Chronic High Blood Pressure
People who have chronic high blood pressure often have stiff and non-compliant arteries due to atherosclerosis. Who does this affects the following:
Blood flow through the arteries
Left ventricular afterload
How Stiff and Non-Compliant Arteries Due to Atherosclerosis Affects Blood Flow Through the Arteries
Arterial stiffness constitutes abnormal stiffening of the walls of large arteries that carries blood from the heart to major organs and parts of the body. High blood pressure leads to arterial stiffness, especially pulse pressure, by increasing pulsatile aortic wall stress accelerating elastin degradation (Ecobici & Stoicescu, 2017). Hypertension is considered an accelerated or severe form of vascular aging and degradation, leading to stiffening of the arteries. Atherosclerosis also contributes to arterial stiffness since it is characterized by the building up of a plague. The plague is composed of cellular waste, cholesterol, fatty substances, fibrin, and calcium. Accumulation of the plaque contributes to arterial thickening constricting the channel, and reducing the blood flow through the arteries (Bergheanu, Bodde, & Jukema, 2017). Arterial stiffness involves more than plaque formation and loss of suppleness of the artery resulting in the blood vessels being unable to properly regulate blood flow and blood pressure. Stiffening of the arteries also results in capillary damages. Damage of capillaries supplying nourishment to essential organs can result in organ failure.
Atherosclerosis damages the innermost layer of the arteries, which disrupts blood flow. Arteries are composed of three layers. The innermost layer of the artery is referred to as endothelium or tunica intima, followed by tunica media and tunica external. The three walls can constrict or narrow depending on the demands of the tissue in question. Any structural changes in arteries result in a reduction in aortic compliance. Compliance refers to the capacity and ability of a hollow vessel or organ to expand and increase in volume due to increased transmural pressure. Arteries with higher compliance translate to vessels that deform easier under pressure (Homan & Cichowski, 2019). Veins have higher compliance compared to arteries. Stiffness of the arteries decreases arterial compliance. Atherosclerosis causes the formation of a plague surrounded by a fibrous cap. The cap may tear or rupture, resulting in an injury to the arterial wall. A clot is formed in the artery to respond to the injury sealing the area (Bergheanu, Bodde, & Jukema, 2017). This may result in a heart attack due to complete blockage of blood flow into the heart muscles. Arterial blockage and non-compliance may result in poor circulation in the other parts of the body, such as the legs and the pelvis. Blockage of blood flow to the arteries supplying blood to the brain may result in a stroke. Arterial stiffness and non-compliance, therefore, affect blood flow through the artery by completely blocking the flow of blood or reducing blood flow through the arteries to other parts of the body. The results of the blockage vary depending on the part of the body affected and the severity of the stiffness causing total or partial blockage of blood supply in the body.
How Stiff and Non-Compliant Arteries Due to Atherosclerosis Affects Left Ventricular Afterload
Afterload is a term used to refer to the pressure that the heart functions against to eject blood during a ventricular contraction or systole and is usually proportional to the average pressure in the arteries (LaCombe & Lappin, 2019). An increase in the aortic and pulmonary pressure results in an increase in afterload in both the right and left ventricles. Changes in the afterload take place as a way of adapting to the changing demands of the cardiovascular system. The pressure exerted on the arteries’ walls is lowest if the blood vessels are of low stiffness and high compliance. A high compliant and elastic arterial wall generates a narrow pulse pressure. Low wall tension translates to a lower workload for the heart. Stiff and non-compliant arteries result in greater pulse pressure and increase the workload of the heart.
Elevated high blood pressure results in increased left ventricular afterload since the left ventricle has to work harder and under greater pressure to eject blood into the aorta. The left ventricle is required to generate a higher pressure greater than the pressure in the arteries to push the blood into the aorta. Stiff and non-compliant arteries generate a higher pressure than the normal pressure hence an increase in left ventricular afterload to pump the blood into the aorta. Increased left ventricular afterload facilitates the opening of the aortic valve due to the pressure gradient created by the stenotic and calcified aortic valve (LaCombe & Lappin, 2019). The increased afterload increases the workload of the ventricles. Long-term increased workload results in hypertrophy. Left ventricular hypertrophy refers to the thickening of the muscles of the ventricle due to the progressive workload. Left ventricular hypertrophy is a risk factor for diastolic and systolic heart failure and sudden death in patients suffering from high blood pressure.
Elevated blood pressure increases stress on the walls of the arteries, accelerating elastin degradation resulting in non-compliance. Atherosclerosis, on the other hand, contributes to stiff arteries due to the presence of plaque. The results of stiffness and reduced compliance are decreased blood circulation or complete blockage of blood depending on the severity of the stiffness as it may result in a blood clot. It also increases left ventricular afterload as the ventricles generate high pressure to push blood into the narrow aorta.