Mitral valve repair in uremic congestive cardiomyopathy

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Mitral Valve Repair in Uremic Congestive Cardiomyopathy Jen-Ping Chang, MD, and Chiung-Lun Kao, MD Division of Thoracic and Cardiovascular Surgery, Chang Gung Memorial Hospital at Kaohsiung, Taiwan, Republic of China

Background. There is limited reported experience on mitral valve repair in patients with chronic renal failure. This study was designed to evaluate the outcomes of mitral valve repair in patients suffering from congestive heart failure as a result of uremic cardiomyopathy and severe mitral regurgitation requiring chronic hemodialysis. Methods. From 1995 to 2002, 5 women, ages 41 to 64 years (53 ⴞ 8 years), with uremic congestive cardiomyopathy and end-stage renal disease on chronic hemodialysis who underwent mitral valve repair for severe mitral regurgitation were identified retrospectively and followed for clinical and echocardiographic outcomes. The preoperative New York Heart Association functional class was 3.8 ⴞ 0.45. Results. All patients had good results immediately after surgical mitral valve repair with no more than mild

mitral regurgitation. During the follow-up at an average of 22.4 ⴞ 14.9 months (range, 3 to 41 months) postoperatively, all patients returned to New York Heart Association functional class I. Neither mitral calcification nor increasing peak transmitral gradient (or decreasing mitral valve orifice area) was notable by two-dimensional echocardiography. No reoperation was required. Conclusions. Although accelerated calcification of the repaired mitral valve and high incidence of failure of the reconstruction had been reported in patients with endstage renal disease, based on our experience we advocate mitral valve repair when this can be safely performed, especially in patients with uremic congestive cardiomyopathy, in view of the added advantage of retaining the native valve in such patients. (Ann Thorac Surg 2003;76:694 –7) © 2003 by The Society of Thoracic Surgeons

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for organic mitral valvulopathy as a surgical option among patients with ESRD and severe MR requiring chronic HD has been reported in limited articles, and the conclusions remain controversial [11, 12]. The purpose of this study was to evaluate the intermediate-term results of mitral valve repair when performed in patients with UCC and severe MR, requiring maintenance HD for ESRD.

he burden of cardiac disease is high in patients with end-stage renal disease (ESRD) requiring chronic hemodialysis (HD). Uremic congestive cardiomyopathy (UCC) with significant mitral regurgitation (MR) results from volume overload and causes left ventricular dilatation and systolic dysfunction owing to arteriovenous shunting, salt and water overload, and anemia. The prognosis for this cardiac disorder is poor [1, 2]. Interventions with potential for improving UCC, including using angiotensin-converting enzyme inhibitors, normalizing the underlying risk factors [1, 2], persistent ultrafiltration [3], and renal transplantation [4], have been under investigation. In patients with chronic HD, the high risk of dystrophic calcification of a biologic prosthetic valve has been reported [5, 6]. On the other hand, anticoagulant-related complications after mechanical prosthetic valve replacement have been emphasized as well [7, 8]. Mitral valve repair is clearly superior to replacement in the general population when this can be safely performed in view of the advantages of reduced operative mortality and complication rate, preservation of left ventricular function, freedom from anticoagulation, and lower long-term risk of endocarditis [9, 10]. Assessment of mitral valve repair Accepted for publication March 28, 2003. Address reprint requests to Dr Chang, Division of Thoracic and Cardiovascular Surgery, Chang Gung Memorial Hospital at Kaohsiung, 123, Ta-Pei Rd, Niao Sung Hsiang, Kaohsiung Hsien, Taiwan, R.O.C.; e-mail: [email protected].

© 2003 by The Society of Thoracic Surgeons Published by Elsevier Inc

Material and Methods Hospital records were reviewed for all patients with ESRD receiving chronic HD who underwent mitral valve repair and other concomitant procedures (tricuspid valve repair, radiofrequency maze IV procedure) for UCC with severe MR at the Chang Gung Memorial Hospital at Kaohsiung. Patients with evidence of primary organic mitral valvulopathy or ischemic heart disease before HD or patients without a preexisting history of ESRD who required HD only during the perioperative period were excluded from the study group. Between January 1995 and August 2002, 197 patients underwent mitral valve repair. Among these patients, there were 5 women (average age, 53 ⫾ 8 years; range, 41 to 64 years) with ESRD undergoing HD at the time of surgery and continuing thereafter. The preoperative New York Heart Association functional class was 3.8 ⫾ 0.45. In the 12 months before surgery, these patients had 3 to 5 (mean, 3.1 ⫾ 0.9) hospital admissions for congestive heart failure. The left ventricular ejection fraction by echocar0003-4975/03/$30.00 PII S0003-4975(03)00673-8

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Table 1. Patient Demographics, Echocardiographic and Cardiac Catheterization Features, and Operative Procedures

Age (y) 56 64 50 41 54 a

Sex

NYHA Class

Dialysis Duration (mo)

F F F F F

4 4 3 4 4

62 91 29 3 33

Associated Diseases DM, HP, HT DM, HP, HT DM, HP, HT HT, HP HT

EF

LVEDP/CWP (mm Hg)

MR Severity (0 – 4)

0.37 0.27 0.44 0.35 0.67a

31/33 37/37 27/30 38/41 21/23

4 4 4 4 4

Operative Procedures (ring size, mm) MAP (32) MAP (28) MAP (30), TAP MAP (32), TAP MAP (32), TAP, RFM

Measured during 8.0 ␮g · kg⫺1 · min⫺1 dobutamine infusion.

CWP ⫽ capillary wedge pressure; DM ⫽ diabetes mellitus; EF ⫽ ejection fraction; HP ⫽ hyperparathyroidism; HT ⫽ hypertension; LVEDP ⫽ left ventricular end-diastolic pressure; MAP ⫽ mitral annuloplasty; MR ⫽ mitral regurgitation; NYHA ⫽ New York Heart Association; RFM ⫽ radiofrequency maze procedure; TAP ⫽ tricuspid annuloplasty.

diography was 0.42 ⫾ 0.15 (range, 0.27 to 0.67). The only patient with an ejection fraction of 0.67 was receiving a dobutamine infusion at a dose of 8.0 ␮g · kg⫺1 · min⫺1 and maximal vasodilator therapy preoperatively. Maintenance HD had been undergone for an average of 43.6 ⫾ 33.8 months (range, 3 to 91 months) at the time of surgery, and for 66.1 ⫾ 45.1 months (range, 17 to 123 months) at the time of follow-up. All patients were hypertensive. Four of the 5 patients exhibited symptoms of secondary hyperparathyroidism, and 3 had insulin-dependent diabetes. Two of the 5 patients underwent mitral valve repair only. Three underwent concomitant tricuspid valve repair, and 1 underwent concomitant radiofrequency maze IV procedure that had been developed in our center for ablation of associated chronic atrial fibrillation [13]. Mitral valve repair with the CarpentierEdwards Physio Annuloplasty Ring (Edwards Lifescience LLC, Irvine, CA) was performed for pure regurgitation in all patients for the underlying etiology of mitral annularventricular apparatus dilation secondary to the altered left ventricular geometry that was exclusively noted in UCC and dilated cardiomyopathy. The height and area of the anterior mitral leaflet and intertrigonal distance were measured under direct vision. Then a ring one size less than the corresponding measured values was selected for implantation. No patient required a complex repair. No patient had significant mitral calcification at the time of surgery. The detailed patient demographics, echocardiographic and cardiac catheterization features, and operative procedures are listed in Table 1.

Results Medical records were reviewed for operative mortality, subsequent mortality, morbidity, and requirement for reoperation. All patients had effective resolution of mitral regurgitation after surgery and were weaned from cardiopulmonary bypass with aid of low-dose catecholamine parenteral infusion only. We dialyzed our patients on the day before operation and subsequently on the second postoperative day, then resumed usual maintenance HD protocol. Patients exclusively underwent modified ultrafiltration concomitantly during cardiopulmonary bypass for fluid regulation. No patient required

prolonged mechanical ventilator support or hospital stay. The average mitral valve orifice area and peak mitral valve gradient obtained by predischarge twodimensional echocardiography 7 days after surgery was 2.6 ⫾ 0.4 cm2 (range, 2.2 to 3.2 cm2) and 10.6 ⫾ 0.9 mm Hg (range, 10 to 12 mm Hg), respectively. During the follow-up period of 22.4 ⫾ 14.9 months (range, 3 to 41 months), there was no late mortality or morbidity. All 5 patients are in New York Heart Association functional class I and have remained in sinus rhythm, including the patient with preoperative chronic atrial fibrillation after successful concomitant radiofrequency maze IV procedure. Postoperative echocardiography at 1 week, 3 months, and then every 6 months revealed both mitral and tricuspid valves functioning with less than mild regurgitation without any detectable leaflet calcification or evidence of decreased mitral valve orifice area (average, 2.6 ⫾ 0.5 cm2; range, 2.2 to 3.5 cm2) or increased peak transmitral gradient (average,10.8 ⫾ 1.3 mm Hg; range, 10 to 13 mm Hg). Improved postoperative ejection fraction of 0.56 ⫾ 0.10 (range, 0.47 to 0.69) and reduced left ventricular end-diastolic (from 168.4 ⫾ 20.1 mL/m2 to 113.2 ⫾ 36.3 mL/m2) and end-systolic volume (from 91.0 ⫾ 37.7 mL/m2 to 51.6 ⫾ 26.3 mL/m2) were demonstrated, too. The postoperative echocardiographic data and clinical evolution in these patients are summarized in Table 2.

Comment In chronic uremia, cardiomyopathy manifests as systolic dysfunction, inadequate left ventricular hypertrophy, or left ventricular dilatation. These cardiac disorders are known to be associated with an adverse prognosis [1, 2]. In our 5 patients, all had cardiomyopathy manifested as inadequate left ventricular hypertrophy and dilatation after a long period of HD without previous evidence of primary mitral valvulopathy or ischemic heart disease. Considering the systolic dysfunction, there was a patient with ejection fraction of 0.67; however, this value was measured when she was receiving high-dose catecholamine and vasodilator support for intractable heart failure. Thus, all 5 of these patients could be included in the

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CHANG AND KAO MITRAL REPAIR AND UREMIC CARDIOMYOPATHY

Table 2. Postoperative Echocardiographic Data and Clinical Evolution Total (n ⫽ 5) Variables

Pre 2

ESV (mL/m ) EDV (mL/m2) EF NYHA class MR (grade 0 – 4) PTMG (mm Hg) MVOA (cm2) Follow-up (mo)

Post

91.0 ⫾ 37.7 51.6 ⫾ 26.3 168.4 ⫾ 20.1 113.2 ⫾ 36.3 0.42 ⫾ 0.15 0.56 ⫾ 0.10 3.8 ⫾ 0.45 1 4 0.6 ⫾ 0.5 10.6 ⫾ 0.9a 10.8 ⫾ 1.3 2.6 ⫾ 0.4a 2.6 ⫾ 0.5 22.4 ⫾ 14.9

p Value ⬍0.05 ⬍0.05 NS ⬍0.001 ⬍0.001 NS NS

a

Measured by predischarge transthoracic echocardiography 7 days after mitral valve repair.

EDV ⫽ end-diastolic volume; EF ⫽ ejection fraction; ESV ⫽ endsystolic volume; MR ⫽ mitral regurgitation; MVOA ⫽ mitral valve orifice area; NS ⫽ not significant; NYHA ⫽ New York Heart Association; PTMG ⫽ peak transmitral gradient.

category of UCC. The documented risk factors for these disorders include older age, ischemic heart disease, hyperparathyroidism, hypertension, anemia, smoking, and diabetes mellitus. Classic strategies for improving these particular disorders include normalization of hematocrit with erythropoietin, improvements in uremia therapy, and using angiotensin-converting enzyme inhibitors [1, 2]. Recently, persistent ultrafiltration is advocated for prevention of unrecognized hidden fluid overload in a patient with UCC [3]; however, it is time-consuming and lacks long-term study of its effectiveness. Parfrey and colleagues [4] suggest that correction of the uremic state by renal transplantation leads to resolution of UCC. After cardiac surgery, all 5 of our patients have been included as candidates for renal transplantation; however, transplantation is not without drawbacks and donor organ shortage is still a worldwide problem. Hence, at present, there is no definitive therapeutic modality available in patients with UCC and severe MR who suffer from intractable congestive heart failure despite maximal medical treatments. In patients with dilated cardiomyopathy, MR leads to a cycle of more volume overload of the already dilated left ventricle, with further annular dilation, worsened MR, and congestive heart failure, and it predicts a poor survival [14]. Bolling and colleagues [15, 16] advocate liberal use of mitral valve repair in patients with endstage cardiomyopathy and MR to reduce left ventricular overload and, consequently, end-diastolic volume to achieve symptomatic improvement and survival benefit. As this concept is becoming more popular, more patients are undergoing mitral valve procedures for end-stage cardiomyopathy [17–19]. Actually, our strategy is an extension of this valuable concept. Hypothetically, worsening heart failure in patients with UCC and significant MR could mimic the pathophysiologic disorder in patients with dilated cardiomyopathy resulting from annular dilation and MR secondary to the chronic volume overloading. This pathophysiologic process could be stabi-

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lized or improved by correction of the MR. Considering the high risk of dystrophic calcification with biologic prosthetic valves [5, 6] and documented anticoagulantrelated complications after mechanical prosthetic valve replacement [7, 8] in patients with ESRD on chronic HD, neither type of valvular prosthesis satisfies the demand. Hence, in this particular group of patients, mitral valve repair is clearly superior to replacement when this can be safely performed in view of the advantages of reduced operative mortality and complication rate, preservation of left ventricular function, freedom from anticoagulation, and lower long-term risk of endocarditis [9, 10]. There is limited reported experience on mitral valve repair in patients with chronic renal failure. Assessment of mitral valve repair for organic mitral valvulopathy as a surgical option among patients with ESRD with severe MR requiring chronic HD has been reported by Sim and coworkers [11] in a patient with ruptured chordae and another with rheumatic valvulopathy with favorable short-term results. In contrast, Lewandowski and colleagues [12] reviewed their experiences of mitral valve repair in 10 patients with ESRD and moderate to severe MR (4 ischemic, 3 infective, 2 rheumatic, and 1 degenerative) who were receiving chronic dialysis and found that despite good early surgical result, accelerated calcification of the repaired mitral valve and a rapid increase in postoperative transmitral gradient resulted in high incidence of failure of the reconstruction. Importantly, the pathologic anatomy of the MR in our patients with UCC is quite different from those reported patients. The mitral leaflets and the subvalvular apparatus are almost intact by gross inspection in our patients, and the functional MR is predominantly believed to occur as a result of progressive annular dilation with subsequent loss of coaptation of the valve leaflets. These findings are quite similar to the findings in patients with dilated cardiomyopathy and severe MR [20]. Consequently, all our patients underwent mitral valve repair as suggested by Bolling and colleagues [16] by means of a remodeling ring annuloplasty, with implantation of an undersized semiflexible remodeling ring (Carpentier-Edwards Physio Annuloplasty Ring) only. No patient required a complex repair such as leaflet resection or chordal transfer, which may be required for reconstruction of the organic mitral valvulopathy. We believe that the simplicity of this reparative technique applied to our patients without excessive manipulation of the mitral structures strongly corresponds to prevention of accelerated calcification of the repaired valve or a rapid increase in transmitral gradient. The peak transmitral gradients after mitral valve repair with implantation of an undersized semiflexible remodeling ring in our patients are a little bit higher than the gradients reported by Bolling and colleagues [15, 16]; however, the measured mitral valve orifice area of 2.6 ⫾ 0.5 cm2 after the follow-up period of 22.4 ⫾ 14.9 months is satisfactory. There is not any detectable late leaflet calcification or evidence of increased transmitral gradient or decreased mitral valve orifice area as reported by Lewandowski and colleagues [12]. Based on our limited experience, we believe the

stable, mild peak gradients across the mitral valve will last longer and might be better tolerated in our patients. In our patients, not only did the functional class improve but also no patient has had a worsening clinical status during follow-up. Importantly, the echocardiographic analyses in these patients revealed a significant trend toward decreased left ventricular volumes after the operation without clinical evidence of shifting of intravascular volume status. Ejection fraction increased also, but did not reach statistical significance. Improvement in echocardiographic measurements of ventricular function are not necessarily anticipated, because left ventricular function has been shown to decrease after mitral valve repair, presumably as a result of loss of the lowimpedance left atrial chamber associated with correction of mitral regurgitation, which might be expected to lead to further systolic impairment of preexisting ventricular dysfunction [15]. Finally, the role of the concomitant ablative procedure for chronic atrial fibrillation should be emphasized. Because anticoagulant-related complications in this particular group of patients are serious [7, 8], we believe that restoration of sinus rhythm and atrial transport function in patients with ESRD on chronic HD after successful ablative procedure will achieve further improvement in quality of life and survival benefit. In conclusion, based on our very limited experience, we advocate mitral valve repair when this can be safely performed in view of the added advantage of retaining the native valve for patients with UCC and severe MR. Although longer term follow-up in a larger population is mandatory, mitral valve repair may allow new strategies in such patients, yielding improvement in symptomatic status and echocardiographic outcomes.

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