Changes in left ventricular size during parabolic flights by two-dimensional echocardiography and level set method

Area of Science:

• Cardiovascular Physiology
• Space Medicine
• Biomedical Engineering

Background:

• Understanding cardiac adaptation to altered gravity is crucial for space exploration and terrestrial applications.
• Previous research has indicated potential changes in cardiovascular dynamics under microgravity and hypergravity, but detailed chamber size analysis requires further investigation.

Purpose of the Study:

• To quantify changes in left ventricular (LV) chamber size and function in response to varying gravitational forces.
• To investigate the impact of hypergravity (1.8 Gz) and microgravity (0 Gz) on LV end-diastolic and end-systolic areas, and fractional area change.

Main Methods:

• Utilized 2-D transthoracic echocardiography during parabolic flights to assess cardiac chambers.
• Employed a semi-automatic segmentation procedure based on level set methods for LV endocardial border detection.
• Analyzed LV cavity area and fractional area change across three gravity phases: 1 Gz, 1.8 Gz, and 0 Gz.

Main Results:

• At 1.8 Gz, LV end-diastolic and end-systolic areas significantly decreased by 10.7% and 21.6% respectively, compared to 1 Gz.
• During 0 Gz, LV end-diastolic and end-systolic areas increased by 11.2% and 11.1% respectively, compared to 1 Gz.
• Fractional area change increased by 20.9% at 1.8 Gz and remained unchanged at 0 Gz, while LV filling due to atrial contraction increased by 39% at 0 Gz.

Conclusions:

• Gravitational stress induces significant, predictable changes in LV chamber dimensions and function.
• Hypergravity leads to LV volume reduction, whereas microgravity causes LV volume expansion.
• These findings highlight the dynamic nature of cardiac adaptation to altered gravity environments.