The amount of blood pumped out of the heart (cardiac output), the tone of the walls of the arteries (vascular resistance), and the volume and viscosity of the blood influence the pressure (expressed in millimetres of mercury) of the blood against the walls of the arteries. Each blood pressure measurement has two numbers.
The first or top number is systolic blood pressure (pressure within the arteries during systole, when the heart is contracting). The second or bottom number is diastolic pressure (pressure within the arteries when the heart is relaxing). Normally, systolic pressure is the higher number. During IECP treatment sessions, diastolic pressure is increased and systolic pressure is decreased, usually to a degree that diastolic pressure exceeds systolic pressure.