New CV Risk-Assessment Guidance Counts Stroke With CHD Risk

November 12, 2013

WASHINGTON, DC — Formal standards for cardiovascular risk assessment had been an integral but secondary part of the third Adult Treatment Panel report and its updates a decade ago, which focused on blood cholesterol management. The latest recommendations have split off to form the 2013 ACC/AHA Guideline on the Assessment of Cardiovascular Risk, designed as a platform for the other new guidance on cholesterol management, obesity, and lifestyle goals for preventing CV disease.

Innovations in the new CV risk-assessment guidelines, which were released today by the ACC and AHA, reflect a focus on atherosclerosis as a chronic disease that extends beyond the heart [1]. Compared with risk-assessment principles in earlier society-endorsed guidelines, the new document:

  • Adds stroke to the coronary events traditionally covered by the equations for predicting future risk.

  • Has a primary focus on 10-year risk of atherosclerosis-related events, plus a secondary focus on assessing lifetime risk for adults aged 59 or younger who aren't at high shorter-term risk.

  • Provides adjunct formulas for refining risk estimates by race and gender.

  • Acknowledges selective use of coronary-artery calcium (CAC) scores and some other markers to sharpen predictions in some cases.

The National Heart, Lung, and Blood Institute (NHLBI), as the guidelines' original sponsor, handed the baton for supervising their completion and public release to the ACC and AHA last June, as reported by heartwire . They're published simultaneously today in the organizations' flagship journals, the Journal of the American College of Cardiology and Circulation.

At a recent media briefing, Dr Donald Lloyd-Jones (Northwestern University, Chicago, IL), cochair of the working group that completed the new guidances, said the new equations for predicting 10-year atherosclerotic cardiovascular disease (ASCVD) risk are based on a diverse population of nearly 25 000 participants in NHLBI-sponsored cohort studies. They include Atherosclerosis Risk in Communities Study (ARIC), the Cardiovascular Health Study , Coronary Artery Risk Development in Young Adults (CARDIA), and the Framingham Heart Study .

From those observational cohorts, Lloyd-Jones said, "we were able to generate very robust risk equations for both non-Hispanic white men and women and African American men and women." Outcomes in the models include nonfatal MI, death from CHD, and fatal or nonfatal stroke in people initially without ASCVD.

"With the new equations and the new approach, we are actually a lot smarter about identifying people who will benefit from risk-reduction therapies, but we're not necessarily treating all that many more people" compared with strategies developed in earlier guidelines.

"Well-Meaning Experts Will Disagree"

"It is a major step forward that the guidelines now assess risk for both heart attacks and strokes," according to Dr Roger S Blumenthal (Johns Hopkins University, Baltimore, MD). In an email to heartwire , he said he "strongly agrees" with 90% of the document, which was "well-written and evidence-based." As for the remaining 10%, "Well-meaning experts in the field of cardiovascular prevention will disagree on some of the fine points, and this guideline is meant to inform clinical judgment rather than replace it."

For example, he said, "the ASCVD risk score that is used has weaknesses. . . . The committee relied almost entirely on class I evidence from randomized trials. I think that selective use of IIa evidence would have improved the document." When the new scoring system was tested in two large contemporary cohorts, "it performed suboptimally in terms of accuracy and discrimination."

Blumenthal said he reviewed several versions of the guidelines as the ACC liaison on a committee for the National Program to Reduce Cardiovascular Risk (NPRCR), the NHLBI body that shepherded their initial development.

The Model's Risk Predictors

Risk markers to emerge from the cohorts as the strongest predictors of 10-year risk were age, sex, race, total cholesterol, high-density lipoprotein cholesterol, blood pressure, blood-pressure treatment status, diabetes, and current smoking status.

Although no other markers routinely added much to the risk prediction models, Lloyd-Jones said, part of the committee's mandate was to identify others that might sometimes further discriminate risk.

"After reviewing that evidence, we determined that at present there are four markers that may be considered by clinicians and patients if there's still uncertainty after, and I emphasize only after, they've performed the risk-equation exercise." Those are family history, high-sensitivity C-reactive protein (hs-CRP), ankle-brachial index (ABI), and coronary artery calcium (CAC) score.

Of those, Lloyd-Jones said, "family history, if known and reliable, is certainly the easiest to consider in clinical practice. But the work group felt that the evidence was strongest for coronary artery calcification." Although CAC assessment entails "a quite modest degree of radiation exposure," he said, "information gleaned from it is actually the best marker we have to refine our risk-assessment approach in a meaningful way." The test could lead to withholding of treatment in someone who would otherwise be treated, or it could be the determining factor in deciding whether treatment is appropriate.

According to Dr Carl J Lavie (Ochsner Clinical School-University of Queensland School of Medicine, New Orleans, LA), who isn't connected with the guidelines, CAC scores have been helpful in his practice when used selectively. For example, he told heartwire in an email, even in a patient with very high total cholesterol or LDL cholesterol but without other CHD or stroke risk factors and perhaps with a protective high HDL cholesterol, he "would not treat with a statin if they were much over age 50, especially over age 60, and [had] a very low CAC score, especially zero. On the other hand, a patient with multiple risk factors and mildly abnormal lipids who is borderline for statin use can be convinced to take these agents when the CAC score is high or at least well above 0."

"A Step in the Right Direction"

"To keep things simple," Blumenthal observed, the equations don't account for family CVD history, triglycerides, waist circumference, body-mass index (BMI), lifestyle habits, and past smoking history. While the new ASCVD score has evolved to look more widely at events due to atherosclerosis, not just heart attacks, he said, "the inputs to create the score are limited."

Lavie agreed that "it makes sense to factor in family history, as most clinicians have been doing anyway." But he said he would put even more weight on ankle-brachial index as a marker of peripheral vascular disease and especially on CAC scores.

Still, "the new guidelines are a step in the right direction."

Also interviewed by email, Dr JoAnn E Manson (Brigham and Women's Hospital, Boston, MA) agreed that "the new guidelines for assessing cardiovascular risk are a major step forward in identifying patients most likely to benefit from pharmacologic interventions and avoiding 'overtreatment' of patients least likely to benefit."

The guidelines "will substantially improve clinical decision making, especially for women and racial/ethnic-minority groups who were not well served by the previous risk-assessment tools." She said she's "particularly excited" about the increased focus on lifetime risk. "We know that regular physical activity, healthy dietary patterns, and other behavioral factors have a profound impact on prevention of heart disease and stroke, especially when started early in life."

Statins and Risk Status

In the risk-assessment document, "I think the area where most clinicians will struggle is whether you really need to treat individuals with a normal or seemingly optimal lipid profile with a statin just because the ASCVD risk score is greater than 7.5%," Blumenthal said. The new guidelines on cholesterol therapy call for consideration of statin therapy when an individual's 10-year risk of an ASCVD event reaches >7.5%.

"The way that most people will cross the 7.5% threshold is on the basis of chronologic age and mild elevations in their blood pressure or simply being on an antihypertensive agent. The current guidelines recommend statin treatment of what could be excellent lipid values simply because of age, blood-pressure values, and smoking status rather than a true dyslipidemia."

Blumenthal said he believes clinicians "will likely want to consider coronary calcium, hs-CRP, carotid intima-media thickness [IMT] done by a skilled technologist—even though the guidelines did not recommend it for routine use—or the presence of a family history of premature CVD to decide whether long-term statin use is truly indicated."

In fact, the guidelines specifically recommend against incorporating carotid ultrasound IMT measurements into risk prediction, according to Lloyd-Jones. Its success is heavily dependent on operator and reader skill and experience, such that the potential for error can outweigh its prediction value.

The guidelines document says it is endorsed by the American Association of Cardiovascular and Pulmonary Rehabilitation, American Society for Preventive Cardiology, American Society of Hypertension, Association of Black Cardiologists, National Lipid Association, Preventive Cardiovascular Nurses Association, and WomenHeart: The National Coalition for Women with Heart Disease.

Lloyd-Jones reports no conflicts of interest. Disclosures for the coauthors are listed in the paper. Blumenthal reports no conflicts of interest. Lavie discloses that he's "served as a speaker and consultant for many companies that have lipid medications." Manson said she has no financial disclosures.

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