Twiddler's syndrome resulting in right phrenic nerve stimulation: a case report

Phrenic nerve stimulation is an uncommon complication of cardiac implantable electronic devices (CIEDs), and right-sided stimulation is particularly rare. Twiddler's syndrome causes lead retraction that may result in extracardiac stimulation.

An 87-year-old man with a dual-chamber implantable cardioverter-defibrillator (ICD) presented with 5 days of persistent upper abdominal contractions. Examination showed rhythmic diaphragmatic spasms synchronized with ventricular pacing spikes. Electrocardiography revealed ventricular pacing spikes without myocardial capture. Chest radiograph demonstrated right ventricular (RV) lead displacement into the superior vena cava, consistent with Twiddler's syndrome. Temporary reprogramming to AAI pacing eliminated symptoms, and definitive RV lead revision restored normal device function. Although the patient did not attend in-person follow-up due to relocation to another state, communication with the patient's family approximately 1 month after discharge confirmed no recurrence of diaphragmatic spasms.

This case demonstrates a rare mechanism of right phrenic nerve stimulation due to cranial migration of an ICD RV lead. Recognition and timely device reprogramming are essential for the resolution of diaphragmatic spasms.