Circadian Changes Of Heart Rate Turbulence Parameters In Patients With Coronary Artery Disease

Objective:To evaluate circadian variation of heart rate turbulence parameters caused by ventricular premature beats in patients with coronary artery disease.Methods:In 32 outpatients(mean age 62.2±9.7years) of coronary artery disease with enough ventricular premature beats(VBP) in 24-hour Holter monitoring, turbulence onset(TO), turbulence slope(TS), and the number of ventricular premature beats were calculated in 4 equal 4-hour periods during T1 (00:00-04:00),T2 (06:00-10:00), T3(11:00-15:00) and T4(16:00-20:00). Five ventricular premature beats matching the condition were selected in every period, and 3 last sinus RR intervals before VPB and 20 sinus RR intervals after VPB were recorded.TO and TS were calculated based on average RR intervals before and after VPB. TO was defined as a percentage difference between the mean of first 2 RR intervals after a VPB and the 2 last sinus RR intervals before VPB. TS was computed as a maximum positive slope of a regression line assessed over any of 5 consecutive RR intervals within the first 20 sinus RR intervals after VPB.Results:No circadian changes in turbulence onset values were found, while TS displayed significantly higher values during T1 than any other period(12.25, vs.8.83,9.44 and 9.64ms/RR, respectively). There was no statistical difference in TS between T2,T3,and T4.The number of ventricular premature beats displayed significantly lower values during T1 than any other period(76 vs.183,169,165,P<0.008). There was no statistical difference in the number of ventricular premature beats between T2,T3,and T4. The heart rate before ventricular premature beat displayed significantly lower values during T1 than any other period (63 vs.73,70,71, P<0.05).Conclusion:In out-patients with stable coronary artery disease, turbulence slope shows circadian pattern with highest values observed in the night when compared to any other period.