Coronary CT angiography (CCTA) provides long-term incremental value in patients at intermediate risk of coronary artery disease, particularly for those with noncalcified and mixed plaques, according to a five-year follow-up study published online Dec. 24 in the American Journal of Cardiology.
Researchers noted that the accuracy of CCTA "needs to be assessed in management outcome studies in which diagnostic and therapeutic strategies would be decided based on CT alone, without reference to any catheter angiographic results."
They said that this is "the longest follow-up study in the largest homogenous cohort of patients at intermediate risk with no previous coronary artery disease (CAD) who underwent CT to investigate chest pain."
Fabiola B. Sozzi, MD, PhD, from the Monaco Cardiothoracic Centre, Monte Carlo, Monaco, and colleagues evaluated 222 patients (61 percent men) with 64-slice CCTA (Somatom Sensation 64 Cardiac, Siemens Healthcare) from January to October 2005.
Researchers used the following parameters for CT imaging: collimation of 64 x 0.6 mm, tube rotation time of 330 ms and tube current of 450 mA at 120 kV.
They detected coronary plaques in 73 percent of patients: Stenosis was significant in 28 percent, nonsignificant in 45 percent, and 27 percent of patients had normal arteries.
During a mean follow-up of five years (follow-up rate was 87 percent), 30 cardiac events occurred, but no one with normal arteries had an event. Event rate was 1.2 percent in patients with nonsignificant stenosis and 4.2 percent in patients with significant stenosis, while noncalcified and mixed plaques represented an independent predictor of cardiac events.
"A main finding of our study is that plaque composition represents a long-term predictor of cardiac events," they wrote. "Of interest, these two types of plaque composition [noncalcified and mixed] may represent less advanced and possibly less stabilized atherosclerosis compared to dense calcified lesions."
They reported that significant stenosis occurred more frequently in patients who were older, had hypertension and a smoking habit. In addition, patients with significant calcified plaques were on average significantly older then patients with significant noncalcified and mixed plaques.
Sozzi et al. determined that the presence of significant stenosis, proximal stenosis (particularly within the proximal portion of the left anterior descending and left circumflex coronary arteries), multivessel disease and noncalcified and mixed plaques were associated with the worst prognosis.
They also concluded that their findings confirm the "excellent negative predictive value of normal arteries on 64-slice CT."