ASSESSMENT OF LEFT-VENTRICULAR CONTRACTILE STATE BY PRELOAD-ADJUSTED MAXIMAL POWER USING ECHOCARDIOGRAPHIC AUTOMATED BORDER DETECTION

Objectives. We sought to assess the ability of preload-adjusted maxima l power measured by echocardiographic automated border detection (ABD) to quantify left ventricular (LV) contractility by determining the ef fects of alterations in preload, afterload and contractile state. Back ground. Preload-adjusted maximal power can reflect LV contractile stat e relatively independent of changes in loading conditions. Methods. Ei ght anesthetized dogs had placement of aortic electromagnetic flow pro bes, LV and arterial pressure catheters and inferior vena caval (IVC) occluders; four had placement of thoracic aortic balloon occluders. Ec hocardiographic ABD measures of cross-sectional area were used as a su rrogate for LV volume, and flow was estimated as the first derivative of area with respect to time. Power was calculated as the product of f low and pressure. Results. Preload independence during vena caval occl usions was achieved by preload adjustment (divided by[end-diastotic ar ea](3/2)). Afterload independence was demonstrated by preload-adjusted maximal power being unaffected by acute increases in LV systolic pres sure induced by aortic occlusion. ABD preload-adjusted maximal power r eflected changes in contractile state: increasing with dobutamine infu sion from 36 +/- 14 to 70 +/- 15 mW/cm(4) (p < 0.05 vs. control) and d ecreasing with propranolol infusion from 35 +/- 13 to 17 +/- 7 mW/cm(4 ) (p < 0.05 vs. control). These changes were significantly correlated with calculations of preload-adjusted maximal power using aortic how ( r = 0.90, SEE 10.5 mW/cm(4)) and load-independent measures of end-syst olic elastance from pressure-area loops (r = 0.90, SEE 10.6 mW/cm(4)). Calculations of normalized preload-adjusted maximal power using arter ial pressure were also closely correlated with similar calculations us ing LV pressure (r = 0.99, SEE 3%). Conclusions. Preload-adjusted maxi mal power using echocardiographic ABD can predict LV contractile state relatively independent of loading conditions and has potential for cl inical application. (C) 1998 by the American College of Cardiology.