ACC: Calcium predicts future CV events in those with abnormal PET

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NEW ORLEANS—The presence of calcium obtained during PET perfusion imaging enhances risk stratification for future cardiovascular events in patients with abnormal perfusion studies irrespective of the degree of ischemia, according to a scientific poster presented April 3 at the American College of Cardiology (ACC) scientific sessions.

Coronary artery calcification (CAC) can be detected during CT scan for attenuation correction for stress Rb-82 PET myocardial perfusion imaging (MPI). Whether CAC – a known predictor of cardiovascular events – augments risk prediction across varying degrees of PET perfusion abnormalities “remains unknown,” according the researchers.

Therefore, Anupam Kumar, MD, from the nuclear cardiology lab at the Henry Low Heart Center at the Hartford Hospital in Farmington, Conn., and colleagues sought to determine if visually estimated calcium on low-dose CT scan for attenuation correction offers any predictive value for future coronary events in patients with PET perfusion abnormalities.

The researchers identified 827 patients at their facility without CAD who underwent PET MPI for symptom evaluation. They interpreted all studies using the ASNC 17-segment model and classified by summed stress score of normal (0), mildly abnormal (1 to 3), moderately abnormal (4 to 8) and severe (more than 8).

Kumar and colleagues followed the patients for a mean of 1.7 years for the occurrence of composite endpoints (coronary revascularization, unstable angina, non-fatal MI or cardiac death). They calculated the cardiac event rates for all groups with and without CAC, after stratification according to summed stress score.

The researchers reported that overall 34.1 percent of the abnormal group (264 patients) had CAC compared with 5.3 percent in the normal group (563 patients). Also, abnormal subjects with CAC (90 patients) demonstrated a 2.25 times increased risk for events (event rate: 45 vs. 20 percent).

There was an increased risk prediction with CAC in patients with higher summed stress score, Kumar and colleagues concluded, but there was no stastical difference in events for CAC in those with a normal PET (6.6 vs. 4.5 percent).

The authors disclosed that they no conflicts of interest.