Pressure Events of the Cardiac Cycle in the Dog

Abstract

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.

Effects of Work Loads Applied at Various Times in the Cardiac Cycle of the Isolated Dog Heart

“…4 ' ° Calculated durations of isometric contraction, isometric relaxation, and ventricular ejection were comparable to values for normal intact dogs. 10 The level of performance of each of the 12 hearts used was determined by different combinations of filling pressure, aortic resistance, and spontaneous heart rate. Therefore, any average values reported are based on per cent changes in each heart relative to its own control levels.…”

Effect of Nucleosides on Acute Left Ventricular Failure in the Isolated Dog Heart

“…This dynamic resistance to deformation was expressed as the diastolie pressure developed per unit inflow through a circuit of known resistance (dynes X sec/cm. 5 ). Under the controlled hemodynamic conditions of these expeiiments, changes in diastolie impedance were interpreted to indicate changes in the visco-elastic properties determining the distensibility of the ventricle wall.…”

“…5 As long as the duration of the QRS and QT intervals of the electrocardiogram remained unaltered, the rate of change of intraventricular pressure during the period of isometric activity indicated the rate of isometric contraction or relaxation. Variations between control and experimental measurements were concluded to indicate changes in ventricular contractility.…”

Pressure Measurements in the Lesser Circulation of the Newborn Rabbit

“…A line was then drawn through zero and the point y/xk and the slope was not significantly different from that of the regression line. The points in graph B were taken from the literature [Motley et al, 1947;Moscovitz and Wilder, 1956;Adams and Lind, 1957;Ross and Criley, 1965] and subjected to the same statistical analysis with similar results. In fig.…”