The American Heart Association (AHA) uses the term cardiovascular disease (CVD) to describe various diseases that affect the heart and circulatory system. These diseases include coronary artery (heart) disease, hypertension, congestive heart failure, congenital cardiovascular defects, and cerebrovascular disease. CVD is a chronic disease. These diseases frequently progress as people age. This article limits discussion to the two most common forms of CVD—coronary artery disease and hypertension.
Cardiovascular disease is the leading cause of death in the United States, responsible for one death every 33 seconds or 2,600 deaths per day. In 1998 CVD claimed the lives of 949,619 Americans. The second leading cause of death, cancer, was responsible for 541,532 deaths. It is estimated that approximately 60.8 million individuals in the United States have one or more types of CVD. The most common form of cardiovascular disease is hypertension, which affects approximately 50 million Americans, or one in every four individuals. Hypertension is a significant risk factor for the development of other types of CVD, including congestive heart failure and cerebrovascular accidents.
The second most prevalent form of CVD is coronary heart disease or coronary artery disease, which affects approximately 12.4 million individuals. Coronary heart disease includes both angina pectoris (chest pain) and myocardial infarction (heart attack). In 1998 the American Heart Association estimated that 7.3 million individuals had suffered a heart attack, and 6.4 million had experienced chest pain. The third most prevalent form of CVD is congestive heart failure, which affects 4.7 million Americans. Cerebrovascular accidents are the fourth most prevalent form of CVD, affecting 4.5 million individuals. Congenital cardiovascular defects affect 1 million Americans, comprising the fifth most prevalent form of CVD. In general, approximately one in five Americans will develop some form of cardiovascular disease in their lifetime.
Risk factors for CVD may be divided into three classifications: modifiable, nonmodifiable, and contributing factors.
Modifiable factors. Modifiable risk factors are those that an individual can change, including elevated serum cholesterol levels, a diet high in saturated fats, obesity, physical inactivity, hypertension, nicotine, and alcohol use. A serum cholesterol level greater than 200 mg/dl or a fasting triglyceride level more than 200 mg/dl is associated with an increased incidence of coronary artery disease. Obesity is associated with a higher incidence of mortality from CVD. Physical inactivity increases the risk for developing CVD as much as smoking or consuming a diet high in saturated fats and cholesterol.
The National Heart Lung and Blood Institute defines hypertension as a blood pressure greater than 140/90. Hypertension is a significant risk factor for the development of CVD and stroke. The AHA estimates that one in five deaths from cardiovascular disease are directly linked to cigarette smoking. Individuals who smoke are two to six times more likely to develop coronary artery disease than nonsmokers. However, individuals who quit smoking will reduce their risk to levels equivalent to those of a nonsmoker within three years.
Nonmodifiable factors. Nonmodifiable risk factors are those risk factors that an individual cannot change, such as age, gender, ethnicity, and heredity. The incidence of CVD increases as people age. However, 150,000 individuals die from it before 65 years of age. Males are more likely than females to experience CVD, until the age of 65, when the incidence rate equalizes among genders. Young men aged 35 to 44 years old are more than six times as likely to die from CVD than their same-age female counterparts. However, the death rates equalize after 75 years of age. Furthermore, women may experience different symptoms of CVD than those experienced by men, thus causing women to be underdiagnosed or diagnosed at a more advanced stage of the disease.
Ethnicity also plays a role in the development of CVD. Non-Hispanic black males have a higher age-adjusted prevalence of CVD than Caucasian or Mexican-American males. Black and Mexican-American females have a higher age-adjusted prevalence of CVD than Caucasian females. Overall, middle-aged Caucasian males have the highest incidence of heart attacks.
Heredity may also play a role in the development of CVD. Individuals with a family history of early heart disease are at a greater risk for the development of elevated blood lipid levels, which has been associated with the early development of coronary artery disease. Additionally, most individuals who have experienced either chest pain or a heart attack can identify a close family member (father, mother, brother, or sister) who also had or has CVD. It is expected that the role of genetics and heredity will be more fully understood in the future due to the advances associated with the human genome project.
Contributing factors. Contributing factors are those factors that may increase the risk for developing cardiovascular disease. Diabetes mellitus and a stressful lifestyle are examples of contributing factors. Diabetics are more likely than the general population to experience CVD. Additionally, they experience coronary artery disease at an earlier age than the nondiabetic individual. Two-thirds of individuals with diabetes mellitus die from some form of heart or blood vessel disease.
The role of stress in the development of coronary artery disease is not clearly understood. Historically it was believed that individuals with a type A personality were at a greater risk for the development of CVD. However, the research findings were mixed and did not clearly support this relationship. Stress may also increase the process of atherogenesis (formation of plaque in arteries) due to elevated lipid levels.
Ischemic CVD, such as angina pectoris and myocardial infarction, are usually diagnosed based on patient symptoms, electrocardiogram findings, and cardiac enzyme results. Additionally, coronary angiography may be performed to visualize the coronary arteries and determine the exact location and severity of any obstructions. Coronary artery disease can be treated using medical treatments, surgical treatments, or interventional cardiology. The treatment goal for ischemic CVD is to restore optimal flow of oxygenated blood to the heart.
Medical treatment for the patient with angina includes risk factor modification, consumption of a diet low in saturated fats and cholesterol, and administration of pharmacological agents. Medications commonly used to treat chest pain or heart attacks include drugs that decrease cholesterol levels, alter platelet aggregation, enhance the supply of oxygenated blood to the heart, or decrease the heart's need for oxygenated blood. Additionally, the person experiencing an acute anginal attack or a heart attack may also receive supplemental oxygen. Thrombolytic medications may be used to treat a patient experiencing a attack, as they may dissolve the blood clot, thus restoring blood flow to the heart.
The blood flow to the heart may also be restored surgically though the use of a common procedure known as coronary artery bypass grafting (CABG). This procedure bypasses the obstructed coronary artery or arteries, thus restoring the flow of oxygenated blood to the heart. Women have poorer surgical outcomes after coronary bypass surgery than men. Specifically, women have a higher relative risk of mortality associated with CABG, longer intensive care unit stays, and more postoperative complications than men.
Nonsurgical revascularization techniques, such as percutaneous transluminal angioplasty, transmyocardial laser revascularization, or the placement of stents in the coronary arteries, are techniques to restore the flow of oxygenated blood to the heart. Percutaneous transluminal angioplasty involves the insertion of a balloon-tipped catheter into the coronary artery, and inflating the balloon at the location of the vessel obstruction. The balloon widens the blood vessel, restoring blood flow through the obstructed vessel. A wire mesh stent may be inserted into the coronary artery and placed at the location of the obstruction. The stent provides an artificial opening in the blood vessel, which helps to maintain the flow of oxygenated blood to the heart. Transmyocardial laser revascularization is a procedure that uses a laser to create channels in the heart to allow oxygenated blood to reach the heart, and is generally used when other techniques have failed.
Research into the efficacy of cardiac gene therapy is being studied to determine how to eliminate heart disease by replacing malfunctioning or missing genes with normal or modified genes. Gene therapy may be used to stimulate the growth of new blood vessels, prevent cell death, or enhance functioning of genes.
Hypertension is initially treated by behavioral and lifestyle modifications. If these modifications do not successfully manage the individual's hypertension, pharmacological agents are added. The lifestyle modifications recommended to control hypertension include diet, exercise, and weight reduction for the overweight individual. The recommended dietary modifications include increasing consumption of fruits, vegetables, low-fat dairy products, and other foods that are low in saturated fat, total fat, and cholesterol. Furthermore, the individual with hypertension is advised to decrease intake of foods high in fat, red meats, sweets, and sugared beverages. It is advisable for hypertensive individuals to decrease their intake of sodium to less than 1,500 mg/day. Not adding table salt to foods and avoiding obviously salty foods may accomplish this restriction. Doctors suggest that hypertensive individuals limit their consumption of alcohol to one to two drinks per day, and decrease or stop smoking. Smoking causes hardening of the arteries, which may increase blood pressure.
Various classes of pharmacological agents may be used to treat hypertension. They include drugs that relax the blood vessels, causing vasodilation, thus decreasing blood pressure, such as angiotensin converting enzyme inhibitors, calcium channel blockers, angiotensin antagonists, and vasodilators. Drugs such as alpha- and beta-blockers decrease nerve impulses to blood vessels, and decrease the heart rate, slowing blood flow through the arteries, resulting in a decreased blood pressure. Diuretics may also be used to manage hypertension. They work by flushing excess water and sodium from the body, causing a decrease in blood pressure.
Coronary artery disease and hypertension are both chronic diseases that require lifelong treatment. Frequently, interventional cardiology techniques and surgical procedures produce palliative rather than curative results. For example, percutaneous transluminal angioplasty fails in six months in approximately 30 to 60 percent of the cases, resulting in restenosis of the blood vessel. Additionally, 50 percent of the grafts of patients who have undergone coronary artery bypass surgery reocclude within five years. Once this has occurred, the patient may be required to undergo additional procedures or surgery.
Individuals who have experienced a heart attack are at a significantly greater risk for future cardiovascular morbidity and mortality. The death rates for people after experiencing a heart attack are significantly higher than the general public. Twenty-five percent of males and 38 percent of females will die within one year of experiencing a heart attack. Additionally, morbidity from cardiovascular disease is higher in individuals who have previously experienced a heart attack. Two-thirds of all heart attack patients do not make a full recovery. CVD is progressive: Twenty-two percent of males and 46 percent of females who previously experienced a heart attack are disabled with heart failure within six years.
Hypertension increases the rate of atherosclerosis, resulting in common complications such as hypertensive heart disease, cerebrovascular disease, peripheral vascular disease, nephrosclerosis, and retinal damage. Uncontrolled hypertension is strongly correlated with the development of coronary artery disease, enlargement of the left ventricle, and heart failure. Additionally, hypertension is a major risk factor for the development of stroke and end stage renal disease.
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BRENDA C. MORRIS