Reduced Heart Rate Variability in Ischemic Heart Disease Is Only Partially Caused by Ischemia

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Abstract

Background: Reduced heart rate variability (HRV) after acute myocardial infarction (AMI) indicates poor prognosis. HRV in patients with uncomplicated coronary artery disease is reduced, and an association with poor prognosis has been suggested. The mechanism of the HRV reduction is not known, but ischemia is a possibility. Aim: To evaluate, in angina patients with no prior AMI, no other disease and drug-free, if complete revascularization and thus important reduction of ischemia by means of PTCA influences HRV. Patients and Methods: Twenty-four-hour Holter recordings were performed at baseline prior to PTCA in 48 patients with angina and in 41 age-matched healthy control subjects. The recording was repeated 1 and 6 months after complete revascularization. In addition, HRV was registered during controlled respiration in the supine and standing positions and during cold pressure test at baseline in all angina patients and controls and in 17 consecutive angina patients 6 months after PTCA. Results: Compared to controls, angina patients had a significantly reduced mean RR interval (p = 0.02), SD (p = 0.003), rMSSD (p = 0.03), pNN50 (p = 0.03), total power (p = 0.003), low- (p = 0.004) and high-frequency peak (p = 0.04), but normal SDNN, SDANN and LF/HF. One and 6 months after PTCA, 42/46 and 32/40 follow-up patients, respectively, were free of angina. Six months after PTCA, there was a significant recovery of vagal modulation seen in the frequency domain during controlled respiration, but only nonsignificant trends in HRV parameters analyzed over 24 h. Conclusion: Patients with uncomplicated angina had reduced HRV, mainly affecting vagal activity, but normal low frequency variability associated with mortality. Complete revascularization caused a partial normalization of vagal modulation indicating that ischemia may be one of but not the only mechanism of the HRV reduction in uncomplicated chronic coronary artery disease.

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Most cited references 1

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Physical activity influences heart rate variability and very-low-frequency components in Holter electrocardiograms.

L Bernardi, P Sleight, F. Valle … (1996)

A major proportion of RR interval variability in long-term recordings is due to slow (< 0.03 Hz) fluctuations, which seem to be a good predictor of survival after myocardial infarction, whose origin remains unclear. To study the effect of physical activity we compared by spectral analysis of the RR interval in 10 healthy human subjects (aged 28[s.e. 2] years) during 1-h periods each of rest (no activity), alternating rest and mild exercise (rhythmic activity), and normal spontaneous (random) activity. Compared to rest, during both random and rhythmic activities, the RR variance increased significantly (from 5802[1030] to 13388[1448] ms2, P < 0.05, and to 24959[2901], P < 0.001) due to an increase in power below 0.03 Hz (from 3017[467] to 9606[966] ms2, P < 0.01, and to 21 103[2298] ms2, P < 0.001) which explained 55.4, 73.2 and 86.1% of total RR variance, respectively. The amount of RR variability and its slower fluctuations largely depend on physical activity, regardless of its regular or irregular occurrence. Attempts to predict cardiovascular prognosis on the basis of RR fluctuations should therefore take account of the confounding effect of physical activity since healthier subjects would probably be more active.