New guidelines from the American College of Cardiology and the American Heart Association on the assessment of cardiovascular risk and the manipulation of cholesterol levels to mitigate that risk have certainly been in the news. The guidelines appropriately use high quality evidence to abandon old untested or unproven paradigms such as treatment to LDL targets and manipulation of non-HDL cholesterol as a secondary goal. In many ways, the new guidelines should simplify lipid management.
But it doesn’t feel simple right now. The guidelines’ recommendations for statin treatment for particularly high-risk people with known atherosclerotic cardiovascular disease (ASCVD), very high LDL levels, and diabetes haven’t engendered much controversy.
Recommendations for primary prevention in people at lower risk have been the main topic of debate. The updated guidelines point out that the older Adult Treatment Panel III leads to treatment of about 32% of Americans between the ages of 40 and 79 who have diabetes or a 10% risk of experiencing a first myocardial infarction or coronary death in the next 10 years.
By contrast, the new guidelines estimate that about 33% of Americans meet the threshold for taking a statin — based on a 10-year ASCVD risk of at least 7.5%. Still, many observers have worried about the numbers of Americans who would be treated with statins under the new guidelines, around 45 million by one estimate; and the potential for overtreatment of people with less favorable ratios of benefits to risks. Much of the debate has focused on whether the new risk calculator in the guidelines overestimates the 10-year risk of ASCVD in the modern era. As important to determining the number of Americans who might be treated, however, are the risk thresholds at which the guidelines encourage treatment.
The cholesterol guideline recommends statins for primary prevention in 40-75 year-olds for a calculated 10-year ASCVD risk ≥ 7.5% and offering treatment to people with a risk of 5% to <7.5%. What is easily missed in the fuss over the risk calculator and these thresholds is that the guideline recommends that clinicians and patients “engage in a discussion” of the benefits and risks before initiating therapy in primary prevention for these two low-risk groups and that little guidance is provided about the content of those conversations.
As with most guidelines, the cholesterol guideline relies on value judgments regarding tradeoffs between benefits and risks. The expert panel felt that a major ASCVD event such as heart attack or stroke would be far worse than an increase in glucose levels that might lead to diabetes.
Based on those values, the panel felt that benefit far outweighed risk for those with a calculated 10-year ASCVD risk ≥ 7.5%, but acknowledged that the “tradeoffs between ASCVD risk reduction benefit and adverse effects are less clear” for those with a 5% to <7.5% estimated 10-year ASCVD risk.
Shared decision making between patients and physicians recognizes that such tradeoffs are in the eye of the beholder when considering whether to take the statin every day. For example, it is likely that informed people with a 4% versus a 6% risk, or a 7% versus an 8% risk, though on either side of the cutpoints, might well have quite similar treatment preferences. Thus, the guideline recommendation for patient-physician discussions provides an opportunity for patients and clinicians to assess risk and clarify the patient’s health goals and the tradeoffs involved with possible statin therapy.
In his seminal work on “practice policies,” Dr. David Eddy recommended involvement of potential patients in guideline development. These people would be shown “balance sheets” presenting the tradeoffs between benefits and risks, and the distributions of their treatment preferences could be used in guideline formation. Similarly, these balance sheets, the forerunners of modern decision aids, could then be used in practice to tailor guideline recommendations to individual patients for groups in the clinical “grey zones” where not everyone wants or doesn’t want treatment.
The new guidelines would benefit from these balance sheets so that patients can weigh their own preferences and values with the harms and benefits for various risk thresholds; in fact, it is hard to derive the needed information from the texts. One must go to, for example, the Cochrane meta-analysis of trials of statins for primary prevention to learn that risks for all events are reduced about 25% across most conditions raising ASCVD risk and over the spectrum of absolute risk. So a person with an 8% 10-year ASCVD risk might expect to lower that risk to about 6% with statin therapy. Armed as well with the risks of side effects over the same time frame (rather than rates per year as provided in the guideline), and perhaps costs as well, people who would have to take the pills could more effectively participate in these treatment decisions with their clinicians.
As already indicated, the new cholesterol guidelines represent a step forward, particularly in terms of eschewing non-evidence-based LDL treatment targets and consequently avoiding over or under treatment engendered by these targets. It also promotes shared decision making with communication of individualized risk information to patients and acknowledges the need for future research on the “optimal communication of ASCVD risk information.” Hopefully future versions will include new evidence on the preferences of informed patients to better guide the initiation of treatment.
Michael J. Barry is president, and John B. Wong is medical editor, both at the Informed Medical Decisions Foundation.
