Understanding advanced hemodynamic concepts

This article reviews the determinants of myocardial oxygen supply (MVO2) and consumption and revisits the effects of IABC on each. Measurements of MVO2, including diastolic pressure-time index (DPTI), tension-time index (TTI), and endocardial viability ratios (EVR), demonstrate the dramatic effects of balloon deflation and the resulting afterload reduction on MVO2. IABC enhances ventricular outflow, thus decreasing preload; reduces systolic and end-diastolic aortic pressures, causing a decrease in ventricular afterload; magnifies the intrinsic Windkessel effect in the aorta, leading to an increased stroke volume; decreases static work and accordingly, MVO2; and stimulates the baroreceptors, causing a reduction in peripheral vascular resistance. IABC also increase in heart rate. Bedside computers enable the clinician to take a closer look at balloon efficacy via DPTI, TTI, and EVR. New sources of information and understanding may provide opportunities for nurses to ensure optimum patient outcomes.