Weekly variation of the QT dispersion in healthy subjects and in patients with coronary heart disease.

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Abstract

A circadian and seasonal variation of QT dispersion (QTd) has been shown in healthy individuals. Nevertheless, no data exist regarding the weekly influences on the QTd in healthy individuals and in patients with coronary heart disease (CHD).

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Circadian variation in the frequency of onset of acute myocardial infarction.

J E Muller, P H Stone, Z Turi … (1985)

To determine whether the onset of myocardial infarction occurs randomly throughout the day, we analyzed the time of onset of pain in 2999 patients admitted with myocardial infarction. A marked circadian rhythm in the frequency of onset was detected, with a peak from 6 a.m. to noon (P less than 0.01). In 703 of the patients, the time of the first elevation in the plasma creatine kinase MB (CK-MB) level could be used to time the onset of myocardial infarction objectively. CK-MB-estimated timing confirmed the existence of a circadian rhythm, with a three-fold increase in the frequency of onset of myocardial infarction at peak (9 a.m.) as compared with trough (11 p.m.) periods. The circadian rhythm was not detected in patients receiving beta-adrenergic blocking agents before myocardial infarction but was present in those not receiving such therapy. If coronary arteries become vulnerable to occlusion when the intima covering an atherosclerotic plaque is disrupted, the circadian timing of myocardial infarction may result from a variation in the tendency to thrombosis. If the rhythmic processes that drive the circadian rhythm of myocardial-infarction onset can be identified, their modification may delay or prevent the occurrence of infarction.

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QT dispersion: an indication of arrhythmia risk in patients with long QT intervals.

Robert Campbell, J McComb, Jon P. Day (1990)

Homogeneity of recovery time protects against arrhythmias whereas dispersion of recovery time is arrhythmogenic. A single surface electrocardiographic QT interval gives no information on recovery time dispersion but the difference between the maximum and minimum body surface QT interval may be relevant. This hypothesis was tested by measuring the dispersion of the corrected QT interval (QTc) in 10 patients with an arrhythmogenic long QT interval (Romano Ward and Jervell and Lange-Nielsen syndromes or drug arrhythmogenicity) and in 14 patients without arrhythmias in whom the QT interval was prolonged by sotalol. QTc dispersion was significantly greater in the arrhythmogenic QT group than in the sotalol QT group. In patients with prolonged QT intervals, QT dispersion distinguished between those with ventricular arrhythmias and those without. This supports the hypothesis that QT dispersion reflects spatial differences in myocardial recovery time. QT dispersion may be useful in the assessment of both arrhythmia risk and the efficacy of antiarrhythmic drugs.

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Diurnal, weekly and seasonal variation of sudden death. Population-based analysis of 24,061 consecutive cases.

S Willich, Anja C Schreiber, H-R Arntz … (2000)

Several studies have reported circadian and seasonal variations in acute cardiovascular disease. In addition, a weekly variation has been observed in acute myocardial infarction. The aim of our study was to determine the circadian weekly, and seasonal variations of sudden death utilizing population-based data. We analysed the emergency medical system data of Berlin (West) from 1987-1991 with respect to all consecutive sudden deaths in subjects >18 years (n=24 061). There was a marked circadian variation of sudden death, with a minimum between 0 and 6 h and a maximum between 6 and 12 h (P 65 (15.7%). In addition, we found a significant seasonal variation (P 65 years. The present analyses demonstrate marked variations in the occurrence of sudden death with peaks during morning hours, on Mondays, and during winter months. The findings suggest that the onset of sudden death may be associated with endogenous rhythms and external factors including climatic conditions. Copyright 2000 The European Society of Cardiology.