What is the clinical evidence from this study?

Study design: Observational. Population: Microgravity exposure (n=9). Intervention: Long-duration spaceflight vs. Pre-flight baseline. Primary outcome: Left ventricular papillary muscle mass (g) (95% CI -2.42 to -0.32, p=0.017).

November 12, 2025Open Access

Long-duration human spaceflight induces atrophy in the left ventricular papillary muscles

Key Result

Long-duration spaceflight decreased left ventricular papillary muscle mass by 14% (P = 0.017) in male cosmonauts compared to pre-flight baseline.

Study Design

Type

Observational (n=9)

Multicenter

Structured PICO

Does long-duration spaceflight induce left ventricular papillary muscle atrophy in male cosmonauts?

Population

9 male cosmonauts exposed to microgravity during long-duration missions onboard the International Space Station (Expedition 63-69), mean age 44 ± 6 years.

Intervention

Long-duration spaceflight (microgravity exposure) for 247 ± 90 days onboard the ISS, associated with a strict exercise countermeasure protocol.

Comparator

Pre-flight baseline measurements (60-45 days before launch).

Outcome

Left ventricular papillary muscle mass, LV morphology, and function assessed by cardiac MRI.surrogate

Long-duration spaceflight induces a 14% reduction in left ventricular papillary muscle mass and increases mitral annular diameter despite preserved overall LV mass and volumes.

Main Result

Absolute Event Rate: 8.7% vs 10.1%

p-value: p=0.017

Limitations

Post-flight MRI measurements were acquired on average 6 days after landing, potentially missing rapid cardiovascular recovery
Small sample size
Potential variability in individual adherence to the prescribed exercise countermeasure regimen
Use of in-flight per os water-salt supplements and post-flight intravenous infusion may have influenced results
MRI protocols were not specifically designed to evaluate mitral valve morphology and function
Arterial blood pressure was not measured simultaneously with the MRI protocols

Abstract

Microgravity exposure induces cardiac deconditioning, primarily due to hypovolemia and inactivity. Animal models suggest microgravity may cause left ventricular (LV) papillary muscle atrophy, but this has not been studied in humans. This study used MRI to assess LV papillary muscle mass and LV morphology and function in nine male cosmonauts before and 6 ± 2 days after long-duration spaceflight (247 ± 90 days). Spaceflight did not affect LV volumes, ejection fraction, and strain parameters, but increased heart rate (P < 0.001) and cardiac output (P = 0.03). LV papillary muscle mass decreased by 14% (P = 0.017), while LV mass tended to increase (P = 0.083), mitral annular diameter increased (P = 0.004) without mitral leakage, and LV sphericity increased (P = 0.02). These findings suggest LV adapts to space with geometric changes, but microgravity-induced papillary muscle atrophy requires further study for long-term implications.

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