INCREASE OF DAYTIME LF HEART PERIOD VARIA BILITY AFTER 4-WEEK REHABILITATION IN PATIENTS WITH CORONARY-ARTERY DISEASE

In 97 patients hospitalized in a rehabilitation clinic after myocardia l infarction, bypass operation or coronary angioplasty a 24 hour ecg w as recorded at the beginning and end of their hospital stay. From each ecg, heart period variability was calculated using an FFT based spect ral algorithm. Spectral power within the frequency ranges 0.04-0.15 Hz (low frequency, LF), 0.15-0.4 Hz (high frequency, HF) and 0-0.5 Hz (t otal frequency, TF) was integrated for every 10 minute interval. Subse quently the mean of all integrals was evaluated between 8 am and 4 pm as well as between 12 pm and 5 am. At the beginning of rehabilitation variability both during the day and at night was lower in patients wit h multiple vessel disease as well as those after bypass operation when compared to patients with single vessel disease and those without byp ass, respectively. During hospital stay the daytime LF component incre ased significantly (p < 0.005) about 8% over all patients. Other spect ral components of the 24 hour registration showed no relevant changes during rehabilitation. As any change in vagal tone would affect the HF component of the spectrum, the increase in the LF component observed here may be interpreted as a change primarily in sympathetic tone due to rehabilitation. This positive training effect seems to be predomina nt in less seriously diseased patients.