Absence of circadian variation of acute coronary syndrome onset in chronic kidney disease patients

Circadian clock and the onset of cardiovascular events

The onset of cardiovascular diseases often shows time-of-day variation. Acute myocardial infarction or ventricular arrhythmia such as ventricular tachycardia occurs mainly in the early morning. Multiple biochemical and physiological parameters show circadian rhythm, which may account for the diurnal variation of cardiovascular events. These include the variations in blood pressure, activity of the autonomic nervous system and renin-angiotensin axis, coagulation cascade, vascular tone and the intracellular metabolism of cardiomyocytes. Importantly, the molecular clock system seems to underlie the circadian variation of these parameters. The center of the biological clock, also known as the central clock, exists in the suprachiasmatic nucleus. In contrast, the molecular clock system is also activated in each cell of the peripheral organs and constitute the peripheral clock. The biological clock system is currently considered to have a beneficial role in maintaining the homeostasis of each organ. Discoordination, however, between the peripheral clock and external environment could potentially underlie the development of cardiovascular events. Therefore, understanding the molecular and cellular pathways by which cardiovascular events occur in a diurnal oscillatory pattern will help the establishment of a novel therapeutic approach to the management of cardiovascular disorders.

Prevention of cardiovascular events with antiplatelet treatment: does time of intake matter for aspirin and ADP receptor blockers?

Long-term evidence supports a clustering of cardiovascular events in the early morning. Several studies have shown that platelet hyper-reactivity to various stimuli is also present at this period of the day. However, the idea of treatment strategies reflecting the circadian variation in platelet reactivity has been largely neglected so far, and this is true despite the huge number of patients being treated with these drugs. Some pharmacodynamic data suggest that early-morning platelet hyper-reactivity may be overcome by shifting aspirin intake to the bedtime. However, there is lack of evidence whether shifting the time of intake or splitting the daily dose of P2Y12-inhibitors with a regular QD dosing (clopidogrel or prasugrel) to the evening would be effective to overcome platelet hyper-reactivity or to suppress the excess of cardiovascular events observed during morning hours. Further research is warranted to clarify whether such a simple and costless effort like dose shifting or splitting may be beneficial to prevent cardiovascular events.