Appendix B
Glossary of Cardiologic and Epidemiologic Terms
CLINICAL MANIFESTATIONS OF ATHEROSCLEROTIC CARIOVASCULAR DISEASE
Manifestations of atherosclerotic disease may vary due to differences in risk factors and possibly genetic disposition. Atherosclerotic disease in the coronary arteries manifests itself as angina pectoris (40 percent), myocardial infarction (40 percent), and sudden cardiac death (20 percent) (Kannel and Feinlieb, 1972).
Angina pectoris:
Condition due to the narrowing of one or more coronary arteries by atherosclerotic plaques, so that physical exertion, emotion, et cetera, lead to increased cardiac demands for coronary blood flow, which cannot be met, producing symptoms of ischemia such as chest tightness.
Atherothrombotic stroke:
Condition that results from the occlusion of one or more cerebral arteries leading to necrosis of the brain tissue dependent on the blood flow. This may lead to transient (reversible ischemic neurological deficit) or permanent loss of neurologic function. Most frequently, it is due to embolization of the atherosclerotic plaque or the thrombus forming on it (i.e., breaking off of material in the aorta, carotid, or vertebral arteries with material floating downstream until it lodges in one of the smaller cerebral arteries).
Myocardial infarction:
Condition usually due to the total thrombotic occlusion of a coronary artery at the site of an ulcerated atherosclerotic plaque, leading to cessation of blood flow to a portion of the myocardium and subsequent necrosis of the ischemic myocardium. Case fatality rates for myocardial infarction vary but generally are about 30-35 percent in community-wide studies.
Peripheral arterial disease:
The presence of atherosclerosis in the aorta and arteries of the lower extremities can cause inadequate blood flow during exercise, leading to a cramp-like pain called intermittent claudication. Weak-ening of the aortic wall by atherosclerosis can result in aortic aneurysm formation and rupture, which lead to cardiovascular collapse.
Sudden cardiac death:
Death may be due to a massive myocardial infarction but may also be attributable to myocardial ischemic attack, which allows the establishment of arrhythmias characterized by rapid rates and a collapse of cardiac output.
Diseases That May Be Due to Effects of Hypertension on the Cardiovascular System
Hemorrhagic stroke: Neurologic deficit caused by the bursting of an intracerebral artery. The disruption of brain tissue and increase in cranial pressure are often fatal and almost always disabling.
Hypertensive heart disease: Condition in which the heart muscle initially increases in mass due to increase in work against elevated arterial pressure in the aorta. Eventually, the heart may become stiff and unable to fill with blood, or it may dilate with loss of myocardial cells, leading to congestive heart failure.
CARIOVASCULAR RISK FACTORS
A variety of factors have been identified as possibly causative of atherosclerosis and its clinical sequelae. These risk factors can be classified as modifiable or not modifiable. Among modifiable risk factors, the evidence supporting their modification as a way to prevent cardiovascular disease (CVD) can be classified as established, likely, or unproven (Pasternak et al., 1996; Pearson and Fuster, 1996).
Risk factors for which modification has been shown in epidemiologic studies or clinical trials to reduce risk include cigarette smoking , increase in low-density lipoprotein (LDL) cholesterol level (the fraction that carries most of the cholesterol in the blood), a high-fat and high-cholesterol diet, hypertension (high blood pressure, usually defined as >140/90 mm Hg), hypertrophy of the left ventricle (thickening of the cardiac muscle, usually due to high blood pressure), and thrombogenic factors (as evidenced by reduced clinical cardiac events with treatment by aspirin or anticoagulants).
A number of other risk factors have good epidemiologic evidence for their association with CVD, but weaker evidence from clinical trials. These include diabetes mellitus (a metabolic syndrome that includes elevated blood sugar levels), physical inactivity, low levels of high-density lipoprotein (HDL) cholesterol (the lipoprotein fraction thought to be responsible for removing cholesterol from the arterial wall), triglycerides (another form of fat carried in the blood), obesity, and postmenopausal status in women. With the advent of additional
clinical trial data, these risk factors are likely to join those that are considered established.
A number of other risk factors are being investigated for their association with CVD. These include psychosocial factors such as hostility and postinfarction depression; lipoprotein(a) (a lipid with both atherogenic and thrombogenic properties); homocysteine (a metabolite that may be elevated in blood); oxidative stress (an increase in free radicals [e.g., in cigarette smoke] or lack of an antioxidant such as vitamin E); and lack of alcohol consumption (research indicates that one to two drinks of alcoholic beverage per day reduce CVD risk over that of abstinence).
The final group of risk factors that appears to be nonmodifiable includes age, male gender, low socioeconomic status (heart disease in developed countries is associated with poverty), and family history of CVD at <55 years of age in male relatives and <65 years in female relatives.
Epidemiologic Terms and Concepts*
Age adjustment: Process by which a standard age distribution is used to calculate rates so that observed differences cannot be due to age differences in the population.
Attributable risk: Amount or proportion of disease incidence that can be attributed to a specific exposure or risk factor.
Case fatality rates: Number of individuals dying during a specified time after the diagnosis of disease, divided by the number of individuals with the specific disease.
Disability-adjusted life years (DALY): Combination of life years lost due to premature mortality and years lived with disability adjusted for severity (Murray and Lopez, 1997b).
Incidence: Ratio of the number of new cases of the disease occurring in a population during a specified time to the number of persons at risk for developing the disease during that period.
Mortality rates: Total number of deaths in one year divided by the number of persons in the population at mid-year.
Population-attributable risk fraction: Proportion of disease incidence in the total population that can be attributed to a specific exposure or risk factor.
Prevalence: Ratio of the number of cases of disease present in a population at a specified time to the number of persons in the population at the time specified.
Primary prevention: Prevention of the development of disease in a person who does not have the disease.
Primordial prevention: Prevention of the development of risk factors for a disease.
Proportionate mortality: Number of deaths from a single disease in a population at a specified time divided by total deaths in the population at that time.
Relative risk: Ratio of the risk in persons exposed to a risk factor divided by the risk in persons not exposed to the risk factor.
Secondary prevention: Prevention of recurrence of a disease in a person who has already been diagnosed with the disease.
Tertiary prevention: Prevention of disability, poor quality of life, and death in persons with advanced stages of a disease.
Years of life lost (YLL): Number of life years lost prior to a given age of expected survival, usually 65 years.
