Cardiac Effects of Long-Duration Space Flight

Area of Science:

• Cardiovascular physiology
• Space medicine
• Exercise science

Background:

• Cardiac mass and function are sensitive to physical activity and loading conditions.
• Microgravity reduces ventricular wall stress, potentially leading to cardiac atrophy.
• Simulated microgravity for 12 weeks shows cardiac atrophy that can be mitigated by exercise.

Purpose of the Study:

• To evaluate if International Space Station (ISS) exercise countermeasures prevent cardiac atrophy during long-duration space flight.
• To assess the impact of space flight on cardiac mass, volume, and work.

Main Methods:

• Magnetic resonance imaging (MRI) was used to measure left ventricular (LV) and right ventricular (RV) mass and volumes in 13 astronauts before and after a 155-day ISS mission.
• Total cardiac work was assessed before and during space flight.
• Paired-samples t-tests were used for data comparison.

Main Results:

• Total cardiac work was significantly lower during space flight (P=0.008).
• No significant differences were found in LV mass, RV mass, or ventricular volumes post-flight.
• Marginally higher LV stroke volume and ejection fraction were observed post-flight.

Conclusions:

• Current ISS exercise countermeasures appear effective in preventing reductions in cardiac mass and volume during prolonged space flight.
• Despite decreased cardiac work in space, exercise helps maintain heart size and function.
• These findings underscore the efficacy of exercise protocols in mitigating space flight-induced cardiac deconditioning.