Understanding advanced hemodynamic concepts

Abstract

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.