[Left ventricular end-systolic pressure-dimension relation and its sensitility to the positive inotropic factor in...

Left ventricular end-systolic pressure-dimension relation (ESPDR) was generated by the transient occlusion of the inferior vena cava (IVC) or thoracic aorta (AO) in 13 anesthetized open-chest dogs, while the left ventricular pressure was measured by a TP-200T pressure transducer and the anterior-posterior dimension was measured by a pair of ultrasonic crystal implanted in the endocardium and recorded by a Sonomicrometer. The results showed that: (1) the ESPDR was shown to be linear, unaltered by preload or afterload changes; (2) dobutamine produced a significant increase in the slope (Emax) of the ESPDR-IVC and ESPDR-AO relations, without remarkable effect on the dimension-axis intercept (Do). However, the change in Emax was more significant for ESPDR-IVC (174.43 +/- 23.48%, n = 18), as compared with that for the ESPDR-AO (71.02 +/- 12.46%, n = 12); (3) Do of the ESPDR-AO relation was smaller than that of the ESPDR-IVC both under control and during dobulamine infusion. We conclude that the linear ESPDR can be derived in the anesthetized open-chest dogs either by caval occlusion or by aortic occlusion, and the slope appears to reflect left ventricular contractility. However, techniques used to generate the ESPDR may influence results, including the Do and the sensitivity of Emax to the inotropic state.