LONG TERM MICROGRAVITY: A MODEL FOR INVESTIGATING MECHANISMS OF HEART DISEASE
WITH NEW PORTABLE EQUIPMENT (CARD)
Research Area: Cardiovascular and Respiratory Systems
Expedition(s): 14, 19-22, 25-32
Principal Investigator(s): ● Peter Norsk, MD, University of Copenhagen,
Denmark
RESEARCH OBJECTIVES
The Long Term Microgravity: A Model for
Investigating Mechanisms of Heart Disease with New
Portable Equipment (Card) experiment studies blood
pressure decreases in the human body exposed to
microgravity aboard the International Space Station.
Card tests the hypothesis that cardiac output is
increased and arterial resistance is lowered in
microgravity. Blood vessel volume reduction causes
higher sympathetic nervous activity and the sensitivity
of the arterial resistance vessels to this increase is
reduced by weightlessness. Another hypothesis is that
high sympathetic nervous activity is a compensatory
response to the increased cardiac output and blood
flow in the upper parts of the body on the expense of
the lower body parts and that this causes some
degree of vasoconstriction in the arms and legs to
maintain an adequate blood pressure.
RESULTS
The team observed in 8 astronauts a decrease in 24-
hour ambulatory blood pressure of 10 mm Hg
corresponding to a low-dose antihypertensive
medication effect, a 30% increase in cardiac output
and stroke volume, and a 30% decrease in peripheral
systemic vascular resistance. Thus, the conclusion was
that long-term spaceflight (3-6 months) has a
vasodilatory, antihypertensive (lower blood pressure) effect, which purely from a cardiovascular
point of view is healthy. At the same time, an unchanged level of efferent sympathetic nervous
activity was found, which is surprising considering the vasodilatory effects, and which thus
requires further investigation.
PUBLICATION(S)
Christensen NJ, Heer MA, Ivanova K, Norsk P. Sympathetic nervous activity decreases during
head down bed rest but not during microgravity. Microgravity Science and Technology.
September 2007;19(5-6):95-97. doi: 10.1007/BF02919460.
JAXA astronaut Koichi Wakata, Expedition 19
flight engineer, during procedures for the Long
Term Microgravity: A Model for Investigating
Mechanisms of Heart Disease with New Portable
Equipment experiment. ESA/NASA image.