RIVIERA BEACH, FLORIDA—A new guideline from the American College of Cardiology and the American Heart Association simplifies the evaluation and treatment of patients who are at risk of atherosclerotic cardiovascular disease (ASCVD), including stroke, according to an overview presented at the 41st Annual Meeting of the Southern Clinical Neurological Society. The guideline focuses on ASCVD risk, which is defined as 10-year risk of heart attack and stroke, and includes a risk calculator developed from various cohort studies.
The guideline enables clinicians to assess ASCVD risk among Caucasians and African Americans with reasonable accuracy, but it may “grossly overestimate” the risk among other populations such as Hispanics and Asians, said Philip B. Gorelick, MD, Professor in the Department of Translational Science and Molecular Medicine at Michigan State University College of Human Medicine in East Lansing, and Medical Director of Mercy Health Hauenstein Neurosciences, in Grand Rapids, Michigan. Certain ethnicities were underrepresented in the studies on which the risk calculator was based, and as a result, the guidelines may lead to overtreatment of these populations.
Focus Shifts From LDL Cholesterol to ASCVD Risk
The guidelines describe four types of people who should receive treatment to prevent stroke. They include patients with a history of ASCVD (eg, heart attack, peripheral arterial disease, or stroke), patients with an LDL cholesterol level greater than 190 mg/dL, patients with diabetes between ages 40 and 75 with an LDL cholesterol level between 70 and 189 mg/dL and no ASCVD, and patients with an ASCVD risk of 7.5% or greater. The previous protocol had been to adjust treatment based on the patient’s level of LDL cholesterol, but the new guideline focuses on lowering ASCVD risk, Dr. Gorelick noted.
The recommended treatment for these four patient groups is high-dose statin therapy, which generally lowers LDL cholesterol by 50% or more. The guideline suggests that patients who cannot tolerate high-dose statins should take a moderate dose, which lowers LDL cholesterol by between 30% and 50%, or a low dose.
In contrast with previous recommendations, the new guideline does not encourage treatment with nonstatin, cholesterol-lowering drugs. The two organizations based the guideline on a review of evidence from clinical trials, few of which examined nonstatin, cholesterol-lowering drugs. Because little evidence supported these drugs’ efficacy, the researchers made no recommendation about them, said Dr. Gorelick.
In addition to treatment recommendations, the guideline offers advice about lifestyle modifications that can reduce ASCVD risk. The organizations recommend a diet high in fruits, vegetables, and whole grains to lower lipid levels and blood pressure. They also recommend reducing consumption of sugar-sweetened beverages, red meats, sodium, and trans fatty acids. The Dietary Approaches to Stop Hypertension diet may be consistent with many of the guideline’s recommendations, said Dr. Gorelick.
Patients should engage in three or four 40-minute sessions of moderate to vigorous physical activity per week to reduce LDL cholesterol, non-HDL cholesterol, and blood pressure, according to the guideline. Individuals should warm up before exercising and cool down afterward. During exercise, a patient’s heart rate should be between 60% and 85% of his or her age-predicted maximum, according to the guideline.
Guideline May Result in Unnecessary Treatment
Simplicity is one of the guideline’s advantages, said Dr. Gorelick. The recommendations are based on proven therapies, recognize that intensive therapy is superior to less-intensive therapy, and conclude that the benefit of treating LDL cholesterol far outweighs the risk of diabetes or myopathy associated with statin therapy.
One major concern, however, is that the guideline will lead clinicians to overtreat their patients. The risk calculator may overestimate risk by as much as 150% when compared with other cohorts to which the risk calculator was bootstrapped, said Dr. Gorelick. Consequently, as many as 50% of the 33 million middle-aged Americans who have an ASCVD risk lower than 7.5% may receive statins unnecessarily, he added.
Another concern is that the recommendations are based on clinical trials but applied to populations. “No statin trial has used a global risk predictor as an enrollment criterion,” said Dr. Gorelick. Patients who entered the clinical trials on which the guideline is based did not have their ASCVD risk calculated before the researchers decided whether to treat them. “We’re making somewhat of a leap of faith here,” said Dr. Gorelick.
“Guidelines remain important sources of knowledge. However, they have inherent limitations and are not a substitute for clinical judgment and pragmatic reasoning. You’ve got to look at these patients one by one,” concluded Dr. Gorelick.
—Erik Greb