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Zero coronary calcium means very low 10-year event risk
Key clinical point: A coronary artery calcium score of 0 appears to trump the 10-year atherosclerotic cardiovascular disease risk estimator...
ORLANDO – Combining the coronary artery calcium score with the ACC/AHA cardiovascular risk calculator tool enables physicians to refine their decision making about who to recommend for statin therapy, Dr. Salman Waheed reported at the American Heart Association scientific sessions.
He presented an analysis of 1,225 asymptomatic adults followed for a median of 3.9 years in the observational arm of the St. Francis Health Study, an early landmark prospective study of the relationship between electron beam CT coronary artery calcium (CAC) score and cardiovascular event risk.
Bruce Jancin/Frontline Medical News
Dr. Salman Waheed
The 217 subjects who today would not be recommended for statin therapy on the basis of a 10-year atherosclerotic cardiovascular disease risk of 5%-7.4% as determined by the risk calculator included in the 2013 ACC/AHA cholesterol management guidelines (Circulation. 2014 Jun 24;129[25 Suppl 2]:S1-45) would be reclassified as warranting statin therapy if they had a CAC greater than 0, as was the case for 169 of the 217 (78%). Indeed, the presence of a CAC of 1 or more boosted their estimated 10-year risk to 10.8%.
On the other hand, there were 510 patients who would be classified as high risk by the ACC/AHA clinical risk calculator, with a 10-year risk of 7.5%-20%. Taking their CAC score into account would result in 73 being reclassified as low risk and becoming no longer statin candidates because their CAC of 0 was associated with a 10-year event risk of less than 1%. In contrast, for the 447 remaining subjects with a CAC greater than 0, the 10-year risk climbed to 21.9%, according to Dr. Waheed of the University of Kansas, Kansas City.
The composite outcome utilized in this analysis from the St. Francis Heart Study was comprised of nonfatal MI, coronary death, stroke, peripheral arterial revascularization, or coronary revascularization. Of note, heart failure wasn’t included.
Among the 545 subjects deemed at low cardiovascular risk because they weren’t eligible for statin therapy according to the 2013 ACC/AHA guidelines, 209 would be recategorized as high risk on the basis of a CAC score at or above the 80th percentile adjusted for age and gender. The adjusted risk of a cardiovascular event in the high CAC/low clinical risk group was 24.9-fold greater than in the low CAC/low clinical risk group.
“Among those eligible for statin therapy based upon current guidelines, high CAC portends a sixfold higher outcome risk than low CAC,” Dr. Waheed added.
The magnitude of CAC progression over the course of 4 years was similar across the baseline risk categories; however, the absolute CAC progression was greater among those with a high CAC at baseline.
Audience member Dr. Daniel S. Berman observed that the results of Dr. Waheed’s study are highly concordant with an earlier report from the Multi-Ethnic Study of Atherosclerosis in which a CAC of 0 was quite common in patients for whom statins would be recommended under the current ACC/AHA guidelines.
“Your data support the idea that stratification based upon CAC could more personalize the statin recommendations,” said Dr. Berman, chief of cardiac imaging and nuclear cardiology at Cedars-Sinai Medical Center and professor of medicine at the University of California, Los Angeles.
Dr. Donald Lloyd-Jones
Another audience member, Dr. Donald M. Lloyd-Jones, one of the architects of the current guidelines, commented that the analyses from the St. Francis Heart Study and the Multi-Ethnic Study of Atherosclerosis suggest CAC screening coupled with the ACC/AHA risk score provides added value in a select group of patients.
“Your analysis continues to reinforce the point that we probably shouldn’t be doing universal CAC screening because in the people with a 10-year risk of less than 5% the yield is low and the CAC didn’t change anything, while in the people with a 10-year risk of 20% or higher the yield is incredibly high and the CAC didn’t change anything,” observed Dr. Lloyd-Jones, professor and chair of the department of preventive medicine at Northwestern University, Chicago.
“So CAC really is for those intermediate-risk folks where we’re on the bubble, where we might consider withholding therapy. And I’d love to see a trial to show that’s safe, by the way, but maybe that day will come. But we certainly would be comfortable up-classifying somebody if more CAC is present than there should be,” he added.
Dr. Waheed reported having no financial conflicts regarding his study.