[Assessment of cardiac function by left heart catheterization: an analysis of left ventricular pressure-volume...

The mechanical property of the cardiac muscle has been classically analyzed in two ways; shortening of muscle fiber, and the development of tension within the muscle. In the ejecting ventricle, left ventricular (LV) function can be analyzed by the analogous two-dimensional framework of pressure-volume loops, which are provided by plotting the instantaneous volume against corresponding LV pressure. The integral pressure with respect to volume allows to assess a total external ventricular work during ejection. The diastolic pressure-volume relations reflect a chamber stiffness of the ventricle. Force-velocity relations also provide an useful conceptual framework for understanding how the ventricle contracts under given afterload, with modification of preload. In the presence of coronary artery disease, the regional nature of left ventricular contractile function should be defined as well as the global ventricular function as described above, because the latter is determined by the complex interaction of dysfunction of the ischemic myocardium and of compensatory augmentation of shortening of the normally perfused myocardium. We utilized a computer technique to analyze the local wall motion of the ischemic heart by cineventriculography. The boundaries of serial ventricular images are automatically traced and superimposed using the external reference system. Radial grids are drawn from the center of gravity of the end-diastolic image. Measurement of length of each radial grid throughout cardiac cycle provides the analysis of movement of the ventricle at a particular point on the circumference. Using phasic pressure obtained simultaneously with opacification as the common parameter, segmental pressure-length loops are constructed simultaneously at various segments. The loops are similar over the entire circumference in the normal heart, being rectangular in morphology and with synchronous behavior during contraction and relaxation. However, the marked distortion of pressure-length loops with clockwise rotation or figure of eight inscription is observed in the ischemic segments. Systolic work of the ischemic segment diminishes dramatically, and the loops exhibit varying degrees of inclination. The control segment loops also show an inclination to the opposite direction of the ischemic loops. These differences are presumably related to the local redistribution of the myocardial tension during systole in the ischemic ventricle. Thus, the method described should be of particular value in assessing the regional myocardial function in the ischemic ventricle and effects of various interventions which modify ischemia.