Relationship between left-axis deviation and onset of cardiac adverse events in right ventricular pacing

Aims: The electrical axis shows alterations during right ventricular pacing (RVP), including a normal axis and left axis deviation; however, it remains unknown if differences in the electrical axis affect the occurrence of cardiac adverse events. The purpose of this study was to determine whether a left axis deviation increases the incidence of adverse cardiac events compared with a normal axis.

Methods: This study analysed 156 patients with RVP. The patients were divided into two groups: those with left axis deviation after RVP (LAD group) and those with a normal axis (NA group). The primary composite outcome was the new-onset of atrial fibrillation (AF) and worsening heart failure (HF).

Results: The QRS axis of the LAD (n = 77) and NA (n = 79) groups were - 64.5 ± 14.3° and 29.8 ± 36.5°, respectively (P < 0.001). The median follow-up was 1100 days and, regarding primary composite outcomes (hazard ratio, 1.03; 95% confidence interval, 0.64 to 1.65; P = 0.89), 29/77 (37.6%) and 28/79 (35.4%) patients in the LAD and NA groups, respectively, developed AF (hazard ratio, 1.07; 95% confidence interval, 0.64 to 1.81; P = 0.77). Furthermore, 8/77 (10.3%) and 12/79 (15.1%) patients in the LAD and NA groups, respectively, experienced worsening HF (hazard ratio, 0.65; 95% confidence interval, 0.26 to 1.60; P = 0.35).

Conclusion: The risk of cardiac adverse events in patients with RVP (new-onset AF or worsening HF, cardiovascular death, myocardial infarction, and stroke) and overall mortality with LAD is not higher than that with NA.