Electrocardiographic exercise testing and ambulatory monitoring to identify patients with ischemic heart disease at high risk of sudden death.

Prognostic significance of ambulatory electrocardiographic monitoring and exercise testing was studied in 144 patients with established ischemic heart disease. A follow-up study showed that 10 sudden deaths occurred within 2 years. The univariates most strongly associated with the subsequent occurrence of sudden death included reduced maximal exercise heart rate, exercise-induced frequent ventricular arrhythmias, complex ventricular arrhythmias revealed by 24 hour ambulatory electrocardiographic monitoring and onset of S-T segment depression during exercise testing. Groups of patients at very high and very low risk of sudden death were identified using conjunction and inclusive disjunction of the foregoing variable. The presence of bivariate and trivariate combinations was associated with an increase up to 20-fold in the incidence of sudden death. Patients with the poorest prognosis were those who stopped exercise before achieving a high heart rate and who exhibited either pronounced electrocardiographic abnormalities during stress testing or complex ventricular arrhythmias during ambulatory monitoring. Combinations of exercise variables identified patients at a very high risk of sudden death, whereas combinations of monitoring variables appeared to be preferable for defining groups of patients at very low risk. The results obtained suggest that the two methods carry different prognostic information and, therefore, may complement each other in identifying potential victims of sudden cardiac death.