Review of existing guidelines for cardiovascular disease and diabetes shows a continuing reliance on experience and expert opinion.
“There’s nothing like seeing a patient, recommending a guideline, wondering where the heck that came from, then realizing you served on the committee,” mused Sidney Smith, MD. Speaking at the 20th Annual Meeting and Clinical Congress of the American Association of Clinical Endocrinologists, Smith is president at the World Heart Federation, professor of medicine, and director at the Center for Cardiovascular Science and Medicine at the University of North Carolina, Chapel Hill. He reviewed current guidelines, including several hotly debated topics.
According to the Institute of Medicine (IOM), in its current form, habits, and environment, American healthcare is incapable of providing the public with the quality health care it expects and deserves. “To my way of thinking,” said Smith, “those are strong words.” Nevertheless, Smith noted a serious lack of scientific evidence underlying ACC/AHA clinical practice guidelines. He decided he wanted to look at every ACC/AHA guideline ever written. After examining 53 guidelines, he found that much of what we do is still related to experience and expert opinion. There were only three guidelines from the ACC/AHA that have 20% of their recommendations based on evidence level A. Ten out of 17 guidelines had 50% of their recommendations based on expert opinion. The good news was that one guideline, on secondary prevention, had more than 90% of its recommendations based on evidence.
One guideline recommendation Smith focused on was with regard to LDL. He questioned the basis for current recommendations, citing several studies. There has been a correlation between coronary heart disease (CHD) events and LDL-C levels, and existing recommendations are that if a patient has a history of CHD (including diabetes) and LDL is over 130 mg/dL, the patient needs to be on a statin; if LDL is under 100 mg/dL, then statins are unnecessary. However, Smith cited a heart protection study on patients age 40-80, who had diabetes and/or were at high risk. All were started on a statin, but results showed that it did not make a difference where LDL was. After reviewing results from several studies, the consensus was to eliminate the guideline stating optimal LDL should be between 100-130 mg/dL. Instead, Smith said we need to get LDL to less than 100 mg/dL, or less than 70 if a patient is at high risk. In the Cholesterol Treatment Trialists study, after evaluating 14 trials, significant benefits were observed across the board in terms of lowering LDL, with a 20% reduction in vascular events for every 1 mmol/dL reduction in LDL.
In general, Smith said, progressive benefits exist for LDL-C lowering below 70 mg/dL. He concluded by reviewing several new AHA guidelines for CV risk assessment (not necessarily treatment). He said, “But my feeling is that we can’t just look at LDL.” We need to consider presence of diabetes, smoking, and other risk factors for vascular disease. Regardless, there is no disputing we are better off with lower LDL. He also wanted to clear up a common misconception. “The data that statin therapy causes cancer is just not supported by available trial evidence.”