The effect of zacopride on contractile parameters of ventricular trabeculae isolated from the RV, right ventricle of failing human hearts, including: Fdev, peak isometric developed force (A); TTP, time to peak force (B); and RT50, time from peak force to 50% relaxation (C). Superimposed original representative recordings of twitches (normalized to cross-sectional area) in the RV of failing human myocardium (heart # 904475) in the presence of zacopride (5 – 200 µmol/L) showing a concentration-dependent decrease in the Fdev and occurrence of contractile alternans at the highest applied concentration of 200 µmol/L (D). The effect of zacopride on contractile parameters of ventricular trabeculae isolated from the LV, left ventricle of failing human hearts, including, Fdev (E), TTP (F) and RT50 (G). Superimposed original representative recordings of twitches (normalized to cross-sectional area) in the LV of non-failing human myocardium (heart # 820447) in the presence of zacopride (5 – 200 µmol/L) showing a concentration-dependent decrease in the Fdev and occurrence of contractile alternans at the highest applied concentration of 200 µmol/L (H). n = 5 – 7.