Multidetector row CT coronary angiography: technique and preliminary experience

Abstract

Purpose: To report our preliminary experience with multi-slice spiral CT coronary angiography of the coronary arteries.

Materials and methods: 50 volunteers (mean age 61 years, range 45-72) with baseline heart rates below 70 bpm underwent multi-detector row CT coronary angiography (GE Light Speed Plus, 140 kVp, 270 mA, 1.25-mm collimation, 0.5-second rotation time, high quality pitch) with retrospective ECG gating after receiving 140-150 ml of iodinated contrast medium (Iopamiro 300 mg-dl, Bracco, Italy) at a flow rate of 4 ml/sec. Three of the 50 patients had previously undergone coronary procedures (1 anterior descending artery stent, 1 left circumflex artery stent and 1 anterior descending artery percutaneous angioplasty) and three were undergoing follow-up examinations after by-pass surgery. The remaining 44 patients were asymptomatic and had no history of coronary artery disease. All CT angiograms were back-reconstructed from 20 to 80% of the diastolic cycle with 10% increments to establish the phase with fewer "stair-step" motion artefacts for each artery. Patients with heart rates above 70 bpm were administered beta-blockers during the five days preceding the examination in doses appropriate for the patient's clinical characteristics.

Results: The CT room occupation time ranged from 25 to 35 minutes (mean time 27') and the post-processing time from 30 to 60 minutes (mean time 40'). The left anterior descending artery was best visualised in middle diastole (70% of cardiac cycle), the circumflex artery at 60% of the cardiac cycle, and the right coronary artery at 40%. Out of 132 arteries, 19 (14.4%) were considered non-assessable due to "stair-step" motion artefacts, whereas 2 (1.5%) were only partially visualised owing to the presence of extensive wall calcifications. Among the 113 assessable arteries, we observed: 72 normal coronary arteries without stenosis or wall calcifications (54.5%); 28 arteries with minimal wall irregularities and stenoses below 50% (21.2%); 7 stenoses >50% involving the right coronary artery (no. 2), the anterior descending arteries (no. 4) and the left circumflex artery (no. 1) (5.3%). In the remaining 6 patients, optimal visualisation of the stents and venous and arterial surgical by-passes was obtained.

Conclusions: Although further larger-scale studies are required to compare MSCT coronary angiography with CT coronary angiography, the application of MSCT technology to the study of the coronary arteries is a promising technique with a good potential for use in routine clinical practice. In selected patients (with baseline heart rates <70 bpm, or after beta-blocker therapy) it is able to provide very interesting results and could be used as a method of choice for following patients after interventional procedures or as a mass-screening tool to select patients to be referred for coronary angiography.