Cardiovascular Effects of Exposure to Microgravity: A Literature Review

Space exploration has progressed significantly with increased human presence in orbit, the development of space stations, and the planning of increasingly prolonged missions. However, the space environment poses substantial physiological challenges, particularly for the cardiovascular system. According to NASA's Human Research Program, the five primary risks associated with human spaceflight are (1) microgravity, (2) ionizing cosmic radiation, (3) isolation and confinement, (4) closed environmental systems, and (5) great distance from Earth.

The cardiovascular system is among the most extensively studied systems in aerospace medicine because of its adaptive responses to microgravity. Documented changes include altered blood-flow dynamics, disturbances in electrical conduction, and structural effects on the myocardium. These may result in variations in the heart rate (e.g., increased resting heart rate in microgravity), blood volume (e.g., central fluid shift and subsequent plasma volume reduction), and endothelial function (e.g., leading to increased vascular stiffness), as well as a potential predisposition to long-term cardiovascular events (e.g., orthostatic intolerance or arrhythmias). Review Methodology: We conducted a literature review (August 2024 - March 2025) using targeted searches with terms like "astronaut," "spaceflight," "microgravity," "cardiovascular system" to identify peer-reviewed studies on cardiovascular adaptation to spaceflight.

Evidence from studies involving astronauts, animal models, and ground-based simulations has enhanced our understanding of these mechanisms, thereby enabling the development of preventive strategies. These findings not only contribute to the safety and success of future space missions but also provide valuable insights into cardiovascular diseases on Earth, potentially informing novel therapeutic approaches.