Time Course of Left Ventricular Pressure-Volume Relationship under Various Extents of Aortic Occlusion

The author has reported that a variable, e (t) =p (t) /v (t), is approximately unchanged in the areflexive heart of the dog over a wide range of end-diastolic volume of the left ventricle, where p (t) is systolic left intraventricular pressure, v (t) is systolic left intraventricular volume, and t is time from the beginning of systole in each cardiac cycle. e (t) is studied further under various extents of an aortic occlusion, without the change in left intraventricular end-diastolic volume, monitored on left intraventricular end-diastolic pressure of the areflexive heart of the dog. For actual computation, e (t) =p (t) / (1-ρ) -1•vs-∫toi (t) dt, where p (t) is measured by a straingauge electromanometer, ρ is residual volume ratio measured by a thermodilution method, vs is stroke volume as time-integral of ascending aortic flow velocity i (t) in a given cardiac cycle, and i (t) is measured by an electromagnetic flowmeter. End-diastolic volumes of the left ventricle are kept approximately constant by controlling venous return to the heart with a balloon-catheter in the inferior vena cava. The results show that e (t) is approximately unchanged by an ascending aortic occlusion, in spite of the conspicuous changes in p (t), i (t) and v (t) in each dog. Therefore, e (t) is considered to be a steady and characteristic variable of the pumping properties of the areflexive left ventricle.