Combining calcium scoring with CTCA 'might avoid CCA'

19 August 2008

MedWire News: Study findings indicate that selectively combining calcium scoring (CS) with dual-source, 64-slice computed tomography coronary angiography (CTCA) could avoid unnecessary conventional coronary angiography (CCA) in some patients.

As the authors write in the journal Heart, "dual-source CTCA is feasible in a patient population undergoing scanning without heart-rate control and allows the identification and exclusion of significant coronary artery disease (CAD) with a high diagnostic accuracy."

However, they explain, a small number of patients have segments that are judged not evaluative on CTCA and have to undergo CCA examination.

Noting that misclassification of coronary artery stenosis with CTCA is often associated with severe vessel wall calcifications, Hatem Alkadhi (Institute of Diagnostic Radiology, Zurich, Switzerland) and colleagues asked how the combination of CS with dual-source, 64-slice CTCA affects diagnostic accuracy for assessment of coronary artery stenosis, relative to CCA.

They prospectively studied 74 consecutive patients scheduled for CCA due to typical or atypical chest pain, pathologic exercise test, or dyspnea. CCA identified coronary artery stenosis as single-vessel disease in 10.8% of patients, and as multivessel disease in 37.8%.

CS sensitivity and specificity depended on the CS threshold applied: a threshold of 0 for exclusion of significant stenosis revealed no false-negative classifications, while a CS ≥400 resulted in six false-positive patients, providing 100% sensitivity and 70% specificity.

With CTCA alone, five patients were classified as false-positive and one as false-negative, providing 97.2% sensitivity and 86.8% specificity, and correctly recognizing 96.4% of significant stenoses detected by CCA. The authors stress: "We did not exclude not-evaluative segments from analysis but considered them false-positive."

Combined CS and CTCA correctly reclassified all CTCA false-positive patients using the CS threshold of 0, whereas the ≥400 threshold failed to correctly reclassify missed stenosis by CTCA alone, providing 97.2% sensitivity and 84.2% specificity.

With 97.2% sensitivity and 100% specificity following CS in patients with not completely evaluative CTCA segments, the researchers say this combined approach, "can exclude significant CAD with a high diagnostic accuracy and might avoid unnecessary CCA examination in these patients."

Heart 2008; 94: 1154-1161