Heart Rate Variability: for real doctors. Regulation in the disease. Some pathological conditions. Arrhythmias

Yabluchansky N.I., Martynenko A.V.

Heart rate variability: for real doctors. Translation from the Russian version of the book, published at Kharkiv, 2010, 131 p.
The basics and practice of the clinical use of the technology of heart rate variability are outlined for doctors of all specialties and students of medical faculties of universities.

9. Regulation in the disease

Some pathological conditions

Arrhythmias, which associate with a high risk of sudden death, are sensitive to regulatory influences, primarily to the mid-frequency link, with which the steady increase in sympathetic activity is associated.
These data explain the exceptionally high predictive value of HRV at the risk of sudden death.
Arrhythmogenic zones may also depend on the inhomogeneity of the effects of HRV.
Their pathophysiological structure has a neurogenic or humoral nature.
Disturbances in the mid-high-frequency balance increase the vulnerability of the myocardium to malignant tachyarrhythmias, and most often to ventricular arrhythmias.
An increase in sympathetic tone predisposes to a lower threshold for the onset of fibrillation, and in contrast, vagal activity increases it.
The frequency of sudden death increases in the early morning hours, but beta-blockers by lowering sympathetic activity reduce it.
The HRV indices, especially HF, are reduced in patients with a high risk of sudden death.
In the survivors of cardiac arrest, the values of SD and HF power sharply reduces, whereas for the dead they are almost zero.
With long-term observation of a large number of individuals, it was found that with SD less than 25 ms, the risk of sudden death is four times higher than with SD more than 40 ms.
These data confirm that low parasympathetic activity determines the high risk of sudden death, regardless of other risk factors.
The onset of VT is preceded by an increase in the total power of the HRV spectrum, mainly due to LF, without a corresponding rise in HF, which can be explained by a change in autonomous tone toward sympathetic activation.
Circadian changes in the spectral components of HRV also play a significant role in the emergence of life-threatening arrhythmias.
The daily rhythm of HRV changes in such a way that the lowest level of its indicators in the morning after awakening coinciding in time with the highest frequency of sudden death.

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