7.9: Cardiovascular Diseases (CVD)
The cardiovascular system includes the heart, blood vessels, and blood, so any diseases that affect these structures are collectively referred to as cardiovascular diseases (CVD). The most common type of CVD is coronary artery disease, which affects the blood vessels that supply the heart muscle itself (coronary arteries). However, hypertension, stroke, heart failure, and peripheral vascular disease are also included, and can often be co-morbidities (when multiple conditions are present at the same time).
Although CVD may have genetic and biological risk factors, they are highly influenced by lifestyle behaviors and environment. The most common types of cardiovascular diseases are chronic diseases, which can begin the disease process as early as childhood and progress over several decades. The disease process is characterized by changes in the arteries: atherosclerosis and arteriosclerosis.
Arteriosclerosis refers to the hardening and thickening of the arteries. Healthy arteries are elastic, and expand with each heartbeat that pumps a wave of blood flow through them. Chronic inflammation, smoking, diabetes and hypertension (high blood pressure), along with some genetic factors, can cause arteries to become calcified and/or develop fibrous tissue scars that decrease their elasticity. The arteries become stiffer and more resistant to blood flow, which in turn increases blood pressure and makes the heart have to work harder.
Atherosclerosis is a specific type of arteriosclerosis that occurs when fat deposits in the muscular walls of the arteries. These can start with fatty streaks and eventually turn into hard plaques. Arteries can get damaged from hypertension, smoking, and chronic inflammation. Low density lipoprotein (LDL cholesterol) is one way that fat is transported in the bloodstream, and tends to get “stuck” in these damaged areas in the arteries. The body will respond by creating a fibrous scar tissue over the top of the plaque - but over time the plaque can protrude into the artery, restricting blood flow.
Arteriosclerosis can progress over time to the point of causing other problems in the cardiovascular system. Blockages in the coronary arteries can decrease blood flow to the heart muscle (myocardium), called myocardial ischemia. This lack of blood flow can cause chest pain (angina pectoris), particularly when the body is under stress. Eventually this reduction in blood flow to the myocardium can cause those cells to stop contracting - which causes a heart attack or myocardial infarction. Or, if the blood vessels become weakened, they can bulge and/or burst, causing an aneurysm. These conditions can also occur in blood vessels that feed the brain tissue, causing a stroke or transient ischemic attack (mini-stroke).