Electrocardiographic and Electrophysiological Characteristics in Idiopathic Ventricular Arrhythmias Originating From the Papillary Muscles in the Left Ventricle

Abstract

Background-Idiopathic ventricular arrhythmias (VAs) can originate from the left ventricular papillary muscles (PAMs).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 (nϭ7) and posterior PAMs (nϭ12). 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 nonirrigated 8-mm-tip ablation catheter was required to achieve a lasting ablation of the PAM VA origins. During 42% of the PAM VAs, a sharp ventricular prepotential was recorded at the successful ablation site. In 9 (47%) patients, PAM VAs exhibited multiple QRS morphologies, with subtle, but distinguishable differences occurring spontaneously and after the ablation. In 7 (78%) of those patients, radiofrequency lesions on both sides of the PAMs 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 PAM VAs is challenging probably because the VA origin is located relatively deep beneath the endocardium of the PAMs. PAM VAs often exhibit multiple QRS morphologies, which may be caused by a single origin with preferential conduction resulting from the complex structure of the PAMs. (Circ Arrhythm Electrophysiol. 2010;3:324-331.)

Anatomical Consideration in Catheter Ablation of Idiopathic Ventricular Arrhythmias

“…three-dimensional mapping system should be used as a guide for mapping. [16][17][18]31 Patients with papillary muscle IVAs often exhibit variable QRS morphologies spontaneously and/or after the initial ablation lesions. 18 The altered QRS morphologies of papillary muscle IVAs after the ablation may guide the following mapping and catheter ablation.…”

“…7,8 Tricuspid annular IVAs can originate from any region along the tricuspid annulus, but more often originate from the septal aspect, especially in the anteroseptal or para-Hisian region than the free wall. 15 IVAs can arise from intracavitary structures including the papillary muscles [16][17][18][19][20] and moderator band. 21 LV papillary muscle IVAs are known to arise more commonly from the postero-medial papillary muscle than the anterolateral papillary muscle.…”

“…21 LV papillary muscle IVAs are known to arise more commonly from the postero-medial papillary muscle than the anterolateral papillary muscle. 18 The sites of the papillary muscle IVA origins are limited to the base of the papillary muscles. IVAs can rarely originate from the papillary muscles in the RV (see Figure 2).…”

Catheter Ablation for Ventricular Arrhythmias

“…Idiopathic VT arising from the LV papillary muscle is a distinct subgroup but can demonstrate QRS morphology similar to fascicular VT. 48 The arrhythmias can be exercise-induced and catecholamine-sensitive, but most commonly present as PVCs rather than sustained VT. They appear to have a focal automatic mechanism.…”

“…Variations in QRS morphology can be subtle and may be due to preferential conduction to different exit sites or multiple regions of origin. 48 Ablation is technically challenging due to unstable catheter contact with the contracting papillary muscle; the use of intracardiac echocardiography is helpful for visualisation of catheter positioning. Irrigated tip or 8 mm catheters are often necessary for successful ablation due to deeper endocardial origins.…”