A CORRELATIVE STUDY ON DETERMINANTS OF TIME DOMAIN MEASURES OF CARDIAC VAGAL FUNCTION IN HEALTHY SUBJECTS

Abstract

Abstract: Introduction: E: I ratio and r-MSSD are known indicators of cardiac vagal activity. But their determinants are unclear. Objective: To evaluate the determinants of E: I ratio and r-MSSD in healthy subjects. Materials and Methods: 141 healthy subjects were studied. In them body mass index (BMI), Q-T interval, heart rate (HR), systolic, diastolic, pulse and mean arterial blood pressure (MABP) were measured. Age and sex of the subjects were noted. E: I ratio and r-MSSD was estimated from one minute lead II electrocardiogram in supine position. E: I ratio was recorded while breathing at 6 respiratory cycles per minute and r-MSSD was quantified during normal breathing. Data was analyzed by Pearson Correlation Coefficient and unpaired t test. p value less than 0.05 was considered significant. Results: There was positive correlation between E: I ratio and r-MSSD (p = 0.006). E: I ratio and r-MSSD were negatively correlating with age (p < 0.01). r-MSSD was negatively correlating with HR, systolic, diastolic, pulse and MABP (p = 0.0001, 0.01, 0.03, 0.04, 0.01 respectively). r-MSSD did not correlate with BMI and Q-T interval. E: I ratio did not correlate with blood pressure, BMI and Q-T interval. Mean E: I ratio and r-MSSD of males did not differ compared to females. Conclusion: E: I ratio and r-MSSD are correlated. Age is an influencing factor of E: I ratio and r-MSSD. Blood pressure and HR are the other determinants of r-MSSD but not of E: I ratio in healthy subjects.