PRINCIPAL INVESTIGATOR (S ): Arnauld E. Nicogossian, G. Wyckliffe Hoffler, 



Robert L. Johnson, and Richard J. Gowen 



EXPERIMENT TITLE/NUMBER : Determination of Cardiac Size From Chest 



Roentgenograms Following Skylab Missions 



PROGRAM/MISSION : Skylab 2, 3, 4 



CLASSIFICATION : Human ■ 



DISCIPLINE(S) : Cardiovascular 



OBJECTIVES : To measure and evaluate changes in cardiac size. 



PROTOCOL : Standard posteroanterior chest films in systole and diastole were 

 obtained preflight and within a few hours after recovery on each of the Skylab 

 astronauts. Postf light chest X-rays were visually compared to the preflight 

 roentgenograms for possible changes in pulmonary vasculature, lung parenchyma, 

 and bony or soft tissue structures. From these roentgenograms the following 

 measurements were obtained: cardiac and thoracic transverse diameters, 

 cardiothoracic transverse diameter ratio, cardiac area from the product of 

 both diagonal diameters, cardiac silhouette area by planimetry, thoracic cage 

 area and cardiothoracic area ratio. 



EQUIPMENT : X-ray equipment. 



RESULTS : There were significantly decreased cardiac silouette areas, and 

 cardiothoracic transverse diameter ratios postflight. No correlation was 

 found between length of mission and change in size. Normalization occurred by 

 R+5. Postflight echocardiographic analysis showed ventricular dimensions 

 unchanged on Skylab 4. 



CONCLUSIONS : The observed postflight decrease in frontal plane cardiac 

 silhouette size could be attributed to a decrease in myocardial tissue mass 

 and/or intrachamber blood content, anatomical reorientation, or a combination 

 of these factors. Caudad displacement of blood and other fluids together with 

 an absolute decrease in the circulating blood volume could account for the 

 observed decreases in the cardiac silhouette size. A small diastolic size 

 might more clearly delineate a deficit in blood return and chamber filling 

 rather than loss of myocardial mass. 



PUBLICATIONS : 408, 409 



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