Hemodynamic and pharmacologic influences on the left ventricular echo dimension-apex cardiogram loop in dogs

Study of left ventricular pressure-volume relations has been limited by technical problems associated with left ventricular catheterization and angiography. A new approach using simultaneous recording of calibrated left ventricular apex cardiograms and echocardiographic M-mode dimensions was used to observe anesthetized dogs. The effect of various alterations in preload, afterload, and the inotropic state of the left ventricle on echo dimension-calibrated apex cardiogram plots sampled at 0.01 sec intervals was studied to test the method, and to clarify some of the determinants of the area of the loop. These areas were calculated in cm2 and the values of M-mode echo dimension-calibrated apex cardiogram loops and M-mode echo dimension-left ventricular pressure loops were similar in form and magnitude, and standard deviations under various hemodynamic interventions. Moreover, the impedance field, effective stroke field, and filing field were divided by the total surface of the loops. Whereas, alteration in afterload changed the impedance field, variation in preload especially affected the filling field; inotropic background was reflected in the effective stroke field. It is concluded that the value of both M-mode echocardiography and calibrated apex cardiography is enhanced by a combination of the two methods, and opens the possibility of a fresh approach to the noninvasive study of cardiac performance.