Sarcoidosis with incomplete bilateral bundle branch block pattern disappearing following steroid therapy: an electrophysiological study.

A man with a 30-year history of pulmonary sarcoidosis, confirmed by lymph node biopsy and a positive Kveim reaction, developed an incomplete bilateral bundle branch block pattern. Cardiac catherization and angiography revealed normal pressures, hemodynamic parameters and left ventricular contractile pattern; the coronary arteries were patent. His bundle electrograms demonstrated a normal H-V interval that was not altered by atrial pacing. After four weeks of steroid therapy the electrocardiographic abnormality disappeared. However, when restudied at this time, incomplete bilateral bundle branch block pattern could be elicited on atrial pacing and with the extrastimulus technique. Other electrophysiological observations suggested the presence of an AV nodal bypass tract and demonstrated changing intraventricular conduction patterns. The implications of these findings are discussed.