Circadian patterns have been observed for variety of cardiovascular disorders, including cardiac arrhythmias, sudden cardiac death, cerebrovascular events, episodes of stable angina, unstable angina and acute myocardial infarction. The morning predominance of these events has been well documented in a number of large population studies. This fact provides the stimulus for better understanding our own chronobiology and the periodicity of circadian rhythms which contribute to this predominance of adverse events in the morning hours. We now understand that a number of important physiological parameters such as heart rate, blood pressure, vascular reactivity, cardiac contractility, and various hemostatic factors all demonstrate a circardian pattern similar to that described for cardiovascular disorders. Several recent studies have also emphasized the importance of changes in posture, time of awakening, physical activity, mental stress as potential triggers. Circardian patterns have been observed for several supraventricular arrhythmias, premature ventricular beats, ventricular tachycardias including sudden cardiac death. The chronobiological therapeutic systems can help to prevent life threatening events.

        Key words: Circadian rhythm - Arrhythmia - Chronobiology