Cardiac Atrophy and Diastolic Dysfunction During and After Long-Duration Spaceflight: Functional Consequences for Orthostatic Intolerance, Exercise Capacity, and Risk of Cardiac Arrhythmias (99-E377)
Cardiac atrophy appears to develop during space flight or during ground-based analogues, leading to diastolic dysfunction and orthostatic hypotension. Such atrophy may also be a potential mechanism for the cardiac arrhythmias recently identified in some crewmembers after long-duration exposure to microgravity aboard the Mir space station. Recent work by the investigators of this flight experiment has suggested that cardiac atrophy may be progressive, without a clear plateau over at least 12 weeks of bed rest, and thus may be a significant limiting factor for extended duration space missions. The purpose of this experiment is to quantify the extent and time course of cardiac atrophy and identify its mechanisms. The functional consequences of this atrophy will also be determined for cardiac filling dynamics, orthostatic tolerance at 1G and fractional G (Mars and moon) conditions, exercise tolerance, and arrhythmia susceptibility both in space on the International Space Station, and following return to earth.
The main objectives of this experiment are:
• To determine the magnitude of left and right ventricular atrophy associated with long-duration space flight (via pre- and postflight MRI's), to relate this atrophy to measures of physical activity and cardiac work in flight, and to determine the time course and pattern of progression of cardiac atrophy in flight (using cardiac ultrasound)
• To determine the functional importance of cardiac atrophy for orthostatic tolerance and the regulation of stroke volume.
• To identify changes in ventricular conduction and repolarization during and after long-duration space flight.
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Between L-75 and L-60 days, each subject will perform an Exercise Echocardiogram (Echo) and Electrocardiogram (ECG) session, which will include echocardiography measurements before and after submaximal exercise and an ECG recording throughout the session. Holter, ambulatory blood pressure (BP), and activity monitors will be worn for the 24 hours following this session. A Cardiac Magnetic Resonance Image (MRI) and Cardiac Function test (including optional measurements of central venous pressure (CVP), via a peripherally inserted central catheter, and cardiac output during a graded tilt test) will be performed in the L-75 to L-60 timeframe. Between L-21 and L-7 days, a Resting Echo/ECG session followed by 24 hours of Holter, ambulatory BP, and activity monitoring will be performed. Postflight, the Cardiac Function test (without direct CVP measurements) and 24-hour monitoring will be performed on landing day and Exercise Echo/ECG (R+4 and R+14), Resting Echo/ECG (R+7), and Cardiac MRI (R+3 and R+22) sessions are planned. Resting echocardiograms using the Human Research Facility (HRF) Ultrasound with ECG recording will be performed on flight days 14, 30, 135, and R+15 using real-time remote guidance. On flight day 75, an exercise Echo session will be performed with Echo measurements before and after exercise. QT Dispersion and signal averaged ECG measurements will also be recorded at this session. Both the Resting and Exercise Echo sessions will be followed by 24 hours of ambulatory BP/Holter/Activity monitoring. Following the doffing of the ambulatory devices, data from all experiment hardware will be downloaded to the HRF personal computer (PC) or Workstation and downlinked to the ground. In-flight exercise and medication logs will be obtained through data sharing.
This investigation is currently in operation. Results will be available upon completion of the experiment.
Dorfman TA, Levine BD, Tillery T, Peshock RM, Hastings JL, Schneider SM, Macias BR, Biolo G, Hargens AR. Cardiac atrophy in women following bed rest. J Appl Physiol. 2007 Jul;103(1):8-16. Epub 2007 Mar 22. [
Crew health and performance is critical to successful human exploration beyond low Earth orbit.
The Human Research Program (HRP) investigates and mitigates the highest risks to human health
and performance, providing essential countermeasures and technologies for human space exploration.
Risks include physiological and performance effects from hazards such as radiation, altered gravity,
and hostile environments, as well as unique challenges in medical support, human factors,
and behavioral health support. The HRP utilizes an Integrated Research Plan (IRP) to identify
the approach and research activities planned to address these risks, which are assigned to specific
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