Abstract Body (Do not enter title and authors here): Background: Compared to men, women with mitral valve prolapse (MVP) are more likely to present with sudden death, and most women who die suddenly are premenopausal. Repolarization abnormalities are common in patients with MVP-attributed sudden death. However, differences in repolarization between men and women with MVP are not known.

Hypothesis: Repolarization abnormalities are associated with ventricular arrhythmia and are more common in women than men with MVP.

Aims: To investigate associations of ECG repolarization abnormalities with sex and ventricular arrhythmia in MVP.

Methods: We reviewed 12-lead ECGs from 272 adults with MVP for T-wave inversion, ST segment elevation, ST depression, QTc and QT dispersion. Patients were excluded if they had prior MI, coronary artery disease, mitral valve surgery, moderate or severe LVH, heart failure, reduced left ventricular ejection fraction, atrial fibrillation or QRS duration >120ms. Transthoracic echocardiograms were reviewed for mitral regurgitation, mitral annular disjunction, bi-leaflet or myxomatous MVP. Ambulatory ECGs (n=94) were assessed for NSVT or PVCs (> 1% burden) and ECGs for >1 PVC on any 10 second tracing. Associations were evaluated using Fisher’s exact test, Wilcoxon rank-sum test or multiple linear regression.

Results: Among 272 patients, median (IQR) age was 58 (47-67) years, 162 (59.6%) were women, 46 (16.9%) were African American, and 34 (12.5%) had frequent ventricular ectopy. Women and men had similar rates of NSVT (15/66 [22.7%] vs 4/28 [14.3%], p=0.41) and frequent ventricular ectopy (25/162 [15.4%] vs 9/110 [8.1%], p=0.093). The QTc was longer in women (433 [417, 446] vs 423 [406, 442] ms, p=0.023) and in those with NSVT (437 [421, 444] vs 421 [405, 436] ms, p=0.028), but not in those with ventricular ectopy (437 [420, 445] vs 428 [410, 444] ms, p=0.15). There was a trend towards increased QTc in patients with mitral annular disjunction (433 [418, 454] vs 429 [408, 444] ms, p=0.054) and myxomatous MVP (434 [414, 450] vs 427 [408, 444] ms, p=0.076). Female sex was the only independent predictor of QTc (R²=0.14, p=0.0032).

Conclusion: Among patients with mitral valve prolapse, women have longer QT interval than men, and longer QT interval is associated with nonsustained ventricular tachycardia. Subtle or dynamic delay in repolarization may promote malignant ventricular arrhythmias in women. Understanding these relationships may help identify patients at risk for sudden death.