Susceptibility to neuromediated syncope after acute myocardial infarction

• Published in: European journal of clinical investigation Vol. 30; no. 5; pp. 383 - 388
• Main Authors: Wasek, W, Kulakowski, P, Czepiel, A, Klosiewicz--Wasek, B
• Format: Journal Article
• Language: English
• Published: Oxford BSL Blackwell Science Ltd 01.05.2000; Blackwell; Blackwell Publishing Ltd
• Subjects: Adrenergic beta-Antagonists - therapeutic use; Adult; Angiotensin-Converting Enzyme Inhibitors - therapeutic use; Autonomic nervous system; Autonomic Nervous System - drug effects; Autonomic Nervous System - physiopathology; Biological and medical sciences; Cardiology. Vascular system; Coronary heart disease; Electrocardiography, Ambulatory; Follow-Up Studies; Heart; Humans; Incidence; Male; Medical sciences; Middle Aged; myocardial infarction; Myocardial Infarction - diagnosis; Myocardial Infarction - drug therapy; Myocardial Infarction - epidemiology; Prospective Studies; Risk Factors; Space life sciences; syncope; Syncope - diagnosis; Syncope - epidemiology; Syncope - physiopathology; Tilt-Table Test; Human; Nervous system diseases; Infarct; Pathogenesis; Consciousness impairment; Cardiovascular disease; Vasovagal syncope; Coronary heart disease; Myocardial disease; Epidemiology; Incidence; Diseases of the autonomic nervous system; Myocardium; Neurological disorder; Patient position
• ISSN: 0014-2972; 1365-2362
• DOI: 10.1046/j.1365-2362.2000.00641.x

Background Syncope after acute myocardial infarction (AMI) is a common clinical problem. It may be hypothesised that remodelling and neurohormonal changes following AMI may predispose to neuromediated syncope. Design To address this issue we prospectively evaluated the incidence of positive results of head‐up tilt‐table testing in 40 patients following AMI and 40 age and sex matched controls without a history of syncope. The mechanisms of tilt‐induced changes in autonomic tone were assessed using spectral analysis of heart rate variability. The patients were followed‐up for one year. Results Positive results of tilt‐test occurred in 4 (10%) controls and 13 (33%) AMI patients (P = 0.01). No significant differences in sympathovagal interaction (assessed by a low frequency/high frequency ratio) were detected between the groups before tilting (2.9 ± 1.9 vs. 3.1 ± 2.2; NS). However, dynamic changes of this parameter differed significantly during the first 5 symptomless minutes of the active phase of tilt‐test. The ratio increased in the majority of controls (87%) and decreased in the majority of patients (62%) (P < 0.0001). During one year follow‐up, syncope or presyncope occurred in 10 (25%) AMI patients but did not occur in any control subject (P < 0.001). The sensitivity, specificity and predictive accuracy of an early tilt‐test after AMI for the prediction of syncope or presyncope was 70%, 80% and 78%, respectively. Conclusion Patients after AMI are prone to neuromediated reactions. Sympathetic withdrawal seems to be the most likely mechanism of syncope. The role of tilt testing for identification of patients susceptible to syncope or presyncope after AMI needs further investigation.