Safety and feasibility concerns of radiotherapy in the presence of subcutaneous implantable cardioverter-defibrillator

Abstract

Abstract Introduction Radiotherapy (RT) in patients with cardiac implantable electronic devices (CIED) is performed increasingly more frequently. Currently, there is no evidence, whether RT in patients with subcutaneous implantable cardioverter-defibrillator (sICD) is feasible and safe. Purpose To perform the first in-vitro analyses using a model of left lung cancer treated with stereotactic body radiotherapy (SBRT) with the presence of an sICD. Methods Three functional sICDs explanted from patients following the heart transplant underwent RT. In one device (No º3), the lead had to be cut during explantation at ~ 3 cm from the tip. A computed tomography-based SBRT plan was calculated for a left lung tumor (located 3.5 cm from the sICD). Three fractions of 18 Gy with a nominal energy of 6 MV were delivered, and the maximum dose calculated for the sICD was 3.5 Gy. Each sICD and lead were placed on an anthropomorphic phantom in the nominal location. The intervals between fractions were 7 days. The next step was a direct irradiation of the sICD with an open-field RT with 25 fractions of 2 Gy, then 2 of 20 Gy, 1 of 40 Gy, and a final fraction of 100 Gy. Before and after each fraction, the devices were interrogated, and to verify whether RT affects the devices in the possibly least optimistic clinical scenario, high-voltage therapies were turned on for each fraction and off for the intervals between them. Results A major depletion in the battery percentage (from 88% to 16%) between the first and second fraction of RT in device No. 2 was observed, while in two other devices, major reductions in the device battery longevity were observed after the third fraction of RT (from 38% to 14% and from 60% to 15%, respectively). The estimated doses for sICDs in those stages of RT were respectively 1.2 Gy, 3.5 Gy, and 3.5 Gy. Due to a significant drop of the battery longevity in device No 2º, only two remaining sICD underwent the open-field RT. During the direct irradiation, an unannounced shock was delivered during the interrogation directly after the 14th fraction of 2 Gy, in a device with a macroscopically intact lead. An external interference was demonstrated, which was interpreted as an arrhythmia in the ventricular fibrillation zone. The complete device reset occurred in both devices after having received approximately 195 Gy. Conclusions The presented findings strongly indicate an association between RT and the malfunction of the sICD occurring in the anthropomorphic phantom model of left lung tumor, as well as the risk of inappropriate shocks during the open-beam direct radiation on the devices.Battery longevities before and after RT