Pleomorphism of premature ventricular complexes originating from papillary muscles and their myocardial connections

BACKGROUND Patients with arrhythmias originating from papillary muscles (PAPs) often have pleomorphic ventricular arrhyth-mias (PVAs) that can result in failed ablations. The mechanism of PVAs is unknown. OBJECTIVE The purpose of this study was to assess the prevalence and mechanisms of PVAs and the impact on outcomes in patients with focal left ventricular PAP ventricular arrhythmias (VAs). METHODS The sites of origin (SOOs) of VAs in 43 consecutive patients referred for ablation of focal left ventricular PAP VAs were determined by activation and pacemapping. SOOs were classified as (1) unifocal generating a single VA morphology; (2) unifocal from a deeper-seated origin generating multiple VA morphologies; (3) unifocal located on a PAP branching site; (4) multifocal from a single or multiple PAPs generating multiple VA morphologies; and (5) multifocal from a PAP anda different anatomic source. RESULTS Most patients had multiple morphologies (n = 34 [79%]) and multiple mechanisms (79%) generating the different VA morphologies. Most of the patients with PVAs had multiple SOOs from a single or different PAPs (n = 23 [68%]), followed by patients with SOOs from PAP and non-PAP sites (n = 19 [56%]). In 13 patients (38%), single SOOs accounted for the observed PVAs. The frequent observation (n = 20) of changing QRS morphologies after radiofrequency energy delivery targeting a single VA suggests the presence of a deeper focus with changing sites of preferential conduction. CONCLUSION VA pleomorphism in patients with PAP arrhythmias is most often due to premature ventricular complexes originating from different SOOs. The second most common cause is preferential conduction from a single SOO via PAP branching sites.