There are the clinical trials, which refer to fact that connection of the circadian rhythmicity of the cardiovascular events with apnoic episodes may have practical relevance in screening for patients with OSA and may have prognostic clinical value in predicting future cardiovascular Cardiac Arrhythmias -Mechanisms, Pathophysiology, and Treatment 46 events. The risk of sudden death from cardiac causes has peak from h to noon and a nadir from midnight to h. OSA is associated with neurohormonal and electrophysiological abnormalities that may increase the risk of sudden death from cardiac causes, especially during sleep. Gami et al.followed this dependence in people, who died suddenly from cardiac causes. They found that from midnight to h, sudden death from cardiac causes occurred in % of people with OSA, as compared with % of people without OSA. People with sudden death from cardiac causes from midnight to h had a significantly higher apnea-hypopnea index than those with sudden death from cardiac causes during other intervals, and the apnea-hyponea index correlated directly with the relative risk of sudden death from cardiac causes from midnight to h. Thus, people with OSA have a peak in sudden death from cardiac causes during the sleeping hours, which contrasts strikingly with the nadir of sudden death from cardiac causes during this period in people without OSA. The different variation in onset of myocardial infarction was found in patients with and without OSA. Myocardial infarction occurred between h and h in % of OSA patients and % of non/OSA patients. Of all patients having myocardial infarction between h and h, % had OSA. These findings suggest that OSA may be a trigger for myocardial infarction and patients having nocturnal onset of myoacardial infarction should be evaluated for OSA. Future research should address the effects of OSA therapy for prevention of nocturnal cardiac events Kuniyoshi et al., . Besides humans, almost all animals are exposed to periodic repetitions of light and dark cycles during a -hour circadian period to which virtually all physiological functions are synchronized. Disturbance of the internal synchronization of rhythms with the periodicity of the external environment may manifest by increased susceptibility to disease. Surprisingly, there are only few works describing day-time of the experiment running or synchronization of animals to the external environmental periodicity, such as the light-dark LD cycle. It can be a problem, because the LD cycle is given for one of the strongest circadian synchronizators of the animal endogenous rhythms. Therefore, the creation of experimental, in vivo, chronobiological animal models may help reveal some of the relationships between circadian time and biological function, which is sometimes very difficult to study in humans. From this reason, the circadian variability should be considered as important factor especially in the cardiovascular studies.For example, the h course of the myocardial vulnerability showed the highest susceptibility of t...
