Left ventricular peak systolic pressure/end-systolic volume ratio change after dobutamine infusion for predicting left ventricular contractile reserve: comparison with Emax

摘要

OBJECTIVES: Genuine left ventricular contractile function is difficult to assess in the clinical setting. Left ventricular peak systolic pressure/end-systolic volume (Pps/Ves) ratio may be misleading because this index takes no account of the left ventricular end-systolic point and V0 intercept in the pressure-volume relation geographic curve. End-systolic pressure-volume relation and maximum chamber elastance derived from left ventricular pressure-volume loops can provide reliable estimates of contractile function. However, the feasibility of this technique for clinical purposes is limited, because it requires instantaneous measurement of left ventricular pressure and volume. This study assessed the feasibility of using Pps/Ves ratio for predicting the left ventricular contractile reserve by direct comparison with maximum elastance (Emax) derived from left ventricular pressure-volume loops. METHODS: Studies were undertaken in 18 consecutive patients aged 60 +/- 9 years who underwent cardiac catheterization. On-line instantaneous left ventricular volume was derived from the acoustic quantification method by transthoracic echocardiography. Pps was determined by pressure manometer tipped wire and Ves was measured automatically from acoustic quantification software in an ultrasound system. Pps/Ves was compared with Emax derived from each simultaneous pressure-volume loop during inferior vena caval occlusion before and after dobutamine infusion. Emax was determined as the slope of end-systolic points for each loop with the use of an automated iterative linear regression technique. Left ventricular contractile reserve was assessed by evaluating its functional response to 10 micrograms/kg/min of dobutamine infusion. RESULTS: Pps/Ves showed significant correlation with Emax in all patients (r = 0.70, p < 0.0001). However, scattered distribution of V0 value differences were noted. Contractile reserve (Pps/Ves) showed strong correlation with contractile reserve (Emax) despite V0 value differences (r = 0.927, p < 0.0001). CONCLUSIONS: Pps/Ves change after dobutamine infusion may minimize individual V0 distribution. This simple index could be used to evaluate left ventricular systolic performance without requiring the left ventricular pressure-volume relationship and volume unloading maneuver.