Circadian variation of spectral indices of heart rate variability after myocardial infarction

Role of Circadian Rhythmicity in the Heart Rate Variability Preceding Non-Sustained Ventricular Tachycardia

“…3,4 The 24-h cycle of HRV (which is defined as a circadian rhythm) may be an important factor because high sympathetic activity that persists throughout a 24-h period may acceleratereceptor down-regulation 19 and promote a reduction of catecholamine stores in the heart. 20,21 Thus, the patients with reduced circadian rhythmicity of HRV may have impaired autonomic nervous function such as diabetic neuropathy, 12 prior myocardial infarction 13,14 or congestive heart failure. 15,16 Previous studies demonstrated that patients with NSVT also have reduced circadian variation of HRV; 7,10 however, we noted that some patients with NSVT have a preserved circadian rhythm.…”

Non-Invasive Assessment of the Autonomic Nervous System

“…When the power of sympathetic and parasympathetic frequencies were calculated in normalised units an increased low frequency component and diminished high frequency component was observed during resting conditions and over 24-hour electrocardiography recordings [17]. These results indicate sympathetic predominance.…”

Nonlinear Cardiac Dynamics and Morning Dip: An Unsound Circadian Rhythm

“…We calculated low-and highfrequency power by integrating the power spectral density curve in the 0.04 0.15Hz range and over 0.15Hz range 20) . This study aimed to compare different periods of the day with significant differences in mean RR interval and its variance, and we therefore used the normalized units of power 21) . The normalization process consisted of dividing the power of a given component by total power minus the DC component and each normalized power was multiplied by 100.…”

“…The normalization process consisted of dividing the power of a given component by total power minus the DC component and each normalized power was multiplied by 100. The normalized low-and high-frequency component represented sympathetic and parasympathetic acitivity, respectively 20,21) .…”