Alterations of autonomic nervous activity preceding nocturnal variant angina: sympathetic augmentation with parasympathetic impairment.

BACKGROUND

Autonomic nervous discharge has been implicated in the pathogenesis of coronary artery spasm.

METHODS

Cardiac autonomic nervous activities were evaluated from the power of the low-frequency and the high-frequency spectral components of heart rate variability with Holter monitoring in 18 patients with nocturnal variant angina. Samples during the first 512 seconds of each 10-minute period from 60 minutes before to immediately before an anginal attack occurring during the night or at dawn (2:00 to 7:00 AM) were analyzed by fast Fourier transformation.

RESULTS

The R-R interval during the 10- to 0-minute period was significantly shorter than those during the other 10-minute periods. The coefficient of variance of the high-frequency component (0.15 to 0.40 Hz) (CVHF) from the 10- to 0-minute period was not significantly different from the other 10-minute periods. However, both the coefficient of variance of the low-frequency component (0.04 to 0.15 Hz) (CVLF) and the ratio of CVLF and CVHF (CVLF/CVHF) were significantly greater during the 10- to 0-minute period than those during the 30- to 20-minute period, respectively. A significant nighttime fluctuation in the spectral components of heart rate variability with a peak in the CVHF and a nadir in both the CVLF and CVLF/CVHF observed in the control group was blunted in the patients during the attack-free periods while they were medicated with calcium entry blockers.

CONCLUSION

Sympathovagal imbalance, sympathetic activation without parasympathetic augmentation, enhanced in the early morning may play an important role in the genesis of coronary artery spasm in patients with nocturnal variant angina.