Coronary CT Angiography Protocol

Contrast Administration Protocol

• The American Heart Association recommends administering 50-160 mL of iodinated contrast at 4-6 mL/s for coronary CTA, with attention to radiation dose optimization and patient-specific contraindications 1, 2, 3
• The standard protocol involves 60-100 mL of iodinated contrast medium injected at 4-6 mL/s through an 18-gauge or larger antecubital IV cannula, according to the American College of Cardiology 1, 3, 4
• Accurate timing is the major determinant of image quality, using either a test bolus or automated bolus tracking that triggers scanning when aortic enhancement exceeds a predetermined threshold, as recommended by the American Heart Association 1, 3, 4, 5

Pharmacological Premedication

• The American College of Cardiology recommends administering beta-blockers to achieve heart rate ≤60 bpm, which is essential for minimizing motion artifacts on scanners with temporal resolution ≥250 ms 1, 2, 3, 4, 5
• Target heart rate depends on scanner temporal resolution: ≤60 bpm for scanners with 250 ms temporal resolution, ≤75 bpm acceptable for scanners with ≥167 ms temporal resolution, and up to 90 bpm acceptable for dual-source CT scanners, according to the American Heart Association 1, 2, 3, 4, 5
• The American Heart Association recommends administering sublingual nitroglycerin immediately before scanning to achieve coronary vasodilation and improve image quality, particularly for distal vessel visualization 1, 2, 3, 4, 5, 8

Technical Acquisition Parameters

• The American College of Cardiology recommends using spatial resolution of 0.4 mm with 64-slice MDCT, and retrospective ECG gating to reconstruct images during phase of cardiac cycle with least motion 1, 3, 4, 5
• Scan duration is 8-20 seconds depending on scanner generation, as recommended by the American Heart Association 1, 2

Critical Caveats and Limitations

• Heavy coronary calcification causes false-positive findings and may render segments non-evaluable for stenosis assessment, according to the American College of Cardiology 6, 7
• Coronary stents create artifacts that preclude adequate lumen visualization, as recommended by the American Heart Association 6, 7
• Motion artifacts from high heart rates or arrhythmias significantly degrade image quality, according to the American College of Cardiology 6, 7
• Coronary CTA exposes patients to considerably higher radiation than standard radiographs, calcium scoring, or invasive angiography, with an effective dose of 10-21 mSv depending on technique and patient sex, as recommended by the American Heart Association 1, 2, 3, 10
• Radiation dose reduction strategies include ECG-controlled tube-current modulation, reducing tube current during anterior-posterior vs lateral scanning, and using lowest dose necessary for adequate visualization, according to the American College of Cardiology 10