Maximum tolerable afterload and afterload reserve for the evaluation of ventricular performance

The concept of a maximum tolerable afterload and an afterload reserve was proposed for evaluating ventricular function. A maximum tolerable afterload was defined as the systolic ventricular pressure during gradual proximal arterial obstruction, at the point where a distal arterial pressure or flow began to fall. An afterload reserve was defined as the difference between a maximum tolerable afterload and a basal afterload. By using right heart bypass preparations in dogs, a maximum tolerable afterload and an afterload reserve were compared with the ventricular function curve. An improved ventricular function curve was always associated with a greater maximum tolerable afterload and a greater afterload reserve, whereas a depressed function curve with a smaller maximum tolerable afterload and a smaller afterload reserve.