Mechanisms of Ventricular Tachycardias with a 1:1 His-V Relation in Patients with Heart Disease

Ventricular tachycardia (VT) with a 1:1 V-His relation can be seen in bundle branch reentry (BBR) or with passive retrograde activation from scar-related VT (SRR-VT) or reentry using left ventricular (LV) Purkinje fascicles (FPVT). To review the frequency that 1:1 V-His relation occurs and identify differentiating characteristics of these arrhythmias, including new measures obtained during right ventricular (RV) pacing based on orthodromic His-proximal right bundle potential (HisRB) capture and the stimulus to HisRB (S-HisRB) interval approximating RV electrogram to His interval (Egm-HisRBVT). Retrospective review of induced VTs that had a HisRB potential recorded while pacing from the distal RV. From 147 patients, 158 VTs were analyzed. A 1:1 V to HisRB was observed in 86 VTs (54%): 18 BBR-VTs, 8 LV Fascicular/Purkinje-related reentrant VTs (FPVT), and 60 scar-related reentrant VTs (SRR-VT). The HisRB-QRS was >135 msec, falling within the QRS in 87% of SRR-VT; and was 30-135 msec in all BBR-VTs (P<0.001). With RV pacing the HisRB remained 1:1 in 100% of BBR-VTs and 23 (69.7%) of 33 SRR-VTs. A S-HisRB of >135 msec combined with S-HisRB - Egm-HisRBVT difference <30 msec was specific for BBR-VT. In FPVTs the HisRB-QRS timing was more variable and RV pacing was helpful in distinguishing these from BBR-VTs. Retrograde HisRB activation is common in all forms of VT. HisRB timing, and new features based on consideration of orthodromic HisRB activation during RV pacing can help distinguish BBR, SRR-VT and FPVTs.