Comparison of Measured Data between Pre- and Post-Radiotherapy in a Patient with Cardiac Resynchronization Therapy Defibrillator.

Although some researches proved the influence of radiation therapy (RT) on pacemakers and implantable cardioverter defibrillators, little has been reported on cardiac resynchronization therapy defibrillators (CRTDs). We experienced a case of RT on CRTD and had a new finding.A patient with CRTD implanted for dilated cardiomyopathy was diagnosed with lung squamous cell carcinoma and started receiving RT. All the implanted devices, including the main body of CRTD, left ventricular lead (LV), right ventricular lead with high-voltage conductor, and right atrial lead, were from the same manufacturer. The radiation targeted the tumor of 67 mm in diameter in the right superior lobe for 5 min per session. The CRTD was outside the radiation field, which is 65 mm, but the leads were inside. Plan 1 used 2 Gy/fr with 8 megavolt photons, and Plan 1 was irradiated at 0° and 180° for 16 RT sessions. The dosage was increased to 3 Gy for Plan 2 for 4 sessions. Plan 3 used 2 Gy with 6 and 8 megavolt photons, and Plan 3 was irradiated at 27.7° and 200.7° for 11 RT sessions. Changes in measured parameters were assessed before and after RT.Changes in impedance of LV and high-voltage lead exceeded prespecified threshold. However, no significant errors were detected in the CRTD on the dosages and energy we used.We hypothesize that the lead insulator could have been affected by radiation.