September 12, 2003

RESEARCH SUGGESTING PREVENTIVE MEASURES CAN BE HEARTY MEDICINE
By Saul Wilen

More than 60 million Americans have some form of cardiovascular disease. Despite a significant decrease in cardiovascular deaths over the past 30 years, cardiovascular disease continues to represent the most frequent cause of death in the United States today. Advances have been made in prevention, diagnosis, treatment (medical and surgical), and rehabilitation.

However, an emphasis on prevention, which requires an understanding and recognition of the cardiovascular disease risk factors, represents the greatest potential for significant future progress. Armed with this information, approaches to prevent the onset of acquired cardiovascular disease can be instituted through awareness education and early lifestyle changes. These approaches have been demonstrated to show significant results over time.

The cardiovascular system consists of the heart and the blood vessels which carry the blood to all organs and tissues of the body and then return the blood from these areas. The heart is the central pump which propels the blood through the vascular system (a tubular distribution network) consisting of arteries and capillaries, and then returns the blood back to the heart and lungs via the veins. Any process causing damage to the pump and/or the distribution network will result in decreased blood flow and therefore reduced oxygen delivery to organs and tissues. The heart muscle (myocardium) itself has oxygen needs that support its role as the cardiovascular system pump. This oxygen supply is carried through the coronary arteries and then the rest of the coronary vascular system. When an imbalance occurs between the oxygen supply and the oxygen demand, degrees of heart damage and/or pump dysfunction can occur.

These problems happen when there is a primary decrease in coronary blood flow or from an increase in myocardial oxygen requirements, or a combination of the two. The result is myocardial ischemia (decreased oxygen supply to meet the demand) and this is known as ischemic heart disease. Obstructive coronary artery disease caused by atherosclerosis (the deposition in the arterial wall of fatty material with the subsequent development of fibrous plaques and complex lesions) is the most common cause of chronic ischemic heart disease. Various factors including hypertension (elevated blood pressure) and hyperlipidemia (elevated blood levels of fats) can injure the arterial wall lining (endothelium) and initiate the atherosclerotic process.

Cardiovascular diseases
The major acquired cardiovascular diseases include hypertension, myocardial infarction (MI, heart attack, death of a segment of heart muscle), congestive heart failure (CHF, decreased function of the heart as a pump), cerebrovascular accident (CVA, stroke), and rheumatic heart disease. Myocardial infarction is the number one cause of death in the United States. In addition, each year there are approximately 6 million Americans treated for ischemic heart disease. These diseases result in approximately 1 million deaths per year. The disability (morbidity) and deaths (mortality) that result due to these diseases have significant socioeconomic and emotional effects on those who develop the diseases, their families, employers, the health-care delivery system, and society in general.

Most people who experience a heart attack have at least one existing major cardiac risk factor. This was the finding of a recent study published in the Journal of the American Medical Association (JAMA). Existing major Coronary Heart Disease (CHD) risk factors were commonly found in heart attack patients, according to the results. The importance of screening patients by physicians for risk factors to help in the prevention of CHD was emphasized. The study results challenge the belief that CHD events, such as heart attack, frequently occur in the absence of at least one risk factor.

Risk factors
The well-recognized risk factors that contribute to the development of athersclerotic coronary lesions include hypertension, diabetes mellitus, increased low-density lipoproteins (LDLs, fraction of cholesterol) also known as "bad cholesterol," decreased levels of high-density lipoproteins (HDLs, fraction of cholesterol) also known as "good cholesterol," and smoking. Hypertension is regarded as an important contributing factor for the entrance of lipids into the arterial wall. The ingredients of cigarette smoke that are thought to promote atherosclerosis are carbon monoxide (CO) and nicotine. In diabetics it is postulated that circulating substances promote vascular muscle proliferation and a stimulus for increasing the binding of lipoproteins to vascular walls.

High levels of total cholesterol and increased levels of LDLs, and decreased total HDLs have been found to be important risk factors for coronary artery disease. Insulin resistance in diabetics, increased insulin blood levels (hyperinsulinemia), and elevated triglyceride levels have been identified as risk factors for CHD. Recently epidemiological studies have suggested that individuals with elevated blood levels of homocysteine have increased risk for cardiovascular disease. Most studies have shown higher homocysteine levels and/or a greater frequency of elevated homocysteine levels in persons with cardiovascular disease as compared with persons without cardiovascular disease. Whether an elevated homocysteine level is only an acute-phase reactant (predominantly a marker for atherosclerosis) or the result of other factors related to the risks of cardiovascular disease is yet to be determined.

Hyperlipidemia may be secondary (dietary) or primary (due to genetic defects in cellular LDL receptors). The mechanism of the protective effects of HDLs needs further clarification. Recent clinical studies have shown that modification in a clinical setting may be associated with slowing or stopping the progression, or even regression of atherosclerosis. Therefore, in the management of chronic ischemic heart disease, the reduction and modification of risk factors where possible are important.

The rate and severity of CHD worldwide vary greatly among different populations. Additional risk factors established to be related to the incidence and progression of cardiovascular disease, especially coronary artery atherosclerotic disease, are age, sex, obesity, sedentary life-style, smoking, genetic predisposition, oral contraceptives and psychosocial factors. Men have a higher incidence of CHD than women. In the 35- to 40-year-old age range, CHD related deaths of men are five times as frequent as for women. After menopause, women approach the same risk as men. Eighty percent of people who die of a heart attack are age 65 or older. In people younger than 30 years, CHD deaths are primarily linked to hypertension and hyperlipidemia. Obese people (those who weigh more than 30 percent over their ideal body weight) are more likely to develop CHD because of the influence of obesity on blood pressure, blood cholesterol levels, and glucose intolerance resulting in diabetes. Inactivity or sedentary lifestyle is associated with decreases in HDLs. It is difficult to assess the positive effects of exercise on the risk of CHD, but it has been demonstrated that people who exercise actively are at decreased risk.

Psychosocial factors including stress have been linked to CHD. Type A personality, consisting of aggressiveness, competitiveness, and excessive drive, is characteristic of those who develop CHD. This is particularly so when combined with other risk factors such as age, smoking, and high blood lipid levels. Genetic factors have been associated although the role of heredity remains unclear. There is a familial tendency in some cases for hypertension, hyperlipidemia and diabetes. Oral contraceptives when taken by women 45 years and younger have been linked to CHD. In these women, high serum cholesterol levels and triglyceride levels are usually present when they are using oral contraceptives long term.

Intervention strategies
Advances in the treatment of cardiovascular diseases, coronary artery bypass surgery, angioplasty (altering or flattening the plaque in the artery to allow for increased blood flow), and thrombolytic (blood clot busting) therapies in the early occurrence of acute myocardial infarction are significant in controlling symptoms. However, they do not influence the underlying disease processes nor do they alter the atherosclerotic progression in the other coronary arteries. Confronting and changing the risk characteristics which can be addressed will impact the development and progression of cardiovascular disease. These potentially alterable risk characteristics include hypertension, diabetes mellitus, abnormal (high or low) blood levels of cholesterol and its fractions, smoking, obesity, inactivity, and the use of certain medications.

This review of the occurrence, natural history, morbidity, and mortality of cardiovascular disease strongly supports the need for a prevention approach. Twenty percent of heart attacks result in sudden death with two-thirds of these deaths occurring too quickly to receive necessary medical care.

Preventing or at least limiting the consequences of existing risk factors from the earliest possible time and approaches to correct predisposing risks in advance of an acute event are the best considerations in producing the greatest impact on mortality and morbidity. Utilizing preventive medicine/public health measures including education and enhanced public awareness of risk factors, can and will produce improved lifestyle changes that are necessary to protect cardiovascular health.

Saul B. Wilen, M.D., is president and CEO of International Horizons Unlimited (www.intlhorizons.com, 210-692-1268) a national consultation and resources consortium based in San Antonio. Dr. Wilen has a background in medicine and education, and is a recognized authority in prevention strategies, problem solving, systems dynamics, and informatics. He serves on the Public Health and Patient Advocacy Committee of the Bexar County Medical Society.