At operation the hemodynamics of the left side of the heart were studied in six patients without mitral stenosis, and in eight patients with mitral stenosis, by means of simultaneous needle puncture of the left atrium, left ventricle, and aorta. This technic permits analysis of the various phases of the cardiac cycale in normal subjects and in patients with mitral stenosis. The fundamental hemo-(lynamic expression of mitral stenosis is the presence of an elevated left atrioventricular filling pressure gradient, which ranged from 4 to 20 mm.Hg, and after valvulotomy fell in relation to the adequacy of the procedure.O UR knowledge of the human cardiac cycle has been retarded by the inability to study completely the hemodynamics of the left side of the heart. The technique of venous catheterization, which has contributed so much to an analysis of events in the right side of the heart of man1-3 does not permit the direct study of the left heart chambers except in isolated instances of congenital communications between the right and left cavities.Previous investigation of the left side of the circulation has been carried out primarily through animal experimentation.

Simultaneous pressure curves from the cardiac cavities, aorta and pulmonary artery of dogs were recorded by manometers of equal sensitivity. It was found that left ventricular pressure during ejection is practically identical with that of the aorta. In the majority of dogs atrial and ventricular end-diastolic pressures were equal. The temporal relations of events in the right and left heart were similar to those reported in man, but the duration of the cardiac cycle is too dependent on cycle length to permit comparison.T HE classic physiologic studies of Wiggers 1 have defined the dynamic details of the phases of the cardiac cycle in the dog. Wiggers, however, commented upon the technical difficulty experienced in attempting to record simultaneously the three pressure pulses of each side of the heart, i.e., left atrium, left ventricle and aorta or right atrium, right ventricle and pulmonary artery.3 Pressures recorded separately must be reduced to a standard scale of ordinates and artificially superimposed and retraced in order to reproduce graphically and quantitatively the simultaneous pressure relationships of the cardiac cycle. Because of the uncertain reliability of such reconstructed curves, differences of opinion still exist as to the magnitude of the difference between the ventricular and aortic pressures during ejection' and as to the agreement of ventricular and atrial end-diastolic pressures.

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