Asian Cardiovasc Thorac Ann 2005;13:261-266
© 2005 Asia Publishing EXchange Ltd
Analysis of Recurrent Mitral Regurgitation after Mitral Valve Repair
Hong Ju Shin, MD,
Yong Jik Lee, MD,
Suk Jung Choo, MD,
Hyun Song, MD,
Cheol Hyun Chung, MD,
Jae Won Lee, MD
Department of Thoracic and Cardiovascular Surgery, Asan Medical Center, University of Ulsan College of Medicine, Seoul, South Korea
For reprint information contact: Jae Won Lee, MD Tel: 82 2 3010 3580 Fax: 82 2 3010 6966 Email: jwlee{at}amc.seoul.kr, 388-1 Pungnap-2dong, Songpa-gu, Seoul 138-736, South Korea.
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ABSTRACT
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Mitral valve repair was performed in 437 patients with mitral regurgitation from January 1994 to January 2002. The causes of mitral regurgitation were degenerative in 238 (54%), rheumatic in 134 (31%), and others in 65 (15%). The most frequently employed surgical techniques were ring annuloplasty in 417 (95%) cases, new chordae formation in 216 (50%), and quadrangular resection in 117 (27%). The mean follow-up was 29.04 ± 22.81 months. There were 5 (1.2%) early and 5 (1.2%) late deaths. The reoperation rate was 1.6% with 41 (9%) cases of recurrent mitral regurgitation. Of these 22 were procedure-related: incomplete repair in 13, discordant new chordal length in 7, suture dehiscence and leaflet perforation in 1 case each. There were 19 cases of valve related failures: progression of rheumatic disease in 18 and subacute infective endocarditis in 1. Valve-related failure strongly correlated with progression of rheumatic disease. As initial operative success was the prime determinant of repair durability, intraoperative repair assessment with transesophageal echocardiography was essential.
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INTRODUCTION
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Mitral valve (MV) repair is now accepted as the procedure of choice for the treatment of mitral regurgitation (MR).1–2 The advantages over valve replacement include greater freedom from reoperation and endocarditis, superior preservation of left ventricular function, and improved survival.2–5 Despite the relative durability of MV repair, the potential for failure and recurrence remain major drawbacks. As recurrence of MR may not always be procedure-related, we reviewed our experience of MV repair to assess factors that may lead to severe MR secondary to repair failure, with aims to eventually improve the long-term results.
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PATIENTS AND METHODS
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From January 1994 to January 2002, 437 patients undergoing MV repair with or without concomitant cardiac procedures were included in the study. Patients with pure mitral stenosis were excluded. The mean age was 48 ± 15.2 years (range, 12 to 82 years), and there were 206 (47%) men and 231 (53%) women. Preoperative echocardiograms revealed MR grade III in 65 (15%) and grade IV in 372 (85%) patients (Table 1
). The etiologies are listed in Table 2; degenerative and rheumatic disease accounted for the majority of the study population.
The heart was approached via a standard median sternotomy, with bicaval cannulation for drainage, and cardiopulmonary bypass under moderate hypothermia. The MV was exposed through a left atriotomy incision along the Waterston groove. Myocardial protection was afforded by combined intermittent antegrade and retrograde cold blood cardioplegia. The mean cardiopulmonary bypass and aortic crossclamp times were 134 ± 56 min and 95 ± 41 min, respectively. Mitral pathology was determined by direct intraoperative visual inspection followed by histologic confirmation (Table 3). Annular dilatation was the most common cause of MR, followed by chordal elongation and rupture, with the combined incidence of chordal elongation and rupture representing the greatest incidence of MR (Table 3). The operative techniques and concomitant surgery are summarized in Table 4. Generally, techniques of MV repair comprised annuloplasty, new chordae formation, and quadrangular resection, with ring annuloplasty being performed in over 95% of cases. The types of ring used were Carpentier-Edwards (n = 295; Baxter Healthcare, Irvine, CA, USA), Duran (n = 113; Medtronic, Inc., Minneapolis, MN, USA), and the Physio-Ring (n = 9; Baxter Healthcare, Irvine, CA, USA).
The mean follow-up duration was 29.04 ± 22.81 months and it was 96.1% complete with 17 patients lost to follow-up. Medical records were reviewed and the patient, family, or referring physicians were contacted for data collection. Echocardiography was performed in the early postoperative period prior to discharge and later during the follow-up. Recurrence of MR was defined as greater than 3+ or 4+ MR on a scale of 0 to 4+, on the last follow-up echocardiogram. Incomplete repair was defined as > 2+ MR on immediate follow-up echocardiography. Disease progression was classified according to etiology as rheumatic motion limitation, commissural MR, valve prolapse or chordae elongation, and functional MR which was separate from procedure failure.3
Univariate analysis was performed to identify the independent risk factors for recurrent MR. The relationship between etiology, operative- and valve-related risk factors were analyzed by univariate analysis (chi-squared test). A p value of less than 0.05 was considered significant. The cumulative survival and freedom from reoperation were assessed by the Kaplan-Meier method.
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RESULTS
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There were 5 (1.1%) hospital deaths from sepsis (n = 3), low cardiac output (n = 1), and tracheal bleeding (n = 1). There were also 5 late deaths (1.1%). The freedom from late mortality is shown in Figure 1. Reoperation was required in 7 patients (1.6%), of whom 2 underwent repeat MV repair and 5 needed MV replacement (Figure 2). The postoperative echocardiographic data are summarized in Table 5. Recurrent MR (grade III–IV) was noted in 41 (9.4%) patients. The underlying causes of recurrent MR are summarized in Table 6. The relationship between recurrence and etiology of MR is shown in Table 7. There was no single etiological factor significantly affected the incidence of MR recurrence. The relationship between recurrent MR and procedure-related causes is summarized in Table 8. Incomplete repair was found to be a major risk factor for MR recurrence (p < 0.001). The recurrence of MR per procedure-related and valve-related cause is summarized in Table 9. There was no significant difference between the two groups of patients with regard to the underlying etiology of MV disease.
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DISCUSSION
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Mitral valve repair is usually the treatment of choice for MR as it is associated with relatively low early and late mortality rates and also avoids many of the potential complications of prosthetic valve replacement.6 This study demonstrated satisfactory early and late results for MV repair, with early (1.1%) and late (1.1%) operative deaths comparable to other series where operative mortality ranged between 1.3% and 5.5%.2,4,6–7 Our reoperation rate was significantly lower than that of other recent series.3,8–9 While the follow-up duration was relatively short, according to the hazard phase as reported by the Cleveland clinic, our study showed good long-term results.9
Recurrence of MR is an important consideration and many studies have focused on the effects of etiology and repair techniques on the repair durability.2–4,6–7 According to Lessana and colleagues,8 the underlying disease type is an important factor in determining the outcome of mitral repair, with degenerative etiology showing a lower tendency for recurrence. Duran and colleagues10–11 also achieved superior results of MV repair in degenerative or ischemic valve disease compared to rheumatic disease. The disease pattern in this study showed a predominance of degenerative MV disease, defined as MR caused by prolapse or chordal elongation, tear, or rupture, unrelated to either rheumatic or ischemic disease. The MR of degenerative origin tended to be more localized. It is our contention that degenerative MR is probably more often acquired secondary to such causes as long-standing hypertension rather than being hereditary or familial, although connective tissue disease may also be causative. Myxomatous degeneration was defined as MR caused by thickening and myxomatous changes of the leaflets and subvalvular apparatus. Accordingly, the regurgitation in such cases is more diffuse and complex. We rarely observed this type of MR in our series. As the terminology of degenerative disease may be inclusive of similar but definitely distinct entities, we also ruled out the presence of fibroelastic deficiency.
Although MV repair is contraindicated in the presence of severe calcification or extensive fibrosis, good results have been achieved in selected patients with rheumatic valve disease.8 Incomplete repair due to technical reasons was also found to be a significant risk factor for recurrence. Gillinov and colleagues3 reported a relatively low recurrence rate of 7% due to incomplete repair in patients with degenerative etiology, contrasting strongly with our 32% (Table 8
). The effect of operative procedure on MR recurrence was difficult to determine. A review of our early experience showed the degree of residual MR at the time of surgery to be important in determining recurrence. As demonstrated by others, intraoperative transesophageal echocardiography (TEE) was essential for assessing immediate intraoperative integrity of the repair.12–14 According to Saiki and colleagues,14 intra-operative TEE measurements of residual MR did not change significantly on early and late postoperative follow-up TTE. In the past, the fluid filling test was popular for determining the success of MR repair. However, the accuracy of this method was limited by differences in the functioning of the mitral apparatus resulting from the differences in spatial arrangement between the static resting heart and the volume-filled dynamically contracting ventricle8,15. We also relied on TEE for intraoperative assessment of significant residual MR which would necessitate placing the patient on bypass again for further surgery. Although postoperative grade 1+ or 2+ MR on intraoperative TEE did not increase morbidity or mortality, it did lead to a significantly higher rate of MR recurrence requiring reoperation, thus stressing the importance of achieving an initial leak-proof repair.12
Gillinov and colleagues3 classified the causes of failed mitral repair as procedure-related (rupture of previously shortened chordae, suture dehiscence, incomplete initial operation) and valve-related (progressive disease, endocarditis). They found a high proportion of procedure-related repair failures in patients with degenerative disease.16 However, there was a greater overall proportion of valve-related failure (57% vs. 30%), which may have been due to variations in the operative modifications.3 In this study, a greater incidence of procedure-related failure (53% vs. 47%) was observed, but direct comparison with the Gillinov series may not be appropriate as a number of factors not included may be involved. We observed a greater proportion of procedure-related failure (65% vs. 35%) in degenerative disease. This may be attributed in part to the higher incidence of procedure-related failures in the earlier phase of this series (1994–7), with improvement over time as more experience was gained.
Most of the new chordae were created to the anterior mitral leaflet; however, we did not encounter any significant differences in the recurrence rate according to the site of new chordal attachment. The relatively greater incidence of early recurrence of MR in the earlier part of this series was thought to be due mainly to implantation of too short a chorda. Redundancy in chordal length caused problems of delayed rather than immediate or early postoperative MR. The delayed nature was thought to be due to degenerative disease with further progression of the fibrous papillary tip elongation or tear. Therefore, recurrence due to chordal redundancy was less related to technical error. These findings were confirmed by echocardiography and direct intraoperative visualization. In rheumatics, the 73% rate of valve-related failure was significantly higher than the 27% incidence of procedure-related failure, but this was only to be expected because of the progressive nature of the disease in rheumatics.8 Therefore, greater consideration is warranted in selecting MV repair candidates among rheumatics.
In young patients with severe pan-valvular regurgitation, there is no argument regarding the necessity for surgery. However, in the patient presenting with complex MR but no signs of heart failure or deterioration in cardiac function, surgery should be delayed while maintaining close observation. If the MR is simple and easily reparable, surgery should be performed without delay. Patients presenting with symptoms, irrespective of MR type or degree, should also be operated on without delay. In addition, the presence of significant hemolysis or mitral stenosis should be an indication for immediate surgery, irrespective of the degree of MR. In conclusion, MV repair for MR is a relatively safe procedure. In rheumatics, disease progression is a more important cause of failure than the surgical procedure. Regardless, the degree of leakage at the initial operation is the most important risk factor in predicting repair failure. Therefore, intraoperative TEE evaluation is crucial for ensuring good long-term results.
Presented at the 12th Annual Meeting of Asian Society for Cardiovascular Surgery, Istanbul, Turkey, April 19–22, 2004.
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