ALTERATIONS OF SYMPATHOVAGAL BALANCE IN PATIENTS WITH HYPERTROPHIC AND DILATED CARDIOMYOPATHIES ASSESSED BY SPECTRAL-ANALYSIS OF RR INTERVAL VARIABILITY

Spectral analysis of RR interval variability was performed in 35 ambul atory patients with early hypertrophic cardiomyopathy (HCMa, NYHA clas s I), 21 hospitalized patients with advanced hypertrophic cardiomyopat hy (HCMh, NYHA class II or III), and 18 hospitalized patients with dil ated carcdiomyopathy (DCMh, NYHA class I, II or III). Twenty-nine ambu latory subjects (COTa) and 20 hospitalized volunteers (COTh) served as normal controls. The RR interval standard deviation (SD), the high-fr equency power (HF: 0.15-0.40 Hz corrected by the mean RR interval (CCV HF) and the normalized unit of the HF power (NUHF) served as markers o f vagal modulation. Low-frequency power (LF: 0.04-0.15 Hz) corrected b y the mean RR interval (CCVLF) and the normalized unit of LF power (NU LF) were markers of sympathetic modulation. The LF/HF ratio was an ind ex of sympathovagal balance. There was no significant difference in th e 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 rat ios (P<0.05) at night relative to the COTh group. Two patients who lat er died suddenly in the HCMh group had markedly reduced CCVHF values ( 0.2-0.8%) relative io the survivors in the group (mean +/- SD in the m orning, afternoon and night, 1.07 +/- 0.43%). CCVLF and NULF values, a nd LF/HF ratios were higher (P<0.01 in CCVLF and NULF; P<0.005 in LF/H F) and the NUHF value was lower (P<0.02) at night in the DCMh group co mpared to the COTh group. We found no correlation between echocardiogr aphic 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 hyper troph ic cardiomyopathy and dilated cardiomyopathy.