Syncope and an Intra-Hisian Atrioventricular Block After Radiation Therapy: Electrophysiologic Observations and Review of Literature

摘要

We present a case of a patient with recurrent syncope of sudden onset. She had a positive passive head-up tilt test for a mixed type of neurocardiogenic syncope. Additionally, she developed a narrow complex tachycardia on telemetry monitoring. Electrophysiology study revealed an intra-Hisian delay which upon provocation with programmed electrical stimulation, developed into a complete intra-Hisian atrioventricular block. Based on past medical history of radiation therapy for adenocarcinoma of the breast, the etiology of heart block was attributed to the remote effect of radiation-induced cardiac toxicity. Positive head-up tilt test for neurocardiogenic syncope and supraventricular tachycardia were incidental findings that could have confounding influence on management of such patients.