The contentious American Heart Association and American College of Cardiology guidelines, which stirred controversy when unveiled last year, more accurately matched statin assignment to plaque burden compared with older guidance, leading to a "modest" increase in the number of patients who were prescribed statins….
In the single-center, retrospective study of 3,076 adults who were undergoing CT angiography, the probability of prescribing statins rose with increasing plaque burden under the 2013 Guidelines on the Assessment of Cardiovascular Risk (GACR) compared with the 2001 National Cholesterol Education Program (NCEP) Adult Treatment Panel III recommendations.
Under NCEP guidelines, 59% of patients with 50% or more stenosis of the left main coronary artery identified by CT angiogram, and 40% of patients with 50% or more stenosis of other branches would not have been prescribed a statin. The comparable results for the GACR were 19% and 10%, respectively, they wrote online in the Journal of the American College of Cardiology.
"The use of low-density lipoprotein targets seriously degraded the accuracy of the NCEP guideline for statin assignment," they wrote. "The proportion of patients assigned to statin therapy was 15% higher under the GACR. The GACR and NCEP methods partition patients into risk groups in similar ways, but the NCEP method then applies LDL targets to decide who gets statin therapy."
The decision to do away with LDL targets was widely criticized by opponents of the GACR, with critics predicting that the new guidelines would lead to a dramatic increase in the number of people taking statins.
But in the analysis by Johnson and Dowe, the new guidelines increased the proportion of patients assigned to statin therapy by just 15%, which the researchers characterized as "modestly larger" than under the older recommendations.
"If you are willing to consider coronary plaque burden as a surrogate for risk, then our data clearly show that the new guidelines assign statins to people more accurately than the old guidelines did," Johnson said.
Last week, a group from UT Southwestern Medical Center in Dallas reported similar findings, based on their analysis of a subset of patients enrolled in the Dallas Heart Study.
They predicted that among participants (ages 30-65) who would have newly qualified for statin use under the new guidelines, 3.6 to 4.9 cardiovascular events would have been prevented for every 1,000 people screened and newly treated.
The patients included in the analysis by Johnson and Dowe received CT angiography at a single center between February 2004 and November 2009. They presented for various reasons, including stable atypical chest pain, indeterminate stress test results, multiple risk factors, and a strong family history of cardiovascular disease.
Patients younger than age 40 or older than age 75, without known atherosclerotic cardiovascular disease or LDL cholesterol ≥190 mg/dL were not included in the analysis, because the GACR makes no recommendations for such patients, the researchers noted.
Imaging was performed on the 3,076 patients and 65.3% of the cohort was male, with a mean age at the time of imaging of 55.4. The mean age of the women was 58.9. More than 90% of the cohort was Caucasian.
The median Framingham 10-year risk was 10% for men and 3% for women and the most common reasons for undergoing CT angiography were hypercholesterolemia, family history of coronary heart disease, hypertension, smoking, and nonacute chest pain.
At the time of imaging, 1,362 patients (44.3%) were not on statins or other lipid-lowering therapy; the remaining 1,714 patients (55.7%) were on statins. Patients not taking statins had less disease than patients on statins, the authors stated.
Among the main findings, GACR correlated marginally better with plaque and stenosis burden than the older risk estimation guidelines. For all patients, the correlation of segmental plaque burden scores (SPS) with NCEP guidelines 10-year risk estimate was 0.51 (95% CI 0.48-0.54) compared with 0.56 (95% CI 0.53-0.59) with GACR guidelines.
The GACR assigned fewer patients with no plaque to statins and more patients with heavy plaque to statins.
Among patients with heavy plaque (SPS ≥8), 53% would be assigned to statin therapy under NCEP and 92% under the GACR. Among patients with no or trace plaque, 41% would be assigned to statin therapy under NCEP and 36% under the new.
NCEP was more likely to assign statins to patients with little plaque and less likely to assign statins to those with a great deal of plaque.
Johnson and Dowe wrote, "In this study, plaque burden is used as a surrogate for cardiac events, which are the ultimate end point to determine accuracy," "This hypothesis is partially proved in symptomatic patient but remains unproved in the primary prevention setting."
Other study limitations cited by the researchers included the fact that about half the patients were already taking a statin when they entered the study and homogeneous nature of the cohort.
But they concluded that on the basis of their findings, "it is a reasonable hypothesis that the new guidelines will better predict coronary events, given that it better correlates with the severity of underlying atherosclerosis."
- Note that this large retrospective study, using coronary plaque burden as a marker of cardiac risk, found that the new statin-usage guidelines would lead to increased statin therapy in the highest-risk individuals.
- Be aware that controversy regarding the new guidelines center around the inclusion of indications for statins that do not include LDL targets.
Journal of the American College of Cardiology,Johnson K, Dowe DA "Accuracy of statin assignment using the 2013 AHA/ACC cholesterol guideline versus the 2001 NCEP ATP III guideline" JACC 2014; 64: 910-919.