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Management of Asymptomatic Severe Mitral Regurgitation
Abstract & commentary
By Michael H. Crawford, MD
Source: Kang DH, et al. Comparison of early surgery versus conventional treatment in asymptomatic severe mitral regurgitation. Circulation. 2009;119:797-804.
The optimal timing of surgery for asymptomatic severe mitral valve regurgitation (MR) is unclear. Thus, Kang et al from South Korea studied the outcomes of patients treated with early surgery to those treated more conservatively in a prospective observational study. The treatment was at the discretion of the attending physician. Conventional treatment was selected in 286, and early surgery was selected in 161 who met inclusion criteria. Severe MR was defined as a PISA radius > 8 mm. All patients had marked mitral-valve prolapse or flail leaflet. Symptomatic patients, those with a left ventricular (LV) ejection fraction < 60%, LV diameter > 45 mm, atrial fibrillation, significant aortic valve disease, systolic pulmonary artery pressure > 50 mmHg, age > 85 years, or who were not candidates for surgery due to comorbidities were excluded. Patients in whom MR was clearly due to ischemic heart disease also were excluded. Vasodilator drugs were not given to the conservative management group unless another clear indication for them, such as hypertension, was present. Among the surgical group, 94% had mitral valve repair and the remainder had valve replacement. Coronary bypass surgery was done in 19 patients, and all but one patient undergoing valve repair had an annuloplasty ring placed.
Results: Comparing baseline data between the two groups, the surgical cohort had more flail leaflets, a larger effective regurgitant orifice area (EROA), and larger LV diameters. Operative mortality was zero. After a median follow-up of more than 1,900 days, there were no cardiac deaths in the surgical group and 12 in the conventional therapy group (p = 0.008). Cardiac causes of death were heart failure (6), sudden death (4), and endocarditis (2). The composite primary endpoint of operative mortality, cardiac death, repeat surgery, and hospitalization for heart failure occurred in 1% of the operated group and 12% of the conservative group. Using propensity matching, 127 pairs of patients emerged. In this cohort, seven-year, event-free survival was 99% in the surgical group vs. 85% in the conservative group (p = 0.007). In the conservative group, 28% developed criteria for surgery during follow-up. Multivariate analysis showed that pulmonary hypertension, age, and EROA were independent variables that predicted the development of surgical indicators or heart failure. Kang et al concluded that compared to conservative management, early surgery for asymptomatic severe MR decreased cardiac mortality and hospitalization for heart failure.
The timing of surgery in patients with MR remains controversial. This paper, the latest observational study (randomized, controlled trials are unlikely to ever happen) makes several interesting points. First, in this select group of patients, operative mortality and seven-year post-operative mortality were zero. Who were these select patients? They were young; mean age was 52 years. Most had no significant coronary artery disease or other serious comorbidities for surgery. They had truly severe MR (EROA averaged 0.79 cm2), and 39% had flail leaflets. Left ventricular function was preserved, and none had a pulmonary systolic pressure > 50 mmHg. Also, transesophageal echo was preformed in most, and the likelihood of being able to do a repair rather than valve replacement was high since 94% had a repair.
Second, among the conservatively managed patients, factors that increase the operative risk were likely to develop. Heart failure developed in 12% of the conservative group. Most developed pulmonary hypertension, and a few developed infective endocarditis. Third, among the conservatively managed patients who ultimately went to surgery (28%), post-operative LV size was larger than that observed with the early surgery group, even though ejection fraction was not significantly different. This suggests that LV remodeling may have occurred, which could portend a reduced long-term survival.
These results are in contrast to a smaller and shorter follow-up study by Rosenhek et al (Circulation. 2006;113: 2238-2244) of conservatively managed patients who were similar to those in this study (mean age 55 years). They found that survival over 62 months was no different from expected. Surgical criteria developed in 29%; mostly symptoms and post-operative LV function was preserved in all. However, surgical-free survival at six years was only 65%.
What do we do with this data? In an asymptomatic patient with severe MR or a flail leaflet, who is an excellent operative candidate, and TEE demonstrates that repair is feasible, surgery is the best option. In doing second opinions on such cases, my biggest area of disagreement with the primary physician is in the rating of the severity of MR. This study used sophisticated echo techniques to quantitate MR severity. This must be done! If the degree of MR is borderline or the patient is reluctant to have surgery, then watchful waiting is acceptable as long as careful follow-up can be achieved.