ASNC: CTA-Detected Coronary Placque Predicts Risk of Cardiac Events

SAN DIEGO, Sept. 13 -- Low-density coronary plaque detected by multi-slice CT angiography (CTA) predicted an increased risk of cardiac events in the absence of hemodynamically significant stenosis.

CTA identified low-density plaque in almost half of patients who developed unstable angina or myocardial infarction during almost three years of follow-up, Yuichi Sato, M.D., of Nihon University in Tokyo reported at the American Society of Nuclear Cardiology meeting here.

Patients with low-density plaque also had triple the likelihood of acute coronary syndrome during follow-up, Dr. Sato and colleagues found.

"The presence of low-dense plaques on CT without hemodynamically significant stenosis was an independent predictor of future cardiac events [among patients with multiple coronary risk factors]," said Dr. Sato.

Although multi-slice CTA has increased the capability to identify presumed hemodynamically insignificant plaque, the prognostic implications of such detection have never been determined.

So the investigators reviewed records on 810 patients who underwent multi-slice CTA from 2001 through 2005 and were followed for a median of 1,062 days. Low-density plaque was defined as luminal narrowing of 25% to 50% in a vessel 2.0 mm in diameter and a CT density of less than 68 Hounsfield units.

Multi-slice CTA detected low-density plaque in 23% of patients; median CT density was 36.8 HU. Patients with low-density plaque were more likely to be male and had higher rates of diabetes, hyperlipidemia, and smoking compared with patients who had negative CTA studies.

The final adjudicated event rate included 16 patients with unstable angina, five of whom had low-density plaque on CTA, and seven with acute MI, five associated with low-density plaque.

Calculation of annualized cardiac event rates showed that patients with low-density plaque had an acute coronary syndrome rate of 1.82 versus 0.66 among patients with negative CTA results (P