Predictive Role of Intraoperative Impedance in Midterm Pacing Threshold Elevation: Insights From Aveir VR Leadless Pacemaker Implantations.

Introduction: Leadless pacemakers (LPs) are a valuable treatment for bradycardia, with the Aveir offering advanced features, including a protective sleeve and active fixation. This study investigated the intraoperative factors during Aveir VR implantations that predict midterm pacing capture threshold (PCT) elevations and proposed strategies for optimizing the outcomes.

Methods and results: This retrospective study included 67 patients who underwent Aveir VR implantations in two Japanese facilities between March and June 2023, with a 360-day follow-up. The impedance and PCT were measured three times during the procedure (premapping, during the tether mode, and at the end of the procedure). A PCT elevation was defined as that > 1.5 V/0.4 ms during follow-up. PCT elevations were observed in 7 patients (10.4%), all with sinus node dysfunction. The impedance during the tether mode (Imp^te) and end of the procedure (Imp^end) was significantly lower in patients with a PCT elevation (p < 0.001). The receiver operating characteristic curve analysis demonstrated that the Imp^te (AUC: 0.868) and Imp^end (AUC: 0.857) effectively predicted PCT elevations, with a cutoff of > 380 Ω associated with a lower incidence of PCT elevations. For the Imp^te, the sensitivity was 85.7% and specificity 90.0%. Moreover, a high impedance during premapping (AUC: 0.892) predicted an Imp^te > 380 Ω, and when the premapping impedance was > 430 Ω, all cases had an Imp^te > 380 Ω. The median number of days until the PCT elevation was 40 (range: 1-321 days), and in 3 out of 7 patients, PCT elevations were observed more than 270 days after the implantation.

Conclusion: The higher impedance during the implantation was a strong predictor of a midterm favorable PCT. Those findings highlighted the potential for impedance-guided strategies to optimize implantations and output settings. The occurrence of PCT elevations beyond 270 days underscored the need for long-term monitoring and individualized follow-up strategies. Further studies are needed to validate these findings and explore their clinical impact.