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Circadian variations in cardiovascular function and their relation to the occurrence and timing of cardiac events
1Massachusetts College of Pharmacy and Allied Health Sciences, Boston 02115-5896, USA.
Insights
Cardiac events show distinct circadian patterns, peaking in the early morning due to physiological changes. Understanding these rhythms aids in preventing and treating cardiovascular conditions.
Area of Science:
- Cardiology
- Chronobiology
- Physiology
Background:
- Circadian rhythms significantly influence cardiovascular function and disease risk.
- Sympathovagal tone, neurohumoral activity, and vascular tone exhibit 24-hour variations.
- Physiological processes like platelet aggregation and fibrinolysis show circadian modulation.
Purpose of the Study:
- To discuss circadian patterns of cardiac event risk.
- To explore implications for cardiovascular condition prevention and treatment.
- To highlight the early morning vulnerable period for cardiac events.
Main Methods:
- Review of studies on circadian patterns of cardiac events (myocardial infarction, stroke, etc.).
- Analysis of physiological determinants of circadian variation in cardiovascular function.
- Consideration of factors influencing circadian patterns, including disease states and demographics.
Main Results:
- Cardiac events, including myocardial infarction and stroke, frequently occur in the early morning.
- Circadian variations in heart rate, blood pressure, and vasomotor tone are linked to neurohumoral activity.
- Platelet aggregation and plasminogen-activator inhibitor-1 peak, while endogenous plasminogen activator is lowest, around awakening.
Conclusions:
- Circadian patterns of cardiac events align with natural physiological fluctuations, with a consistent early morning vulnerability.
- Conditions like diabetes and heart failure may alter these patterns.
- Dynamic assessment of cardiovascular markers can aid in disease management and therapy selection.
Abstract:
Circadian patterns of risk for cardiac events and their implications for prevention and treatment of cardiovascular conditions are discussed. Sympathovagal tone, a major biological determinant of circadian variation in cardiovascular function, is modulated through circadian patterns of sleep-wake activity. The influence of neurohumoral activity on cardiovascular function is manifested by 24-hour variability in heart rate, blood pressure, and vasomotor tone. Platelet aggregation and plasminogen-activator inhibitor-1 activity peak around the time of awakening. Conversely, endogenous plasminogen activator exhibits a nadir around the time of awakening. Studies of patterns of occurrence of cardiac disorders such as acute myocardial infarction, sudden cardiac death, stroke, and ventricular arrhythmia show an increased occurrence during the period surrounding awakening. These patterns are consistent with observed circadian patterns in cardiovascular function. Diabetes, left ventricular dysfunction, and congestive heart failure may contribute to alterations in patterns of occurrence of cardiac events. Factors such as race, sex, and age may lead to alterations in circadian variation in cardiovascular function. Unusual physical exertion, stress, and anger may act as triggers of an event at any time of day. The circadian patterns of cardiac events follow the natural fluctuations in endogenous physiological processes, with a vulnerable period consistently observed in the early morning; dynamic assessment of markers of cardiovascular function may assist in determining the extent of disease progression and in selecting cardiovascular therapies.