Hyperkalemia-Induced T Wave Oversensing in an Implantable Cardioverter Defibrillator

A 66-year-old female with end-stage renal disease and heart failure with reduced ejection fraction, status post implantable cardioverter defibrillator (ICD) presented to the emergency department with dizziness and fatigue. An electrocardiogram showed sinus rhythm, complete atrioventricular block, and ventricular paced rhythm at 30 beats per minute (bpm). Device interrogation revealed a programmed VVI mode with a lower rate limit of 40 bpm and evidence of T wave oversensing. Serologic studies were remarkable for hyperkalemia (7.9 mmol/dL). The device was initially reprogrammed to provide a higher pacing rate and symptomatic improvement. Both complete AV block and T wave oversensing resolved after correction of hyperkalemia. This case highlights the need for vigilant monitoring of electrolyte imbalances in ICD patients.