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Alterations of autonomic nervous activity in recurrence of variant angina
M Takusagawa1, S Komori, K Umetani
1The Second Department of Internal Medicine, Yamanashi Medical University, 1110 Shimokato, Tamaho, Yamanashi 409-3898, Japan. mtaku@res.yamanashi-med.sc.jp
Objective:
To investigate whether autonomic nervous activity is involved in the recurrence of spontaneous coronary spasm in variant angina.
Design:
Retrospective analysis.
Setting:
Cardiology department of a university hospital.
Patients:
18 patients with variant angina were divided into single attack group (SA; nine patients) and multiple attack group (MA; nine patients) according to the frequency of ischaemic episodes with ST segment elevation during 24 hour Holter monitoring.
Methods:
Heart rate variability indices were calculated using MemCalc method, which is a combination of the maximum entropy method for spectral analysis and the non-linear least squares method for fitting analysis, at 30 second intervals for 30 second periods, from 40 minutes before the attack to 30 minutes after the attack. High frequency (HF; 0.04-0.15 Hz) was defined as a marker of parasympathetic activity, and the ratio of low frequency (LF; 0.15-0.40 Hz) to high frequency (LF/HF) as an indicator of sympathetic activity. The averaged value during the 40 to 30 minute period before an attack was defined as the baseline.
Results:
Compared with baseline, the HF component decreased in both groups at two minutes before the attack (p < 0.01), and the LF/HF ratio decreased at three minutes before the attack (p < 0.01). The baseline LF/HF was lower in the MA group than in the SA group (p < 0. 01).
Conclusions:
A reduction of sympathetic activity may play a key role in determining the recurrence of transient ischaemic events caused by spontaneous coronary spasm in patients with variant angina.