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Ann Thorac Surg 2007;83:2050-2053
© 2007 The Society of Thoracic Surgeons

Original Articles: Cardiovascular

Aortic Valve Replacement With 17-mm St. Jude Medical Prostheses for a Small Aortic Root in Elderly Patients

Tohru Takaseya, MD, PhD, Takemi Kawara, MD, PhD*, Shigehiko Tokunaga, MD, PhD, Michitaka Kohno, MD, Yasuhisa Oishi, MD, PhD, Shigeki Morita, MD, PhD

Department of Cardiovascular Surgery, Clinical Research Institute, National Hospital Organization, Kyusyu Medical Center, Fukuoka, Japan

Accepted for publication January 22, 2007.

* Address correspondence to Dr Kawara, Department of Cardiovascular Surgery, National Hospital Organization, Kyusyu Medical Center, 1-8-1 Chuo-ku Chigyohama, Fukuoka, 810-8563, Japan (Email: kawara{at}kyumed.jp).


   Abstract
Top
 Abstract
Introduction
 Patients and Methods
 Results
 Comment
 References
 
Background: There are few reports about the optimal prosthesis for elderly patients who have small aortic roots with an aortic annular size of less than 19 mm.

Methods: From October 2004 to October 2006, 11 women aged 70 years or older (mean age, 74.9 ± 3.5 years) underwent aortic valve replacement with a 17-mm Regent prosthesis (St. Jude Medical, St. Paul, MN), with the size determined using the manufacturer’s sizer. Clinical status and the results of preoperative and postoperative echocardiography were evaluated.

Results: The patients had a mean body surface area of 1.33 ± 0.13 m2. Preoperative average New York Heart Association (NYHA) functional class was 2.5 ± 0.7. Preoperative echocardiography showed a mean indexed effective orifice area of 0.33 ± 0.14 cm2/m2 and a left ventricular mass index of 175 ± 63 g/m2. Seven patients underwent associated procedures. Postoperative ventilation time was 14 ± 5.6 hours, and the intensive care unit stay was 1.0 ± 0.4 days. No patients died perioperatively. The NYHA functional class improved to class I in 9 patients. No obstruction of valve opening was observed. A significant increase in the mean indexed effective orifice area (0.87 ± 0.10 cm2/m2) and regression of left ventricular mass index were found (114 ± 46 cm2/m2) on postoperative echocardiography.

Conclusions: Aortic valve replacement in elderly patients with small aortic roots (less than 19 mm) using a 17-mm Regent prosthesis showed satisfactory clinical and hemodynamic results.


   Introduction
Top
 Abstract
 Introduction
Patients and Methods
 Results
 Comment
 References
 
The 19-mm Carpentier-Edwards pericardial aortic valve (Edwards Lifesciences, Irvine, CA) offers good hemodynamic performance and long-term valve durability [1]; however, there are no Carpentier-Edwards pericardial aortic valves smaller than 19 mm. Conversely, many reports have been published on the prevention of patient–prosthesis mismatch (PPM), but few on the optimal prosthesis in elderly patients who have small aortic roots of less than 19 mm. The available options in such cases are selection of a 19-mm bioprosthesis with aortic annulus enlargement or root replacement using a 19-mm stentless valve. These procedures provide satisfactory hemodynamics results to prevent PPM, but they prolong the cross-clamp time and may be technically difficult in elderly patients with small aortic roots.

Although long-term anticoagulation may be relatively contraindicated, the use of a new generation of small aortic prostheses becomes an option in elderly patients with small aortic roots. The Regent valve (St. Jude Medical [SJM], St. Paul, MN) was developed as a new device by improving the conventional SJM valve [2]. We investigated the early outcomes of aortic valve replacement (AVR) using a 17-mm SJM Regent prosthesis in elderly Japanese patients with small aortic roots of less than 19 mm.


   Patients and Methods
Top
 Abstract
 Introduction
 Patients and Methods
Results
 Comment
 References
 
Study Population
This investigation, including follow-up studies, was approved by the Ethics Committee of Kyusyu Medical Center, Japan. Informed consent was obtained from all patients for the anonymous use of their data, including follow-up information. Between October 2004 and September 2006, a 17-mm SJM valve was implanted in 12 patients in our hospital. The cohort comprised 11 women (88%), with a mean age of 76.9 ± 3.5 years and a mean body surface area (BSA) of 1.33 ± 0.13/m2. The remaining patient, a 55-year-old man, was excluded because the study only covered those 70 years or older. Preoperative clinical features are summarized in Table 1.


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  		Table 1 Preoperative Data a
 
The 11 patients underwent surgery for aortic stenosis. The most common cause of the aortic stenosis was calcification. Symptoms at admission included angina in 2 patients and syncope or arrhythmia in 4. In 5 asymptomatic patients, a surgical procedure was indicated for calcific appearance of the stenotic valve at echocardiography and high transvalvular gradients. Mean preoperative New York Heart Association (NYHA) functional class was 2.5.

Echocardiography
Standard M-mode dimensions were collected according to the criteria of the American Society of Echocardiography. All Doppler measurements were obtained as the average of three cycles in patients with sinus rhythm or more than five cycles in those with atrial fibrillation. The peak and mean gradients across the prosthesis were calculated according to the modified Bernoulli equation. The effective orifice area was calculated by using the mean of the continuity equation [(LVOT2 x 0.785 x TV1)/TV2], where LVOT is the diameter of the left ventricular outflow tract, and TVI1 and TVI2 are the time-velocity integrals at the LVOT and across the aortic valve, respectively. The left ventricular mass index (LVMI) was calculated from Reichek’s formula [3], and BSA was calculated according to the Dubois formula. Preoperative and postoperative echocardiography data were available for all of the patients. Hemodynamic data, as detected by transthoracic echocardiography, are reported in Table 2.


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  		Table 2 Operative Data a
 
Surgical Technique
The operations were performed through a median sternotomy, with moderate systemic hypothermia and use of cold blood cardioplegia. Prosthesis size was selected according to the size of the aortic annulus, which was determined by the manufacturer’s sizer. Prostheses were implanted supraannularly with noneverting mattress sutures in 8 patients, and with simple interrupted sutures in 3. Gore-Tex pledgets (W. L. Gore & Associates, Flagstaff, AZ) were used in cases with noneverting mattress sutures. The valve prostheses were implanted with their axis perpendicular to the interventricular septum. The annulus was severely calcified in all patients.

Beginning on the first postoperative day, 10,000 U of heparin calcium was administered daily subcutaneously and continued until the prothrombin time (PT) reached a therapeutic range by using sodium warfarin. PT was kept between an international normalized ratio (INR) of between 1.8 and 2.5 in all patients. The antiplatelet drug acetylsalicylic acid (100 mg/day) was also used for all patients.

Follow-Up
Postoperative follow-up was performed by contacting the patients. The mean follow-up was 13 ± 3.1 months. All patients underwent preoperative transthoracic echocardiography to evaluate ejection fraction, peak and mean gradients, mean indexed effective orifice area (EOAI), and LVMI at the time of hospital discharge, or 1 year after the operation. Echocardiographic follow-up was 100% complete.

Statistical Analysis
All data are expressed as the mean value ± standard deviation of means. A statistical comparison of the data was performed using analysis of variance, followed by Bonferroni all-pairs comparison for individual significant differences. All statistical analysis was performed using the Kaleida Graph 3.6 (Synergy Software, Reading, PA), and the Bonferroni adjusted p value < 0.05 was considered statistically significant.


   Results
Top
 Abstract
 Introduction
 Patients and Methods
 Results
Comment
 References
 
Operative Morbidity and Mortality
The 30-day operative mortality was 0%. Seven patients underwent associated procedures consisting of two coronary artery bypass graftings, one ascending aorta replacement, one mitral valve replacement and tricuspid valvuloplasty (TAP), one TAP, one open mitral commissurotomy, and one pulmonary vein isolation with radiofrequency ablation. Cross-clamping time was 145 ± 27 minutes and cardiopulmonary bypass time was 332 ± 45 minutes.

Postoperative ventilation time was 14 ± 5.6 hours. Intensive care unit (ICU) and hospital lengths of stay were 1.0 ± 0.4 and 22 ± 8.9 days, respectively. The postoperative average NYHA class was 1.1 ± 0.14, with 9 patients in class I. Figure 1 shows data on preoperative and postoperative clinical status.


Figure 1
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  		Fig 1. New York Heart Association functional class data before and after aortic valve replacement.

 
One patient was readmitted and treated for cardiac tamponade. After emergency cardiac drainage, she recovered and was discharged from hospital.

Echocardiographic Follow-Up
Echocardiographic results are summarized in Table 3. A significant reduction in peak and mean gradients was observed in all patients, with a mean difference versus preoperative values of 63.5 ± 17.2 and 19.3 ± 14.0 mm Hg, respectively. Postoperative average EOAI was 0.87 ± 0.10, with EOAI exceeding 0.85 in 9 patients.


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  		Table 3 Echocardiographic Data
 
A statistically significant reduction in mean ventricular mass was found (p < 0.01), with a mean difference of 114 ± 46 g/m2. No significant difference was observed between preoperative and postoperative mean ejection fraction. There was no structural failure of the prosthesis and no prosthetic endocarditis. One patient had a moderate paravalvular leak.


   Comment
Top
 Abstract
 Introduction
 Patients and Methods
 Results
 Comment
References
 
As the population ages, more elderly patients become candidates for AVR. Many older Japanese women are physically small in size, and as a result, their aortic valves are also small (<19 mm). The optimal prosthesis for AVR in patients with aortic roots smaller than 19 mm remains an unresolved problem in the older age group. In such cases, the three available options are selection of a 19-mm bioprosthesis with aortic annulus enlargement, root replacement using a 19-mm stentless valve, or a 17-mm mechanical prosthesis that allows implantation.

Castro and colleagues [4] have reported that aortic root enlargement can be performed with minimal added risk relative to standard AVR. Kunihara and colleagues [5] have reported good outcome of full root replacement using a stentless bioprosthesis in elderly patients. Although several good results have been reported, many surgeons believe that these procedures increase postoperative morbidity or mortality [6, 7]. They are technically more difficult, require longer cross-clamp times, and may have greater morbidity than simple valve replacement, especially in elderly patients who often have a calcified aortic root. All things considered, these guidelines are heavily dependent on the experience of the surgeon.

The patients in this study are a high-risk group because the mean age was 75 years and 63% were undergoing a concomitant procedure. Consequently, in the interest of safer surgery, we selected the 17-mm SJM prosthesis, which allows implantation without aortic annulus enlargement. No patients died. All patients could be extubated and leave the ICU on postoperative day 1 and be discharged in less than 4 weeks after operation.

The pump times and aortic clamping time were rather long for simple AVR because many of the subjects underwent concomitant procedures. Also, hospital stay was rather long because of postoperative atrial fibrillation in elderly patients. Our data demonstrate that AVR with a 17-mm SJM valve in elderly patients is a safe and effective option.

Although aortic annulus enlargement and full root replacement using stentless bioprostheses is technically more difficult, and hospital mortality and morbidity are increased, these techniques are recommended to prevent PPM [4, 5]. Many surgeons embrace the concept of valve PPM, which suggests that a small valve may not provide clinical or hemodynamic benefit to a patient in whom high cardiac output across a small EOA produces a high transvalvular gradient [8].

The SJM Hemodynamic plus and Regent were developed as new mechanical valves by improving the conventional SJM valve [2, 9]. Our echocardiographic data revealed satisfactory hemodynamic performance of 17-mm SJM valves in elderly Japanese patients. The average peak gradient, 28.4 ± 11.9 mm Hg across the 17-mm SJM valve, is equivalent to that of the 19-mm Carpentier-Edwards pericardial valve [10]. Unfortunately, the average peak gradient across the 17-mm SJM valve is higher than that of the 19-mm stentless bioprosthesis, and the EOA of the 17-mm SJM valve is smaller than that of the 19-mm Carpentier-Edwards pericardial valve and 19-mm stentless bioprosthesis [10, 11]. It has been demonstrated, however, that the EOAI of an aortic valve prosthesis should not be less than 0.85 cm2/m2 to avoid any significant gradient [7, 8]. In this study, an EOAI exceeding 0.85 cm2/m2 was seen in 82% of patients, accompanying the significant decrease of mean LVMI.

Functional improvement was excellent in our patient group. All patients were in NYHA functional classes I or II. This improvement in functional capacity was thought related to the high hemodynamic performance of the SJM valve. It is thus not advisable to use a 19-mm Carpentier-Edwards pericardial valve with aortic annular enlargement, or a 19-mm stentless bioprosthesis, with greater risk of operation to avoid PPM for elderly patients with the aortic valve of less than 19 mm. This is because the 17-mm SIM valve, with its lower risk, can provide enough valve area and does not become PPM.

The major problems associated with the use of mechanical prostheses were thromboembolism and anticoagulation-related bleeding. Long-term anticoagulation may be relatively or absolutely contraindicated in a significant number of patients aged 70 years or older.

Several reports recommend that mechanical valves do not have unlimited durability in elderly patients. Ninet [12] and Davis [13] and their colleagues, reporting on isolated mechanical AVR in patients older than 70 years, have shown low rates of anticoagulation-related complications. Sawaki and colleagues [14] have suggested that mechanical valves are not a risk for late mortality or morbidity with good PT-INR control (1.8 to 2.2). Mechanical valves have not been used because of their concomitant problems, such as bleeding and embolization; however, they can be used if warfarin control is correctly performed. Warfarin control can be performed with an INR self-management kit, so it was very useful for the subjects in this study [15].

The target INR level in this study of 1.8 to 2.5 was lower than that in reported in Europe and the United States, but almost the same as that in other hospitals in Japan [16, 17]. Our low grade INR level is convenient in Japanese elderly patients with a high risk of bleeding. The target INR level should be higher in Caucasian patients, because it has been confirmed that there is a great difference in the pharmacodynamics of warfarin between Caucasians and Asians. Use of additional antiplatelet drugs, for which efficacy and safely results are controversial [17], should be also considered to reduce thromboembolic events in Japanese patients with a low-grade INR. With well-monitored anticoagulation and platelet inhibition, serious thromboembolism has been reduced [18].

In conclusion, we believe that the 17-mm SJM valve is the optimal choice in elderly patients with small aortic roots of less than 19 mm. There was no perioperative mortality. NYHA functional class improved to class I in most patients. Echocardiography showed a significant increase in the mean EOAI and decrease in LVMI. Further long-term follow up is required to determine the complications of anticoagulation.


   References
Top
 Abstract
 Introduction
 Patients and Methods
 Results
 Comment
 References
 

  1. Carrier M, Pellerin M, Perrault LP, Hebert Y, et al. Experience with the 19-mm Carpentier-Edwards pericardial bioprosthesis in the elderly Ann Thorac Surg 2001;71(5 suppl):S249-S252.[Medline]
  2. Bach DS, Goldbach M, Sakwa MP, Petracek M, Errett L, Mohr F, SJM Regent Study Group Hemodynamics and early performance of the St. Jude Medical Regent aortic valve prosthesis J Heart Valve Dis 2001;10:436-442.[Medline]
  3. Devereux RB, Reichek N. Echocardiographic determination of left ventricular mass in manAnatomic validation of the method. Circulation 1977;55:613-618.[Abstract/Free Full Text]
  4. 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;74:31-36discussion 36.[Abstract/Free Full Text]
  5. Kunihara T, Schmidt K, Glombitza P, Dzindzibadze V, Lausberg H, Schafers HJ. Root replacement using stentless valves in the small aortic root: a propensity score analysis Ann Thorac Surg 2006;82:1379-1384.[Abstract/Free Full Text]
  6. 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]
  7. Bach DS, Cartier PC, Kon ND, Johnson KG, Deeb GM, Doty DB, Freestyle Valve Study Group Impact of implant technique following freestyle stentless aortic valve replacement Ann Thorac Surg 2002;74:1107-1113discussion 1113–4.[Abstract/Free Full Text]
  8. Dumesnil JG, Pibarot P. Prosthesis-patient mismatch and clinical outcomes: the evidence continues to accumulate J Thorac Cardiovasc Surg 2006;131:952-955.[Free Full Text]
  9. 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]
  10. Takakura H, Sasaki T, Hashimoto K, et al. Hemodynamic evaluation of 19-mm Carpentier-Edwards pericardial bioprosthesis in aortic position Ann Thorac Surg 2001;71:609-613.[Abstract/Free Full Text]
  11. 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-S313.[Medline]
  12. Ninet J, Tronc F, Robin J, Curtil A, Aleksic I, Champsaur G. Mechanical versus biological isolated aortic valvular replacement after the age of 70: equivalent long-term results Eur J Cardiothorac Surg 1998;13:84-89.[Abstract/Free Full Text]
  13. Davis EA, Greene PS, Cameron DE, et al. Bioprosthetic versus mechanical prostheses for aortic valve replacement in the elderly Circulation 1996;94(9 suppl):II121-II1251.[Medline]
  14. Sawaki S, Usui A, Abe T, Yoshikawa M, Akita T, Ueda Y. Late mortality and morbidity in elderly patients with mechanical heart valves Asian Cardiovasc Thorac Ann 2006;14:189-194.[Abstract/Free Full Text]
  15. Koertke H, Zittermann A, Wagner O, Koerfer R. Self-management of oral anticoagulation therapy improves long-term survival in patients with mechanical heart valve replacement Ann Thorac Surg 2007;83:24-29.[Abstract/Free Full Text]
  16. Aoyagi S, Arinaga K, Fukunaga S, Tayama E, Kosuga T, Akashi H. Leaflet movement of the ATS valve in the aortic position: unique behavior observed in 19-mm valves Ann Thorac Surg 2006;82:853-857.[Abstract/Free Full Text]
  17. Tominaga R, Kurisu K, Ochiai Y, et al. A 10-year experience with the Carbomedics cardiac prosthesis Ann Thorac Surg 2005;79:784-789.[Abstract/Free Full Text]
  18. Yamak B, Iscan Z, Mavitas B, et al. Low-dose oral anticoagulation and antiplatelet therapy with St. Jude Medical heart valve prosthesis J Heart Valve Dis 1999;8:665-673.[Medline]



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