Arrhythmias Originating in Left Ventricular Papillary Muscles: Clinical Characteristics, Multislice Imaging and Catheter Ablation

Background: Ventricular arrhythmias can arise from the left ventricular papillary muscles. Objectives: The aim of this study was to describe the most relevant features of this type of ventricular arrhythmias and to compare outcomes with either cryoenergy or radiofrequency catheter ablation. Methods: Forty-two patients undergoing catheter ablation for ventricular arrhythmias originating in the left ventricular papillary muscles were included in the study. Mean age was 47±16 years, 70% were men, and median ejection fraction was 55±11%. Ventricular arrhythmias were localized using three-dimensional mapping, multislice computed tomography and intracardiac echocardiography, with arrhythmia foci mapped at either the anterolateral or posteromedial papillary muscles. Ablation was performed using an 8-mm focal cryoablation catheter or a 4mm open-irrigated radiofrequency ablation catheter. Results: All clinical ventricular arrhythmias exhibited a right bundle branch block pattern, with mean QRS duration of 150±13 ms and R>r’ pattern in the left ventricle in 71.4% of cases. Acute success rate was 100% for cryoablation (n=18) and 83% for radiofrequency ablation (n=20) (p=0.06). Ventricular arrhythmia recurrence at 12 months was 4% for cryoablation and 46% for radiofrequency ablation (p=0.02). Use of radiofrequency ablation (HR 0.2; P=0.04) and lack of intracardiac echocardiography (HR 0.1; p=0.01) were associated with higher risk of recurrence.  Conclusions: Right bundle branch block morphology with left ventricular R>r’ pattern and QRS duration >135 milliseconds are the most frequent clinical characteristics of these ventricular arrhythmias Use of cryoablation and intracardiac echocardiography were associated with lower recurrence rates, while radiofrequency ablation was associated with 20% increase of clinical arrhythmia recurrence after ablation.