IJBEM, Vol. 5, No. 1, 2003

Recovery After Graded Exercise Testing: An Under-Appreciated Time of Great Prognostic Value

Michael S Lauer

Department of Cardiovascular Medicine, Cleveland Clinic Foundation, Cleveland, OH, USA

Abstract. During graded exercise testing heart rate increases due to a withdrawal of parasympathetic tone and an increase in sympathetic tone. Immediately after exercise, during the period known as recovery, the parasympathetic nervous system reactivates while sympathetic tone declines leading to a fall in heart rate. ¹ As extensive research has shown that even subtle alterations of autonomic nervous system dysfunction are strongly predictive of death across a wide spectrum of patient populations ^2-4 , we hypothesized that alterations in heart rate decline during recovery should be predictive of death. The decline in heart rate immediately after exercise is known as heart rate recovery. ⁵ Analyses of tens of thousands of patients from different centers have consistently shown that decreased heart rate recovery is associated with an increased risk of death and/or cardiovascular events. ^5-8 The association of heart rate recovery with prognosis is independent of age, gender, standard risk factors, exercise capacity, chronotropic response, ST-segment changes, imaging evidence of ischemia, left ventricular systolic function, angiographic severity of coronary disease, and use of beta-blockers. ^5-9 When heart rate recovery is combined with other prognostic exercise findings, like exercise capacity and chronotropic response, it can be used to easily and inexpensively identify people at varying risks of major events. ¹⁰ Why an attenuated heart rate recovery is predictive of risk is not clear. One possibility is that the decreased vagal tone it reflects weakens that heart 's ability to withstand injury that could stimulate serious ventricular arrhythmias. In order to study this possibility, we examined the association of frequent ventricular ectopy during and immediately after exercise with mortality. ¹¹ In line with our a priori hypothesis, we found that frequent ventricular ectopy during recovery was a stronger predictor of risk of death than frequent ventricular ectopy during exercise. This finding, based on analysis of a cohort of over 29,000 patients, is consistent with an emerging realization that the recovery period after exercise is a time when valuable prognostic information is easily obtainable.

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