Is Bileaflet Mitral Valve Prolapse Associated with Sudden Death?

Abstract & Commentary

Edward P. Gerstenfeld, MD Professor of Medicine, Chief, Cardiac Electrophysiology, University of California, San Francisco

Dr. Gerstenfeld does research for Biosense Webster, Medtronic, and Rhythmia Medical.

Source: Sriram CS, et al. Malignant bileaflet mitral valve prolapse syndrome in patients with otherwise idiopathic out of hospital cardiac arrest. J Am Coll Cardiol 2013;62:222-230.

Mitral valve prolapse (MVP), characterized by displacement of the mitral valve into the left atrium during systole, was first described by Barlow in 1966. MVP "syndrome" refers to the association of MVP with palpitations and atypical chest pain in young patients. There has been some association of MVP with sudden cardiac arrest (SCA), primarily from autopsy studies finding pathologic signs of MVP in up to 10% of SCA survivors. However, given the high prevalence of MVP in the general population, a true association with SCA risk has been controversial.

The laboratory at the Mayo clinic analyzed records from 1200 consecutive patients seen in their genetic Heart Rhythm clinic between July 2000 and December 2009. In this database, all patients had received transthoracic echocardiography and standard electrocardiograms, and the majority received 24-hour Holter monitors. All patients underwent extensive genetic testing and those found to have inherited channelopathies were excluded. All other patients who experienced unexplained cardiac arrest, resuscitated ventricular tachycardia, or ventricular fibrillation were included. A blinded reviewer reviewed all echocardiograms and strictly defined the presence of single or bileaflet MVP as systolic displacement of the mitral valve > 2 mm into the left atrium in the parasternal long axis view, along with thickened or myxomatous mitral valve leaflets.

The authors identified 24 patients with unexplained cardiac arrest, normal QT intervals, and negative genetic testing (median age 33.5 years, 67% women). Bileaflet MVP was identified in 10 of 24 patients (42%, 9 females) with mitral regurgitation graded as mild in five, moderate in four, and severe in one patient. Biphasic or inverted T waves in the inferior leads were more commonly found in bileaflet MVP patients. Holter monitors were available in 9 of 10 SCA patients, and had significantly higher burden of premature ventricular contractions ([PVCs] 67 vs 23 PVCs/hr, P = 0.002), nonsustained ventricular tachycardia (7/9 patients), and ventricular bigemeny (9/9 patients) compared to those without MVP. A pattern of PVCs with alternating axis originating from the left ventricular outflow tract and papillary muscle/fascicular system was noted in seven of nine MVP patients who experienced SCA. Three patients underwent invasive electrophysiologic study and were found to have multiple PVC foci, typically originating near the left ventricular papillary muscles. After a mean of 1.8 years additional follow-up after the incident SCA, the only predictor of recurrent ventricular arrhythmias requiring defibrillator therapy was the presence of bileaflet MVP (odds ratio, 7.2; 95% confidence interval 1.1 to 48; P = 0.028). The authors concluded that there is a small subset of MVP patients characterized by bileaflet prolapse, female sex, and frequent complex ventricular ectopy who can have life-threatening ventricular tachyarrhythmias.

Commentary

The prevalence of MVP in the general population using strict echocardiographic criteria is 2-3%; however, some reports have more loosely described MVP in up to 30% of asymptomatic patients. The association of MVP with sudden death in autopsy studies often creates concern among patients informed they have MVP. However, a true association with MVP and sudden death has remained controversial. The current small series is interesting because all the patients who experienced SCA had echocardiograms and electrocardiograms available for review. The presence of bileaflet MVP in 42% of the cohort with unexplained SCA is certainly notable. However, several important qualifiers apply. The authors studied the incidence of SCA in a highly selected and specific population of SCA survivors. Thus, analogous to the early repolarization syndrome, which was recently described in a disproportionate number of survivors of cardiac arrest,¹ the overall risk in the general population with MVP remains small. However, cardiologists are often asked to evaluate patients with recurrent syncope or cardiac arrest, or family members of SCA patients. This study highlights some important characteristics of a high-risk cohort that are worth noting. First, all of the described patients had "bileaflet" prolapse, which may be more specific than the single leaflet prolapse often described. These patients also had repolarization abnormalities (biphasic or inverted T waves) in the inferior leads, and Holter monitors showing complex ventricular ectopy, typically ventricular bigemeny in an alternating pattern of inferior and superior axis. Although the mechanism of these PVCs is unclear, it is certainly plausible to speculate that these originate from structural abnormalities in the mitral valve apparatus. Also noteworthy is the finding that the majority of patients experiencing SCA were young women and many of the patients had only mild or moderate mitral regurgitation.

Therefore, before giving a patient the diagnosis of MVP, strict echocardiographic criteria should be applied. The majority of patients with asymptomatic single leaflet MVP have a benign prognosis. However, this report brings to light a potential higher risk cohort of patients with bileaflet MVP, repolarization abnormalities in the inferior ECG leads, and complex ventricular ectopy. While implantation of an implantable defibrillator in such patients is certainly premature, close follow-up or referral of high-risk patients for further evaluation is certainly warranted. Prospective studies of such patients will be difficult given the small population with these characteristics, but would certainly be useful for determining the optimal management strategy for these patients.

REFERENCE

1. Haïssaguerre M, et al. Sudden cardiac arrest associated with early repolarization. N Engl J Med 2008;358:2016-2023.