# Extravascular implantable cardioverter and leadless pacemaker interactions

## TL;DR

This study explores the safe coexistence of leadless pacemakers and extravascular ICDs, finding minimal risk of interference under certain conditions.

## Contribution

The study evaluates interactions between leadless pacemakers and extravascular ICDs, providing safety thresholds for their combined use.

## Key findings

- Pacing pulses ≤0.24 ms and ≤3 V minimally impact VF detection by extravascular ICDs.
- Monte Carlo simulations showed a 0–4% probability of undesired interactions under clinical conditions.
- Device proximity affects sensed pacing pulse amplitude, but pacemaker orientation does not.

## Abstract

Traditional cardiac pacing and defibrillation devices rely on leads connected to a subcutaneous pulse generator, which can result in complications such as vascular damage, infection, or lead failure. Advances in technology have led to the development of leadless pacemakers, which combine the battery, circuitry, and electrodes into a single self-contained unit, and extravascular implantable cardioverter-defibrillators (ICDs), which position electrodes outside the vasculature. These innovations offer promising alternatives for patients requiring both defibrillation and pacing, particularly those unable or unwilling to accommodate traditional leads. However, the interactions between extravascular ICDs and leadless pacemakers remain largely unexplored and currently lack regulatory approval for combined use. This study evaluates the interactions between leadless pacemakers and extravascular ICDs to assess their simultaneous operation.

In-silico simulations, saline-tank experiments, and Monte Carlo simulations were conducted to evaluate device interactions, focusing on ventricular fibrillation (VF) detection during pacing conditions. Ventricular fibrillation detection was unaffected by pacing pulse widths ≤0.24 ms, with a pacing pulse-to-VF amplitude ratio of ≤2 considered safe. Wider pulse widths or higher outputs progressively increased the risk of VF undersensing. Experiments confirmed that pacing pulses ≤3 V and ≤0.24 ms minimally impacted VF detection. Proximity of device affected pacing pulse amplitude sensed by the ICD, but pacemaker orientation did not. Monte Carlo simulations indicated a 0–4% probability of undesired interactions under clinically relevant conditions.

Extravascular ICDs and leadless pacemakers may safely coexist, with a low observed risk of VF undersensing in our study. Further clinical studies are needed to confirm these findings.

Graphical Abstract