Exercise-induced left bundle branch block (LBBB) is rare, but portends higher major cardiac events risk in the presence of coronary disease. It is more benign without coronary disease. We present a case of chest pain with exercise-induced LBBB with unusual features. A 59-year-old female was referred for evaluation of atypical chest pain. She was on medications for hypertension, dyslipidemia, and hypothyroidism. She denied tobacco or alcohol use. She underwent a Bruce protocol exercise treadmill

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... test. Her resting heart rate was 76 beats per minute (BPM) and blood pressure was 150/85 mmHg. She was able to exercise for 8 min, achieving 9 METS. Her peak heart rate was 140 BPM without ischemic ST changes. At that heart rate, she developed LBBB, and complained of her usual chest discomfort. Her peak blood pressure was 209/83 mmHg. The test was terminated, and the patient was allowed to rest. Her rhythm continued to be LBBB for 2 min and 30 sec into recovery until, at a heart rate of 110 BPM, a premature ventricular contraction (PVC) resulted in resolution of LBBB. Shortly thereafter, her chest pain resolved. Subsequent cardiac catheterization revealed normal coronary arteries, ejection fraction (EF), and wall motion. Exercise-induced LBBB associated with chest pain may be a manifestation of underlying coronary disease and indicate poor prognosis. It renders the stress test uninterpretable and mandates its termination. However, certain clinical and electrocardiographic features may provide clues to non-ischemic etiology.