Both Selective and Non-Selective His Bundle, but not Myocardial, Pacing Preserve Ventricular Electrical Synchrony Assessed by Ultra-High-Frequency ECG.

BACKGROUND: Right ventricular myocardial pacing leads to non-physiological activation of heart ventricles. Contrary to this, His bundle pacing preserves their fast activation. Ultra-high-frequency ECG (UHF-ECG) is a novel tool for ventricular depolarization assessment.

OBJECTIVE: To describe UHF-ECG depolarization patterns during myocardial and His bundle pacing.

METHODS: Forty-six patients with His bundle pacing to treat bradycardia and spontaneous QRSs without a bundle branch block were included. UHF-ECG recordings were performed during spontaneous rhythm, pure myocardial para-Hisian, and His bundle capture. QRS duration, QRS area, depolarization time under specific leads, and the UHF-ECG derived ventricular dyssynchrony index were calculated.

RESULTS: One hundred and thirty-three UHF-ECG recordings were performed in 46 patients (44 spontaneous, 28 selective, 43 non-selective His bundle, and 18 myocardial captures). The mean QRS duration was 117 ms for spontaneous, 118 ms for selective, 135 ms for non-selective, and 166 ms for myocardial capture (p < 0.001 for non-selective and myocardial capture compared to each of the others). The calculated dyssynchrony index was shortest during spontaneous rhythm 12 ms (p = 0.02 compared to selective, p = 0.09 compared to nonselective), it did not differ between selective and non-selective His bundle capture (16 vs. 15 ms, p = 1) and was longest during myocardial capture of the para-Hisian area (37 ms) (p < 0.001 compared to each of the other types of ventricular activation).

CONCLUSION: In patients without bundle branch block, both types of His bundle, but not myocardial, capture preserve ventricular electrical synchrony as measured using UHF-ECG.