Abstract 10793: Prognostic Value of Late Heart Rate Recovery After Treadmill Exercise
Introduction: Heart rate recovery (HRR) after exercise (EX) can be divided into an early, rapid and a late, slower period. Early 1-minute HRR is an established predictor of survival. However, complete HRR after EX takes much longer than 1 minute and is a complex interplay among intrinsic, sympathetic, and parasympathetic components. The prognostic value of this later component of HRR after EX has not been well studied.
Methods: A cohort of patients underwent treadmill EX with SPECT imaging. Early and late HRR were recorded in addition to standard variables. Late HRR was measured as the % recovery from peak EX to rest ([rest RR-interval - 5-minute recovery RR-interval]/[rest RR-interval - peak EX RR-interval]*100). All-cause mortality was obtained from a national database to compute length of survival with ≥7 years of follow-up for all patients. A nested multivariable Cox proportional hazards model tested the incremental value of late HRR over established variables (age, sex, classical cardiac risk factors, prior revascularization, body mass index, cardiac medications, and treadmill, ECG, and SPECT parameters).
Results: 2,082 patients (age 55±11 years, 57% male) were included. 196 deaths (9.4%) occurred during an average 9.5 years of follow-up. Survival differed among late HRR quartiles with a univariate hazard ratio of 0.28 (95%CI 0.17-0.46, p<0.001). 17 of 26 established variables were significant univariate predictors at p<0.05 and 23 of 26 at p<0.20. Late HRR improved a multivariate model (including 1-minute HRR, age, diabetes, EX time, EF, beta-blocker) compared to baseline (Δχ2=8.66, p=0.003), with an adjusted hazard ratio of 0.58 (95%CI 0.41-0.84, p=0.004).
Conclusions: Late HRR at 5 minutes after treadmill exercise is an independent prognostic marker for all-cause mortality, improving the multivariable model including 1-minute HRR. The importance of both components likely reflects the different pathophysiologic bases for early and late HRR.
- © 2011 by American Heart Association, Inc.