Association Between Delayed Heart Rate Recovery and Incident Hypertension: A Revisit of CARDIA

To the Editor: I read with interest the article “Delayed Heart Rate Recovery Is Strongly Associated With Early and Late-Stage Prehypertension During Exercise Stress Testing” by Aneni et al.,1 which reported that in a cross-sectional analysis, delayed heart rate recovery (HRR) was independently associated with early and late stages of prehypertension among asymptomatic patients undergoing stress testing. The authors recommended that further studies are needed to determine the usefulness of measuring HRR in the prevention and management of hypertension. As is known, cardiac autonomic dysfunction, as measured by heart rate variability, is associated with new-onset hypertension in the Atherosclerosis Risk in Communities Study and the Framingham Heart Study.2,3 However, reports regarding the association between HRR after peak exercise and incident hypertension are rare. Ali Kizilbash et al. demonstrated in the Coronary Artery Risk Development in Young Adults (CARDIA) study that delayed baseline HRR was associated with a higher cross-sectional level but not longitudinal (15-year follow-up) increases in systolic blood pressure. Although a significant relationship of faster HRR with longitudinal increase in diastolic blood pressure was observed, the relationship was small and clinically irrelevant.4 The findings from CARDIA that delayed HRR is not associated with the development of hypertension may have answered, in part, the questions raised by Aneni et al. However, because the participants in CARDIA were young adults at entry, the results in CARDIA may not be appropriately applied to the middle-aged people in this study. Moreover, to avoid bias, correct interpretation of comparisons of HRR is dependent on standardization of the exercise protocol. Therefore, the combination of cardiac chronotropic incompetence and delayed HRR as a measure of autonomic dysfunction during exercise should be considered to evaluate incident hypertension in the future. The author declared no conflict of interest.