Circadian changes in heart rate turbulence parameters.

Heart rate turbulence is a novel method to identify patients at risk of cardiac death, and to date, there are no data concerning its circadian changes. In 46 coronary patients (mean age 63 +/- 8 years) with at least 100 ventricular premature beats in 24-hour Holter monitoring, turbulence onset, turbulence slope, and heart rate variability parameters were calculated in 3 equal 4-hour periods during morning, afternoon, and night. No circadian changes in turbulence onset values were found, while TS displayed significantly lower values during afternoon than during morning or night hours (5.08, vs. 7.08 and 7.99 ms/RR, respectively). Some heart rate variability parameters also showed lower values in the afternoon, not in the morning hours. In conclusion, in hospitalized patients with stable coronary artery disease, turbulence slope shows circadian pattern with lowest values observed in the afternoon when compared to morning and night hours.