Radiation tolerance of contemporary implantable cardioverter-defibrillators.

BACKGROUND: Implantable cardioverter-defibrillators (ICDs) are complex instruments using integrated circuit technology. Previous studies suggested risk to the device when exposed to a radiation environment. Little data is available on contemporary ICD systems. OBJECTIVES: The purpose of the present study was to assess the ability of contemporary ICD designs to resist the damaging effects of direct exposure to therapeutic doses of radiation. METHODS: Four contemporary ICDs and four legacy ICDs devices were exposed to escalating doses of photon irradiation (XRT) from a 6-MV linear accelerator. Escalating doses were administered over 8 days to a maximum cumulative dose of 131.11 Gy or catastrophic failure. RESULTS: Each legacy device had catastrophic failure following the 6th XRT session, characterized by failure to deliver shock therapy. All four contemporary devices remained fully functional following the 8th and final XRT session (P = 0.03). The cumulative, survived radiation dose was significantly different between the contemporary and legacy groups (131.11 vs. 41.11 Gy, P = 0.01). Changes seen in the legacy devices were sudden and not anticipated by trends in prior sessions. CONCLUSION: The results of this study suggest that contemporary ICD designs may be more robust than earlier designs in a radiation environment.

Myocardial stunning following defibrillation threshold testing.

Implantable cardioverter-defibrillators (ICDs) have a proven mortality benefit in appropriately selected people. Several retrospective studies, though, have postulated that appropriate ICD therapy may lead to fatal, pulseless electrical alternans (PEA). This case report describes an episode of transient PEA from myocardial stunning and standstill following defibrillation threshold testing. The risk of post-shock myocardial stunning and standstill should be kept in mind as a potential complication of testing. With rapid recognition and prompt intervention, this complication is potentially reversible.