Cardiovascular Risk Factors in the Circadian Rhythm of Acute Myocardial Infarction

Alterations of circadian rhythms and their impact on obesity, metabolic syndrome and cardiovascular diseases

Circadian system is comprised by central circadian pacemaker and several peripheral clocks that receive information from the external environment, synchronizing the circadian clocks. It is widely known that physiology is rhythmic and that the rupture of this rhythmicity can generate serious consequences. Circadian clocks, led by suprachiasmatic nucleus (SCN) in the central nervous system, are the responsible for generating this biological rhythmicity. These clocks are affected by external signals such as light (changes between day and night) and feeding rhythms. In this review, the basic principles of the circadian system and current knowledge of biological clocks are addressed, analyzing the relationship between circadian system, food intake, nutrition, and associated metabolic processes. In addition, the consequences occurring when these systems are not well coordinated with each other, such as the development of cardiovascular and metabolic pathologies, will be thoroughly discussed.

Fluctuations in coagulation activity among patients with atrial fibrillation who are stably anticoagulated

Atrial fibrillation is an important independent risk factor for stroke and increases the risk of systemic embolism. The individual risk depends on several clinical, environmental and biological factors. Additionally, a hypercoagulable state with abnormalities of hemostasia, thrombosis and platelet function have been observed in atrial fibrillation. This arrhythmia is also influenced by a disrupted circadian rhythm of hypercoagulable status implicated in the genesis of cardiovascular and cerebral diseases. The beneficial effect of oral anticoagulation therapy in atrial fibrillation has been confirmed by several studies. However, circadian variations in the degree of anticoagulation in these patients have also been described. In this review, the authors analyze the factors that might condition diurnal variations in thrombogenesis, hypercoagulability, and the extent of anticoagulation in patients with atrial fibrillation.

Are there ethnic differences in the circadian variation in onset of acute myocardial infarction?

We hypothesised that ethnicity may influence the circadian pattern in acute myocardial infarction (MI), in view of the potential differences in genetic background, cardiovascular risk factors and cultural habits. To test our hypothesis, we studied 340 consecutive acute MI patients (268 males; mean age 61.6+/-12.3 years) from two different city-centre teaching hospitals in Birmingham (United Kingdom) and Alicante (Spain). A different circadian rhythm in MI onset was observed between the ethnic groups (p=0.001), with a significantly higher number of acute MI onset occurring between midnight and noon in British Caucasians and Indo-Asians. In contrast, Mediterranean Caucasians showed the converse circadian pattern, with most of the acute MI events happened between noon and midnight. Indo-Asian patients were the youngest patient group and showed the highest prevalence of diabetes and increased body mass index. Mediterranean patients had the highest prevalence of smokers but their mean serum cholesterol was the lowest. No differences in sex, blood pressure, height and weight were observed. In conclusion, this study has shown a different circadian rhythm in acute MI onset between 3 ethnic groups from two different city-centre teaching hospitals in Birmingham (United Kingdom) and Alicante (Spain) and, for the first time, provide data in the Indo-Asian population. Further studies are required to determine the pathophysiological mechanism(s) underlying these differences.