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Downgrading risk to minimize statin use in an era of increased statin eligibility
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The 2013 American College of Cardiology/American Heart Association guidelines introduced the 10-year atherosclerotic CVD risk estimator to guide clinician–patient risk discussions about statin therapy. Anyone with a 10-year atherosclerotic CVD risk of at least 5% should have a detailed clinician–patient risk discussion about the pros and cons of starting on long-term statin therapy.
However, the risk estimator relies heavily on chronologic age and systemically considers certain groups such as black men older than 55 years as high risk (even if they have near optimal lipids), while doing a suboptimal job of identifying true low-risk individuals who may not glean benefit from lipid-lowering therapy in the next decade.
Not all adults older than 55 years need a statin. Identification of those who don’t need a statin despite having an elevated risk estimate is important. This is where the concept of downgrading one’s risk becomes relevant by identifying protective risk markers.
This concept is defined as a favorable result on a test that predicts prognosis but when directly altered does not necessarily alter risk. Protective risk markers can improve the shared decision-making process and reduce the number of patients who are initiated on statin therapy.
A strong protective risk marker may allow identification of truly low-risk individuals who are much less likely to receive a net benefit from preventive pharmacologic therapy. Due to their high sensitivity and higher negative predictive values, there is increasing interest in the value of subclinical atherosclerosis imaging tests such as a coronary artery calcium (CAC) score of 0 as potential protective risk markers.
CAC score
The CAC test uses noncontrast, cardiac-gated CT scan images of the heart to visualize the presence and amount of coronary calcium buildup. Calcium deposits in the coronary arteries are indicative of hardening due atherosclerotic plaques. The CAC score is a reliable marker of total atherosclerotic plaque burden and is the most powerful single tool for CV risk assessment.
The test is fast, relatively inexpensive (often less than $100) and associated with few drawbacks, which include radiation exposure and incidental findings. The radiation exposure is roughly equivalent to that received with two mammograms. Incidental findings on the CT scan, such as nodules in the lungs, require follow-up in about 5% of people.
CAC score for downgrading risk
A recent study by Nasir and colleagues published in the Journal of the American College of Cardiology in October explored the implications of CAC testing among those deemed statin eligible by the new ACC/AHA guidelines in the MESA population during a 10-year follow-up period. Half of the population had an atherosclerotic CVD (ASCVD) risk estimate of at least 7.5% and another 12% had an estimated risk of 5% to 7.4%. All such individuals are eligible to consider statin therapy. However, 41% of the MESA study participants had a CAC of 0 and had a very low ASCVD event rate during the next decade.
Among those with an ASCVD score of at least 7.5% and CAC score of 0, the incidence of ASCVD events was about half that observed in those with any CAC (ie, CAC > 0): 4.9% vs. 10.5%. Likewise, among those with estimated 10-year risks of 5% to 7.4%, 57% had a CAC score of 0 and their average observed risk was 1.5%.
Thus, there is a low-risk group even among those who are now statin eligible per the recent guidelines. Identifying this group of patients can help us fine-tune our treatment strategies and maximize treatment of those who would likely derive the most benefit. This can further lead to improved resource allocation, and it can also have a meaningful effect on the shared decision-making process.
The study by Nasir and colleagues further demonstrated that the CAC score is of limited utility in the groups at extremes of risk, such as those with 10-year estimated risks less than 5% and more than 20%. Among those with an estimated risk less than 5%, use of the CAC score rarely reclassified patients into a higher-risk category, and among those with an estimated risk more than 20%, the CAC score rarely down-classified patients to a lower-risk group.
Application in clinical practice
Most clinicians do not adequately consider tests to de-escalate one’s risk, and therein make the decision not to start statin therapy in selected patients an easier one.
When clinician–patient risk discussion leads to uncertainty, the recent guidelines focus on tools that can help up-classify one’s risk, thereby increasing one’s candidacy for a statin. These include family history of premature CAD, LDL at least 160 mg/dL, CAC score, carotid intima-media thickness measurement and plaque determination.
The latest JACC study by Nasir and colleagues makes the case that there is merit in being able to downgrade one’s risk. The absence of CAC can make the patient that is already not eager to start a lifelong medication more comfortable about the fact that not doing so likely will not increase their risk for adverse events during the ensuing decade.
Summary
With the broadening statin eligibility by recent guidelines, there are three major challenges:
- Nearly two-thirds of the adult population are candidates for therapy.
- Significant overestimation of risk by the ACC/AHA guidelines risk estimator has been repeatedly documented.
- Patients are often averse to taking lifelong pills, especially if not clearly at risk.
Although the most recent guidelines do not mandate a statin prescription for all patients with a risk estimate more than 7.5%, the results of the ASCVD risk score serve as a conversation starter regarding what can be done to further mitigate risk in the long term. Potential side effects and costs should be considered in the decision algorithm, as well as the expected risk reduction. The CAC score results can add particular value in about 40% of individuals, who likely will have no CAC.
The important role of protective risk markers in this population becomes more evident as does its potential to help drive high-quality patient–doctor discussions.
- Reference:
- Nasir K, et al. J Am Coll Cardiol. 2015;doi:10.1016/j.jacc.2015.07.066.
- For more information:
- Tolu Adesiyun, MD, is a postdoctoral fellow in the Johns Hopkins cardiology division. Seth S. Martin, MD, is assistant professor of medicine at the Johns Hopkins Ciccarone Center for the Prevention of Heart Disease and a Cardiology Today Editorial Board member. Roger S. Blumenthal, MD, is director of the Johns Hopkins Ciccarone Center for the Prevention of Heart Disease and is the CHD and Prevention Section Editor for Cardiology Today. Blumenthal can be reached at rblument@jhmi.edu.
Disclosure: The authors report no relevant financial disclosures.