Reduced HRV is found in patients with different diseases, e.g., diabetes mellitus. Reduced HRV has also been used as a predictor of the risk for sudden cardiac death after myocardial infarction and other heart diseases.
HRV is most often analysed by power spectrum analysis. The power spectral density gives a quantitative measure of the total variability of the fluctuations around the mean value, but it also provides estimates of the frequency and power of the different components in the signal, information that has been associated with different physiological mechanisms. Abnormal HRV patterns can be due to both autonomic dysregulation, which often results in reduced HRV, but also because of heart rate rhythm disturbances due to cardiac arrhythmia and conduction disturbances, which often results in high HRV. Such abnormal patterns may be difficult to detect if only HRV is analysed , but may become obvious if several cardiovascular signals are analysed simultaneously, such as HRV and respiration.
Both HRV and oscillations in blood pressure variability (BPV) reflect short-term regulatory mechanisms. Many different approaches have been applied to assess information regarding the function of the complex cardiovascular system, a system that includes multiple feedback loops. One such feedback loop is cardiac autonomic control in response to baroreceptive information. Of particular interest in our current projects is the question regarding normal and abnormal patterns in the short-term interactions between HRV and blood pressure oscillations.