2013 ACC/AHA Guidelines on the Assessment of Cardiovascular Risk: A Report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines
The Work Group addressed two concerns:
- The need to recommend or develop a risk assessment approach that could be used easily in primary care settings; and
- The determination and answer to a few critical questions that could be used to refine risk assessment in clinical practice.
The 2 critical questions they posed and answered were:
- “ What is the evidence regarding reclassification or contribution to risk assessment when high-sensitivity C-reactive protein (hs-CRP), Apolipoprotein B (ApoB), glomerular filtration rate (GFR), microalbuminurina, family history, cardiorespiratory fitness, ankle-brachial index (ABI), carotid intima-media thickness (CIMT), or coronary artery calcium (CAC) score are considered in addition to the variables that are in the traditional risk scores?” (pg 10)
- “Are models constructed to assess the long-term (≥15 years or lifetime) risk for a first cardiovascular disease (CVD) event in adults effective in assessing variation in long-term risk among adults at low and/or intermediate risk, whether analyzed separately or combined?” (pg 10)
These recommendations for risk assessment focus on a more broad population of adults without signs or symptoms of atherosclerotic cardiovascular disease (ASCVD), who merit evaluation for the primary prevention of ASCVD. These do not apply to those with clinically-manifest ASCVD or to highly-selected subgroups such as those with symptoms suggestive of CVD who require diagnostic strategies rather than risk assessment.
Since none of the risk assessment tools or novel risk markers examined were evaluated in randomized controlled trials with clinical events as outcomes, the experts tried to balance understanding of individual risk for CVD and the potential benefit of treatment versus the risk for potential harm if treatment was initiated. The previously used Framingham Risk Calculator was abandoned as it is based on an exclusively white population. The new guidelines recommend that these new Pooled Cohort Equations be implemented in practice as soon as possible for non-Hispanic Whites and African Americans, 40-79 years of age and considered in other ethnic populations. See http://my.americanheart.org/cvriskcalculator . Using the new Pooled Cohort Risk Equations, the authors estimate that 32.9% of adults will have a 10-year risk of at least 7.5% for a first hard ASCVD event.
Although this calculator is not a perfect tool, it is an improvement over previous methods of calculating risk as it estimates a broader based ASCVD outcome [i.e., it includes nonfatal and fatal stroke, not just nonfatal heart attack or coronary heart disease (CHD) death] and expands to include risk estimates for African Americans.
The expert work group also recommends if after assessment using the Pooled Risk Equation calculator, “a risk-based treatment decision is uncertain, assessment of 1 or more of the following – family history, hs-CRP, CAC score, or ABI- may be considered to inform treatment decision making.”
None of the additional markers recommended for improved risk stratification have been evaluated in randomized controlled trials (RCT). The work group only reviewed potential tests that were available in research data bases from other types of research (not RCTs) that had a minimum follow-up period of 10 years. The tests also had to be considered “feasible” and issues such as costs, reliability, availability, downstream testing, and the risk of the tests were included in the evaluation before any recommendations were made. The recommendations in this category reflect expert author opinions regarding additional testing that “show some promise for clinical utility among the novel risk markers, based on limited data.” (pg 19)
The tests that met the above inclusion criteria for examination were:
- Blood and urine biomarkers: ApoB, creatinine (or estimated GFR), hs-CRP, and microalbuminuria; and
- Measures of subclinical atherosclerosis: ABI, CAC, and CIMT
The work group determined that coronary artery calcium (CAC) is “likely to be the most useful of the current approaches to improve risk assessment among individuals found to be at intermediate risk after formal risk assessment.” (pg 19) For example, in 6,722 subjects enrolled in the Multi-Ethnic Study of Atherosclerosis (MESA) trial, adding CAC to conventional risk prediction resulted in an overall 25% net reclassification index (NRI).
They found evidence that family history was indeed an “independent contributor” to risk appraisal and “unequivocally” support the inclusion of family history for improved risk estimation.
The work group also found “strong evidence” linking CRP with CHD events and stated they found consistent evidence that adding CRP improved risk stratification in those considered to be at intermediate risk. They quote results from a meta-analysis published in 2010 called the Emerging Risk Factors Collaboration that found “associations with ischaemic vascular disease depend considerably on conventional risk factors and other markers of inflammation” (pg 27). Relatedly, evidence supports improved risk prediction when hs-CRP is added to traditional risk factor stratification models.
The authors found that ankle-brachial index (ABI), the test commonly used to screen for/diagnose peripheral artery disease, is “associated with total CHD risk and leads to a significant reclassification”. This test is easily done in primary care offices in a short period of time. Measurements of blood pressure and flow are taken in the feet and arms using a regular blood pressure cuff and an ultrasound device. If the ankle pressure is at least 90% of the arm pressure, the test results are considered normal.
They determined tests measuring cardiorespiratory fitness, ApoB, albuminuria, and GFR were of “uncertain value” in risk prediction. Furthermore, the expert work group stated that “CIMT is not recommended for routine measurement in clinical practice for risk assessment for a first ASCVD event.” (pg 11). The evidence for this recommendation included review of a meta-analysis of 14 population based cohorts (n=45,828) published in the Journal of the American Medical Association in 2012. The net reclassification index was only 3.6% for those determined to be at intermediate risk according to traditional measures via Framingham Risk Scoring. There were also concerns regarding reliability of the testing due to measurement issues and a lack of standardization for CIMT measurement.
In adults without ASCVD, the guidelines recommend assessment of traditional ASCVD risk factors every 4 to 6 years in adults aged 20 to 79 and to estimate the 10 year ASCVD risk every 4-6 years in adults aged 40 to 79 years.
The work group also recommends for adults aged 20 to 59 years without ASCVD who are not at high short term risk, the consideration of assessing lifetime ASCVD (or 30-year) risk based on traditional risk factors.
Reference: Goff DG, Lloyd-Jones DM, Bennett G, et al. 2013 ACC/ AHA guidelines on the assessment of cardiovascular risk: A report of the American College of Cardiology/American Heart Association task force on practice guidelines. Circulation Published on line November 12, 2013. Online ISSN: 1524-4539.