PO-04-068 STEREOTACTIC ARRHYTHMIA RADIOTHERAPY DOES NOT ALTER TECHNICAL IMPLANTABLE CARDIOVERTER-DEFIBRILLATOR FUNCTION: DETAILED SAFETY RESULTS OF THE PROSPECTIVE STARNL-1 TRIAL

Abstract

Stereotactic arrhythmia radiotherapy (STAR) is a new potential treatment for patients with therapy-refractory ventricular tachycardia (VT). During STAR, the pro-arrhythmic substrate receives high-dose irradiation in a single fraction. Inherently, part of the implantable cardioverter-defibrillator (ICD) lead tips, leads and the site of lead insertion receive radiotherapy dose as well. This may directly, or indirectly due to induced fibrosis at the site of lead insertion, affect technical ICD functioning. To evaluate the effects of STAR on technical ICD functioning. The STARNL-1 was a prospective, single arm, pre-post intervention study. Patients with recurrent VT despite high doses of anti-arrhythmic drugs and after one or more catheter ablation(s) were considered therapy-refractory. Six patients were treated with a single radiotherapy dose of 25 Gy to the pro-arrhythmic substrate. Per protocol, ICD battery longevity and ICD parameters lead impedance, lead sense, and lead capture of the atrial/ventricular leads were collected from ICD readouts pre-therapy, within the first 24 hours after therapy and at 3 and 12 months after therapy. During targeting, the ICD generator was considered an organ at risk. The ICD leads and lead tips were not taken into account, therefore the ICD lead tips were retrospectively delineated to calculate the received radiotherapy dose. Since this study was not powered for statistical comparison of ICD parameters, ICD parameters were described. All six patients were male (age 54-83 years) and suffered from ischemic cardiomyopathy (left ventricular ejection fraction 24-52%). Four patients completed 12-month follow-up. Five patients had a dual-chamber ICD and one patient had a single-chamber ICD. The ICD generator received a median radiotherapy dose of 0.01 Gy (range 0.00-0.12 Gy), the atrial lead a median radiotherapy dose of 3.9 Gy (range 0.7-7.2 Gy), and the ventricular lead a median radiotherapy dose of 16.8 Gy (range 0.2-24.7 Gy). There was no sudden drop in battery longevity during follow-up. As can be appreciated from Table 1, atrial and ventricular lead impedance, sensing and capture were not altered during 12-month follow-up. Figure 1 shows a line graph of the ventricular lead impedance. STAR for VT does not alter technical ICD functioning within the first 12 months after treatment.Tabled 1ICD parameter results.ICD parameterPre-therapyWithin 24h after therapy3m12mAtrial lead impedance, Ohm419 (330-550)419 (310-550)433 (340-490)404 (390-440)Atrial lead sensing, mV1.8 (0.6-5.0)3.3 (0.9-5.0)2.0 (0.5-5.0)1.6 (0.6-5.0)Atrial lead capture, V0.69 (0.38-1.00)0.56 (0.50-1.00)0.56 (0.38-1.00)0.56 (0.38-0.75)Ventricular lead impedance, Ohm499 (390-766)465 (350-867)455 (360-838)460 (390-737)Ventricular lead sensing, mV12.0 (7.2-19.4)12.0 (11.7-20.1)12.0 (4.4-20.3)11.9 (11.7-19.9)Ventricular lead capture, V1.00 (0.63-3.50)0.88 (0.63-3.50)1.00 (0.63-3.88)0.88 (0.50-2.50)All parameters are provided as median (range). Open table in a new tab