Heart rate recovery after exercise: a study by wavelet analysis

The reduction in heart rate (HR) during the first min of recovery immediately after a maximal exercise stress test (GXT) has recently been found to be a powerful and independent predictor of mortality. A modified continuous wavelet transform (CWT) designed in our lab, is used to perform time-dependent spectral analysis during the non steady-state conditions created by GXT. This method provides dynamic measures of the low frequency (LF) and high frequency (HF) peaks, associated with autonomic activity. A group of 18 patients underwent GXT using the Bruce Protocol. Five of 18 patients demonstrated pathologic delta HR (≤ 18 bpm), while 13 patients displayed normal delta HR (≫ 18 bpm). Patients with pathologic delta HR displayed significantly (p < 0.05) lower HF fluctuations at one-min post exercise than did the controls. Attenuated delta HR upon recovery from GXT is indeed associated with abnormal vagal function, as assessed by CWT.