Possible space flight-induced catecholamine cardiomyopathy: Neil Armstrong's last 20 lunar minutes William J RoweFormer Assistant Clinical Professor of Medicine, Medical University of Ohio at Toledo, Ohio, USAAbstract: The hypothesis underpinning this paper is that space flight may predispose to catecholamine cardiomyopathy. Catecholamine levels in space are twice those of the supine levels on Earth. Serum magnesium levels are significantly reduced, with potential vicious cycles triggered by elevation of catecholamines. These are conducive to coronary vasospasm with clot formation from oxidative stress and calcium overload, and ultimately, temporary impairment of left ventricular function could occur. Experimental animals in space have shown a significant increase in norepinephrine levels with various microcirculatory disorders and serious myocardial pathology. During extravehicular activity (space walks), astronauts show heart rates of 150–174 beats per minute. Before exposure to the iron-laden dust brought into the habitat on his space suit, Neil Armstrong's heart rates on the lunar surface were 130–160 beats per minute, and accompanied by dyspnea on two occasions during his last 20 minutes on the moon. A stress test done on the day after splashdown was consistent with "ischemic left ventricular dysfunction". To support this hypothesis, echocardiography on the international space station might show left ventricular hypokinesia. Alpha adrenergic blockade, correction of invariable significant magnesium deficits, along with correction of invariable atrial natriuretic peptide deficits, may counteract the vasoconstrictive action of norepinephrine.Keywords: space flight, catecholamines, cardiomyopathy, magnesium, oxidative stress, heat intolerance, calcium