Anatomical Insight Into Idiopathic Ventricular Arrhythmias Originating From the Papillary Muscles

The papillary muscles (PAMs) are important sites of origin of idiopathic ventricular arrhythmias (VAs). Although catheter ablation of idiopathic PAM VAs has proven to be an effective treatment, these arrhythmias remain challenging compared with other idiopathic VAs despite advances in technologies and techniques. This is related to the unique anatomical challenges of these structures. PAMs are anatomically unique in their location, morphology, histologic composition, and connections with surrounding structures. Electrophysiological studies and catheter ablation of PAM VAs have revealed specific electrocardiographic and electrophysiological characteristics of idiopathic PAM VAs, such as inconsistent precordial transition, discordant QRS axis, multiform VA morphologies, and preferential conduction. Anatomical studies with the aid of imaging modalities, such as intracardiac echocardiography, computed tomography, and cardiac magnetic resonance, have helped define the anatomical background underlying these electrocardiographic and electrophysiological characteristics. This article reviews the unique anatomy of PAMs from an electrophysiological standpoint to better understand the anatomy of the PAMs and thereby improve the outcomes of catheter ablation of idiopathic PAM VAs.