Meta-analysis illustrates cardiac CT can effectively assess coronary artery disease

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Researchers from The Netherlands concluded that cardiac CT can effectively assess hemodynamically relevant coronary artery stenosis after evaluating studies that included more than 1,300 patients.

Alexander Meijer, MSc, and colleagues from Leiden University Medical Center, systematically reviewed 22 articles to assess the diagnostic performance of thin-slice (0.625 mm) multidetector CT coronary angiography (CCTA) compared with invasive coronary angiography for the detection of significant (>50 percent) stenosis. All patients in the analysis underwent CCTA on either a 40- or 64-slice CT scanner.

The study consisted of 1,331 patients and researchers analyzed 10,561 coronary artery segments. It appears in the December edition of the American Journal of Roentgenology.

On a patient level, researchers found a 98 percent sensitivity rate for detecting significant coronary artery stenosis; specificity was 91 percent. On a segmental level, sensitivity and specificity were 91 percent and 96 percent, respectively.

CCTA better classified stenosis in proximal compared to distal segments. Sensitivity and specificity for proximal segments were 94 percent and 96 percent, respectively, compared with 85 percent and 97 percent, respectively, for distal segments. Disease prevalence had no influence on CCTA sensitivity, researchers said.

Investigators recalculated sensitivity and specificity taking into account corrections for CT exams that yielded nonevaluable patients or nonevaluable segments. Differences on a patient level were not statistically significant. On a segmental level, however, decreases in specificity for proximal and distal segments were statistically significant: 96 percent vs. 92 percent and 97 vs. 92 percent, respectively.

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"The results indicate that in patients with an intermediate clinical probability of coronary artery disease, cardiac CT scans may avoid the use of invasive catheter angiography. Catheter-based angiography is currently the gold standard for coronary artery evaluation, but it is an invasive technique, has a small percentage of "major" complications and it is relatively expensive," said senior author Lucia J.M. Kroft, MD.

Recent meta-analyses have shown improved performance of 64-slice CT over 16-slice scanners. This report shows results of a larger amount of publications, in which researchers additionally investigated the effect of proximal versus distal coronary artery segments.

Researchers concluded that the excellent sensitivity and good specificity on the patient level make 40- and 64-slice CT scanners with small (0.625 mm) detectors and fast-rotating x-ray tubes (rotation time < 0.5 second) excellent tools for detecting or ruling out significant coronary artery stenosis in a carefully selected subgroup of patients suspected of significant CAD.

They further stated that a “high sensitivity on a patient level is of vital importance in ruling out disease; the lower the sensitivity, the more often disease will be missed. Specificity plays an important role in the reduction of the overall cost of the evaluation of suspected CAD. The higher the specificity, the fewer patients will undergo unnecessary invasive coronary angiography due to a false-positive finding.”

Investigators said that the examination of proximal versus distal segments is relevant because the location of stenosis may have impact on left ventricular (LV) function. “On echocardiography stress testing, significantly greater wall motion abnormalities have been found among patients with proximal than among those with middle and distal stenosis,” they wrote.

They also said that in patients after left anterior descending coronary artery myocardial infarction, LV functional recovery has been found delayed and the LV chamber enlarged in patients with proximal lesions, whereas LV function was found preserved among patients with distal lesions.”

In essence, CCTA better detects hemodynamically relevant stenosis in proximal segments where there may be greater clinical impact.

"Multi-slice CT is increasingly being used as a daily practice in the evaluation of patients with chest pain and yet, up until now, its efficacy has not been proven. Our study has made a contribution to that direction," said Meijer.