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

Q: What are the key findings of this study?

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

Q: 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).

Q: What does this research mean for the field?

Long-duration spaceflight decreases left ventricular papillary muscle mass by 14% in male cosmonauts compared to pre-flight baseline. Novelty: ClaimNovelty.NOVEL_FINDING. Consensus alignment: ConsensusAlignment.NEUTRAL.

Cyril Tordeur; Elza Abdessater; Amin Hossein; Fabio Righetti; В. Е. Синицын; Е. А. Мершина; Elena Luchitskaya; Enrico G. Caiani; Vitalie Faoro; Jens Tank; Philippe van de Borne; Pierre‐François Migeotte; Jérémy Rabineau

doi:10.1038/s41526-025-00531-7

November 12, 2025npj MicrogravityOpen Access

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

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Key result

Long-duration spaceflight linked to a ~14% decrease in LV papillary muscle mass in male cosmonauts.

95% CI -2.42 to -0.32
P=0.017
n=9

Figures

Why the study?

Animal models suggest microgravity may cause left ventricular papillary muscle atrophy, but whether this occurs in humans had not been studied.

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

Key Points

To assess the effects of long-duration spaceflight on left ventricular papillary muscle mass as well as left ventricular morphology and function in humans using magnetic resonance imaging.
Conducted cardiac magnetic resonance imaging in N=9 male cosmonauts pre-flight and 6 ± 2 days after long-duration spaceflight missions lasting 247 ± 90 days.
Measured left ventricular (LV) volumes, ejection fraction, myocardial strain parameters, LV papillary muscle (PPM) mass, and mitral valve dimensions.
Left ventricular papillary muscle mass decreased by 14% post-flight (8.7 ± 1.8 vs. 10.1 ± 1.8 g; P = 0.017; mean difference 95% CI -2.42 to -0.32 g), reducing the PPM/LV mass ratio (0.059 ± 0.009 vs. 0.075 ± 0.015; P = 0.005).
Cardiac geometry shifted toward higher sphericity (0.50 ± 0.05 vs. 0.49 ± 0.05; P = 0.020) and increased mitral annular diameter in the 4-chamber view (36.8 ± 4.4 vs. 34.8 ± 4.0 mm; P = 0.004) without mitral leakage.
Post-flight heart rate increased (59 ± 6 vs. 51 ± 7 bpm; P < 0.001) and cardiac output increased (6.0 ± 1.0 vs. 5.2 ± 1.3 L/min; P = 0.030), while ejection fraction, LV volumes, and strain showed no significant changes.

Study Design

Type

Observational (n=9)

Multicenter

No

Structured PICO

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

P

Population

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

I

Intervention

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

C

Comparator

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

O

Outcome

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

Main Result

Absolute Event Rate: 8.7% vs 10.1%

p-value: p=0.017

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.

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
Limitations of the present MRI protocols regarding full investigation of mitral valve function
Lack of direct assessment of mitral valve prolapse and leakage

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Implication

May signal selective papillary atrophy in microgravity; leaves open mitral valve effects and need for prospective validation.

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.

Discussion

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Cite This Study

Tordeur et al. (2025) conducted an observational in Microgravity exposure (n=9). Long-duration spaceflight vs. Pre-flight baseline was evaluated on Left ventricular papillary muscle mass (g) (95% CI -2.42 to -0.32, p=0.017). Long-duration spaceflight decreased left ventricular papillary muscle mass by 14% (P = 0.017) in male cosmonauts compared to pre-flight baseline.

synapsesocial.com/papers/6a1203351dce72a77db4c365 https://doi.org/10.1038/s41526-025-00531-7

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

Figures

Key Points

Study Design

Structured PICO

Main Result

Limitations

Ask about this paper

Implication

Abstract

Discussion

Cite This Study

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

Figures

Key Points

Study Design

Structured PICO

Main Result

Limitations

Ask about this paper

Implication

Abstract

Discussion

Cite This Study

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