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.