Published: Mar. 2, 2007
Updated: Apr. 12, 2010
Widespread screening for CVD could pinpoint who’s vulnerable
Why is cardiovascular disease still the number one killer in the Western world when risk factors are well known and risk-reduction strategies are widely available?
The Screening for Heart Attack Prevention and Education (SHAPE) Task Force has an answer. This group of leading cardiologists says that focusing on the identification and treatment of known risk factors is ineffective at identifying individuals at greatest risk for heart attack and stroke.
Instead, they say, a prevention policy based on identifying cardiovascular disease (CVD) long before symptoms appear would be far more effective at identifying vulnerable patients and preventing the consequences. It's estimated that initially, 50 million people could qualify for screening.
What’s wrong with current guidelines? Current guidelines do not recognize nonobstructive coronary atherosclerosis as a risk equivalent for coronary artery disease, even though most heart attacks are caused by nonobstructive plaques.
Rather, current guidelines measure risk indirectly through factors known to influence risk, such as smoking, high blood pressure and high cholesterol. The problem is that most people in the U.S. over age 40 have one or more risk factors, whether they develop CVD or not. When risk factors are so widely present, they are no longer effective in predicting the development of CVD in individuals.
Additionally, current guidelines are good at identifying people at very low or very high risk of having a heart attack or stroke within 10 years. However, most people fall into an intermediate risk group, and most heart attacks occur in this group.
The widely accepted practice of screening for asymptomatic cancers of the breast and colon to identify early disease has drastically reduced deaths from these causes.
The SHAPE Task Force advocates the same approach with CVD. Screening men and women with no symptoms would enable thousands of people who are unaware they have atherosclerosis, and who are vulnerable to heart attack or stroke, to be identified.
The severity of their asymptomatic disease could be combined with assessment of known risk factors to pinpoint at-risk patients who need treatment, which could be individualized in proportion to risk.
SHAPE guidelines (July 17, 2006, supplement to American Journal of Cardiology) recommend noninvasive screening of all asymptomatic men aged 45-75 and asymptomatic women aged 55-75. Those at very low risk or already identified as having CVD would be excluded.
Noninvasive tests would be used in screening. Measuring carotid intima media thickness (CIMT) with ultrasound and coronary artery calcification score (CACS) with CT are recommended, because they have been proven to provide “direct evidence for the presence and extent of atherosclerosis … and … prognostic information of proven value regarding the future risk of MI and stroke,” say the authors.
Those with negative scores on CACS or CIMT would be classified as lower risk (if they have no conventional risk factors) or moderate risk (if they have risk factors). Treatment would consist of lowering to or maintaining LDL levels at less than 160 mg/dL. Rescreening would be done in five to 10 years.
Positive tests are further stratified by test scores. For those deemed at moderately high risk, LDL lowering to less than 130 mg/dL would be recommended.
For high risk patients, an LDL goal of under 100 mg/dL would be recommended. Those at very high risk would receive aggressive therapy to lower LDL to under 70 mg/dL, plus a test for myocardial ischemia. If positive, angiography would be performed. Lifestyle changes would be recommended for all patients.
A blood test for C-reactive protein, a marker of inflammation, or ankle-brachial blood pressure, a measure of peripheral vascular disease, could be used to further delineate risk.
Because age is a nonvariable risk factor for CVD, all men and women over age 75 would be assumed to be at high risk and given LDL-lowering therapy without testing.
SHAPE also recommends educating all individuals in high risk categories and their closest relatives about early warning signs of heart attack so they will seek immediate medical care when symptoms occur.
Such a screening program could drastically reduce the large number of first heart attacks -- about 875,000 -- suffered every year. If all of the 50 million qualified were screened, the Task Force estimates 500,000 heart attacks and thousands of strokes per year could be prevented.
Is SHAPE’s program the answer? “It’s obvious that new strategies are needed to fight the growing epidemic of atherosclerotic CVD. In my view, early detection and treatment of high-risk subclinical atherosclerosis is a leading candidate to fulfill that role,” says Valentin Fuster, MD, PhD, former chairman of the American Heart Association.
"Although definitive evidence on whether such a treatment will result in significant reduction of heart attack, stroke, or death still remains to be seen, I am glad a meaningful preventive approach is recommended by SHAPE to target a much earlier phase of atherosclerotic CVD," says Wei Jiang, MD, Associate Professor of Medicine, Associate Professor of Psychiatry and Behavioral Sciences, Division of Biological Psychiatry, Duke University Medical Center.
"Meanwhile, people can do much to improve cardiovascular health. Engaging in routine exercise, avoiding junk food, and managing daily emotional distress are not costly preventive measures. Everyone can do this without relying on fancy machines and expensive pills."
SHAPE guidelines recommend: