64-MDCT Accurate but Can’t Replace Conventional Coronary Angiography

The objective of a recent study was to evaluate the accuracy of 64-MDCT
coronary angiography in a multicenter international study.

In this study, positive and negative predictive values of 64-MDCT versus
conventional angiography were 91% and 83%, respectively, indicating that 64-
MDCT is accurate, but not able to replace conventional angiography.

Design/Participants
Prospective trial involving 291 patients who had both 64-MDCT coronary
angiography and conventional coronary angiography. The invasive angiogram was
performed within 30 days of the CT. Patients with Agatston calcium scores >600
were excluded.

All patients had suspected symptomatic coronary artery disease and were
referred for conventional coronary angiography. This multicenter trial
involved nine hospitals in seven countries.

Methodology
All CTs were performed using a 64-MDCT scanner. For the CT angiogram,
retrospective ECG gating was used. Sublingual nitrates were administered prior
to scanning; if the heart rate was >70 bpm, ?-blockers were given. Multi-
segment reconstructions were performed with a 0.5-mm slice thickness and 0.3-
mm overlap. A single independent core laboratory analyzed all raw images, and
two independent observers visually graded stenoses.

Stenoses were graded as follows: no stenosis; 1% to 29% stenosis; 30% to 49%
stenosis; 50% to 69% stenosis; 70% to 99% stenosis; and occlusion. Segments
with a visual stenosis >30% subsequently had the degree of stenosis manually
quantified with commercially available software. Conventional coronary
angiography was performed using standard techniques. A significant stenosis
was considered with ?50% narrowing.

Results
On conventional coronary angiography, 56% of patients had a significant
stenosis. On a per-patient basis, the diagnostic accuracy of CT angiography
for stenosis ?50% revealed an area under the curve (AUC) of 0.93 (95% CI, 0.90
to 0.96), with a sensitivity of 85% (95% CI, 79 to 90), a specificity of 90%
(95% CI, 83 to 94), a positive-predictive value (PPV) of 91% (95% CI, 86 to
95), and a negative-predictive value (NPV) of 83% (95% CI, 75 to 89).

On a per-vessel basis, the diagnostic accuracy of CT angiography for stenosis
50% revealed an AUC of 0.91 (95% CI, 0.88 to 0.93). The degree of stenosis as
evaluated by CT compared with conventional angiography was well correlated (r
=0.81; 95% CI, 0.76 to 0.84).

Radiation doses for MDCT angiography were 13.8 ± 1.2 mSv for men and 15.2 ±
2.4 mSv for women.

Conclusions
MDCT angiography is accurate for the diagnosis of significant (?50%) coronary
stenosis in symptomatic patients, but since the PPV is 91% and the NPV is 83%,
it cannot replace conventional catheter angiography.

Reviewer’s Comments
It is an interesting finding that the NPV of MDCT in this multicenter trial is
only 83%, a value lower than that of several other studies comparing MDCT with
conventional angiography.

Author: Vineet R. Jain, MD

Reference:
Miller JM, Rochitte CE, et al. Diagnostic Performance of Coronary
Angiography by 64-Row CT. N Engl J Med; 2008;359 (November 27):
2324-2336: