The results of a study showed that the heart-rate profile during exercise and recovery is a predictor of sudden death.

Changes in heart rate during and after exercise are mediated by the balance between sympathetic and vagal activity.
Since alterations in the neural control of cardiac function contribute to the risk of sudden death, researchers tested the hypothesis that among apparently healthy persons, sudden death is more likely to occur in the presence of abnormal heart-rate profiles during and after exercise.

A total of 5713 asymptomatic men, aged 42-53 years, none of whom had clinically detectable cardiovascular disease, underwent exercise testing between 1967 and 1972.

A research, led by Xavier Jouven from Université Paris-5, Hôpital Européen Georges Pompidou, Paris, examined the data of exercise testing.

During a 23-year follow-up period, 81 persons died suddenly.

Men with a resting heart rate that was more than 75 beats per minute had nearly 4-fold increase of risk of sudden death from myocardial infarction ( relative risk, RR= 3.92 ); in subjects with an increase in heart rate during exercise that was less than 89 beats per minute the risk was 6-fold higher ( RR= 6.18 ); and in subjects with a decrease in heart rate of less than 25 beats per minute after the termination of exercise the risk was doubled ( RR= 2.20 ).

Source: The New England Journal of Medicine, 2005


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