Influence of the Maximum Heart Rate Attained during Exercise Testing on Subsequent Heart Rate Recovery

BACKGROUND: Abnormal heart rate recovery (HRR) following exercise testing has been shown to be a predictor for adverse cardiovascular events. The actual maximum heart rate (MHR) attained during the exercise test does not however have a distinct significance in traditional HRR assessment. The objective of this study was to investigate the role of MHR in HRR. METHODS: This prospective study consisted of 164 patients (62% male, mean age 53.7 + or - 11.7 years) who were referred for a symptom-limited standard Bruce Protocol treadmill exercise test, based on clinical indications. The patients were seated immediately at test completion and the heart rate (HR) recorded at one and two minutes postexercise. A normal HRR was defined as a HR drop of 18 beats per minute or more at the end of the first minute of recovery. The HRR profile of patients who reached > or = 85% of their maximum predicted heart rate (MPHR) during peak exercise were then compared to HRR profile of those who could not. RESULTS: One hundred twelve patients (Group A) achieved a MHR > or = 85% of MPHR during peak exercise whereas 52 patients (Group B) did not. Chi-square analysis showed a higher incidence of normal HRR in Group A compared to Group B (p = 0.029). Analysis of variance with repeated measures showed that group A had a greater HRR at the first minute F(1,162)= 6.98, p = <0.01) but not the second minute (F(1,162)=1.83, p = .18) postexercise. CONCLUSION: There is a relation between the peak heart rate attained during exercise and the subsequent HRR. A low peak heart rate increases the likelihood of a less than normal HRR. Assessment of the entire heart-rate response seems warranted for more thorough risk-stratification.