By Michael H. Crawford, MD, Editor

SYNOPSIS: A study of patients with mitral valve prolapse and mild to moderate mitral regurgitation showed that over a 4.5-year follow-up period, only mitral annular diameter among several echo parameters predicted the development of severe mitral regurgitation.

SOURCE: Ma JI, Igata S, Strachan M, et al. Predictive factors for progression of mitral regurgitation in asymptomatic patients with mitral valve prolapse. Am J Cardiol 2019;123:1309-1313.

In patients with mitral valve prolapse (MVP) and mild to moderate mitral regurgitation (MR), it is unclear which echocardiographic measurements predict progression to severe MR, which can be a criterion for surgical intervention. Investigators performed a retrospective, observational study of patients with MVP identified by echocardiography between 2010 and 2015. They excluded patients with left ventricular ejection fraction (LVEF) < 60%, symptoms, severe MR, or prior adverse events. Of the 254 patients with MVP discovered, 82 met the inclusion criteria. Their mean age was 65 years. Thirty-six patients had mild MR, and 46 had moderate MR. The primary endpoint was progression to severe MR defined as a regurgitant volume of > 60 mL, a regurgitant fraction > 50%, or an effective regurgitant area of > 0.4 cm².

Several echo parameters related to the mitral valve and the left heart chambers were obtained. Of note, baseline mean tricuspid valve peak regurgitation gradient was 18 mmHg, mean left atrial volume index was 35 mL/m², mean LV end-diastolic volume index was 56 mL/m², and mean LVEF was 62%. During the 4.5-year follow-up period, severe MR developed in 50% of patients with moderate MR. Moderate MR developed in 17% of mild MR patients, but no mild MR patient developed severe MR. Mitral E wave velocity (> 85 cm/s), LV end-diastolic volume index (> 65 mL/m²), and mitral annulus diameter (> 39 mm, an average of four-chamber and two-chamber views) were highly sensitive for predicting the development of severe MR. After adjustments for age and sex, only annulus diameter significantly predicted progression to severe MR (hazard ratio, 1.14; 95% confidence interval, 1.03-1.26; P = 0.01). The authors concluded that mitral annular diameter may be of value for predicting which asymptomatic patients with mild to moderate MR due to MVP will progress to severe MR.

COMMENTARY

According to U.S. guidelines, there are no indications for surgical intervention in MVP patients with moderate MR unless they are undergoing cardiac surgery for some other reason. Thus, the achievement of severe MR is an important milestone. It is recommended that patients with moderate MR be followed by echocardiograms every one to two years. Based on the results of this study, the authors recommended more frequent follow-up in moderate MR patients with mitral annular diameters > 39 mm. This finding is unique since annular diameter is not mentioned in the guidelines, presumably because the available data did not support its use. The only echocardiographic parameters mentioned in the guideline are end-systolic volume, LVEF, and estimated pulmonary artery systolic pressure (PASP). LVEF < 60% was an exclusion criterion in this study. End-systolic volume index and estimated PASP were not predictive. Other than mitral annulus diameter, the only other echo measures that looked promising due to high sensitivity for developing severe MR were mitral E wave velocity and LV end-diastolic volume index. Still, neither was significant in the adjusted multivariate regression analysis.

Since none of the patients with mild MR developed severe MR over the 4.5-years follow-up, the results of this study are driven by the 46 moderate MR patients, 50% of whom developed severe MR. This was a small, select group, which the authors admitted limits the ability to control for all potential confounders. Also, in this retrospective, observational study, there was no control over when patients underwent repeat echoes. In addition, there are no data on whether outcomes would improve by using annular diameter to predict who was going to develop severe MR. Finally, the quantitation of MR in patients with MVP, who often exhibit eccentric jets, is challenging. In this study, 17% of patients with moderate MR exhibited improvement in the severity of MR over the follow-up period. Is this real or a methodologic issue? Considering the difficulty in identifying the patient with MVP and moderate MR who needs surgical intervention instead of more watchful waiting, I am going to add annular diameter to the echo measures I follow to determine the frequency of follow-up.