Abstract 2672: Electrocardiographic and Electrophysiological Characteristics in Idiopathic Ventricular Arrhythmias Originating From the Papillary Muscles in the Left Ventricle; Relevance for Catheter Ablation
Background-Idiopathic ventricular arrhythmias (VAs) can originate from the left ventricular papillary muscles (PMs). This study investigated the electrophysiological characteristics of these VAs and their relevance for the results of catheter ablation.
Methods and Results-We studied 19 patients who underwent successful catheter ablation of idiopathic VAs originating from the anterior (n=7) and posterior PMs (n=12). Although an excellent pace map was obtained at the first ablation site in 17 patients, radiofrequency ablation at that site failed to eliminate the VAs and radiofrequency lesions in a relatively wide area around that site were required to completely eliminate the VAs in all patients. Radiofrequency current with an irrigated or non-irrigated 8-mm tip ablation catheter was required to achieve a lasting ablation of the VA origins. During 42% of the PM VAs, a sharp ventricular pre-potential was recorded at the successful ablation site. In 9 (47%) patients, PM VAs exhibited multiple QRS morphologies with subtle but distinguishable differences occurring spontaneously and after the ablation. In the anterior PM VAs, the R wave amplitude in the inferior leads was larger, that in lead aVR was smaller, depth of S waves in lead aVL was larger, and QRS duration was longer during the VAs ablated on the anterior side as compared with those ablated on the posterior side of anterior PMs. In the posterior PM VAs, the depth of S waves in the inferior leads was smaller, R wave amplitude in lead aVL was smaller, and QRS duration was longer during the VAs ablated on the lateral side as compared with those ablated on the septal side. In 7 (78%) of those patients, radiofrequency lesions on both sides of the PMs where pacing could reproduce an excellent match to the 2 different QRS morphologies of the VAs, were required to completely eliminate the VAs.
Conclusions-Radiofrequency catheter ablation of idiopathic PM VAs is challenging probably because the VA origins is located relatively deep beneath the endocardium of the PMs. PM VAs often exhibit multiple QRS morphologies which may be caused by a single origin with preferential conduction resulting from the complex structure of the PMs (a complex of myocardial strands with some separations in them on the basal and apical sides).