Abstract 14917: Single-beat Estimation of Preload Recruitable Stroke Work
Introduction: The preload recruitable stroke work (PRSW) slope, Mw, is a load-insensitive measure of contractility, but its clinical application has been limited by the need to record multiple beats over a wide volume range. In a previous study, we found that Mw is an end-systolic pressure when the end-systolic dimension is equal to the dimension-axis intercept of the PRSW relationship, Dw.
Hypothesis: We hypothesized that the ratio of Mw to mean ejection pressure (Pm, i.e., stroke work/stoke volume), defined as K, is primarily determined by baseline hemodynamic conditions, providing a simple means of estimating single-beat Mw as K*Pm.
Methods: Pressure-dimension loops were recorded in 14 conscious dogs equipped with sonomicrometers and micromanometers. Multiple-beat left ventricular (LV) Mw was determined during vena caval occlusion under various hemodynamic conditions. Univariate and multivariate linear regression analysis was used to assess the relationship between K and conventional baseline single-beat hemodynamic parameters.
Results: Various hemodynamic conditions yielded an Mw range from 25 to 147 mmHg and a K range from 0.26 to 1.0. Univariate predictors of K included LV end-systolic dimension, LV end-diastolic dimension, maximum ventricular pressure, fractional shortening (FS), max dP/dt, stroke dimension, and regional stroke work (rSW). On multivariate analysis, FS (p<0.0001), max dP/dt (p=0.001), and rSW (r=0.04) were independent predictors of K. Predicted K based on this multivariate regression model was strongly related to multiple-beat K (r=0.90, p<0.0001). Mw almost equaled mean ejection pressure (K = 0.95+-0.04), with FS over 0.3 or max dP/dt over 4,000 mmHg/s. Moreover, K was mathematically identical to Ees/Ea, a marker of ventricular-arterial (VA) coupling; thus, Ees was also accurately estimated from baseline single beats.
Conclusions: The ratio of Mw to mean ejection pressure reflects VA coupling, which is strongly correlated with conventional hemodynamic parameters. This single-beat method accurately estimates a marker of VA coupling as well as a load-insensitive measure of contractility in the PRSW framework, and thus provides a powerful tool for precisely assessing cardiovascular dynamics.
Author Disclosures: R. Inuzuka: None. H. Senzaki: None.
- © 2016 by American Heart Association, Inc.