Surgery for Mitral Valve Prolapse
abstract & commentary
Synopsis: Older, obese, and hypertensive patients with MVP are more likely to develop severe MR and require surgery; the increased risk seen in men may be due in part to their higher blood pressure and weight.
Source: Singh RG, et al. Am J Cardiol 2000;85: 193-198.
Mitral valve prolapse (mvp) is generally a benign disorder, but some patients eventually develop severe mitral regurgitation (MR) and require valve surgery. Since little is known about which subgroup of MVP patients will develop severe MR and progress to surgery, Singh and colleagues from Cornell University designed a case-controlled study to examine this issue. From their longitudinal study of MVP patients they selected 117 with pure, uncomplicated MVP (MR severity 0-2+), excluding those with Marfan syndrome, coronary artery disease, or moderate to severe MR (3-4+). These "controls" were compared to 54 "cases": patients with moderate to severe MR due to MVP in a longitudinal follow-up study. The controls were aged 16 to 73 years (mean 35), and their average body mass index (BMI) was 22 kg/m2. Two-thirds of the controls were women. The cases were older (56 years), more likely men (61%), and were heavier (BMI 24). Also, the cases had larger left atria and ventricles, higher blood pressures, and more often had a history of hypertension. Multivariate independent predictors of severe MR were male sex (odds ratio [OR] = 3.0) and age older than 45 years (OR 14.5). After up to an 11-year follow-up in the patients with severe MR, 59% underwent surgery mainly because of exertional dyspnea. Independent predictors of need for surgery were: age older than 45 years (OR 5.6) and BMI more than 22.5 (OR 3.0). The cumulative risk of surgery in all MVP patients was estimated based on their experience in these prospective trials and national data about numbers of mitral valve surgeries. The critical assumptions were that 25% of mitral valve surgeries are for severe MR due to MVP, and that 5% of women and 3% of men have MVP. Accordingly, the cumulative risk in women younger than 65 years old is 0.8% and 2.6% in men; in women older than 65 years it is 1.4% and 5.5% in men. Singh et al conclude that older, obese, and hypertensive patients with MVP are more likely to develop severe MR and require surgery; the increased risk observed in men may be in part due to their higher blood pressure and weight.
Comment by Michael H. Crawford, MD
The quest for MVP subgroups that are at increased risk of complications is important because this is a common disease with a generally low risk of complications. Previous studies have identified structural abnormalities of the valve on echocardiography as an important predictor of complications. Also, ECG ST-T wave changes are predictive. In addition, the presence of an MR murmur on physical examination is a risk factor for infectious endocarditis. This study demonstrates that reversible factors such as high blood pressure and obesity are important. Age is also a potent predictor, but probably because blood pressure and weight increase with age. In addition, age or the passage of time allows for wear and tear to affect the valve (MR begets MR). Male sex was also a strong predictor, but probably because men are generally heavier than women and have higher blood pressures.
This study has several limitations, including the cross-sectional nature of the original patient characteristic determinations, selection bias toward more symptomatic patients who came to the attention of the doctors at this tertiary referral center, and the relatively small number of patients (174). Their estimates of the cumulative risk of developing severe MR and needing surgery should be viewed with caution because of the major assumptions involved in this estimation. However, it is encouraging that the cumulative risk in women of all ages is about 1%. The higher risk in men is concerning, but difficult to understand. It may be the effect of hypertension and obesity in men, but this probably does not explain all the difference. Perhaps MVP is a different disease in men with a different genetic profile. Or perhaps MVP is more often acquired in men due to unrecognized ischemic heart disease or other conditions more common in men.
The major messages from this study are that it is especially important to try to control obesity and hypertension in patients with MVP and that men should be followed more aggressively until we understand their higher proclivity to progress.
The most powerful predictor of the development of severe mitral regurgitation in patients with mitral valve prolapse is:
a. high blood pressure.