By Abraham Kim, AuntMinnie.com staff writer

March 16, 2019 -- Should coronary artery calcium (CAC) scoring be a routine part of PET/CT stress testing for assessing an individual's risk of heart disease? Yes, according to researchers from Utah who explained why in a Saturday presentation at the American College of Cardiology (ACC) 2019 meeting in New Orleans.

In a previous study presented at the ACC meeting in 2018, Viet Le and colleagues from the Intermountain Medical Center Heart Institute in Salt Lake City reported that the presence of calcium in the coronary arteries of patients increased their likelihood of undergoing coronary angiography and revascularization within the first 60 days after examination, as well as their risk of having a major adverse cardiac event within two years.

Expanding upon their prior work, the researchers re-examined data from 5,547 patients who presented with chest pain and underwent rubidium (Rb-82) PET/CT exams between April 2013 and July 2016. They also obtained the CAC scores of the patients from the PET/CT scans and discovered that approximately 45% had positive calcium scores, which they defined as a score of 0 or higher.

The researchers found that patients with positive PET/CT CAC scores were at a markedly higher risk of having an adverse cardiac event within the first 90 days, compared with those whose PET/CT scans showed no indication of calcification. Patients with positive CAC scores were also more likely to have obstructive coronary artery disease (CAD) and undergo an invasive revascularization procedure within four years, compared with patients without positive calcium scores. All of these differences were statistically significant (p < 0.0001).

Proportion of patients with cardiac events by PET/CT CAC score
  PET/CT CAC = 0 PET/CT > 0
Coronary angiography 3.4% 10.1%
Obstructive CAD 0.6% 6.5%
Revascularization 0.5% 6.9%

Le and colleagues additionally categorized the data based on an individual's degree of ischemic burden, i.e., the extent to which coronary blood flow was restricted. An analysis of the data revealed that the differences in 90-day and four-year outcomes for those with and without a positive calcium score maintained statistical significance regardless of a patient's severity of ischemia.

Acquiring calcium scores from PET/CT scans can help emergency department clinicians quickly determine which patients with nonacute chest pain are most at risk for a future cardiac event -- allowing for early initiation of risk-reducing lifestyle changes, Le noted in a statement from the hospital.

"Through these results, we're seeing more clearly that the presence of coronary artery calcium can help us to predict who is more likely to have a cardiac event, not only later in life, but when symptoms are present ... and hopefully, medically intervene in time to stop it," he said.


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