DIFFERENCES IN SOME CIRCADIAN PATTERNS OF CARDIAC-ARRHYTHMIA, MYOCARDIAL INFARCTIONS AND OTHER ADVERSE VASCULAR EVENTS

Background. Results from unpublished data on the incidence of adverse vascular events and from several published studies are reevaluated chr onobiologically.Methods and results. Cosinor methods indicate 1. a cir cadian variation in the incidence of paroxysmal supraventricular tachy cardia (PST), of broadly classified ventricular arrhythmia (VAr), and of atrial fibrillation (AF); 2. a statistically significant difference in the timing of the circadian rhythm of PST and VAr versus that of A F; and 3. a further difference in the timing of these rhythms from tha t in the incidence of myocardial infarctions (MI). Electrocardiographi c records for spans longer than 24h show the extent of day-to-day vari ability in circadian characteristics of the given patient and indicate the presence of even lower-frequency components, notably along the sc ale of a week, that may underlie weekly and half-weekly patterns of mo rbidity and mortality. Conclusion. Beyond alterations in the about 1-H z periodicity of the heart, predictable changes along the scales of th e day and the week may constitute a clue to the etiopathology of a giv en condition and provide a basis for treatment timing. The assessment of unfavorable changes in the lower frequency components may provide a lead time long enough to prompt the institution of preventive, rather than curative, intervention.