TEMPORAL VARIATION IN ACUTE AORTIC DISEASES: ONLY A RANDOM PHENOMENON?
Roberto Manfredini, M.D., University of Ferrara, Italy
Chronobiology is a branch of biomedical sciences devoted to the study of biological rhythms, that according to cycle length, are classified into: circadian (period of around 24 hours), ultradian (less than 24 hours), and infradian (more than 24 hours, e.g., days, weeks, months), and their interactions with bodily functions. The cardiovascular system is a suggestive example of such organization, since arterial blood pressure, heart rate, vascular tone, coagulation/fibrinolysis, exhibit rhythmic changes. Chronoepidemiology deals with the interaction between biological rhythms and onset of different diseases, and many studies have yielded rhythmic variations in the occurrence of myocardial infarction, stroke, and pulmonary embolism. Acute aortic rupture or dissection (AARD) represent life-threatening conditions characterized by high mortality, and many studies have explored the possible existence of rhythmic patterns as well. A recent meta-analysis from our group on the available literature, showed an evident and significant preference for occurrence of AARD during Winter months (particularly in December), on Monday, and during morning hours (6am – noon). These results, strengthened by their uniformity in different countries, provide further confirmation that the temporal variation in acute aortic diseases does not simply reflect a random phenomenon. Many different pathogenetic mechanisms may explain the existence of a temporal variation in the onset of acute cardiovascular diseases. On one hand, a constellation of unfavourable factors, each of them probably not so harmful if taken alone, but reinforced by their contemporary presence, could trigger overt disease. On the other hand, the potential negative role of external or internal disruption of circadian clocks located in the peripheral organs, including cardiomyocytes, vascular smooth muscle cells and endothelial cells, could also play a role.