HISTORY A 28-year-old female presented for pre-operative evaluation prior to non-cardiac (uterine fibroid tumor) surgery. The resting ECG at this time revealed sinus arrhythmia with complete heart block with a junctional escape rhythm and a ventricular rate of 43 bpm. The patient complained of mild dyspnea with stair climbing, but was otherwise asymptomatic PHYSICAL EXAMINATION The patient was in no apparent distress and resting BP was 80/50 mm Hg. Physical examination was unremarkable with the exception of a III/VI systolic ejection murmur best appreciated at the lower left sternal border and a soft, non-tender movable abdominal mass. DIFFERENTIAL DIAGNOSIS Complete (Third Degree) Atrio-Ventricular Heart Block. TEST AND RESULTS Although high grade A-V Block is considered a relative contraindication for exercise testing, this patient was referred for an exercise ECG stress test to assist in determining if a electronic pacemaker or other therapy was necessary. A symptom limited maximal ECG treadmill test was performed using the Bruce Protocol. The resting HR prior to the test was 47 bpm and resting blood pressure was 70/50 mm Hg. During the first stage of the test the patient converted to sinus rhythm with a first degree A-V Block (P-R Interval of 360 ms). The patient achieved an estimated 10.2 METs, with a HRpeak of 122 bpm, and a peak blood pressure of 122/70 mm Hg. No ectopy was noted during exercise, no ST segment changes occurred during exercise or recovery and the patient remained asymptomatic. The test was terminated due to inability to keep pace with the treadmill. FINAL WORKING DIAGNOSIS Complete (Third Degree) Atrio-Ventricular Heart Block TREATMENT AND OUTCOMES Based on the exercise testing results, no medical therapy or electronic pacemaker was recommended at this time and the patient was permitted to undergo surgery for the uterine fibroid tumors. This case illustrates that although complete heart block is a relative contraindication to exercise testing, in some patients the benefits of testing outweigh the risks.