Assessment of slope of end-systolic pressure-volume line of in situ dog heart.

The purpose of this study was to establish a new method of assessment of the slope (Emax) of the end-systolic pressure-volume line (ESPVL) of the in situ heart. In anesthetized open-chest dogs, an isovolumic contraction was produced by an aortic occlusion after steady-state ejecting contractions in the left ventricle. We plotted ventricular pressure measured with a catheter-tip manometer against time integral of aortic flow measured with an electromagnetic flowmeter of the last ejecting and the first isovolumic contraction, assuming the same end-diastolic volume. ESPVL was drawn from the peak isovolumic pressure-volume point tangential to the left upper corner of the +/- 3.0 (SE) mmHg/ml (n = 9 dogs) in control run and was increased by 59 +/- 19% under isoproterenol and decreased by 47 +/- 9% after propranolol. Emax was little changed by atrial pacing. We conclude that Emax by this aortic occlusion method is useful for assessment of left ventricular contractility of the in situ dog heart.