|Cugini P et al.|
Disorder and circadian periodicity in within-day variability of sinusal R-R intervals in myocardial infarcted patients
Journal of Clinical and Basic Cardiology 2000; 3 (1): 53-58
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Keywords: Chaos, Chronobiologie, Entropie, Herzfrequenz, Holter, nichtlineare Dynamik, Chaos, chronobiology, entropy, heart rate, Holter monitoring, nonlinear dynamics
The present study investigates whether the disorder in nonlinear variability of human heart rate shows a periodic pattern along the 24-h scale in postinfarct patients (PIP). The aim is to detect whether there are chronoalterations between disorder and periodicity in heart rate variability (HRV) that can contribute to explaining the postinfarct risk of sudden cardiac death. The study was performed in 7 asymptomatic PIP, who have had an acute myocardial infarction, complicated by ventricular arrhythmias, three months prior to the research. The control group was constituted by 10 clinically healthy subjects (CHS). Each one of the CHS and PIP underwent a Holter electrocardiogram. The sinusal R-R intervals (SRRI) of each dynamic Holter monitoring were detected and partitioned in units of one hour to cover the 24-h span. The hourly-qualified values of the SRRI were analyzed in their disorder using the Information Entropy (E) method. The hourly-qualified mean values of both the SRRI and E were, further, analyzed for their eventual circadian rhythm (CR), via the Cosinor method. A clear nychtohemeral variability was found in the hourly-qualified mean values of both the SRRI and E. This variability during the day was found to have a significant CR. However, the oscillatory extent for the E CR was found to be less pronounced in PIP as compared to CHS. In addition, the oscillatory acrophase of the E CR was found to be shifted to the night in PIP as compared to CHS. The lack of the matutinal increase of disorder in HRV may be speculatively regarded as a mechanism for explaining why the PIP are more exposed to the risk of sudden cardiac death in the morning hours. J Clin Basic Cardiol 2000; 3: 53-8.