Abstract
Recovery from exercise can be divided into an early, rapid period and a late, slower period. Although early heart rate (HR) recovery 1 minute after treadmill exercise independently predicts survival, the prognostic value of late HR recovery has not been well studied. The aim of this study was to evaluate the independent prognostic value of late HR recovery for all-cause mortality. A total of 2,082 patients referred to the nuclear cardiology laboratory of an urban academic medical center for treadmill exercise with imaging from August 1998 to December 2003 were followed for all-cause mortality. During 9.9 ± 1.5 years of follow-up, 196 deaths (9%) occurred. To avoid overlap with early HR recovery or the baseline HR, late HR recovery was defined as the percentage of the cycle length change between rest and peak exercise that had been recovered after 5 minutes. Lower values represent impaired recovery, by analogy with 1-minute HR recovery. Impaired late HR recovery was a significant univariate predictor of all-cause mortality (hazard ratio 0.28 per percentage, 95% confidence interval 0.17 to 0.46, p <0.001). It significantly improved a nested, multivariate model (change in chi-square 8.66, p = 0.003), including 1-minute HR recovery, with independent prognostic value (adjusted hazard ratio 0.58, 95% confidence interval 0.41 to 0.84, p = 0.004). In conclusion, late HR recovery after treadmill exercise stress adds prognostic value for all-cause mortality to a multivariate model including early, 1-minute HR recovery.
