Left Ventricular Volume in Man Measured by Thermodilution*

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Abstract
Left ventricular volume has been studied in 39 human subjects by the thermodilution technic. Ob-servations were made at rest and during infusion of norepinephrine and isoproterenol. The average end-diastolic volume in 12 subjects with the least cardiac disease was 96 [plus or minus]20 ml/m2 with an end-systolic (residual) fraction of 0.56. End diastolic volume was normal in mitral stenosis. Severe aortic stenosis was associated with either normal or increased end-diastolic volume. Residual fraction, however, was invariably increased in this disease and in subjects with heart failure due to other causes. Norepinephrine infusion increased end-diastolic volume in the normal group. Isoproterenol decreased end-diastolic volume in the normal group, but tended to increase volume in subjects with aortic stenosis. This difference in response was attributed to the fixed resistance of aortic stenosis acting to cause intraventricular hypertension, which was not seen in other subjects. Mathematical evidence has been presented to indicate under what circumstances the spherical model may validly be used for structural analysis of volume changes. Mean systolic force and mean shortening rate of the left ventricle can be determined, but ventricular stresses cannot be accurately assessed. Force-shortening rate analysis has shown that shortening rate increased in all normal subjects given isoproterenol, but was virtually unchanged in 6 of 7 subjects with severe aortic stenosis given isoproterenol.