An unusual cause of abnormal intrathoracic impedance in a patient with arrhythmogenic right ventricular cardiomyopathy.

A device interrogation for a 32-year-old woman with arrhythmogenic right ventricular cardiomyopathy and an implantable cardioverter-defibrillator capable of monitoring intrathoracic impedance demonstrated a dramatic increase in her OptiVol Fluid index levels in the absence of clinical heart failure. The timing of her intrathoracic impedance changes correlated with plasma volume changes during an uneventful pregnancy without cardiovascular complications. The strengths and limitations of intrathoracic impedance are described in the context of the physiology of pregnancy.