New Clinical Practice Guidelines for Preventing Heart Disease and Stroke
By Michael H. Crawford, MD
Professor of Medicine, Lucie Stern Chair in Cardiology, Director, Cardiology Fellowship Program, Chief of Clinical Cardiology, University of California, San Francisco
Dr. Crawford reports no financial relationships relevant to this field of study. This article originally appeared in the January 2014 issue of Clinical Cardiology Alert.
Synopsis: The American College of Cardiology and the American Heart Association released new guidelines for preventing heart disease and stroke. Dr. Crawford provides expert opinion and commentary on why these new guidelines are so important.
1. What is the significance of these new guidelines?
The new guidelines change the focus of cholesterol lowering treatment from cholesterol levels to the patient's risk of developing atherosclerotic cardiovascular disease (ASCVD). The committee recognized that despite decades of study, there are not strong data to support the use of LDL-cholesterol targets in individual patients. This is no surprise to clinicians who see myocardial infarction patients with cholesterol values in the normal range. We were taught that they still needed cholesterol-lowering therapy because their levels are too high for them. By focusing on an individual patient's risk, this problem is circumvented.
2. What are the biggest changes from the previous guidelines?
The new guidelines describe four groups of high-risk patients that need cholesterol-lowering therapy. The first three are not different from the old guidelines: patients with known atherosclerotic disease, diabetics, and those with an LDL > 190 mg/dL. The fourth is new — non-diabetic patients aged 40-75 years with LDL cholesterol between 70-189 mg/dL and a 10-year risk of ASCVD of ≥ 7.5%. The second big change is that cholesterol lowering is defined as LDL cholesterol lowering, since there is insufficient data to support other targets. The third change is that LDL lowering therapy should be statins only, since there are insufficient data to support the use of other agents alone or in combination with statins.
3. Why are these changes important?
These changes are important because they represent a shift in our assessment of how best to manage ASCVD and the risk of ASCVD. The most difficult part will be deciding who is at high risk for developing ASCVD. Once that decision is made, treatment actually becomes much simpler and straightforward.
4. What does this mean for physicians in their daily practice?
Physicians now have to assess who has a ≥ 7.5% risk of developing ASCVD in 10 years, and this is the main area of controversy with the new guidelines. The committee developed a new risk calculator that included data on African Americans, which is a defect of the commonly used Framingham risk calculator that was developed from data in largely European Americans. However, critics have commented that the new calculator overestimates risk to the extent that one-third of Americans between 40-75 years of age and every man older than 65 years would need statin therapy. Whether this is appropriate or not is debatable, but clearly more work needs to be done on risk calculation methods. In borderline risk cases, the physician should consider other factors that are not in the risk calculator, such as family history of premature ASCVD, LDL > 160 mg/dL, hs CRP ≥ 2.0, a coronary CT calcium score > 300 or the 75th percentile, and an ABI < 0.9. Second, LDL cholesterol will still need to be measured to guide therapy. The goal now is to lower LDL at least 30-50% depending on how high it is at baseline, rather than aiming for a specific numerical target. Third, the non-statin, cholesterol-lowering therapies are not necessary, but can be considered if the patient cannot take statins or can only tolerate low doses. Fourth, the new guidelines exclude patients < 40 years or > 75 years old, with symptomatic heart failure or end-stage renal disease. Physicians must use their own judgment with these patients.
5. What does this mean for patients?
Patients are going to have to lose their fixation on their cholesterol numbers and start thinking about lowering their risk in many ways. Hopefully, this new focus will encourage patients to modify risk factors beyond cholesterol. Also, patients should stop relying on unproven remedies for lowering their risk and seriously consider major lifestyle modifications and statin therapy if necessary.
6. What are the next steps physicians and patients should take?
Physicians need to develop a brief talk on the new guidelines to educate their patients. It could be given to each patient as a paper handout, posted on a website, or played on a video in the waiting room. Patients need to consider that medicine is not a static field and changes to how we manage ASCVD and the risk of ASCVD will change over time, but that these changes are for the better.