[The assessment and clinical significance of heart rate variability]

Heart rate variability (HRV) is a phenomenon to generation through the sinus node consecutive impulses in the different succession. HRV is regarded as a marker of autonomic nervous system tone of the heart. To assess HRV following methods: time domain, frequency domain and non-linear analysis are known. Time domain parameters correlate with frequency domain parameters. Some parameters can be used substitution, particularly reflect parasympathetic activity: rMSSD, pNN50 and HF. In clinical practice the most useful is time domain analysis based on 24-hours ecg Holter monitoring. Among time domain parameters the most significant prognostic value has SDNN. Decreased HRV following many diseases has been described. Significant prognostic value of decreased HRV after myocardial infarction (MI) and in patients with chronic heart failure (CHF) has been proved. Decreased HRV after MI is independent as well as ejection fraction (EF) sudden cardiac death risk factor. In patients with SDNN value below 50 ms high risk of cardiac death is observed. SDNN should be estimated on 7th day of MI to evaluate patients with high risk of sudden cardiac death. In patients after MI with ventricular tachycardia (VT) before VT decreased HRV is described. During MI beneficial influence of infarct-related artery patency on HRV is observed. HRV correlates with EF and infarct site too. HRV in patients with CHF correlates with EF and functional severity of CHF. Correlation between decreased HRV and increased mortality in CHF has been shown. In diabetic patients decreased HRV is observed. Following diabetes examination of HRV is useful to estimate early phase of autonomic neuropathy. Increase HRV parameters is observed in the course of beta-adrenolytic and converting enzyme inhibition treatment. In other diseases, including heart transplantation prognostic value of HRV and its clinical significance are still investigated.