Clinical and electrophysiological characteristics of idiopathic ventricular arrhythmias originating from the slow pathway region.

BACKGROUND

The slow pathway region (SPR) is commonly targeted during ablation of atrioventricular nodal reentrant tachycardia. However, its role in idiopathic ventricular arrhythmias (IVAs) remains unknown.

OBJECTIVE

The purpose of this study was to describe the electrocardiographic and electrophysiological characteristics of IVAs that were successfully ablated from the SPR.

METHODS

Medical records of consecutive patients undergoing ablation of IVAs in the para-Hisian region between 2010 and 2018 were reviewed to identify subjects whose ventricular arrhythmias were targeted from the SPR.

RESULTS

Among 63 patients with para-Hisian IVAs undergoing ablation, the SPR was targeted in 12 (20%; mean age 64 ± 7 years; 9 men). All patients presented with ventricular premature depolarizations manifesting left bundle branch block morphology with variable precordial transition (leads V2-V5) and a mean QRS duration of 131 ± 11 ms. In all cases, leads I and aVL had positive forces (R or Rs) and lead aVR had negative forces (QS or Qr). In the majority of cases, lead II had positive forces (R or Rs; n = 9 [75%]) and lead III had negative forces (rS or QS; n = 9 [75%]). Mean activation at the SPR was 31 ± 5 ms pre-QRS. All patients had initial ablation with radiofrequency, resulting in junctional rhythm in 9 (75%); 3 (25%) patients required additional cryoablation. Ablation was successful in 11 patients (92%). One patient required a permanent pacemaker for heart block but subsequently recovered intrinsic conduction.

CONCLUSION

The SPR can be a source of IVAs, which can be safely and successfully ablated in most cases using radiofrequency energy. IVAs arising from this location manifest unique electrocardiographic features.