Estimation of preload recruitable stroke work relationship by a single-beat technique in humans

Abstract

The slope of the preload recruitable stroke work relationship (Mw) is a highly linear, load-insensitive contractile index. To investigate whether Mw can be determined from a single steady-state beat, 45 patients were studied during cardiac catheterization. Single-beat Mw (SBMw) was calculated directly from the baseline stroke work and baseline left ventricular (LV) end-diastolic volume (EDVB), and the volume-axis intercept (Vw) was estimated as k × EDVB + ( k − 1) × LVwall, where k is the ratio of the epicardial shell volumes corresponding to Vw and EDVB and LVwall is the wall volume. The mean of individual k values was 0.72 ± 0.04, which correlated with LV mass significantly ( r = 0.60, P < 0.001). SBMw calculated from a constant k of 0.7 predicted Mw well ( r = 0.88, P < 0.0001), and the prediction improved slightly when k was estimated from individual LV mass ( r = 0.93, P < 0.0001). Subgroup analyses revealed that the single-beat technique also worked in patients with small or large LV mass or volume or with regional wall motion abnormalities. The absolute change in SBMw after dobutamine infusion also correlated with that in Mw. In conclusion, Mw can be estimated from a steady-state beat without alteration of preload.