What are the indications for Coronary Computed Tomography (CT)?

Indications for Coronary Computed Tomography (CT)

Coronary CT angiography (CCTA) is primarily indicated for patients with low to intermediate pretest probability of coronary artery disease (CAD), particularly when other non-invasive tests are inconclusive or contraindicated. 1

Primary Indications for Coronary CT

Symptomatic Patients Without Known CAD

• Low to intermediate pretest probability of obstructive CAD:

  • CCTA is appropriate for patients with chest pain and low-to-intermediate pretest probability of CAD 1
  • Superior diagnostic performance compared to exercise ECG and SPECT (sensitivity 94.6%, specificity 76.3%) 2
  • Can reliably exclude obstructive CAD with post-test probability below 15% in patients with pretest probability up to 74% 2

• Inconclusive or non-diagnostic prior testing:

  • When non-invasive functional testing is inconclusive 1
  • When echocardiography is suboptimal or inadequate 1

Calcium Scoring

• Risk stratification in asymptomatic patients:
  • Appropriate for intermediate CHD risk patients (10-20% 10-year risk) 1
  • Appropriate for low-risk patients with family history of premature CHD 1
  • Not recommended for repeat testing or general screening 1

Heart Failure Evaluation

• New onset or established heart failure:
  • Appropriate in patients with reduced left ventricular ejection fraction with low or intermediate pretest CAD probability 1
  • Can rule out obstructive CAD in patients with low-to-intermediate pre-test probability and equivocal non-invasive stress tests 1

Preoperative Assessment

• Prior to non-coronary cardiac surgery:
  • Appropriate for intermediate pretest CAD risk patients 1
  • Uncertain utility in low pretest CAD risk patients 1
  • Alternative to invasive angiography in low-risk patients candidate for valve surgery 1
  • Not appropriate for preoperative evaluation for non-cardiac surgery 1

Coronary Stent Evaluation

• Limited utility except in specific scenarios:
  • Only appropriate for left main stents 1
  • Uncertain utility for larger stents (≥3mm) after longer time periods (≥2 years) 1
  • Generally not recommended for routine stent evaluation 1

Cardiac Structure and Function Assessment

• Appropriate indications include:
  • Coronary anomalies evaluation 1
  • Congenital heart disease assessment 1
  • Right ventricular function evaluation 1
  • Left ventricular ejection fraction assessment when other imaging is inadequate 1
  • Prosthetic heart valve evaluation 1
  • Myocardial viability assessment when other modalities are inadequate or contraindicated 1

Specialized Indications

• Electrophysiology procedure planning:
  • Appropriate prior to EP procedures for anatomic mapping 1
• Cardiac surgery planning:
  • Appropriate prior to repeat sternotomy in reoperative cardiac surgery 1
• Suspected arrhythmogenic right ventricular dysplasia:
  • Appropriate for evaluation 1

Clinical Pitfalls and Caveats

• Radiation exposure concerns:

  • Modern scanners allow coronary imaging at decreasing radiation doses 1
  • Should be weighed against diagnostic benefit, especially in younger patients 1

• Contraindications:

  • Cardiac arrhythmias (atrial fibrillation, frequent premature beats) may compromise image quality 3
  • Renal insufficiency (eGFR <60 mL/min/1.73m²) due to contrast requirements 3
  • Allergy to iodinated contrast agents 3
  • Implanted pacemakers and defibrillators generally preclude CMR as an alternative 1

• Technical limitations:

  • Heavy coronary calcification (calcium score >1000) may limit diagnostic accuracy 3
  • Stent evaluation is limited by stent size and time from implantation 1
  • Thin mobile structures may not be well visualized due to acquisition period and voxel dimensions 1

Comparison with Other Modalities

• CCTA vs. Invasive Coronary Angiography:

  • CCTA has excellent negative predictive value for excluding significant CAD 4
  • Invasive angiography remains gold standard for definitive stenosis assessment 3

• CCTA vs. Functional Testing:

  • CCTA demonstrates significantly better diagnostic performance than exercise-ECG and SPECT 2
  • Positive predictive value ≥50% at lower pretest probability thresholds (10% for CCTA vs. 40% for ECG and 28% for SPECT) 2

• CCTA vs. Other Imaging:

  • Echocardiography remains first-line for valve assessment 1
  • CT offers excellent spatial resolution and unrestricted access in shorter acquisition times than CMR 1
  • CMR provides better tissue characterization and functional assessment without radiation 1

CCTA is FDA-approved for diagnostic evaluation of patients with suspected coronary artery disease 5, and its appropriate use continues to evolve as technology improves and evidence accumulates.