Abstract
Measurement of the area of the frontal silhouette of the human heart as registered on an X-ray plate permits calculation of the total heart volume with an average error of less than ±5% (studies on “fresh” cadavers, Keys and Friedell 1 ). By means of the multiple slit roentgenkymograph (cf. Johnson, 2 Roesler 3 ), it is possible to trace the outlines of the living human heart in both (ventricular) systole and diastole of a single cardiac cycle (Keys and Friedell 4 ). From measurement of these areas the volume of the heart in systole and in diastole can be calculated. The error in volume estimation from the frontal area is mainly a reflection of abnormality in the relation between frontal and anterior-posterior shape of the heart. Since these abnormalities must be reflected both in systole and in diastole, the error in the estimation of the difference of volumes should be relatively small.
The difference between the volume of the heart in systole and in diastole should be directly related to the stroke output if the valves allow no back flow. The precise numerical relation, however, could not be predicted a priori because the auricular and ventricular cardiac cycles are not absolutely simultaneous in phase. In addition, the difference between the areas of the systolic and diastolic kymogram outlines must be underestimated because the kymogram only registers excursions in one of the 2 planes of the surface of projection.
We have developed a procedure in which roentgenkymograms are made immediately before and after acetylene rebreathing experiments. By this means we obtain estimates of diastolic and systolic volumes of the heart from the kymograms and of the cardiac stroke output by the method of Grollman. 5
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