Marlene Busko

July 23, 2015

LAS VEGAS, NV — An incidental finding of a high coronary artery calcium (CAC) score (>300 Agatston units) despite a normal myocardial perfusion imaging (MPI) test does not always trigger guideline-recommended preventive therapy. A study at a Veteran Affairs (VA) center found that although most clinicians recognized the need for more aggressive risk-factor modification in patients with elevated CAC scores, at least 10% of these high-risk patients did not receive aspirin or statin therapy[1].

Their center's nuclear-stress-test equipment automatically acquires CAC scores, Dr Anita Wokhlu (University of Florida, Gainesville) explained to heartwire from Medscape here at a poster session at the Society of Cardiovascular Computed Tomography (SCCT) 2015 Annual Scientific Meeting. However, "not everybody really knows what to do [with these patients with a high CAC score, and there is] only one little line in the ACC guidelines" about this, she noted.

"I've been doing this for 25 years. I invented the calcium score, and [this main finding] doesn't surprise me at all," commented Dr Warren Robert Janowitz (Baptist Health Systems, Miami, FL), who along with Dr Arthur S Agatston (Baptist Health Systems) codeveloped the eponymous calcium scoring system for early detection of coronary atherosclerosis.

"What are you supposed to do with these ultrahigh [coronary artery] calcium scores?" Wokhlu asked Janowitz. "You do aggressive risk-factor modification," he replied. "You treat [these patients] as if they have coronary disease and lower their risk factors as much as you can."

"One of the hurdles [may be] the tendency of physicians [to tell a patient], 'The stress test is negative—you're fine,' " suggested poster session comoderator Dr Issam Mikati (Northwestern University, Chicago, IL). Wokhlu agreed, adding that the patients have multiple risk factors and clinicians may feel that they are already optimizing therapy. Clinicians may need more education, and the MRI report could mention that 300 Agatston units is a cutoff, she agreed.

Does a High CAC Score Prompt Aggressive Therapy?

Markedly elevated CAC scores (>300 Agatston units) predict a higher risk of adverse cardiovascular events. However, it was unknown if clinicians changed patients' therapies if an MPI test was normal but included a CAC score of 300 Agatston units or higher.

Wokhlu and colleagues performed a retrospective analysis of data from 299 patients without known CAD who underwent MPI during 2010 to 2011 at the VA medical center in Gainesville. The MPI tests were mainly requested by primary-care providers, but in a third of cases, a cardiologist was asked to evaluate a patient's symptoms.

A total of 263 patients had a normal perfusion study, and 220 patients had a CAC less than 300 Agatston units.

However, 79 patients had a CAC of 300 Agatston units or higher, and 62 patients had both a high CAC score and normal nuclear stress test.

Compared with patients with a CAC score of less than 300 Agatston units, those with a high CAC score were older (mean age 66 vs 58 years, P<0.001) and more likely to have hypertension (86% vs 71%, P=0.01) and diabetes (44% vs 29%, P=0.012).

At baseline, patients with a high CAC score were also more likely to be receiving statins (66% vs 46%, P=0.003) and aspirin (67% vs 44%, P<0.001).

A higher percentage of patients with high vs lower CAC scores had perfusion abnormalities on MPI (22% vs 9%, P<0.001).

Clinicians made a clinical note of nonobstructive CAD or increased cardiovascular risk in 21 of the 62 patients who had normal MPI findings but a CAC of 300 Agatston units or higher (34%).

At 6 months, 25 of the 62 patients with a high CAC and normal nuclear stress test (40%) had changes in aspirin, anticholesterol, and/or antihypertensive therapies; 11% started aspirin and 21% had changes to their cholesterol-lowering therapy.

"At least some providers were tuned into the fact that these are high-risk patients, but the numbers are small and . . . not all providers made a decision to do anything," Wokhlu said.

Because 43% of patients had diabetes, many were probably already on optimal therapies to prevent cardiovascular disease. However, of the 15 patients (24%) not on statins, only three had a documented contraindication and only seven had an LDL-cholesterol level of less than 70 mg/dL. Only 5% of patients had noted contraindications to aspirin or statins.

Interestingly, among patients who had a normal MPI test, there was a trend to more cardiovascular events (catheterization, revascularization, MI, cardiovascular hospitalization, and all-cause death) at 1 year in those who had a high CAC score vs those who did not (15% vs 6%, P=0.056). This was largely driven by catheterization and revascularization.

Percentage of Patients With Normal MPI and High CAC Who Received Cardiovascular Preventive Medications

Medication Before MPI test, patients % 6 mo after MPI test, patients % P
Aspirin 71 82 <0.001
Statin 68 76 <0.001
ACE inhibitor/ARB 69 74 <0.001
Beta-blocker 35 44 0.002

CAC=coronary artery calcium
High CAC= >300 Agatston units
MPI=myocardial perfusion imaging

"I think that in the past 2 years, 300 [Agatston units] has become a cut point" for high CAC scores, Wokhlu said. "Hopefully, [with more recent data] we'd see better results." The group is considering adding a statement to MPI reports, such as "a CAC score 300 Agatston units or greater indicates the presence of CAD."

Wokhlu had no relevant financial relationships.


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