DETERMINATION OF THE EXTERNAL WORK AND POWER OF THE LEFT VENTRICLE IN INTACT MAN.

1. 1. Measurements of the external work and power of the left ventricle have been made in 19 subjects. Computations were based on instantaneous measurements of pressure, velocity, and flow in the ascending aorta. 2. 2. In 11 subjects without known cardiovascular disease the resting stroke work index ranged from 51 to 90 Gm.M./M.2 per beat. The average minute work index was 5.2 Kg.M./M.2 per minute in the same group. 3. 3. The administration of 1-norepinephrine produced not only a rise in the total work performed, but also a change in the temporal pattern of work accomplishment whereby the increase in power output was most pronounced during the latter half of the ejection period. 4. 4. In 6 individuals with nonvalvular heart disease but normal external work output, increases in external power during late systole, relative to the normal, were found. In 3 subjects with work values below 50 Gm.M./M.2 per beat, there was both a general diminution in the levels of power achieved and an altered pattern of work performance. 5. 5. The factors relating to the manner of work accomplishment by the intact ventricle have been discussed.