The effects of acute afterload change on systolic ventricular function in conscious dogs with normal vs. failing hearts

Background: To date, no data exist on the linearity and, therefore, the usefulness of the preload recruitable stroke work (PRSW) and end‐systolic pressure–volume (ESPVR) relationships during acute afterload changes in heart failure. Aims: Our aim was, therefore, to characterize both relationships in a model of ventricular pacing induced heart failure at baseline and during acute changes in afterload. Methods: Dynamic left ventricular volume and transmural pressure were measured in 10 conscious dogs using sonomicrometry and micromanometry under control conditions and during heart failure produced by 3 weeks of rapid right ventricular pacing. Afterload was varied from baseline with intravenous infusions of nitroprusside and phenylephrine. Left ventricular function was assessed using the PRSW and ESPVR relationships. Results: Cardiac output demonstrated a linear inverse relationship with afterload in both normal and failing hearts (r2>0.5, P