One-plane cineangiographic measurement of left ventricular volume uses angiocardiograms taken in the right anterior oblique view. Its basic assumption is that the third (unvisualized) dimension, depth from septum to free wall, is of the same magnitude and behaves in the same way as the visualized short axis. Examination of this assumption with biplane x-ray equipment revealed that the unmeasured length averages 7% less and varies directly with the length of the measured short axis. Volumes measured correlate well with consecutive studies using serial biplane x-rays and are systematically somewhat larger than volumes obtained in autopsy specimens injected with barium sulfate paste. The method is tolerant of variations in positioning of the patient, is convenient, yields repeatable analyses from one experienced observer to another, allows 60 volume measurements per second so that rapid cardiac events can be studied, and the small doses of x-rays and contrast medium permit several observations at one catheterization session. This means that effects of drugs and other interventions can be studied by the informative techniques of semi-continuous volume measurement and pressure-volume analysis.
Left ventricular dimensions from routine clinical one-plane cineangiograms were combined with left ventricular pressure measurements to permit calculation of left ventricular wall stresses. The 25 patients included 12 with normal left ventricular dynamics, 6 with volume overload, 3 with outflow obstruction, and 4 with cardiomyopathy. Average stresses calculated on the basis of an ellipsoid model agreed with average values obtained from the exact solution of a thick-walled elastic ellipsoidal shell. Peak values were 150 to 625 g/cm 2 in the circular direction and 75 to 365 g/cm 2 in the longitudinal direction. A fiber-corrected stress was defined which represents a force per muscle fiber. The variation in fiber-corrected stress during the cardiac cycle may be considerably different from the variation in simple stress.The force-velocity characteristics of circular fibers for the 25 patients are presented. The data on peak wall stress overlap in the four groups of patients. Peak velocity of circumferential fiber shortening varied from 0.44 to 0.63 lengths/sec in patients with myocardial weakness and varied from 0.74 to 2.56 lengths/sec in the other patients. Contractile element velocity was determined during ventricular ejection when the rate of force change equaled zero. Contractile element velocity of shortening was 0.22 to 0.32 lengths/sec in the cardiomyopathy group and 0.50 to 1.32 lengths/sec in the other patients.
ADDITIONAL KEY WORDScontractile element velocity of shortening left ventricular wall thickness cardiac muscle mechanics B The force developed by a contracting muscle is a function of the velocity of contraction. The force-velocity relation was first determined for skeletal muscle (1, 2) and more recently has also been determined in isolated cardiac muscle (3-5). The mechanical behavior of the intact heart is a complicated function of its geometry as well as of the contractile behavior of individual muscle fibers. The performance of the heart may be determined by cineangiography
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