Asian Cardiovasc Thorac Ann 2007;15:386-391
© 2007 Asia Publishing EXchange Ltd
Results of Isolated Valve Replacement in Hemodialysis Patients
Wataru Kato, MD,
Kazuyoshi Tajima, PhD1,
Sachie Terasawa, MD1,
Keisuke Tanaka, MD1,
Akihiko Usui, PhD,
Yuichi Ueda, PhD
Department of Cardiothoracic Surgery, Nagoya University Graduate School of Medicine
1 Department of Cardiovascular Surgery, Nagoya Daini Red Cross Hospital, Nagoya, Japan
For reprint information contact: Wataru Kato, MD, Tel: 81 52 744 2375, Fax: 81 52 744 2383, Email: kwataru{at}med.nagoya-u.ac.jp, Department of Cardiothoracic Surgery, Nagoya University Graduate School of Medicine, 65, Tsurumai-cho, Showa-ku, Nagoya, Aichi 466-8550, Japan.
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ABSTRACT
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Frequent bleeding complications and poor long-term results have been reported after valve replacement in hemodialysis patients. We use mainly bileaflet mechanical valves with low-dose warfarin therapy (target international normalized ratio, 1.8–2.0) in such cases. Data of 27 hemodialysis patients undergoing isolated valve replacement from 1993 to 2002 were retrospectively analyzed. Bileaflet mechanical valves were selected in 23 patients and bioprostheses in 4. Those with mechanical valves were treated with mild anticoagulation therapy. There were 3 (11.1%) early deaths due to ischemic colitis, interstitial pneumonia, and ventricular arrhythmia. There were 3 late deaths and 5 bleeding complications during follow-up. The overall survival rate was 85.2% at 3 years and 72.9% at 5 years. The survival rate of patients with mechanical valves was 82.6% at 3 years and 76.7% at 5 years. One patient with a bioprosthesis experienced structural valvular deterioration after 3 years. The results demonstrate an acceptable long-term outcome. A bileaflet mechanical valve managed with mild anticoagulation therapy is a reasonable strategy for hemodialysis patients.
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INTRODUCTION
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The number of long-term hemodialysis patients has been increasing in accordance with improvements in hemodialysis management.1 Calcified degeneration of the aortic valve and mitral valve annulus is common in patients on long-term hemodialysis.2–4 In addition, frequent use of arteriovenous access and compromised immunity caused by chronic renal failure increase the risk of bacterial endocarditis.5 Thus the number of hemodialysis patients requiring cardiac valve surgery is likely to increase. Mechanical valves are considered more feasible in such cases because bioprosthetic valves are more prone to calcified deterioration. However, recent studies have shown poor survival of dialysis patients after valve replacement, and no significant difference in clinical outcome between mechanical and bioprosthetic valves.6–10
Some of these studies have reported a high incidence of bleeding complications among patients undergoing mechanical valve replacement.6,7 A recent textbook indicates that mechanical valves are contraindicated for patients on hemodialysis.11 However, Ura and colleagues12 found good early and late results with bileaflet mechanical valves in dialysis patients treated with low-dose warfarin therapy. We choose mainly bileaflet mechanical valves for hemodialysis patients, and bioprosthetic valves only for those > 70 years old. Patients who receive mechanical valves are treated with mild anticoagulation therapy: target international normalized ratio (INR) of 1.8–2.0 for both aortic and mitral valve replacement. The purpose of this study was to evaluate the early and late results of isolated valve replacement in hemodialysis patients.
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PATIENTS AND METHODS
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We retrospectively analyzed 27 consecutive patients on hemodialysis undergoing isolated valve replacement at Nagoya Daini Red Cross Hospital from 1993 to 2002. Eighteen patients who had concomitant coronary artery bypass grafting (CABG) were excluded from the study. There were 15 men and 12 women. The mean age was 62.6 ± 8.8 years (range, 49–82 years). Mean duration of hemodialysis was 13.9 ± 7.3 years (range, 1–26 years). The major cause of endstage renal disease was glomerulonephritis. Only 2 patients had diabetic nephropathy (Table 1
). Mean preoperative New York Heart Association functional class was 2.5 ± 0.8.
In hemodialysis patients, valve replacement with a mechanical prosthesis is classified as a class II or IIa indication, and valve replacement with a bioprosthesis is classified as a class III indication by the American College of Cardiology/American Heart Association Task Force on Practice Guidelines.13 We mainly selected bileaflet mechanical valves: CarboMedics standard mitral and reduced aortic valves (CarboMedics, Inc., Austin, TX, USA) were used in 21 patients; ATS AP valves (ATS Medical, Inc., Minneapolis, MN, USA) were used in 2 patients who had a small aortic annulus. Bioprosthetic Medtronic Mosaic valves (Medtronic, Inc., Minneapolis, MN, USA) were implanted in 3 patients > 70 years of age, and one received a stentless valve (Medtronic Freestyle).
Three patients required emergency surgery. All operations were performed using cardiopulmonary bypass (CPB) and cardiac arrest with cold blood cardioplegia. Deep hypothermic circulatory arrest was required in 2 cases due to severe calcification of the ascending aorta. Causes of valve disease were calcified stenosis in 22 patients, rheumatic disease in 3, annuloaortic ectasia in 1, and infectious endocarditis in 1. The patients who had a bioprosthesis were aged 70–82 years. Concomitant procedures were the maze operation (modified Cox III) in 4 and tricuspid valve annuloplasty in 2 (Table 2). All patients received routine hemodialysis on the day before the operation. Only hemofiltration was conducted during CPB. At the end of CPB, the serum potassium level was < 4.0 mEq·L–1. Hemodialysis resumed on the 1st postoperative day. If the patient was hemodynamically unstable, continuous hemofiltration was applied. Patients with a mechanical valve were managed with warfarin therapy. Those who had a bioprosthesis were also given warfarin for the first 3 months after surgery. Warfarin therapy was started generally on the 2nd postoperative day. No antiplatelet drugs were used for either type of valve. Warfarin was adjusted to maintain an INR of 1.8 to 2.0 after all valve replacements. The mean follow-up period was 44 ± 26 months (range, 12–109 months). One patient was lost to follow-up 40 months after the operation.
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RESULTS
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As most patients (25/27) had severe calcified valvular lesions due to chronic uremia, mean aortic cross clamp time (134 ± 44 min; range, 72–207 min) and operative time (424 ± 121 min; range, 270–672 min) were prolonged. Mean volume of hemofiltration during CPB was 5,735 ± 2,089 mL (range, 1,270–12,000 mL). Postoperative mechanical ventilation extended to 35 ± 44 hours (range, 16–208 hours), and the mean hospital stay was 41 ± 25 days (range, 15–111 days). Hemodialysis was started on the 1st postoperative day in all except 2 patients who required continuous hemofiltration because of hemodynamic instability. Postoperative complications are listed in Table 3. Both cases of ischemic colitis were operated on an emergency basis; there were severe calcified lesions in the celiac and superior mesenteric arteries, and hemodynamic instability was present before and after surgery. The 30-day mortality was 11%. New York Heart Association functional class recovered to 1.3 ± 0.6 early postoperatively (Figure 1) and remained at 1.3 ± 0.6 during long-term follow-up. There were 7 valve-related complications (Table 4), but no thromboembolic events. Redo valve surgery was performed successfully in a patient who developed prosthetic valve endocarditis. One patient who had a bioprosthesis in the mitral position suffered heart failure due to severe regurgitation caused by structural valve deterioration 3 years after the operation. She underwent medical treatment alone because she refused reoperation, and died of gastrointestinal bleeding 43 months postoperatively. One patient was hospitalized for heart failure caused by atrial fibrillation that was converted to normal sinus rhythm with an antiarrhythmic drug. One patient died of ventricular arrhythmia during hemodialysis 3 months after surgery. The overall survival rate was 85.2% at 3 years and 72.9% at 5 years. The survival rate of patients with mechanical valves was 82.6% at 3 years and 76.7% at 5 years (Figure 2).
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DISCUSSION
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Fishbein and colleagues14 reported accelerated calcification as a complication of glutaraldehyde-fixed porcine valves in dialysis patients. Lamberti and colleagues15 also found accelerated calcification of porcine valves in patients with endstage renal disease. After these early reports, the concept of accelerated calcification of bioprosthetic valves in dialysis patients was widely accepted, and mechanical valves have mainly been used in such patients. However, recent studies have noted a poor survival rate of dialysis patients undergoing valve replacement, with no significant difference in late results among those with mechanical and bioprosthetic valves (Table 5).6–10 Some have reported a high incidence of bleeding complications and stroke associated with mechanical valves. Even bioprosthetic valves may have a risk of early deterioration due to accelerated calcified degeneration, and these reports concluded that a bioprosthetic valve is also a suitable option for dialysis patients because they are expected to have a poor survival rate.
In the present study, the overall survival rate of dialysis patients after isolated valve replacement of 85.2% at 3 years and 72.9% at 5 years is clearly better than in previous reports, and might be due to differences in concomitant procedures and postoperative anticoagulation therapy for those with mechanical valves. We excluded patients with CABG because we tried to clarify the long-term result of isolated valve replacement. Some studies reported that concomitant CABG increased operative mortality and the risk of cardiac death in the follow-up period.9,10 In the 18 patients who received valve replacement and CABG in the same period, survival was 55.4% at 3 years and 36.9% at 5 years, which was significantly lower than in the isolated valve replacement group ( p = 0.036). The major etiology of renal failure in patients who required CABG was diabetic nephropathy. Exclusion of concomitant CABG patients resulted in fewer diabetic patients; thus there were only 2 diabetic patients in this study. Hirose and colleagues16 reported that diabetic patients on hemodialysis undergoing CABG had significantly worse long-term survival. Therefore, concomitant CABG might increase late mortality in patients who have undergone valve replacement.
Some previous studies reported a high incidence of bleeding complications or stroke associated with mechanical valves. Lucke and colleagues6 noted that patients with mechanical valves suffered a high rate of bleeding complications and cerebrovascular accidents. Brinkman and colleagues7 also found a high rate (17/34) of bleeding episodes and stroke in patients with a mechanical valve; this would reduce the survival rate. We managed hemodialysis patients with a mechanical valve using low-dose warfarin. Our target INR was 1.8–2.0 for both aortic and mitral valve replacements. This is because minor bleeding complications (such as nasal bleeding or bleeding from cannulation sites) often occur among hemodialysis patients receiving warfarin therapy when their INR exceeds 2.0.
In this study, even patients receiving mechanical valves clearly showed a lower morbidity. During the mean follow-up of 44 ± 26 months, there were bleeding complications in 4 of 20 survivors, and no thromboembolic events occurred. Recently, lower-intensity anticoagulation therapy has been demonstrated to result in a lower rate of bleeding complications with bileaflet mechanical valves, without increasing the rate of thromboembolism.17 Ura and colleagues12 reported an excellent clinical outcome with bileaflet mechanical valves under low-dose warfarin therapy in hemodialysis patients. It has been shown that such patients have multiple disorders of hemostasis.18 They always use heparin for anticoagulation during hemodialysis 3 times a week. Thus they have a high risk of bleeding complications, and mild anticoagulation therapy may reduce the chance of bleeding complications and result in better long-term clinical outcomes.
Bioprostheses were used in only 4 patients because they were selected exclusively for those over 70 years old. There was one incidence of early structural valve deterioration. Some recent studies reported that early structural valve deterioration was uncommon, even in dialysis patients, but others showed that it occurred even in new-generation bioprosthetic valves.7,8 Therefore, we recommend that bioprostheses should be limited to elderly patients only. A bileaflet mechanical valve managed with mild anticoagulation therapy is a reasonable strategy for isolated valve replacement in hemodialysis patients.
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REFERENCES
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- Maher ER, Young G, Smyth-Walsh B, Pugh S, Curtis JR. Aortic and mitral valve calcification in patients with end-stage renal disease. Lancet 1987;2(8564):875–7.[Medline]
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ABSTRACT
INTRODUCTION
