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CT Coronary Angiography

Coronary CT angiography is a non-invasive, ECG-synchronized study that visualizes the coronary artery lumen and wall, enabling detection and grading of stenosis and characterization of atherosclerotic plaque. It has a very high negative predictive value, making it an excellent gatekeeper to exclude significant coronary artery disease in patients with stable or acute chest pain and low-to-intermediate risk. Adequate heart-rate control and rhythm are essential for diagnostic image quality.

Indications

  • Stable chest pain with low-to-intermediate pretest probability of coronary artery disease
  • Acute chest pain in the emergency department to exclude significant CAD (with low-intermediate risk)
  • Assessment of suspected coronary anomalies or origin/course of anomalous vessels
  • Evaluation of coronary artery bypass graft patency and complex percutaneous intervention planning
  • Equivocal or inconclusive functional/stress testing
  • Pre-procedural planning (e.g., before valve intervention such as TAVI) and coronary calcium scoring for risk stratification

Contraindications & Cautions

  • Iodinated contrast allergy (premedicate) and significant renal impairment (weigh contrast risk)
  • Uncontrolled tachycardia or arrhythmia (e.g., atrial fibrillation) limiting gating quality
  • Inability to hold breath or cooperate; severe obesity may limit image quality
  • Contraindications to rate-controlling beta-blockers (severe asthma, decompensated heart failure, high-grade AV block) and to nitrates (hypotension, PDE5-inhibitor use)
  • Pregnancy: justify and dose-optimize; generally deferred unless essential
  • Extensive coronary calcification may cause blooming and reduce diagnostic accuracy

Patient Preparation

  • Screen renal function, contrast allergy, pregnancy, and current medications (PDE5 inhibitors)
  • Achieve target heart rate (typically <60-65 bpm) with oral and/or IV beta-blockade per protocol
  • Administer sublingual nitroglycerin immediately before acquisition to dilate coronaries (if not contraindicated)
  • Avoid caffeine before the study; establish large-bore (18-20 G) right antecubital IV access
  • Attach ECG leads, coach breath-hold, and confirm regular rhythm before scanning
  • Explain the procedure and obtain consent; keep resuscitation facilities available

Technique & Parameters

  • ECG-gated acquisition: prospective (axial, low-dose) for stable low heart rates, retrospective (helical) when function or arrhythmia handling is needed
  • Submillimeter collimation (0.5-0.75 mm) for high spatial resolution of small coronary vessels
  • IV contrast ~50-80 mL of high-concentration iodinated agent at 5-6 mL/s with saline chaser; bolus tracking in the aortic root
  • High-pitch or wide-detector single-heartbeat acquisition where available to minimize dose and motion
  • Coverage from the carina/tracheal bifurcation to below the diaphragm to include grafts when relevant
  • Reconstruct multiple cardiac phases; use MPR, MIP, and curved reformats for vessel analysis; perform Agatston calcium score on a non-contrast gated series

Systematic Review

  • Assess overall image quality, contrast opacification, and motion/step artifacts before interpretation
  • Evaluate coronary dominance and origins; identify any anomalous origin or course
  • Analyze each segment (per SCCT/AHA model) for stenosis severity and plaque
  • Characterize plaque as calcified, non-calcified, or mixed and note high-risk features
  • Review bypass grafts and stents for patency, occlusion, or in-stent restenosis (allowing for blooming)
  • Assess cardiac chambers, myocardium, valves, and pericardium within the field
  • Review the aorta, pulmonary arteries, and lung bases/mediastinum for non-coronary findings

Key Findings & Significance

  • Luminal stenosis graded by CAD-RADS (minimal, mild, moderate, severe, occluded)
  • Non-calcified or mixed plaque with positive remodeling and low attenuation: higher-risk plaque
  • Napkin-ring sign and spotty calcification: vulnerable plaque features
  • High Agatston calcium score correlating with atherosclerotic burden and cardiovascular risk
  • Anomalous coronary origin with an interarterial course: potentially high-risk anomaly
  • Graft occlusion or stenosis and in-stent restenosis
  • Myocardial hypoperfusion, aneurysm, or thrombus as ancillary findings

Differential Considerations

  • Apparent stenosis: true atherosclerotic narrowing vs calcium blooming vs motion artifact
  • Filling defect in a graft/vessel: thrombus/occlusion vs poor opacification/mixing artifact
  • Non-calcified plaque vs coronary vessel wall thrombus vs myocardial bridging (dynamic narrowing)
  • Chest pain with normal coronaries: microvascular disease, myocarditis, pericarditis, or non-cardiac cause
  • High calcium score with unassessable lumen: consider functional testing or invasive angiography
  • Anomalous vessel: benign course vs malignant interarterial course requiring further evaluation

Pearls & Pitfalls

  • Heart-rate and rhythm control are the single biggest determinants of diagnostic quality
  • Dense calcification and stents cause blooming that overestimates stenosis; state when segments are non-evaluable
  • Report using standardized CAD-RADS to guide downstream management
  • Myocardial bridging is common and usually benign but should be reported when the tunneled segment is deep/long
  • Always look beyond the coronaries: pulmonary emboli, aortic dissection, and lung pathology may explain symptoms
  • Motion artifact typically affects the right and distal circumflex arteries; reconstruct alternative phases

Structured Report

  • State protocol, gating method, heart rate, contrast, and image quality/evaluability
  • Report coronary dominance, anomalies, and per-vessel/segment stenosis with CAD-RADS category
  • Characterize plaque type, burden, and high-risk features; include calcium score
  • Comment on grafts, stents, chambers, valves, and pericardium
  • Note non-coronary/incidental thoracic findings
  • Impression: overall CAD severity (CAD-RADS), management implication, and follow-up or further testing recommendation

References

  • SCCT Guidelines for Performance and Interpretation of Coronary CT Angiography
  • CAD-RADS 2.0 Reporting and Data System (SCCT/ACR/NASCI)
  • ACC/AHA Guideline for the Evaluation and Diagnosis of Chest Pain
  • ACR Appropriateness Criteria: Chest Pain - Suspected Coronary Artery Disease

Educational clinical decision support only. Protocols vary by institution and equipment; always confirm with a qualified radiologist and local guidelines before clinical use.