RESUMO
Three groups of subjects were included in this study. Group I: 50 subjects with no evidence of structural heart disease to study normal heart rate variability indices using time domain analysis in normal children. Group II included 30 patients with congenital left to right shunt with no evidence of heart failure. Group III included 20 patients with congenital left to right shunt and heart failure. All groups are both age and weight matched. Based on analysis of 24 hours ambulatory electrocardiographic monitoring data we noticed no significant difference between group I and group II in all time domain indices while there was significant reduction of all indices in group three compared to other 2 groups [P <0.001 for both SDNN and SDANN and <0.01 for pNN50 and rMSSD] using one way ANOVA]. We concluded that, the presence of heart failure in patients with CHD augments sympathetic nervous system activity in those patients and is responsible for the genesis of arrhythmias in them