Reviewer: Dr. Bengisu Keskin Meriç

Name of the Study: Computed tomography guided invasive Coronary angiography in patients with a previous coronary artery bypass graft surgery trial (GREECE trial): Rationale and design of a multicenter, randomized control trial

Published Congress: EuroPCR

Background: While invasive coronary angiography (IKA) remains the gold standard for imaging the coronary arteries, cardiac computed tomography angiography (CBTA) is applied as an alternative approach to ICA. The ICA of patients with CABG is associated with longer fluoroscopy time and contrast dose compared to patients without CABG. CBTA, which provides high diagnostic accuracy in detecting artery and graft occlusions, is at least as successful as ICA in graft imaging. Especially in these patients, the image quality of CBTA, which is a shorter duration and non-invasive examination, is equivalent to IKA. Administration of CBTA prior to ICA in patients with CABG can reduce the total amount of contrast material and the radiation dose exposed without affecting the sensitivity and specificity of the imaging test.

Objectives: The aim of this study; is to investigate whether less contrast material use, less procedure time and less radiation exposure can be achieved in daily clinical practice by the aid of IKA under the guidance of CBTA.

Methods: The study is a multicenter, prospective randomized study. In this study; Hemodynamically stable patients with a prior history of CABG and an indication for coronary angiography were randomized to either one invasive coronary angiography only (control group) or a coronary CT angiography followed by an invasive coronary angiography.

Patients with STEMI, very high or high risk NSTEMI, hemodynamically unstable, GFR below 30, contrast agent allergy, uncontrolled arrhythmia, and BMI above 40 were not included in the study.

The primary outcome of the study was considered a reduction in the total contrast volume usage. Secondary outcomes were; Total contrast volume usage during coronary angiography, total procedure time, number of catheters used during the whole procedure and interventional coronary angiography, total fluoroscopy time, radiation dose during the whole procedure and coronary angiography, complications during the procedure, major adverse cardiac events within 3-4 and 30 days after the procedure (death, re-intervention, cardiac rehospitalization, non-fatal MI, and non-fatal stroke) and development of contrast-induced nephropathy. A total of 274 participants were planned to be included in the study. It was planned to apply CBTA to the patients in Group A, and then CT-guided IKA according to the results. It is arranged so that the contrast drug to be applied during both CBTA and CBTgIKA is the same and the time between them does not exceed 30 hours. In Group B. patients, it was planned to apply only IKA for imaging both natural coronary arteries and grafts.

The hypothesis of the study is that a patient in Group A will receive 140 ± 30 ml of contrast material, while a patient in Group B will receive 170 ± 70 ml of contrast material. Therefore, the difference between the two groups will be 30 ml.

Results: In the study, 84 patients in the Group A arm and 69 patients in the Group B arm were included. The mean age of the patients included in the study were similar [group A: 70.2 (8.4), group B 70.8 (8.3) ]. Total contrast material used  [ Group A 209.1(105), Group B 165.3 (82.4) p:0.006) ], contrast material used during coronary angiography [Group A 175.7 (60.5), Group B 125.3 (66.1) p<0.001 ] was found higher in group A and reached statistical significance. Number of catheters used [Group A 2.8 (2-4), Group B 3.2(2-4) p:0.049 ]  and total procedure time [Group A 28.5 (27.3), Group B 38.4 (24.5)  p:0.022 ] were statistically higher in group B. No difference was observed between the groups in PCI  [Group A 18 (20.5), Group B 20 (29) p:0.261  ]  and total fluoroscopic time [Group A 643.2 (690), Group B 714.3(501) p:0.480 ].

The exposed radiation dose was found to be significantly higher in group A [Group A 24.66, Group B 11.91 p<0.001). Major adverse cardiac events in 3-5 days [Group A 0 (0%), Group B 8 (11.6%) p:0.001 ]  and within 30 days [Group A 4 (5%), Group B 11 (16%) p:0.023) were statistically higher in group B. Statistical difference was not observed between two groups for

complications within 1-6 hours [Group A 6 (7.1%), Group B 2 (2.9%) p:0.261]  and contrast-related nephropathy [Group A 13 (16%), Group B 8( 13.8%) p:0.714 ]  

Conclusion: The study failed to meet the primary endpoint. More contrast agents were used in the intervention arm compared to the control arm, but had no effect on contrast-related nephropathy. The exposed radiation dose was also found to be significantly higher in group A. However, group A was associated with less procedure time and a lower incidence of MACE.

Interpretations: Although the study did not reach the primary outcome, CBTA-guided invasive angiography was associated with lower MACE rates. Better results can be obtained with larger studies with a newer technology (512-slice CT).