The effects of cardiac rehabilitation on heart rate variability in patients with coronary heart disease

September 2005    Volume 12, Issue 5   Br J Cardiol 2005;12:368-70

Authors:
Joseph PA Delaney, John Kelly, Gavin Sandercock, David A Brodie

Structured exercise, as a therapeutic intervention, is central to cardiac rehabilitation (CR). Following myocardial infarction (MI), cardiac autonomic activity becomes disordered, often resulting in loss of vagal reflexes and increased sympathetic activity. Sympathetic hyperactivity predisposes towards ventricular fibrillation, while vagal reflexes are considered to have a cardio-protective effect.
The activity of the autonomic nervous system (ANS) can be measured non-invasively by analysis of heart rate variability (HRV), which is a characteristic that can potentially be increased by physical activity. Coarse-graining spectral analysis (CGSA) of HRV is a sensitive, non-invasive technique commonly used to evaluate cardiac autonomic activity. HRV allows the examination of parasympathetic and sympathetic function via the analysis of the various components of the frequency domain. High frequency spectral power (HF, 0.15–0.40 Hz) is generally considered to be a measure of cardiac parasympathetic modulation, whereas low frequency power (LF, 0.04–0.15 Hz) reflects both parasympathetic and sympathetic control.
The purpose of this study was to determine the effects of a predominantly exercise-based cardiac rehabilitation programme over a six-month period on cardiac autonomic modulation, using power spectral analysis of HRV.

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