TOC | Cardiology    Mitral Valve Prolapse

Prevalence and Clinical Outcome of Mitral-Valve Prolapse

The New England Journal of Medicine -- July 1, 1999 -- Vol. 341, No. 1  (Abstract)   
See the Editorial |  Correspondence
Lisa A. Freed, Daniel Levy, Robert A. Levine, Martin G. Larson, Jane C. Evans, Deborah L. Fuller, Birgitta Lehman, Emelia J. Benjamin

Background.
Mitral-valve prolapse has been described as a common disease with frequent complications. To determine the prevalence of mitral-valve prolapse in the general population, as diagnosed with the use of current two-dimensional echocardiographic criteria, we examined the echocardiograms of 1845 women and 1646 men (mean [±SD] age, 54.7±10.0 years) who participated in the fifth examination of the offspring cohort of the Framingham Heart Study.

Methods.
Classic mitral-valve prolapse was defined as superior displacement of the mitral leaflets of more than 2 mm during systole and as a maximal leaflet thickness of at least 5 mm during diastasis, and nonclassic prolapse was defined as displacement of more than 2 mm, with a maximal thickness of less than 5 mm.  

Results.
A total of 84 subjects (2.4 percent) had mitral-valve prolapse: 47 (1.3 percent) had classic prolapse, and 37 (1.1 percent) had nonclassic prolapse. Their age and sex distributions were similar to those of the subjects without prolapse. None of the subjects with prolapse had a history of heart failure, one (1.2 percent) had atrial fibrillation, one (1.2 percent) had cerebrovascular disease, and three (3.6 percent) had syncope, as compared with unadjusted prevalences of these findings in the subjects without prolapse of 0.7, 1.7, 1.5, and 3.0 percent, respectively. The frequencies of chest pain, dyspnea, and electrocardiographic abnormalities were similar among subjects with prolapse and those without prolapse. The subjects with prolapse were leaner (P<0.001) and had a greater degree of mitral regurgitation than those without prolapse, but on average the regurgitation was classified as trace or mild.

Conclusions.
In a community-based sample of the population, the prevalence of mitral-valve prolapse was lower than previously reported. The prevalence of adverse sequelae commonly associated with mitral-valve prolapse in studies of patients referred for that diagnosis was also low. (N Engl J Med 1999;341:1-7.)

Lack of Evidence of an Association between Mitral-Valve Prolapse and Stroke in Young Patients

The New England Journal of Medicine -- July 1, 1999 -- Vol. 341, No. 1   (Abstract)
Dan Gilon, Ferdinando S. Buonanno, Marshall M. Joffe, Marcia Leavitt, Jane E. Marshall, J. Philip Kistler, Robert A. Levine

Background.
Previous studies have reported a high prevalence of mitral-valve prolapse among patients with embolic stroke (28 to 40 percent), especially among young patients (those less than or equal to 45 years old); this finding has practical implications for prophylaxis. However, diagnostic criteria for prolapse have changed and are now based on three-dimensional analysis of the shape of the valve; use of the current criteria reduces markedly the frequency of such a diagnosis and increases its specificity. Previously described complications must therefore be reconsidered.

Methods.
In a case-control study, we reviewed data on 213 consecutive patients 45 years of age or younger with documented ischemic stroke or transient ischemic attack between 1985 and 1995; they underwent complete neurologic and echocardiographic evaluations. The prevalence of prolapse in these patients was compared with that in 263 control subjects without known heart disease, who were referred to our institution for assessment of ventricular function before receiving chemotherapy.

Results.
Mitral-valve prolapse was present in 4 of the 213 young patients with stroke (1.9 percent), as compared with 7 of the 263 controls (2.7 percent); prolapse was present in 2 of 71 patients (2.8 percent) with otherwise unexplained stroke. The crude odds ratio for mitral-valve prolapse among the patients who had strokes, as compared with those who did not have strokes, was 0.70 (95 percent confidence interval, 0.15 to 2.80; P=0.80); after adjustment for age and sex, the odds ratio was 0.59 (95 percent confidence interval, 0.12 to 2.50; P=0.62).

Conclusions.
Mitral-valve prolapse is considerably less common than previously reported among young patients with stroke or transient ischemic attack, including unexplained stroke, and no more common than among controls. Using more specific and currently accepted echocardiographic criteria, therefore, we could not demonstrate an association between the presence of mitral-valve prolapse and acute ischemic neurologic events in young people. (N Engl J Med 1999;341:8-13.)

Editorial

Perspectives on Mitral-Valve Prolapse

The New England Journal of Medicine -- July 1, 1999 -- Vol. 341, No. 1
Rick A. Nishimura, M.D. &  Michael D. McGoon, M.D.   Mayo Clinic -  Rochester, MN 55905

More than three decades ago, Barlow and Bosman described a constellation of clinical findings consisting of non-ejection systolic clicks and a late systolic murmur, T-wave abnormalities, and systolic aneurysmal billowing of the posterior mitral leaflet into the left atrium on left ventriculography. (1) Since then, the syndrome of mitral-valve prolapse has been portrayed as the most common form of valvular heart disease, with a reported prevalence of 5 to 10 percent in the general population and an even higher prevalence among young women. (2,3) Though it is a predominantly benign condition, devastating complications have been ascribed to mitral-valve prolapse, including cerebral embolic events, infective endocarditis, severe valvular regurgitation requiring operation, (4,5) and even sudden death. (4,5,6) The seeming contradiction that mitral-valve prolapse could be prevalent and benign, on the one hand, but potentially malignant and a frequent substrate for catastrophic events, on the other, has led to confusion on the part of clinicians, investigators, and commentators. The controversy is exemplified by editorials with titles such as "Prolapse Paranoia," (6) "Mild Mitral Regurgitation and the Mitral Prolapse Fiasco," (7) and "Mitral Valve Prolapse -- Harbinger of Death or Variant of Normal?" (8)

What are the explanations for the disparate points of view? Early findings of a high prevalence and a high rate of complications were reported by large subspecialty centers with a resulting referral bias that favored patients with clinical features reflecting severe abnormalities. Moreover, some studies retrospectively identified a high prevalence of mitral-valve prolapse among patients with adverse events. Although these studies gave the impression that mitral-valve prolapse predisposed a patient to an adverse outcome, they did not assess the absolute risk of an event. Perhaps the most confusing aspect was the lack of universally accepted, standardized methods of diagnosis. Diagnostic techniques have included auscultation, phonocardiography, M-mode and two-dimensional echocardiography, left ventricular angiography, and direct histopathological inspection of the mitral-valve apparatus. Even with the use of a single standard technique, such as M-mode echocardiography, the diagnostic criteria have varied, with prolapse defined as bowing of the leaflets from 1.5 to 3 mm beyond the mitral-valve annulus into the left atrium during systole.

Several important concepts have emerged in the past two decades that have cleared up some of the confusion about the diagnosis and prognosis of mitral-valve prolapse. Initially, the application of M-mode echocardiographic criteria for prolapse to two-dimensional echocardiographic studies seemed to result in an epidemic of the abnormality, with a prevalence of up to 30 percent among otherwise healthy young people.   Subsequently, echocardiographers have recognized that the nonplanar "saddle shape" of normal mitral leaflets could give the appearance of prolapse in certain echocardiographic views. (9) Equally important, mitral-valve prolapse came to be understood not as a single entity but as a spectrum of abnormalities with varied clinical, echocardiographic, and pathological features. (2,10,11) At one end of the spectrum are patients with leaflet redundancy as a result of marked myxomatous proliferation of the spongiosa and elongation of the chordal apparatus. At the other end are those with morphologically normal-appearing leaflets that bulge into the left atrium. Although the findings in all these patients may meet the generic definition of prolapse, only those with abnormal valve morphology appear to be at risk for complications, and those patients can be identified with the use of echocardiography. (2,10,11)

In this issue of the Journal, two studies -- one by Freed et al. (12) and one by Gilon et al. (13) -- add to our growing knowledge of this abnormality. Using updated echocardiographic criteria, Freed et al. have shown that the true prevalence of mitral-valve prolapse in an unselected, community-based sample of ambulatory subjects is low (2.4 percent). Gilon et al. showed that mitral-valve prolapse is no more common among young patients with unexplained cerebral embolic events than among control subjects, again using the new, proper echocardiographic definitions of prolapse. This additional information supports the evolving concept that the majority of patients with a diagnosis of mitral-valve prolapse are not at high risk for the devastating complications. Nonetheless, the true disease cannot be ignored, since there is a subgroup of patients in whom infective endocarditis or severe mitral regurgitation may develop, requiring mitral-valve surgery, or who may be at risk for sudden death. (3,4,5,10,11)

What recommendations should follow from this information?

A single echocardiographic examination is warranted for patients with a midsystolic click or characteristic murmur to identify or rule out mitral-valve prolapse and other entities with similar physical findings. The use of echocardiography to look for mitral-valve prolapse is not indicated in patients with atypical chest pain, palpitations, anxiety disorders, or other noncardiac symptoms that are occasionally attributed to this disorder. (2) Echocardiography may also be useful to rule out other cardiac causes of embolism, but rarely, if ever, should mitral-valve prolapse be considered the cause.

Patients with primary mitral-valve prolapse require instructions for prophylaxis against infective endocarditis, particularly those with a systolic murmur. For patients with normal-variant prolapse and no murmur, prophylaxis is optional and probably unnecessary. (2)

Meticulous follow-up is warranted for patients with the primary form of mitral-valve prolapse, especially if substantial mitral regurgitation is present. Long-standing volume overload of the left ventricle can lead to left ventricular myocardial dysfunction, even in asymptomatic patients with a normal ejection fraction. Mitral-valve repair is now possible in many patients and has a low operative mortality (<2 percent) and an excellent long-term outcome, providing an impetus for early surgery. (14)

Mitral-valve prolapse has caused confusion and concern on the part of both patients and physicians. Over the past two decades, we have slowly learned about the epidemiology, pathophysiology, diagnosis, and treatment of this condition. Also, we now know how to recognize the normal-variant form. This information has allowed a rational approach to the patient with mitral-valve prolapse that will help us avoid the panic that was previously associated with this diagnosis.

     

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