January 19th, 2012

CT Angiography Found Less Helpful in Patients With High Calcium Scores

Computed tomography angiography (CTA) has been proposed as a less invasive method to exclude obstructive coronary artery disease (CAD), but no consensus has been achieved about its clinical role in different patient subsets. Now a new report published in JACC from the CORE-64 (Coronary Artery Evaluation Using 64-Row Multidetector Computed Tomography Angiography) study shows that CTA may not be worthwhile in people with a calcium score of 600 or above or who already have a high pre-test probability of having CAD.

The CORE-64 investigators compared CTA and quantitative coronary angiography (QCA) in 371 patients. (A previous report published in NEJM excluded 80 patients with a calcium score of 600 or above.) They found that CTA accurately ruled out obstructive CAD in two groups:

  • patients with low coronary calcium scores and with a low or intermediate pre-test risk of CAD
  • patients with a calcium score of 0 with any pre-test risk of CAD

The negative predictive value of CTA in the group of patients with calcium scores of 600 or greater was 0.50 (0.16-0.84).

In an accompanying editorial, Steve Nissen writes that the study findings suggest that CTA “probably should not be used for diagnostic purposes in patients with substantial coronary calcification.” Nissen also points out that “the radiation dose from CTA is equivalent to 3 to 7 diagnostic catheterizations.” Until CTA is more fully evaluated in clinical trials, writes Nissen, “coronary imaging using CTA should be used sparingly, with full recognition of the radiation burdens and risks of misdiagnosis.”

2 Responses to “CT Angiography Found Less Helpful in Patients With High Calcium Scores”

  1. No surprises in this study. Every study that has looked at CTA has demonstrated a significant reduction in the accuracy and negative predictive value of CTA when the calcium score is above 400, much less 600. This remains a major limitation to CTA technology and it would be wise to do a calcium score and if the calcium score is >600, don’t bother with the CTA. It would be even better if the patient had a calcium score as a screening test and appropriate therapies could be offered before the CTA seemed necessary.

    Leave it to Steve Nissen to again mis-characterize the radiation dose form CT coronary imaging. Using current state of the art protocols, CTA should be done with 5 to 8 msv of radiation, equivalent to 1 or 2 diagnostic catherizations. That said, I do agree with him that CTA should be reserved for very specific situations as it is not a screening test.

    However, coronary calcium imaging should be increased as it is the best screening test we have, up to 10 times more predictive than conventional risk factors according to the MESA study. Radiation for an EBT calcium score is 0.7 meq equivalent of 1 mammogram or 1/3rd of a very quick diagnostic angiogram, or using a 64 slice CT it can be done for 1.5 to 3 msv.

    Competing interests pertaining specifically to this post, comment, or both:
    I have an ownership interest in and work at a facility that has the ability to do EBT calcium imaging. I do not order or perform coronary CTA.

  2. Matthew Carr, MD says:

    I can’t belive DR Nissen, whon I have respected for his principled stands in the past, is passing on blatant misinformation about the radiation involved in cta. IN our labs a retrospective gated cta with tube current modulation delivers about 4 msv to an 150 pound pt, while a coronary angio alone at the lowest frame rate and middle magnifciation comes in at about 8 msv. Wth the new iterative reconsruction methis we should be abl to e hte ct doe dow to 2.5 to 3.5. I think the hysteria regarding radiation dose has led some experts to play on peoples fears unecessarily.BTW a 220 pound pt in a cath lab usng maginfied views and 30 frame per second cine can receive easity 25 to 40 msv for just a cath

    Competing interests pertaining specifically to this post, comment, or both: