Introduction. Circadian rhythms are endogenous, approximately 24-hour oscillations that coordinate nearly all physiological systems, including cardiovascular function. The suprachiasmatic nucleus serves as the central pacemaker, synchronizing peripheral clocks in the heart, vasculature, and kidneys to generate daily fluctuations in blood pressure, heart rate, endothelial function, coagulation, myocardial metabolism, and autonomic tone. Disruption of circadian organization – through extrinsic factors (shift work, irregular light exposure, altered feeding schedules) or intrinsic factors (aging, inflammation, genetic clock-gene variants) – has been strongly linked to increased cardiovascular morbidity and mortality.
Material and methods. A bibliographic search was conducted in PubMed, Scopus, and Web of Science for English-language publications (2000–2025), focusing on the circadian rhythm, cardiovascular disease, hypertension, chronotherapy, and critical illness. Keywords included “circadian rhythm,” “cardiovascular disease,” “hypertension,” “chronotherapy,” and “intensive care.” Original research, clinical trials, meta-analyses, and experimental studies were eligible; studies addressing circadian blood pressure variability and its relation to outcomes in critically ill patients were specifically examined. Filters required full-text availability and publication dates from 2000 to 2025. The search yielded 276 full-text articles, of which 79 representative sources were selected for this narrative review.
Results. This review synthesizes current evidence demonstrating that circadian clocks regulate essential cardiovascular processes and that their disruption contributes to disease pathogenesis. Observational data on circadian blood pressure variability are discussed, showing that the attenuation of normal hemodynamic oscillations is associated with a worse prognosis. Particular attention is given to the extrinsic and intrinsic factors that modulate circadian alignment, with implications for the management of patients in intensive care.