Exercise-induced myocardial ischaemia complicated by paroxysmal complete atrioventricular block

Abstract

This study describes a case of exercise-induced myocardial ischaemia accompanied by complete atrioventricular block (CAVB). A 59-year-old man with major depression, treated with regular imipramine and lithium for 20 years, experienced syncope episodes during exercise. Exercise, testing initially, identified ST depression in the inferior leads, and later found CAVB resulting in syncope and seizure. The patient recovered completely after resuscitation. Myocardial ischaemic markers were negative, but 35% stenosis was detected in the distal left main coronary artery by angiography. The combined use of verapamil, nitrate and aspirin was treated as the possible coronary spasm. Repeat treadmill caused negative ischaemic study or exercise-induced arrhythmia, 7 days later. The pathophysiology of the very rare exercise-induced paroxysmal CAVB has been reviewed.Exercise-induced complete atrioventricular block (CAVB) in patients with normal resting electrocardiogram is rare (1-4). This study reports the clinical features of a 59-year-old male with recurrent syncope on exercise, caused by CAVB without conduction system abnormalities at rest. To our knowledge, this study is the first to describe a case of exercise-induced myocardial ischaemia resulting in paroxysmal CAVB as the initial presentation in a 59-year-old male. C A S E R E P O R TA 59-year-old male presented to our out-patient department, complaining of syncope that lasted for 5 min after exercise in the morning, on June 17, 2003. The man regularly took imipramine (112 mg per day) and lithium carbonate (600 mg per night) for major depression. Clinical examination was unremarkable. Resting ECG revealed sinus rhythm. The patient underwent a treadmill test immediately after presenting at our clinic. After 3 min of performing the stage 1 exercise test, the patient complained of chest discomfort with ST elevation in the inferior leads and V2 (Figure 1). The patient then suddenly collapsed and suffered a CAVBinduced seizure (Figure 2A). Subsequently taken ECG displayed persistently elevated ST in the inferior leads and V1 with reciprocal ST depression in V2 to V6 ( Figure 2B). Following 4-min emergent resuscitation, the patient recovered completely except for persisting sinus tachycardia (Figure 3). Sequential cardiac troponin-I and creatine kinase MB were normal. Other test results included elevated uric acid (12.4 mg/dl, normal range: 2.5-7.5 mg/dl) and cholesterol (219 mg/dl, normal limit: below 200 mg/dl). Blood levels of imipramine and lithium carbonate were both within normal limits. Chest X-ray, echocardiography and brain computer tomograph were all unremarkable. 1 h later, emergent coronary angiography indicated 35% stenosis in the distal left main coronary artery with TIMI 4 flow, and no obvious thrombus was demonstrated. However, the patient refused to perform ergonovine provocation for coronary artery or electrophysiological studies. Under the impression of coronary spasm, the patient was treated daily with aspirin (100 mg), verapamil SR (240 mg), isosorbide-5-m...

ECG of the Month

“…In humans, exercise-induced AV block that occurred either spontaneously or as a rare complication of an exercise-stress test has been reported. [1][2][3][4][5][6][7] One proposed mechanism for this tachycardia-dependent AV block is acute ischemia of the conduction system as a result of the exerciseinduced tachycardia. The myocardial ischemia during exercise is secondary to increased myocardial oxygen consumption and decreased duration of diastole, both of which result in decreased oxygen delivery.…”

Complete atrioventricular block during exercise: New insights from an old test

“…Indeed, an ischemic defect affecting the atrioventricular (AV) node has been described as a possible cause of exercise-induced CAVB [10,13,14]. Besides significant epicardial CAD, arterial vasospasm has also been described a possible cause of CAVB [15]. In the present case, however, both etiologies seem unlikely, given the absence of significant epicardial CAD (specifically in the right coronary artery) and the absence of chest pain or ST segment elevation prior to the development of CAVB during the exercise test.…”