Technology of HRV cannot be applied for diagnostics of the regulative systems, when interactions in the system "regulation - heart" are violated.

The cases or periods of frequent extrasystoles, paroxysmal tachycardia, ... arrhythmia are not analysed. To avoid errors, the intervals which are free from ectopic systoles are analysed or methods of replacing these intervals with expecting sinus systoles are used. Modern diagnostic systems carry out such procedures automatically.

When the sinus node weakness syndrome is expected the differential diagnosis of cardiac and non-cardiac regulatory reasons might be performed with the help of combination of HRV and electrophysiological methods.

But even in cases when HRV technology is inapplicable for diagnostics of the regulatory systems state it still may be used for its direct purpose (estimation of HRV and estimation of its component values). One of the examples is the study of the RR-interval distribution in atrial fibrillation patients: unimodal distribution testifies that the fibrillation is stable and does not threaten the life while bimodal distribution is a symptom of the non-stable arrhythmia and a high risk of the life-threaten dysrhythmias is present. Naturally, the approach to such patients has to be totally different. In the first case it will be enough to obtain normosystoles and in the second case it will be necessary to undertake measures for stabilization of the arrhythmia.