MSCT is not very accurate after all

Diagnostic Accuracy of 64-Slice computed tomography coronary angiography: Prospective, Multicenter, Multivendor Study. Meijboom et. al. JACC 2008 52:2135 - 44.

1. This trial assess how accurate is 64 multislice CT angiography (MSCT) in detecting significant coronary artery disease when compared to the conventional coronary angiogram (CCA). CCA is the gold standard for diagnosing coronary artery disease.

2. The study recruited 360 patients with stable and unstable angina. All patients underwent both MSCT and CCA. Out of 360 patients, 246 have significant coronary artery narrowing (using the gold standard CCA).

3. Out of 246 with significant coronary artery narrowings, 244 were detected with MSCT (99% sensitive). So it is fairly accurate in thse group of patients which are symptomatic.

4. Of those without significant coronary artery narrowings, 114 patients, 41 of then were wrongly labelled as having significant narrowings by MSCT (64% specific).

5. If you have angina with negative MSCT, the chance of you not having significant coronary narrowings is 97%. When you angina and have a positive MSCT, the chance of you having significant coronary narrowing is 86%.

Summary

1. The patients in this study have symptoms, so there are quite a lot of them would have significant coronary heart disease. I would usually subject them directly to coronary angiogram espcially if they have ECG changes or elevated cardiac markers. MSCT in this situation is rather redundant. If the patient do not have ECG or ecardiac markers changes, I would subject them to either stress testing with or without imaging.

2. MSCT is not really that accurate in this group of patients especially if it is positive.

3. Nevertheless, if you have clear, negative MSCT, rest assured, you dont have significant coronary artery narrowing.

4. So back to square one, I only reserve MSCT to patient with chest pain who cannot exercise and for those with interconduction delay (eg bundle branch blocks).

5. With judicious and careful CCA, the amount of contrast use and total radiation can be significantly less than MSCT. The average radiation exposure from MSCT varries from 9.5 to 13.6 mSv, compared to CCA, 0.8mSv (which is about 10 times of routine CCT). The average amount of contrast for CCA is about 30 mls, as compared to 75 to 100 mls for MSCT.