Heart Rate Variability in Unexplained Syncope Patients Versus Healthy Controls: A Comparative Study.

Background Syncope or fainting is the sudden and transient loss of consciousness. This could lead to an increase in mortality due to sudden cardiac death or comorbidity in these patients. Heart rate variability (HRV) is a noninvasive bedside procedure for assessing the cardiovascular autonomic function. There may be an abnormal alteration in the HRV parameters in syncope patients. This can be used for looking into cardiovascular autonomic changes in syncope. This would help in early diagnosis and intervention. Objective The aim of this present study was to compare the HRV parameters between unexplained syncope patients and age-matched healthy controls and to find a correlation between HRV parameters and cardiovascular parameters like pulse and mean blood pressure. Materials and methods A five-minute continuous electrocardiogram (ECG) was recorded and HRV analysis was done by ADInstruments' PowerLab (Oxford, United Kingdom) for 25 cases and 25 controls. Results The mean standard deviation of the RR interval (SDRR) in milliseconds was found to be significantly lower in the cases (21.93 ± 3.53) as compared to controls (71.27 ± 27.40). The mean value of the low-frequency to high-frequency ratio (LF/HF) was significantly higher in cases (1.43 ± 0.40) as compared to controls (0.98 ± 1.07). However, there was no significant correlation between the pulse, blood pressure, and HRV measures. Conclusion The findings suggest a sympathetic predominance in the cases of unexplained syncope as compared to the controls.