When the heart contracts during its pumping phase (systole), the coronary vasculature is squeezed by the powerful contraction of heart muscle, limiting the flow of blood to and within the muscle (myocardium). The myocardium must therefore receive most of its oxygenated blood during its period of relaxation (diastole), when large coronary arteries are most receptive to blood flow. Muscles, especially the large weight-bearing ones of the lower body, contain large numbers of blood vessels that cumulatively hold a large volume of blood. During IECP® treatment, at the onset of each diastole, compressive air cuffs that surround the muscles of the lower body are quickly inflated in rapid succession, first at the calves, then at the lower thighs, then at the upper thighs and buttocks.
The rapid and precisely timed "squeezing" of the muscles sends a wave of blood (and pressure) that travels toward the heart through both veins and arteries. The sequential compression ensures that the waves generated in the more distant calf muscles can pass under the next cuffs (lower thighs) and be reinforced (not trapped) by the second and third compressions of the sequence. The result of the combined compressions is an increase in venous return (delivery of deoxygenated blood to the right atrium), and an "augmentation" or enhancement of diastolic pressure, which improves myocardial perfusion (flow of blood through the coronary arteries and to the heart muscle.