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Cardiac Case Study

HP is a 78 year old woman with a history of inferior myocardial infarction in 1989 complicated by transient asystole and right bundle branch block. She was treated medically and did well until 9/94 when a routine stress test revealed 3 mm ST segment depression in leads V2 through V6. No angina was noted; exercise was limited by dyspnea and fatigue. Cardiac catheterization revealed a 50% left main lesion, 75% LAD lesion, 95% mid RCA occlusion with 55% ejection fraction. The patient underwent coronary artery bypass graft surgery on 9/30/94: internal mammary artery to the LAD, vein grafts to the obtuse marginal and RCA. Post-operative course was complicated by supraventricular tachycardia at a rate of 160 bpm which was successfully converted to NSR with propranolol. The patient was discharged home on propranolol and aspirin and began outpatient cardiac rehabilitation on 10/24/94. One week after beginning cardiac rehabilitation, the patient arrived in her usual state of health with a resting HR of 92, BP = 130/60, NSR without ectopy. After 15 minutes of treadmill ambulation at a moderate pace (2.2 mph, 2% grade) she suddenly developed. extreme fatigue accompanied by frequent sinus pauses, the most significant being a 4 second pause (see Figure 1). Blood pressure was 110/60 and marked pallor was noted. She returned to baseline within the next 10-15 minutes while reclining in a chair. The propranolol was discontinued by her physician. Over the ensuing days, the patient began to complain of palpitations; 24 hour Holter monitor revealed paroxysmal episodes of atrial fibrillation and atrial tachycardia. She was unable to tolerate Pronestyl (GI side effects) and was referred back to cardiac rehabilitation on Cardizem. Unfortunately, she again developed symptomatic bradycardia with exercise (Figure 2). HP underwent permanent pacemaker implantation on 11/29/94. She resumed cardiac rehabilitation three weeks later and progressed very well. HP's case demonstrates the value of a monitored exercise program in that we were able to clearly document her arrhythmias and correlate them with her accompanying symptoms and hemodynamic response to exercise. In addition, the efficacy of various antiarrhythmic medications was evaluated under stress which provided her physician with valuable information.