Which cardiac tests should be performed to evaluate a partially occluded coronary artery?

Cardiac Testing for Partially Occluded Coronary Arteries

For a partially clogged coronary artery, coronary computed tomography angiography (CCTA) combined with fractional flow reserve derived from CT (FFR-CT) is the recommended first-line test to simultaneously assess anatomical severity and hemodynamic significance. 1, 2

Initial Diagnostic Strategy Based on Clinical Likelihood

Low to Moderate Pre-test Probability (>5%–50%)

• CCTA is the primary recommended test to diagnose obstructive coronary artery disease and estimate risk of major adverse cardiac events 1
• CCTA achieves 91-95% sensitivity and 83-92% specificity for detecting significant coronary stenosis 2
• A negative CCTA effectively rules out obstructive disease with post-test probability dropping to 1-2% 1

Moderate to High Pre-test Probability (>15%–85%)

• Functional imaging tests are recommended when pre-test probability exceeds 15% 1
• Options include stress echocardiography, SPECT/PET myocardial perfusion imaging, or cardiac MRI perfusion 1
• These tests diagnose and quantify myocardial ischemia while estimating risk of major adverse cardiac events 1

Enhanced Assessment of Intermediate Stenoses

FFR-CT for Hemodynamic Significance

• FFR-CT should be added to CCTA when intermediate severity stenosis (40-90% diameter) is detected to determine if the lesion causes ischemia 1, 2
• FFR-CT correctly reclassifies 68% of false-positive CCTA results as true negatives, dramatically reducing unnecessary invasive procedures 2
• This approach addresses the critical limitation that 50-90% stenoses on anatomical imaging do not reliably predict functional significance 1

Sequential Testing Strategy

• When CCTA shows intermediate stenosis but functional significance remains uncertain, perform functional stress testing (echocardiography, SPECT, PET, or CMR) as the next step 1
• In patients with 20-60% pre-test probability, sequential anatomical-functional testing provides optimal diagnostic accuracy 1
• A positive stress test after abnormal CCTA increases post-test probability to 82-90%, confirming need for invasive angiography 1

Invasive Coronary Angiography with Pressure Assessment

When to Proceed Directly to Invasive Testing

• Invasive coronary angiography (ICA) is recommended as first-line test in patients with very high (>85%) clinical likelihood, severe refractory symptoms, or angina at low exercise levels 1
• Radial artery access is mandatory when ICA is performed, reducing mortality and major bleeding compared to femoral access 1

Mandatory Functional Assessment During ICA

• Coronary pressure assessment (FFR or iFR) must be available and used during ICA to evaluate functional severity of intermediate stenoses (40-90% diameter) before revascularization decisions 1
• FFR ≤0.80 or iFR ≤0.89 indicates hemodynamically significant stenosis requiring revascularization 1
• For left main stenoses (40-70% diameter), FFR/iFR measurement or intravascular ultrasound (IVUS) should be performed 1

Critical Contraindications and Pitfalls

CCTA Should Not Be Performed When:

• Severe renal failure, decompensated heart failure, or extensive coronary calcification is present 2
• Fast irregular heart rate, severe obesity, or inability to cooperate with breath-hold commands exists 1, 2
• Severe calcification causes blooming artifacts that overestimate stenosis severity 1

Common Diagnostic Errors to Avoid

• Do not rely on coronary calcium scoring alone—16% of symptomatic patients with zero calcium score still have myocardial ischemia on provocative testing 2
• Do not assume visual stenosis severity on CCTA or ICA predicts ischemia—pressure-wire assessment is essential for intermediate lesions 1
• FFR-CT is not validated for bypass grafts or in-stent assessment and must not be used in these situations 2
• Exercise stress testing on resting ECG with ≥0.1 mV ST-depression or in patients taking digitalis is not recommended for diagnostic purposes 1

Specific Test Selection Algorithm

For Ruling Out Obstructive Disease

• Use CCTA in patients with low-moderate pre-test probability who can tolerate contrast and have adequate image quality 1
• Negative CCTA has extremely high negative predictive value and excellent long-term prognosis 1

For Confirming Ischemia-Causing Stenosis

• Use stress imaging (echo, SPECT, PET, or CMR) in patients with moderate-high pre-test probability or when CCTA shows intermediate stenosis 1
• Exercise stress is preferred over pharmacological stress whenever the patient can exercise adequately 1
• PET myocardial perfusion imaging is preferred over SPECT when available, offering superior accuracy and lower radiation 1

For Guiding Revascularization Decisions

• Invasive FFR/iFR measurement during ICA is mandatory for all intermediate stenoses before proceeding with revascularization 1
• Systematic routine pressure assessment of all vessels is not recommended—reserve for intermediate lesions only 1