Assessing Cardiovascular Risk Is Still An Imperfect Science
Respected NBC “Meet the Press” moderator Tim Russert's sudden fatal heart attack earlier this year at the age of 58 was a shock to all. His friends, colleagues and audience all had the same question: Why him?
Coronary attacks and strokes kill some 600,000 Americans each year — and nearly two thirds of them don't even make it to the hospital because they had what's called “silent CHD.” Without warning, a plaque ruptures and a blood clot forms, blocking a coronary artery and causing a heart attack. The same thing happening in the carotid arteries that supply blood to the brain causes a stroke.
The kind of plaque most likely to rupture is cholesterol-filled and inflamed, says Judith S. Hochman, M.D., Harold Snyder Family Professor of Cardiology at New York University School of Medicine. Expensive imaging tests can show these blockages, but insurance usually covers it only after a first heart attack or stroke, or when your doctor already suspects a severe blockage.
No matter how expensive or accurate, diagnostic tests can reveal the direction in which your health is heading, but cannot predict your destination.
Says Hochman: “Risk factors such as smoking, high cholesterol, high blood pressure, diabetes, overweight/obesity and family history tell us almost everything we need to know.”
The chart on pages 14–15 describes the most often-used tests, and what they can and cannot tell your doctor about your future risk.
BP Blood Pressure
CAD Coronary Artery Disease
CHD Coronary Heart Disease
CRP C-Reactive Protein
CT Computed Tomography
DBP Diastolic Blood Pressure (bottom number; heart at rest)
HDL High-Density Lipoprotein (“good” cholesterol)
HF Heart Failure
LDL Low-Density Lipoprotein (“bad” cholesterol)
RF Risk Factor
SBP Systolic Blood Pressure (top number; heart pumping)
TC Total Cholesterol
* Coverage can vary substantially; always check with your provider.
** Intermediate risk includes 2+ risk factors such as smoking, hypertension (BP greater than or equal to 140/90 mmHg or on antihypertensive medication), low HDL cholesterol (less than 40 mg/dL), family history of premature CHD (CHD in male first-degree relative less than 55 years or in female first-degree relative less than 65 years), and age (men 45 years or older, women 55 years or older). High risk includes coronary heart disease (past heart attack, angina) or its equivalents (peripheral arterial disease, abdominal aortic aneurysm, carotid artery disease, diabetes) and 2+ risk factors.
NEW SCREENING TESTS ON THE HORIZON
CORONARY CALCIUM CT SCAN
When first introduced, this test was used only when a patient had chest pain, but now “the calcium CT scan is becoming more clinically accepted for asymptomatic patients with multiple risk factors,” says David Bluemke, M.D., Ph.D., Director of Radiology and Imaging Sciences at the National Institutes of Health Clinical Center in Bethesda, MD. Quick and highly accurate, the test shows calcium deposits in plaques, indirectly indicating heart attack risk. Even a low calcium score (1–100) signals a doubling of risk. The test is usually noninvasive, unless the type of scanner used requires injection of a contrast dye. There is ongoing debate and research concerning the appropriateness of using the coronary calcium scan. Insurance doesn't yet cover this new test, and cost can vary.
In addition to the standard blood glucose test for diabetes, early next year the American Diabetes Association (ADA) is expected to recommend assessing average glucose (AG), which shows average blood sugar level over two or three months. The AG doesn't fluctuate between meals and is an accurate measure of the overall glucose level. This simple blood test measures the amount of glucose attached to red blood cells, which varies less than blood sugar. It's the best way to see if you have diabetes or how well diabetes is controlled.
Genetic testing involves analyzing a sample of blood or other body fluid for biochemical, chromosomal or genetic markers that suggest cardiovascular disease. Many heart disease and stroke risk factors are passed on from parent to child — for example, through genes that regulate how the body processes cholesterol. Genetic testing has been an inconsistent predictor, but future breakthroughs may make it possible to identify CV risk and tailor a personalized treatment regimen for a specific patient.
© 2008 American Heart Association, Inc.