Assessment of left ventricular contractile state by preload-adjusted maximal power using echocardiographic automated border detection

J Am Coll Cardiol. 1998 Mar 15;31(4):861-8. doi: 10.1016/s0735-1097(98)00005-9.


Objectives: We sought to assess the ability of preload-adjusted maximal power measured by echocardiographic automated border detection (ABD) to quantify left ventricular (LV) contractility by determining the effects of alterations in preload, afterload and contractile state.

Background: Preload-adjusted maximal power can reflect LV contractile state relatively independent of changes in loading conditions.

Methods: Eight anesthetized dogs had placement of aortic electromagnetic flow probes, LV and arterial pressure catheters and inferior vena caval (IVC) occluders; four had placement of thoracic aortic balloon occluders. Echocardiographic ABD measures of cross-sectional area were used as a surrogate for LV volume, and flow was estimated as the first derivative of area with respect to time. Power was calculated as the product of flow and pressure.

Results: Preload independence during vena caval occlusions was achieved by preload adjustment (1/[end-diastolic area]3/2). Afterload independence was demonstrated by preload-adjusted maximal power being unaffected by acute increases in LV systolic pressure induced by aortic occlusion. ABD preload-adjusted maximal power reflected changes in contractile state: increasing with dobutamine infusion from 36+/-14 to 70+/-15 mW/cm4 (p < 0.05 vs. control) and decreasing with propranolol infusion from 35+/-13 to 17+/-7 mW/cm4 (p < 0.05 vs. control). These changes were significantly correlated with calculations of preload-adjusted maximal power using aortic flow (r = 0.90, SEE 10.5 mW/cm4) and load-independent measures of end-systolic elastance from pressure-area loops (r = 0.90, SEE 10.6 mW/cm4). Calculations of normalized preload-adjusted maximal power using arterial pressure were also closely correlated with similar calculations using LV pressure (r = 0.99, SEE 3%).

Conclusions: Preload-adjusted maximal power using echocardiographic ABD can predict LV contractile state relatively independent of loading conditions and has potential for clinical application.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Aorta / physiology
  • Blood Flow Velocity
  • Cardiac Output
  • Cardiotonic Agents / pharmacology
  • Constriction
  • Dobutamine / pharmacology
  • Dogs
  • Echocardiography* / methods
  • Myocardial Contraction* / drug effects
  • Pressure
  • Propranolol / pharmacology
  • Stroke Volume
  • Vena Cava, Inferior / physiology
  • Ventricular Function, Left*


  • Cardiotonic Agents
  • Dobutamine
  • Propranolol