Summary and Review of the 2004 AHA Guidelines

 

In Circulation (Volume 109, page 672, Feb 2004) includes the new American Heart Association (AHA) guidelines for prevention of cardiovascular disease in women. These recommendations were based on a rigorous evaluation of nearly all the available scientific evidence to date by a panel of 27 experts on cardiovascular disease and women’s health. The importance of heart disease prevention for women can hardly be overemphasized. Coronary heart disease is the single greatest killer of American women, extinguishing more lives (approximately one death per minute) than the next seven leading causes of female mortality. Interestingly, women’s perception of the leading threats to their lives is not in tune with reality (see Figure 1). According to a recent Gallop poll, women are far more concerned about cancer, and, in particular, breast cancer, than about heart disease.

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This fact is a testimony to the effectiveness of the public information and education programs of the American Cancer Society and the National Cancer Institute, and certainly women are well-advised to continue pursuing appropriate measures to prevent cancer, including regular breast examinations, annual mammograms and PAP smears, etc. Nonetheless, women should be aware that far more is known about risk factors for heart disease than for cancer, and, in general, heart disease risk factors are more susceptible to interventions. The coronary arteries supply the heart muscle with blood. Coronary artery disease, which is the most common cause of heart problems in adults, is due to a complex and prolonged process called atherosclerosis. This word translates literally as "artery hardening." Atherosclerosis is extremely common. It appears to begin as early as childhood or adolescence, and proceeds slowly during the entire lifespan. The process starts with small deposits of cholesterol and fat in the walls of the arteries called "fatty streaks." Next, white cells from the blood invade these streaks and ingest the fat, so that clusters of "foam cells" form within the streaks, which are now called plaques. Next, some of these cells die leaving areas of fatty debris. Cell death provokes inflammation and scarring, causing a "cap" of fibrous scar tissue to form over the plaque. Crystals of calcium phosphate tend to deposit in the dead material, making the arteries brittle.

As the plaques grow thicker, the inside of the affected areas of the arteries narrow, so that blood flow is obstructed. When the narrowing reaches 80% or more of an area of coronary artery, symptoms of angina, (chest pain during stress or exercise), may occur. There is a tendency for plaques to break down, losing their fibrous caps. When this happens the blood comes in contact with fatty and dead material, causing a clot (thrombus) to form. Such clots may block the artery completely causing a heart attack (myocardial infarction) as an area of heart muscle, deprived of blood flow and oxygen, dies. Such episodes are frequently fatal, and, even when survived, leave the heart scarred and prone to rhythm abnormalities and reduced function (heart failure).

Fortunately, over the last 30 years or more, medical science has learned a great deal about the factors that contribute to atherosclerosis and heart attacks and how they can be measured and altered. The new AHA guidelines describe a scale for classifying a woman’s heart attack risk and, based on this classification, recommend graded interventions to reduce this risk.

Factors that classify women into the "high risk" category (probability of a heart attack greater than 20% in the next five years) are:

• A previous heart attack or angina
  
• Symptoms from arterial disease in arteries other than the coronaries
  
  • Aortic aneurysm
    
  • Stroke (cerebrovascular disease)
    
  • Peripheral artery disease
    
• Diabetes
  
• Chronic kidney disease
  

An "intermediate risk" classification (probability of a heart attack 10-20% in the next five years) is made for:

• More than a minimal amount of coronary artery calcium (seen on special x-rays) without symptoms
   
• The metabolic syndrome (abdominal obesity, high blood sugar and insulin levels, high blood pressure, and low plasma HDL cholesterol and high triglyceride levels)
   
• Multiple risk factors (such as elevated LDL cholesterol with high blood pressure)
   
• Markedly elevated levels of a single risk factor
   
• First degree relative with early onset heart disease (male less than 55 years, female less than 65 years)
   

The "lower risk" (probability of a heart attack less than 10% in the next five years) category may include women with one or more risk factors, depending on the severity .

Finally, "optimal risk" is used to describe women with low levels of known risk factors and a heart-healthy lifestyle.

The article in Circulation also includes a detailed scoring sheet for determining heart disease risk category by age, range of total cholesterol, levels of HDL ("good") cholesterol, smoking history, and blood pressure. A similar, but more detailed scoring sheet is available on the web at http://www.nhlbi.nih.gov/guidelines/cholesterol/index.htm. Not included on this scoring sheet are other known risk factors such as C-reactive protein (also known as "CRP," a marker of inflammation), coronary calcium determined by X-ray scanning, glucose intolerance (high sugar and insulin levels) best determined by a glucose tolerance test, size classification of blood cholesterol particles, Lp(a) (a modified lipid particle in blood), or homocysteine (a product of amino acid metabolism), all of which are independently associated with increased heart disease risk.

We believe there is enough evidence supporting the importance of the additional risk factors above, to take them into consideration in ultimate determinations of risk. However, currently no simple scheme exists for including these factors in a "risk score." To reach the most accurate estimate of heart attack risk, we recommend that, between the ages of 40 and 55, women should have this entire set of risk factors measured. Because atherosclerosis appears to accelerate after the menopause, and because lipid profiles (total, LDL and HDL cholesterol and triglycerides) tend to change for the worse at menopause, we further suggest that these measures be obtained within a few months after menses cease.

The current recommendations of the AHA panel for cardiovascular disease prevention in women provide important and useful information for women and their physicians. Early intervention to prevent atherosclerosis progression and age-appropriate assessment of risk factors would substantially reduce the rate of coronary heart disease, the number one killer of American women. Unfortunately, the science supporting these clinical considerations is far from perfect. More and better research is needed.