CAD is a chronic process that affects the arteries perfusing the heart, brain, and kidneys. CAD includes arteriosclerosis(thickening, reduced elasticity, and calcification of the arterial wall), atheroschlerosis(type of arteriosclerosis that causes reduced myocardial blood flow), and arteritis(inflammation of the arterial wall, usually due to infection or auto-immune response). Atherosclerosis causes reduced blood flow to the myocardium because of buildup of plaque like cholesterol, lipids, and cellular debris infiltrating the intimal lining of the arterial wall. The myocardium normally extracts 75% of available oxygen from the coronary arteries. If the oxygen requirement is not met, then the myocardial blood flow needs to be increased. However, the arteries in CAD are not able to dilate because of the plaque buildup and calcification. As a result the heart needs to increase force of contraction in order to increase blood flow, and thus increasing cardiac output. “The result of all the unmet oxygen needs is the shift to anaerobic metabolism and myocardial tissue hypoxia, which results in angina.” CAD and HTN contribute to HF because the heart needs to increase the force and contractility to maintain tissue perfusion.
(Osborn, 2014 p920)
CHF
CHF includes cardiovascular response to inadequate perfusion and series of neurohormonal response in addition to structural abnormality. The systemic response to compensate for inadequacy is to increase cardiac output. Cardiac output is determined by heart rate and stroke volume. Additionally, stroke volume is influenced by three factors; contractility, preload (the volume of blood in the left ventricle at the end of a diastole), and afterload (pressure of resistance the ventricles must overcome to eject blood during systole).
Preload is assessed by measuring the right atrial pressure and is affected by any restriction. The example that Figueroa & Peters (2006) provides is an increase in positive pleural pressure (seen in COPD or asthma) will reduce ventricular filling. The compensatory mechanism that responds to the decrease preloa