Management of Functional Mitral Regurgitation
January 1, 2016
By Michael Crawford, MD, Editor
SYNOPSIS: In symptomatic patients with coronary artery disease, left ventricular ejection fraction < 30%, and significant mitral valve regurgitation, coronary bypass graft surgery (CABG) or CABG plus mitral valve repair should be considered.
SOURCES: Samad Z, et al. Management and outcomes in patients with moderate or severe functional mitral regurgitation and severe left ventricular dysfunction. Eur Heart J 2015;36:2733-2741.
Vahanian A, Iung B. Severe secondary mitral regurgitation and left ventricular dysfunction: A ‘deadly combination’ against which the fight is not over! Eur Heart J 2015 Oct;36:2742-2744.
Symptomatic moderate-to-severe mitral regurgitation (MR) and a left ventricular ejection fraction (LVEF) < 30% is considered a class IIb indication for surgical correction, but with little supporting evidence (level C). Thus, investigators from Duke University queried their database from 1995-2000 to identify such patients and determine their long-term outcomes with different treatment strategies. They excluded patients with primary or organic MR and prior mitral valve surgery. Follow-up visits occurred 6 months after surgery and yearly thereafter. Survival data were available on 99% of patients. The primary endpoint was death, left ventricular assist device placement, or cardiac transplant. The median follow-up of the 1441 patients was 4.7 years. The median age was 64 years, and 39% were women. MR was moderate in 70% and severe in 30%. Most had heart failure symptoms (83%). Physicians pursued medical therapy in 75% at 1 year, percutaneous coronary intervention (PCI) in 8%, coronary bypass graft surgery (CABG) in 6%, CABG plus mitral surgery in 7%, and mitral surgery alone in 4%. Surgeons performed mitral valve repair in 95% of those who had surgery. Among the 52% of patients who had coronary artery disease (CAD), those who had CABG (hazard ratio [HR], 0.56; 95% confidence interval [CI], 0.42-0.76) and CABG plus mitral valve surgery (HR, 0.58; 95% CI, 0.44-0.78) had improved event-free survival. PCI was of borderline benefit (HR, 0.78; 95% CI, 0.61-1.00), but isolated mitral valve surgery was not beneficial (HR, 0.64; 95% CI, 0.33-1.27; P = 0.2). Propensity score adjustments for baseline differences in the treatment groups showed that mitral valve surgery was associated with better event-free survival (HR, 0.69; 95% CI, 0.53-0.88), and among the CAD patients, mitral valve surgery was superior to medical therapy (HR, 0.71; 95% CI, 0.52-0.95). The authors concluded that in symptomatic patients with moderate-to-severe MR and severe left ventricular dysfunction, those who had mitral valve surgery experienced higher event-free survival.
COMMENTARY
The management of significant MR in symptomatic patients with an LVEF < 30% is controversial. This retrospective observational study from Duke University attempted to shed light on the decision process in such patients. In this series, three-fourths of patients received medical therapy and one-fourth underwent a procedure. Those who underwent a procedure had more severe MR, higher LVEFs, and were more likely to have CAD. One-third of the procedures were PCI, which was of borderline benefit. The rest underwent surgery and after propensity score adjustments, mitral valve surgery was associated with better survival. However, a subgroup analysis showed that only those who had CABG or CABG plus mitral valve surgery benefitted. Isolated mitral valve surgery did not increase survival. The issue is whether any of the patients on medical therapy would have benefited from surgery. Clearly, if they had CAD and myocardial ischemia or viable myocardium, they probably would have. If not, they may not have.
The strengths of this study included the large number of patients, 5 years of follow-up, a homogeneous population of functional MR, and a skilled team. Weaknesses included the retrospective, nonrandomized study and the exclusive use of visual estimation of MR severity in this age of echo Doppler quantitation. Also, this was a study of predominantly surgical repair vs medical therapy. There is no description or standardization of such medical therapy. Finally, in many ways, the study is dated because there are no viability assessments, and mitral clipping and transcutaneous valve delivery are only used in a handful of patients.
The approach to symptomatic patients with significant (moderate to severe) MR and an LVEF < 30% should be as follows. First, optimize medical therapy for heart failure with maximally tolerated doses of the standard medications and resynchronization therapy, if indicated. Second, quantitate the severity of MR. If moderate-to-severe or severe, consider a procedure if the patient remains symptomatic on maximal medical therapy. If ischemic or viable myocardium is demonstrated, then consider CABG with mitral valve repair. If the heart valve team deems this not feasible or too risky, then consider PCI with mitral valve clipping or transcutaneous replacement. Fortunately, there are several prospective trials underway concerning these issues that should help refine our approach to these difficult patients.