New guidelines developed by the international Screening for Heart Attack Prevention and Education (SHAPE) task force will enable physicians to identify asymptomatic patients at high risk for initial myocardial infarction in time to implement interventions to reduce cardiovascular risk, according to a presentation at the annual meeting of the American College of Cardiology.

"Scientific understanding of the causal chain of heart attack has advanced along with technologies capable of improving our ability to identify those at risk, but our physicians lack new guidelines for using the latest knowledge and technology to actually prevent heart attacks," said Morteza Naghavi, MD, chairman of the SHAPE Task Force. "Every year, nearly half of heart attack victims (over 650,000 in the United States) are unaware of their vulnerability to a near future heart attack until it happens. And more than 220,000 of them die within an hour; this is unacceptable. Essentially, they each are a walking time bomb and completely unaware."

"The SHAPE Guideline is a new approach based on identification of subclinical atherosclerosis as a first step and then incorporating additional information derived from traditional risk factors of the disease with the option of incorporating additional new and emerging biomarkers," said P.K. Shah, MD, chairman of the SHAPE Task Force Editorial Committee. "It is designed to improve our ability to identify 'the Vulnerable Patient,' individuals at risk of a heart attack in the near future who do not exhibit overt signs and symptoms of cardiovascular disease."

The task force encourages virtually all men at least 45 years of age and women at least 55 years of age to participate in the expanded screening program: The only people who would be exempt are those classified as very low risk based on the following criteria: total cholesterol lower than 200 (mg/dl), blood pressure lower than 120 over 80 (mmHg), no history of any type of diabetes, no smoking, and no family history of myocardial infarction.

The initial evaluation step is to identify subclinical atherosclerosis. The two current noninvasive techniques to do this involve detection of coronary artery calcium with computed tomography or carotid wall thickness and presence of plaque with ultrasound. The guidelines define a negative person as an individual with a coronary calcium score (CCS) of zero or carotid intima-media thickness (CIMT) lower than the 50th percentile.

If the subject does not have established risk factors, the guidelines categorize them as Lower Risk and recommends retesting in five years. If any of the traditional risk factors exist, the patient is considered Moderate Risk and the guidelines recommend treating the risk factors according to existing guidelines and retesting in five years.

Persons with a coronary calcium score greater than zero or intima-media thickness higher than the 50th percentile are considered positive for subclinical atherosclerosis. The guidelines divide this population into three subgroups: Moderately High Risk, High Risk, and Very High Risk.

Moderately High Risk: Persons with a coronary calcium score greater than zero but less than 100 and less than the 75th percentile, or carotid intima-media thickness between the 50th and 75th percentile and no discernable plaque buildup.

High Risk is defined by a coronary calcium score greater than the 75th percentile or greater than 100. These patients are considered appropriate for aggressive lifestyle modifications to lower low-density lipoprotein cholesterol. If calcium score is greater than 400 or greater than the 90th percentile, additional testing for myocardial ischemia is recommended. High Risk patients with no evidence of ischemia are still treated with an even lower low-density lipoprotein goal (less than 70) than patients with less extensive atherosclerosis. Persons who have evidence of ischemia fall into the very high-risk group.

Very High Risk is defined by the presence of ischemia. The guidelines recommend that these patients undergo coronary angiography. This group also requires the most aggressive therapy.

"We are not saying we have discovered a magic wand to eradicate heart attack today," said Naghavi. "The SHAPE initiative calls to foster an environment of searching for more cost-effective and simplified approach to identify those at different stages of progression toward a future heart attack, long before one occurs. We are not there yet."