Endocavitary Structures in the Outflow Tract: Anatomy and Electrophysiology of the Conus Papillary Muscles : Ablation and Mapping of the Conus Papillary Muscle

The aim of this study was to investigate the prevalence of mitral valve prolapse (MVP) and its association with ventricular arrhythmias in a cohort with "unexplained" out-of-hospital cardiac arrest.

Premature ventricular complexes (PVCs) and ventricular tachycardia (VT) with origin in the left ventricular papillary muscle have recently been described. There are no prior studies describing the characteristics of the ventricular arrhythmias (VAs) arising from the right ventricular papillary muscles (RV PAPs). Among 169 consecutive patients who underwent a catheter ablation of a VA, eight patients with RV PAPs were identified (seven men, mean PVC burden 17.0% +/- 20%). A control group consisted of 10 consecutive patients with arrhythmias originating from the right ventricle (10 women, mean PVC burden 13.9% +/- 12.8%). All patients underwent cardiac magnetic resonance imaging (MRI). Intracardiac echocardiography was used to identify the site of origin of the RV PAP arrhythmias. The site of origin of a total of 15 distinct PAP arrhythmias was mapped to the following papillary muscles: posterior (n = 3), anterior (n = 4), or septal (n = 8). Postablation echocardiograms did not reveal new tricuspid regurgitation. During a mean follow-up of 8 +/- 9 months, there were no adverse outcomes. The PVC burden was reduced from 17% +/- 20% preablation to 0.6% +/- 0.8% postablation in the RV PAP group and from 13.9% +/- 12.8% to 0.3% +/- 0.4% in the control group. The QRS complex was broader in the RV PAP group compared with in the control group (163 +/- 21 ms vs. 141 +/- 22 ms; P = .02). RV PAP arrhythmias originating from the posterior or anterior RV PAPs more often had a superior axis with late R-wave transition (>V4) compared with septal RV RAP arrhythmias, which more often had an inferior axis with an earlier R-wave transition in the precordial leads (