SPACEFLIGHT  VOL 43:83, 2001.

Astronaut James lrwin gives a military salute while standing beside the deployed US flag during the Apollo 15 lunar surface EVA at the Hadley-Apennine landing site.

Astronaut's heart problem

Sir,
In reference to the article Apollo: The Lost Flights (Spaceflight, September 2000) few are aware of the cardiovascular risks to astronauts, even on relatively short space missions.

On Apollo 15 with three EVA'S On the lunar surface lasting up to seven hours Scott and lrwin became quite dehydrated as a result of malfunction of their in-suit water devices. Scott's apparatus functioned only partially while Irwin's device didn't function at all [1].

In addition, the crew trained for months in "intense summer heat" conducive to a magnesium deficit prior to the mission, which would be aggravated by a loss of storage sites for Mg in the skeletal muscle, even from a brief mission of only 12 days [2,3].

The invariable dehydration complicating hypokinesia and microgravity [2,3] compounding the dehydration stemming from malfunction of the in-suit water devices, combined with Mg ion deficiency, could have been responsible for cardiac rhythm disturbances both astronauts experienced, life-threatening in the case of lrwin, with loss of consciousness for a brief period while transferring to the command module [3]. It was postulated that there was a potassium deficiency as well contributing to these rhythm disturbances [1.2]. Both lrwin and Scott experienced severe pain of the fingertips, primarily while wearing gloves on the lunar surface, but in the case of lrwin, possibly causing significant sleep deprivation as well [1].

This severe pain may have been the result of spasm of the blood vessels of the fingers along with fluid trapped distally at the fingertips; this symptom could provide a warning that similar mechanisms - related to high levels of vessel constrictors, such as adrenaline combined with a Mg deficit - could cause spasm of the coronary vessels compromising blood flow to the heart. Thus the second space-related syndrome (the Apollo 15 Space Syndrome) was recently described. [2]

Furthermore, during re-entry, lrwin was extremely short of breath and felt "as if an elephant was standing on my chest". He found it impossible to talk, whereas the others had no apparent difficulty speaking during re-entry [1]. This description is consistent with a brief episode of congestive heart failure with angina secondary to marked peripheral resistance during re-entry at 7G's.

It is conceivable that as a result of this mission, lrwin suffered heart muscle or at least coronary vascular damage, predisposing to a documented heart attack 21 months later [3]. In 1991, at age 61, lrwin died.

William J. Rowe, MD
Former Assistant Clinical Professor of Medicine
Medical College of Ohio at Toledo

References
1. J.B. lrwin and W.A. Emerson Jr, To Rule the Night: The Discovery Voyage of Astronaut Jim lrwin, Philadelphia, Holman, 1973. pp.72-120.
2. W.J. Rowe, The Apollo 15 Space Syndrome, Circulation 97, 1998, pp. l 19-120.
3. W.J. Rowe, Potential myocardial injuries to normal heart with prolonged space missions: The hypothetical key role of magnesium, Magnes Bull. 22,2000, pp.15-19