CHICAGO – Coronary computed tomography angiography provides long-term prognostic information and may predict hard cardiac events in patients with diabetes and suspected coronary artery disease, judging from findings from a new study.

Specifically, diabetic patients with no CT evidence of coronary artery disease (CAD) had an excellent prognosis, with no cardiac events recorded over 62 months of follow-up.

In contrast, cumulative event-free survival rates for hard cardiac events and all cardiac events were 78% and 56% in patients with nonobstructive CAD, and 60% and 16% in those with obstructive CAD (P = .0001), Dr. Daniele Andreini reported at the annual scientific sessions of the American Diabetes Association.

"The excellent outcome in diabetic patients with completely absent [disease findings on] CTs is clinically relevant because it suggests that CT angiography can help to identify the truly low-risk patient, and can be used to reassure regarding the outcome of diabetes with suspicion of coronary artery disease, with a warranty period of 5 years," said Dr. Andreini of Istituto di Ricovero e Cura a Carattere Scientifico, Milan.

The study provides much-needed data on the long-term prognostic role of CT angiography in diabetic patients, with just two prior studies limited to 20 and 33 months’ follow-up reporting that multidetector CT angiography can predict major adverse events (Diabetes Care. 2010;33:1358-63 and Radiology 2010;256:83-92).

Session moderator Dr. William Cefalu, chief and professor of endocrinology, diabetes, and metabolism at Louisiana State University, New Orleans, asked how likely it is that clinicians will order CT screening in diabetics in light of the controversy over screening asymptomatic patients.

The American Heart Association, American College of Cardiology, and Society for Computed Tomography have recommended against the use of CT angiography for screening, especially in nonsymptomatic patients, responded Dr. Andreini, "But I am not so sure that this is correct in diabetes." He suggested that screening in this subset of patients can be performed with a very low dose of less than 1 millisievert of ionizing radiation, and that "other methods we use to screen diabetics are completely lacking in accuracy."

In a separate interview, Dr. Cefalu said the study was well characterized and the analysis comprehensive but that it may be a matter of comparing apples to oranges in terms of translating the results to the community where CT machine settings and precision varies. The other question is how cost effective screening would be.

"Whether this can be applicable in the community, it has to be cost effective, it has to be precise and it has to have prognostic value, and for a lot of the CT scans we have in the community, we don’t have that information just yet for translating these findings to the community," he said.

Study details

The study involved 429 consecutive patients with diabetes who were prospectively enrolled after presenting to an outpatient clinic or were admitted to hospital for cardiac evaluation for new onset chest pain (35%), abnormal stress test (27%), or multiple cardiovascular risk factors (27%). All multidetector CT coronary angiography exams were performed with a 64-slice scanner (VCT, GE Medical Systems), with dose modulation attained with electrocardiographic gaiting. Images were analyzed via multiplanar reconstruction on postprocessing work stations and interpreted by two expert readers, who were blinded to the patients’ clinical data. The mean effective radiation dose of the exams was 8.7 mSv.

The patients’ mean age was 65 years, mean body mass index 27.2 kg/m², and 33% had a high pretest likelihood of CAD.

Among 390 evaluable patients, 90 patients had no coronary disease, 69 nonobstructive (<50%) CAD, and 231 obstructive (at least 50%) disease.

After an average clinical follow-up of 62 months, 279 events occurred, of which 117 were hard events (9 cardiac deaths, 66 nonfatal myocardial infarctions, and 42 unstable anginas) and 162 late revascularizations, Dr Andreini said.

In multivariate analysis, significant independent predictors of hard cardiac events were: three-vessel disease at least 50% (hazard ratio 5.21; P = .01), left main coronary artery disease at least 50% (HR 5.35; P = .01), and the number of segments with noncalcified (HR 1.84; P less than .0001), mixed (HR 1.39; P =.003), and calcified plaques (HR 1.62; P less than .0001).

Significant independent predictors of all cardiac events (including revascularization) were one-vessel disease (HR 3.94; P = .006), two-vessel disease (HR 4.82; P = .0001), three-vessel disease (HR 7.93; P less than .0001), left main CAD (HR 7.92; P = .005) and number of segments with mixed (HR 1.40; P less than .0001), and calcified (HR 1.18; P = .01) plaques, he reported.

Dr. Andreini and a coauthor reported serving on the speakers bureau for GE Healthcare.

pwendling@frontlinemedcom.com

CT angiography predicts cardiac events long-term in diabetics