Space Flight-Related Endothelial Dysfunction with Potential Congestive Heart Failure
Despite invariable dehydration on space flights there is the potential for congestive heart failure resulting from endothelial dysfunction of the coronary and peripheral vessels. After space flights of only a few weeks experimental animals show significant increased norepinephrine concentrations in heart tissue and destructive changes of mitochondria with serious myocardial pathology with atrophy and endothelial injuries with narrowing and occlusions of the microcirculation.
On Apollo 15 forty-one yr old Irwin and Scott both had severe pain and edema of the fingertips (Apollo 15 Space Syndrome) postulated to result from vasospasm. Irwin lost consciousness during bigeminy after severe dehydration. During reentry at 7 g's he had severe substernal chest pain and was so dyspneic he could not speak and had an acute myocardial infarction 21 months later.
Reduced or non-detectable plasma cyclic GMP (second messenger of nitric oxide) and insulin resistance shown by elevated C-peptide excretion occur during space flights and both can be a result of microvascular endothelial dysfunction. There is decreased thirst excess diuresis and atrophy of water storage sites in muscle reduced plasma volume and early reduction of extracellular fluid and later of intracellular fluid triggering angiotensin and catecholamine elevations (pro-oxidants). Magnesium ion deficits from atrophy of bone and skeletal muscle storage sites are also conducive to oxidative stress trigger vicious cycles with both angiotensin and catecholamines and also cause insulin resistance. Thrombocytopenia contributing to vascular endothelial growth factor reductions have both been shown on space flights. Reduced vascular endothelial growth factor expression from insulin resistance can also lead to endothelial dysfunction.
Conclusions: congestive heart failure secondary to both coronary and peripheral endothelial dysfunction can occur on space flights despite invariable dehydration.
Presented at the 8th World Congress on Heart Failure ---Mechanisms and Management,.Washington D.C., July 13-16, 2002.