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.
Keywords:
E: I ratio - r-MSSD - blood pressure - heart rate - vagal function - healthy subjects
