Vagal tone augmentation to the atrioventricular node in humans: Efficacy and safety of burst endocardial stimulation

ECG (lead II) and endocardial electrogram recorded at the coronary sinus ostium (CSO). Atrial pacing (90 bpm) is delivered by the permanent lead screwed in behind the CSO. A: Burst stimulation (50 Hz) during the effective atrial refractory period is initiated at the asterisk. B: 2:1 AV block is evoked after a few bursts and disappears immediately after stimulation is interrupted (#).

Asynchronous burst stimulation (90 bursts/minute) during rapidly conducted atrial fibrillation (mean ventricular rate 160 bpm) starts at the asterisk. Progressive burst voltage increase allows significant ventricular rate reduction, as seen in the second line (mean ventricular rate 80 bpm). Third line shows ventricular rate increase after vagal stimulation is interrupted (#).

Anteroposterior (A) and latero-lateral (B) X-ray views. The permanent ventricular passive fixation lead is implanted in the right ventricular apex. The second lead is screwed in at the right atrial septum (asterisk) behind the coronary sinus ostium, a location suitable for both standard atrial pacing/sensing and AVNS.

A: Number of group A subjects in whom AV nodal conduction modulation (lined bars) and advanced AV block (solid bars) were functionally induced at different pulse durations and burst rates. B: Mean voltages (group A) needed to functionally induce AV nodal conduction modulation (lined bars) and advanced AV block (full bars) at different pulse durations and burst rates. C: Same as panel A for patients in group B. D: Same as panel B for patients in group B. AF = atrial fibrillation; SR = sinus rhythm.