Rate-Dependent Left Bundle Branch Block in an Ambulatory Surgery Patient: A Case Report.

A 52-year-old woman, ASA II (American Society of Anesthesia classification II) scheduled for cholecystectomy in an ambulatory center, exhibited a wide-complex tachycardia with ectopy on the monitor after induction with propofol and succinylcholine. Blood pressure remained stable; amiodarone was administered for presumed ventricular tachycardia. A 12-lead electrocardiogram (ECG) showed a new left bundle branch block (LBBB) at 98 beats per minute (bpm), which resolved when the heart rate slowed. Surgery was postponed, and both the LBBB and ectopy recurred frequently during the next 24 hours in the intensive care unit, particularly at heart rates >90 bpm. Troponins were normal, and the patient was diagnosed with a rate-dependent LBBB and cleared for surgery.