Copyright © 1995 by the European Society of Cardiology.
© 1995 The European Society of Cardiology
Alterations of sympathovagal balance in patients with hypertrophic and dilated cardiomyopathies assessed by spectral analysis of RR interval variability
Department of Cardiovascular Medicine, School of Medicine, Tokai University Isehara, Japan
revised 20 September 1994; accepted 11 October 1994.
Correspondence: Teruhisa Tanabe, MD, Department of Cardiology, School of Medicine, Tokai University, Bohseidai, Isehara, Kanagawa, 259-11, Japan
Abstract
Spectral analysis of RR interval variability was performed in 35 ambulatory patients with early hyperirophic cardiomyopathy (HCMa, NYHA class I), 21 hospitalized patients with advanced hypertrophic cardiomyopathy (HCMh, NYHA class II or III), and 18 hospitalized patients with dilated cardiomyopathy (DCMh. NYHA class I, II or III Twenty-nine ambulatory subjects (COTa) and 20 hospitalized volunteers (COTh) served as normal controls. The RR interval standard deviation (SD), the high-frequency power (HF: 0·15–0·40 Hz) corrected by the mean RR interval (CCVHF) and the normalized unit of the HF power (NUHF) served as markers of vagal modulation. Low-frequency power (LF: 0·04–0·15 Hz) corrected by the mean RR interval (CCVHF) and the normalized unit of LF power (NULF) were markers of sympathetic modulation. The LFIHF ratio was an index of sympathovagal balance.
There was no significant difference in the SD, CCVHF, NUHF, CCVLF, NULF or the LF/HF ratio between the HCMa and COTa groups. At night, the SD was lower in the HCMh group relative to the COTh group (P<0·01). The HCMh group demonstrated lower CCVHF and NUHF values (P<0·01), higher NULF values (P<0·01) and higher LF/HF ratios (P<0·05) at night relative to the COTh group. Two patients who later died suddenly in the HCMh group had markedly reduced CCVHF values (0·2–0·8%) relative to the survivors in the group (mean ± SD in the morning, afternoon and night, 1·07 ± 0·43%). CCVLF and NULF values, and LF/HF ratios were higher (P<0·01 in CCVLF and NULF; P<0005 in LF/HF and the NUHF value was lower (P<002) at night in the DCMh group compared to the COTh group. We found no correlation between echocardiographic parameters and the CCVHF, NUHF, CCVLF, NULF or the LF/HF ratio.
These changes in the power spectrum of heart rate variability suggest alterations in sympathovagal balance with reduced vagal and increased sympathetic outflow to the heart in patients with advanced hypertrophic cardiomyopathy and dilated cardiomyopathy.
Key Words: Hypertrophic cardiomyopathy • dilated cardiomyopathy • RR interval variability • power spectral analysis • echocardiography
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