Predictors of increase in pacing threshold after transcatheter pacing system implantation due to micro-dislodgement

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 (Impte) and end of the procedure (Impend) was significantly lower in patients with a PCT elevation (p < 0.001). The receiver operating characteristic curve analysis demonstrated that the Impte (AUC: 0.868) and Impend (AUC: 0.857) effectively predicted PCT elevations, with a cutoff of > 380 Ω associated with a lower incidence of PCT elevations. For the Impte, the sensitivity was 85.7% and specificity 90.0%. Moreover, a high impedance during premapping (AUC: 0.892) predicted an Impte > 380 Ω, and when the premapping impedance was > 430 Ω, all cases had an Impte > 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.

Fluoroscopic Predictors of Acceptable Capture threshold during the Implantation of the Micra Transcatheter Pacing System

Introduction

Few predictors of low capture threshold before the deployment of the Micra transcatheter pacing system (Micra TPS) have been determined. We aimed to identify fluoroscopic predictors of an acceptable capture threshold before Micra TPS deployment.

Methods

Sixty patients were successfully implanted with Micra TPS. Before deployment, gooseneck appearance of the catheter shaft was quantified using the angle between the tangent line of the shaft and the cup during diastole in the right anterior oblique (RAO) view. The direction of the device cup toward the ventricular septum was evaluated using the angle between the cup and the horizontal plane in the left anterior oblique (LAO) view.

Results

Of the 95 deployments we evaluated, 56 achieved an acceptable capture threshold of ≤2.0 V at 0.24 ms. In this acceptable threshold group, the deflection angle of the gooseneck shaft was significantly larger and the device cup was placed more horizontally with a lower elevation angle compared with those in the high threshold group. A deflection angle of ≥6° and an elevation angle of ≤30° were identified as the predictors of an acceptable capture threshold after deployment. An acceptable capture threshold was achieved in 24/31 (77.4%) patients in whom either angle criterion was satisfied at the first deployment.

Conclusions

Diastolic gooseneck appearance of the delivery catheter in the RAO view or near‐horizontal direction in the LAO view predicts an acceptable capture threshold after deployment. The shape of the delivery catheter before deployment should be evaluated using multiple fluoroscopic views to ensure successful implantation of Micra TPS.