HEART RATE ASYMMETRY IN VARIOUS CLINICAL SCENARIOS
The physiological phenomenon of heart rate asymmetry (HRA) is caused by an unequal contributions of heart rate decelerations and accelerations to the variance, structure and complexity of heart rate variability (HRV). With the use of the properties of variance and the Poincaré plots of RR intervals, the HRA has been observed for the short-term, long-term and total HRV. The application of the monotonic runs method of RR intervals has revealed that heart rate decelerations and accelerations create different patterns responsible for the microstructure of heart rate and HRA. The use of Shannon entropy for the analysis of probability distribution RR intervals have shown that heart rate decelerations and accelerations contribute differently to the heart rate complexity. First clinical studies show that HRA is reduced in patients with type 1 diabetes, chronic heart failure or patients with aortic stenosis and a higher NYHA functional class. The analysis of the microstructure of HRA has a prognostic value for mortality (including sudden cardiac death) in survivors of myocardial infarction or patients who have clinical indications for exercise testing. This approach helps to identify preterm neonates at risk of sepsis. On the other hand, the reversed microstructure of HRA is found in patients with the severest form of the obstructive sleep apnea syndrome. HRA is helpful in understanding how HRV is generated but it also gives relevant clinical information. Further prospective studies are necessary to better understand HRA, its mechanisms and additional clinical relevance.