November 12th, 2013
After Long Wait, Updated U.S. Cardiovascular Guidelines Now Emphasize Risk Instead of Targets
Updated cardiovascular health guidelines were released today by the American Heart Association (AHA) and the American College of Cardiology (ACC). The guidelines are designed to provide primary care physicians with evidence-based expert guidance on cholesterol, obesity, risk assessment, and healthy lifestyle.
The new guidelines reinforce many of the same messages from previous guidelines, but also represent a sharp change in philosophy. That change is most evident in the new lipid guidelines, in which the focus has shifted away from setting numerical targets for cholesterol levels in favor of treatment decisions based on individual risk status.
“This guideline represents a departure from previous guidelines because it doesn’t focus on specific target levels of low-density lipoprotein cholesterol, commonly known as LDL, or ‘bad cholesterol,’ although the definition of optimal LDL cholesterol has not changed,” said Neil J. Stone, chair of the lipid expert panel that wrote the new guideline. “Instead, it focuses on defining groups for whom LDL lowering is proven to be most beneficial.”
The long-awaited and often controversial guidelines are the successors to the extremely influential NHLBI guidelines, including the Adult Treatment Panel (ATP) series of guidelines that brought cholesterol to the consciousness of millions of people. Earlier this year the NHLBI announced that it would no longer issue guidelines but would, instead, provide support for guidelines produced by other organizations. Following the NHLBI announcement, the AHA and the ACC said that they would take over publication of the guidelines.
This summary of the guidelines and the news around them is broken out into several topics. Click on one of the links below to jump ahead.
The new lipid guideline identifies four groups of patients for whom statin therapy is indicated:
- People who already have cardiovascular disease (secondary prevention).
- People with LDL levels 190 mg/dL or higher. Many of these will have familial hypercholesterolemia.
- People with type 2 diabetes who are between 40 and 75 years of age. (This is the age group where the evidence base is strongest.)
- Patients who are not known to have cardiovascular disease but who have an estimated 10-year risk for cardiovascular disease of 7.5% or higher and who are between 40 and 75 years of age. (The guideline provides formulas and links for calculating 10-year risk.)
The guideline recommends high-intensity statin therapy for the first two groups. The last two groups are suitable for moderate-intensity therapy, though some patients with type 2 diabetes may benefit from high-intensity treatment.
“We were unable to find solid evidence to support continued use of specific LDL cholesterol or non-HDL treatment targets,” said Stone. Although targets have been used extensively in clinical practice, he said that treating to specific targets can often lead to undertreatment of high-risk groups and overtreatment of low-risk groups.
Routine use of non-statin therapies is not endorsed in the new guideline. “We found that non-statin therapies really didn’t provide an acceptable risk reduction benefit compared to their potential for adverse effects in the routine prevention of heart attack and stroke,” said Stone.
Stone also pointed out that there will be some people who may not be in one of the four groups but who may still benefit from statin treatment. “We provide guidance for physicians to try to determine whether or not” these patients would also qualify.
In the new guideline for assessing cardiovascular risk in adults, the risk equations now predict risk for both heart attack and stroke — previous guidelines focused exclusively on coronary heart disease. “We realized quickly that we were leaving a lot of risk on the table by not also including stroke,” said the risk assessment co-chair, Donald Lloyd-Jones. He said that including stroke was particularly important for women and African-Americans.
After much debate, the committee that developed the guideline found that new risk markers should not be used for routine risk assessment. The new guideline relies on the traditional risk factors of age, race, sex, total and HDL cholesterol levels, blood pressure level, blood pressure treatment status, diabetes status, and current smoking status.
The committee identified four additional markers, said Lloyd-Jones “that may be considered by clinicians and patients if there is still uncertainty after — and I emphasize only after — they have performed the risk equation exercise.” The four additional markers are history of premature cardiovascular disease in the immediate family, coronary artery calcium score, high-sensitivity C-reactive protein, and the ankle-brachial index. The guideline specifically recommends against the routine use of carotid intima-medial thickness (CIMT), saying that it may be useful as a research tool but that broader use is not warranted because of the large amount of inter- and intra-operator variability.
Primary care physicians have little training or expertise in dealing with obesity, said Donna Ryan, co-chair of the obesity guideline. Because they are “operating in a culture that has a lot of misinformation about weight management,” the guidelines are designed to provide authoritative information that primary care physicians can use to help their patients. The guidelines offer advice about several key questions:
- Who needs to lose weight?
- What are the benefits of weight loss?
- How much weight loss is needed?
- What is the best diet?
- What is the efficacy of lifestyle intervention?
- What are the benefits and risks of bariatric surgical procedures?
The committee recommends that physicians continue to use current BMI and waist circumference cut points. They state that benefits begin with weight loss as little as 3%, but the committee urges physicians to focus on helping their patients achieve a 5-10% weight loss in the first 6 months.
The committee examined the evidence for at least 17 different diets. “We came down loud and clear that there is no ideal diet for weight loss and that there is no superiority for any of the diets we examined,” said Ryan. The choice of diet “should really be determined by the patient’s preferences and health status,” she said.
The guidelines offer yet another endorsement for bariatric surgery for high-risk patients, including adults with a BMI of 40 or higher and adults with a BMI of 35 or higher who have two other cardiovascular risk factors such as diabetes or high blood pressure. The guideline does not recommend weight loss surgery for people with a BMI under 35 and does not recommend one surgical procedure over another.
The new guidelines don’t cover pharmacotherapy, including the two new obesity drugs approved in the past year. Ryan said the committee hoped to address this subject in future updates.
The new lifestyle management guideline focuses on diet and exercise, said committee co-chairs Robert H. Eckel and Alice Lichtenstein. “The new focus,” said Eckel, is to “increasingly emphasize dietary patterns” such as the Mediterranean Diet or the DASH diet. These diets feature fruits, vegetables, and whole grains, include low-fat dairy products, poultry, fish, and nuts, and limit red meat, sweets, and sugar-sweetened beverages. The committee recommends limiting intake of saturated fat, trans fat, and sodium. Finally, they recommend that physical activity should average 40 minutes of moderate to vigorous activity 3-4 times a week.
The new guidelines seek to emphasize a global assessment of risk, and that statin and lifestyle treatment should be aimed to reduce risk and not just an isolated LDL number. Although LDL cholesterol remains important, said Lloyd-Jones, statins “don’t only treat cholesterol… really they are risk-reducing agents.”
Lloyd-Jones calculated that under the old ATP 3 guidelines, treating people with a 10-year risk for coronary disease over 20% and people with diabetes would lead to treatment in about 15-16% of U.S. adults. Under the new framework, the four criteria, including the 7.5% threshold for primary prevention, results in 31% of American adults being eligible for statin treatment. This is about the same percentage of people who would have been eligible under the old criteria if the threshold had been lowered to a 10%, 10-year risk plus diabetes, said Lloyd-Jones.
“I think the way to think about it is that with the new equations and the new approach we are actually a lot smarter about identifying the people who will benefit from risk reduction therapies, but we’re not necessarily treating all that many more people than if we were using the old optional level,” he said.
“We weren’t concerned with treating more or less people,” said Stone. “We were concerned with treating the people who benefit the most.”
Asked whether physicians may be confused by the new change in emphasis and the absence of target treatment goals, Stone said that “once clinicians get used to this approach they may find it a lot simpler.” Lloyd-Jones explained that “we’re not abandoning the measurement of LDL, because it’s perhaps our best marker of understanding whether patients are going to achieve as much benefit as they can with the dose of statin that they can tolerate, and it’s also for the clinician an important marker of adherence. If the LDL is not coming down it’s an important flag that there may be a problem.” Stone said that a follow-up lipid panel should not be used “to see whether you’ve reached a target but to encourage a discussion that focuses on both adherence” to lifestyle and appropriate statin treatment.
It is worth noting, however, that although the lipid guideline has placed less emphasis on LDL, the lifestyle management guideline remains yoked to LDL. The recommendation against saturated fat is based on epidemiology and studies that show the effect on LDL of saturated fat. “The effect of reductions in saturated fat on LDL-C are unequivocal,” said Eckel.
One guideline — the also highly-anticipated successor to the JNC hypertension guideline — was not released today and will not be published by the AHA and the ACC. AHA President Mariell Jessup sent the following statement:
“The NHLBI did originally commission a writing panel to develop the next JNC hypertension guidelines as part of this entire prevention portfolio. When the NHLBI asked the ACC/AHA Joint Task Force to assume the guideline process moving forward, the hypertension writing panel — as of this date — declined to be a part of the process. Thus, the ACC/AHA will proceed to develop hypertension guidelines, in conjunction with a number of other relevant societies (primary care and specialty groups), beginning in 2014.
What I do not know currently is the status of the manuscript that the originally commissioned hypertension writing panel created, nor am I certain that any manuscript that may be published will be called JNC 8.
In the meantime, the ACC/AHA, in conjunction with the CDC, will unveil a hypertension algorithm developed primarily to be part of an overall systems approach for primary care clinicians, to enhance the detection and control of hypertension in this country. We are very excited about this statement and hope it will be incorporated in many offices.”