with a small aortic annulus; however, very few data are available pertaining to the efficiency of this prosthesis. The incidence of PPM and the influence of this prosthetic valve on mid-term and long-term prognoses remain unclear. The primary objective of this study was therefore to investigate the clinical short-term and mid-term outcomes, including hemodynamics, after AVR with the 17-mm Regent prosthesis.


   Patients and Methods
Top
 Abstract
 Introduction
 Patients and Methods
Results
 Comment
 References
 
Patient Population
From February 2005 through December 2007, 23 patients with aortic stenosis underwent elective, isolated AVR with a 17-mm Regent prosthesis (St. Jude Medical, St. Paul, MN) at our institution. This group excluded patients who underwent AVR with concomitant procedures. The patients ranged in age from 63 to 85 years (mean age, 74.6 ± 6.3 years). Nineteen patients (83%) were women. Mean body surface area (BSA) was 1.41 ± 0.13 m2 (range, 1.19 to 1.65 m2). Twelve patients (52%) were in New York Heart Association functional class III or class IV preoperatively. Patients' preoperative demographic and clinical characteristics are shown in Table 1. Our study followed the guidelines of the Ethical Review Board of Jichi Medical University. All of the patients had previously granted permission for use of their medical records for research purposes.


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  		Table 1 Preoperative Patient Characteristics and Operative Data
 
Operative Techniques
Aortic valve surgery was performed through a standard median sternotomy. Cardiopulmonary bypass was initiated after cannulation of the ascending aorta, superior vena cava, and inferior vena cava. A left ventricular vent was inserted by means of the right upper pulmonary vein. Antegrade and retrograde cold blood cardioplegia was administered intermittently to maintain cardiac arrest. Moderate hypothermia was applied. After complete excision of the diseased aortic valve, the diameter of the aortic annulus was measured with sizers (St. Jude Medical) for selection of the appropriate size prosthesis. The 17-mm St. Jude Medical Regent prosthesis was implanted in the intraannular position with the use of 2-0 polyester everting mattress sutures in 17 patients and 2-0 interrupted braided polyester sutures in 6 patients. Warfarin sodium was started on the day of surgery and continued thereafter so that the international normalized ratio of prothrombin time was maintained between 2.0 and 2.5.

Echocardiography
Standard M-mode dimensions were obtained according to the American Society of Echocardiography criteria. The mean of three measures on two different cardiac cycles was taken. The following variables were obtained: end-diastolic septal thickness, left ventricular end-diastolic dimension, and end-diastolic left ventricular posterior wall thickness. All Doppler measurements were averaged from more than three cycles in patients with sinus rhythm and more than five cycles in those with atrial fibrillation. Maximum pressure gradients were calculated from the complete Bernoulli equation. Left ventricular mass was calculated according to the Devereux formula [4]. The effective orifice area was determined by the standard continuity equation and indexed to BSA. Preoperative echocardiographic data are summarized in Table 2.


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  		Table 2 Echocardiographic Data
 
Follow-Up
The follow-up transthoracic echocardiographic data were collected in 21 (91%) of the 23 patients at a mean follow-up time of 14.0 ± 10.0 months after surgery. Clinical status of each patient was evaluated by means of direct hospital visits and telephone interviews. Mean follow-up time was 20 ± 11 months (range, 5 to 39 months).

Statistical Methods
Data are reported as mean ± standard deviation. Preoperative and postoperative echocardiographic data for all patients were compared and analyzed by paired Student's t test. Patients were divided into two groups: those with and those without PPM at discharge. Differences between these groups were analyzed by {chi}2 test or unpaired Student's t test as appropriate. Actuarial survival was calculated by the Kaplan–Meier method. All analyses were performed with SPSS software (version 10.1; SPSS Inc, Chicago, IL). A probability value of less than 0.05 was considered significant.


   Results
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 Abstract
 Introduction
 Patients and Methods
 Results
Comment
 References
 
Operative Morbidity and Mortality
Overall hospital mortality was 0%. Postoperatively, 6 patients experienced atrial fibrillation and 1 patient had a cerebral infarction. Operative data are summarized in Table 1. No patient needed perioperative intraaortic balloon pumping or percutaneous cardiopulmonary support for hemodynamic instability. No patient was readmitted.

Echocardiographic Follow-Up
Preoperative and postoperative echocardiographic measurements are shown in Table 2. Follow-up echocardiography revealed a significant decrease in maximum and mean left ventricular–aortic pressure gradient, a significant decrease in left ventricular mass index (LVMI), and a significant increase in mean EOAI. The EOAI at discharge ranged from 0.61 to 1.34 cm2/m2 (mean, 0.94 ± 0.19 cm2/m2). The prevalence of PPM, defined as an EOAI of less than 0.85 cm2/m2 at discharge, was documented in 8 patients (35%). In comparison to the group of patients without PPM, the group with PPM had a significantly larger BSA and proportion of males (Table 3). Echocardiographic data in patients with PPM (8 patients) and those without PPM (15 patients) are compared in Table 3. Although the EOAI at discharge was significantly lower in patients with PPM than in patients without PPM, follow-up EOAI did not differ significantly between the two groups. The presence of PPM at discharge did not affect the decrease in LVMI.


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  		Table 3 Clinical Profiles and Echocardiographic Data in Patients With and Without Prosthesis–Patient Mismatch at Discharge
 
Clinical Follow-Up and Valve-Related Events
During the follow-up period, 1 patient died of renal cancer. The 2-year survival rate was 96%. All patients were assessed for physical capacity according to New York Heart Association classification during follow-up. Although 12 patients (52%) had New York Heart Association class III or IV symptoms preoperatively, all improved to class II or better by 18 months after AVR (Fig 1). Valve-related events including valve thrombosis, structural malfunction, and paravalvular leakage did not occur in any patient during the follow-up period.


Figure 1
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  		Fig 1. Preoperative and follow-up New York Heart Association functional class.

 

   Comment
Top
 Abstract
 Introduction
 Patients and Methods
 Results
 Comment
References
 
Elderly Japanese are smaller in size than their Western counterparts. Therefore, the aortic annulus of the Japanese is smaller, proportionate to their body size. It has been shown that the ideal EOAI should exceed 0.85 cm2/m2 [2, 5]. In the case of patients with a small aortic annulus, careful evaluation is needed to achieve an EOAI of more than 0.85 cm2/m2 after AVR surgery. This ideal EOAI may be associated with better postoperative physical capacity, and short-term and long-term survival [2, 3, 6]. During the past 20 years, we have performed aortic root enlargement to insert an artificial valve proportional to body size. Such enlargement of the aortic annulus is based on the premise that a large-sized prosthesis favorably influences late clinical outcome [7]. Castro and colleagues [8] performed aortic root enlargement procedures in 114 patients to avoid moderate to severe PPM. Del Rizzo and associates [9] reported that a stentless valve resembled the native aortic valve and provided a larger internal diameter and good flexibility, leading to superior hemodynamic performance and improved left ventricular function. However, aortic annulus enlargement and implantation of the stentless valve have been shown to result in prolonged cardiopulmonary bypass and ischemic times [8, 10]. Such surgical modification is now seldom necessary because advances in the design of prostheses have improved hemodynamic performance considerably. The 17-mm St. Jude Medical Regent valve with an effective orifice area of 1.30 cm2 can be applied in patients with a BSA of less than 1.5 m2, resulting in an EOAI of more than 0.85 cm2/m2.

The main consequence of PPM is generation of abnormally high transprosthetic gradients across the aortic valve, resulting in increased left ventricular work. Prosthesis–patient mismatch is also associated with a smaller decrease in the LVMI and more cardiac events during the follow-up period [11, 12]. Blais and coworkers [6] noted that PPM is an independent risk factor for short-term mortality in patients who have undergone AVR. Prevention of PPM has been reported to improve postoperative functional class or exercise tolerance and the incidence of late sudden deaths [3, 13]. However, some investigators have reported that the influence of PPM on prognosis after AVR surgery remains controversial [11, 14, 15].

The decrease in the LVMI is considered to be a result of favorable remodeling derived from AVR. Because of the regression of myocardial cellular hypertrophy, the left ventricular mass in patients with aortic stenosis decreased by approximately 30% after AVR [16]. Incomplete regression of the residual gradient across the prosthesis has been associated with an increased long-term mortality rate [17]. Interestingly, in the present study, the presence of PPM at discharge did not affect the reduction in the LVMI during the follow-up period. A third of our patients undergoing AVR with the 17-mm St. Jude Medical Regent prosthesis showed PPM (EOAI < 0.85 cm2/m2) at discharge. An approximate 35% decrease in LVMI was documented during follow-up in patients with PPM, as well as in patients without PPM. However, it must be noted that in the present study there was only 1 patient with severe PPM, defined as an EOAI of less than 0.65 cm2/m2 at discharge. So, we need to look more carefully into the impact of PPM in the future.

Many studies have evaluated the effect of a 19-mm prosthesis on both left ventricular mass regression and clinical outcome. Sawant and coworkers [18] reported satisfactory long-term performance of the 19-mm St. Jude Medical prosthesis in the small aortic root, irrespective of the BSA. In another series, left ventricular mass regression continued more than 10 years after AVR with a 19-mm mechanical valve [19]. To the contrary, Gonzalez-Juanatey and colleagues [12] reported that the 19-mm aortic prosthesis continued to create significant obstruction of the left ventricular outflow tract. There are few reports regarding the 17-mm mechanical prosthesis, and controversy remains as to whether this valve is beneficial and safe in both the short and long term. Amarelli and colleagues [20] and Takaseya and associates [21] have reported satisfactory clinical improvement and significant left ventricular mass regression after AVR with 17-mm mechanical prostheses. However, these studies included data after AVR with and without concomitant procedures. In our small series, the in-hospital mortality rate after AVR with the 17-mm mechanical prosthetic valve was 0%. In comparing preoperative and follow-up echocardiographic measurements, we found a significant decrease in maximum and mean left ventricular–aortic pressure gradient, a decrease in the LVMI, and an increase in the mean EOAI. These findings suggest that implantation of a 17-mm Regent valve provides not only excellent operative results but also good mid-term survival, associated with the better hemodynamic results. Milano and coworkers [11] evaluated clinical outcomes in patients who received a 19-mm St. Jude aortic prosthesis and reported a decrease in the follow-up LVMI of 18% ± 9%. In our series, the reduction in LVMI was 34% ± 19%, surprisingly better than that in patients with a 19-mm prosthesis. Maselli and coworkers [22] reported the reduction in LMVI expressed as a percentage of the preoperative LVMI in homograft and freestyle groups to be 40.1% ± 15.9% and 29.1% ± 11.7%, respectively. Thus, the 17-mm Regent prostheses achieved a reduction in the postoperative LVMI at mid-term after AVR, as well as the homografts or freestyle prostheses, even though these are applied in patients with a small aortic annulus and a mean BSA of 1.41 m2.

In summary, the results of AVR with the 17-mm Regent prosthesis are promising in terms of survival, physical capacity, and hemodynamic performance. Thus, the 17-mm prosthesis could be a reasonable alternative, especially in patients with a small aortic annulus. Although we confirmed the safety of the prosthesis for 20 months of follow-up, long-term outcomes remain unclear. It is imperative to evaluate the late results of AVR with the 17-mm prosthesis. We also need to confirm our results in a larger patient group.


   References
Top
 Abstract
 Introduction
 Patients and Methods
 Results
 Comment
 References
 

  1. Rahimtoola SH. The problem of valve prosthesis-patient mismatch Circulation 1978;58:20-24.[Abstract/Free Full Text]
  2. Pibarot P, Dumesnil JG. Hemodynamic and clinical impact of prosthesis-patient mismatch in the aortic valve position and its prevention J Am Coll Cardiol 2000;36:1131-1141.[Abstract/Free Full Text]
  3. Hirooka K, Kawazoe K, Kosakai Y. Prediction of postoperative exercise tolerance after aortic valve replacement Ann Thorac Surg 1994;58:1626-1630.[Abstract/Free Full Text]
  4. Devereux RB, Reichek N. Echocardiographic determination of left ventricular mass in man. Anatomic validation of the method. Circulation 1977;55:613-618.[Abstract/Free Full Text]
  5. Pibarot P, Dumesnil JG, Jobin J, Cartier P, Honos G, Durand LG. Hemodynamic and physical performance during maximal exercise in patients with an aortic bioprosthetic valve. Comparison of stentless versus stented bioprostheses. J Am Coll Cardiol 1999;34:1609-1617.[Abstract/Free Full Text]
  6. Blais C, Dumesnil JG, Baillot R, Simard S, Doyle D, Pibarot P. Impact of prosthesis-patient mismatch on short-term mortality after aortic valve replacement Circulation 2003;108:983-988.[Abstract/Free Full Text]
  7. Sommers KE, David TE. Aortic valve replacement with patch enlargement of the aortic annulus Ann Thorac Surg 1997;63:1608-1612.[Abstract/Free Full Text]
  8. Castro LJ, Arcidi Jr JM, Fisher AL, Gaudiani VA. Routine enlargement of the small aortic root: a preventive strategy to minimize mismatch Ann Thorac Surg 2002;74:31-36.[Abstract/Free Full Text]
  9. Del Rizzo DF, Goldman BS, Christakis GT, David TE. Hemodynamic benefits of the Toronto stentless valve J Thorac Cardiovasc Surg 1996;112:1431-1446.[Abstract/Free Full Text]
  10. Kon ND, Westaby S, Amarasena N, Pillai R, Cordell R. Comparison of implantation techniques using freestyle stentless porcine aortic valve Ann Thorac Surg 1995;59:857-862.[Abstract/Free Full Text]
  11. Milano AD, De Carlo M, Mecozzi G, et al. Clinical outcome in patients with 19-mm and 21-mm St. Jude aortic prostheses: comparison at long-term follow-up Ann Thorac Surg 2002;73:37-43.[Abstract/Free Full Text]
  12. Gonzalez-Juanatey JR, Garcia-Acuna JM, Fernandez MV, et al. Influence of the size of aortic valve prostheses on hemodynamics and change in left ventricular mass: implications for the surgical management of aortic stenosis J Thorac Cardiovasc Surg 1996;112:273-280.[Abstract/Free Full Text]
  13. Kratz JM, Sade RM, Crawford Jr FA, Crumbley AJ, Stroud MR. The risk of small St. Jude aortic valve prostheses Ann Thorac Surg 1994;57:1114-1119.[Abstract/Free Full Text]
  14. Medalion B, Blackstone EH, Lytle BW, White J, Arnold JH, Cosgrove DM. Aortic valve replacement: is valve size important? J Thorac Cardiovasc Surg 2000;119:963-974.[Abstract/Free Full Text]
  15. Pibarot P, Dumesnil JG, Lemieux M, Cartier P, Metras J, Durand LG. Impact of prosthesis-patient mismatch on hemodynamic and symptomatic status, morbidity, and mortality after aortic valve replacement with a bioprosthetic heart valve J Heart Valve Dis 1998;7:211-218.[Medline]
  16. Krayenbuehl HP, Hess OM, Monrad ES, Schneider J, Mall G, Turina M. Left ventricular myocardial structure in aortic valve disease before, intermediate, and later after aortic valve replacement Circulation 1989;79:744-755.[Abstract/Free Full Text]
  17. Levy D, Garrison RJ, Savage DD, Kennel WB, Castelli WP. Prognostic implications of echocardiographically determined left ventricular mass in the Framingham heart study N Engl J Med 1990;322:1561-1566.[Medline]
  18. Sawant D, Singh AK, Feng WC, Bert AA, Rotenberg F. Nineteen-millimeter aortic St. Jude Medical heart valve prosthesis: up to sixteen years' follow-up Ann Thorac Surg 1997;63:964-970.[Abstract/Free Full Text]
  19. Ito S, Kawahito K, Tanaka M, et al. Long term effects of 19mm bileaflet aortic valve prosthesis Jpn J Cardiovasc Surg 2005;34:167-171.
  20. Amarelli C, Della Corte A, Romano G, et al. Left ventricular mass regression after aortic valve replacement with 17-mm St Jude Medical mechanical prostheses in isolated aortic stenosis J Thorac Cardiovasc Surg 2005;129:512-517.[Abstract/Free Full Text]
  21. Takaseya T, Kawara T, Tokunaga S, Kohno M, Oishi Y, Morita S. Aortic valve replacement with 17-mm St. Jude Medical prostheses for a small aortic root in elderly patients Ann Thorac Surg 2007;83:2050-2053.[Abstract/Free Full Text]
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