Simple electrocardiographic index for A4-wave amplitude of the VDD leadless pacemaker

A4-wave amplitude (A4-amplitude) is a crucial factor determining the percentage of atrioventricular synchrony (%AVS) in a mechanical sensing-based VDD leadless pacemaker (VDD-LP). We hypothesized that 12-lead electrocardiographic (ECG) parameters related to right atrial (RA) excitation could predict A4-amplitude.

We aimed to investigate the relationship between A4-amplitude and 12-lead ECG parameters reflecting RA excitation and assess its predictive power for achieving an appropriate A4-amplitude associated with high %AVS.

This single-center, retrospective, observational study enrolled consecutive patients undergoing VDD-LP implantation. The relationship between A4-amplitude and the positive peak amplitude of the P wave in lead II (P2), the positive peak amplitude of the P wave in lead V₁ (V1P), and the sum of P2 and V1P (V1PP2) were assessed.

Of the 67 patients undergoing VDD-LP implantation, 46 without atrial fibrillation bradycardia were enrolled. They had a data set of manual atrial mechanical sensing tests and 12-lead ECG. Among P2, V1P, and V1PP2, only V1PP2 was correlated with A4-amplitude (R ²=0.10; P=.029). In 30 patients in VDD pacing mode, the median %AVS was 67.8%. The A4-amplitude cutoff for %AVS ≥ 67.8% was 3.2 m/s² (area under the curve [AUC] 0.81; P=.002). For A4-amplitude ≥ 3.2 m/s², V1PP2 had moderate predictive power (AUC 0.72; P=.007). In 30 patients without sick sinus syndrome, the predictive power of V1PP2 for A4-amplitude ≥ 3.2 m/s² was increased (AUC 0.80; cutoff value 110 μV; sensitivity 83%; specificity 71%; P=.011).

V1PP2, reflecting RA excitation, was related to A4-amplitude and had moderate predictive power. Notably, its predictive power increased when limited to patients without sick sinus syndrome. V1PP2 is a simple ECG predictor of A4-amplitude.