Table 2.
Comparison of non-invasive imaging tests for the assessment of myocardial ischaemia in patients with previous coronary artery bypass grafts—features, strengths, and limitations.
| Imaging modality | Stressor | Accessibility/risks | Ischaemia / perfusion | Viability and function | Coronary anatomy | Quantitative perfusion |
|---|---|---|---|---|---|---|
| Stress echo | • Exercise, dobutamine, vasodilator | • Widely available • Often requires use of contrast for image quality • No radiation • Risk associated with dobutamine in the context of LV dysfunction |
• Limited LV coverage • Less sensitive to identify subtle RWMA • Arrhythmia and abnormal septal motion limit performance • Spatial resolution: 1 × 1–3 × 3–6 mm3 |
• Viability assessment suboptimal compared to CMR and PET | • N/A | • Requires use of microbubbles and associated with technical challenges • Linear relationship between blood flow and tracer |
| CMR | • Mainly vasodilator • Dobutamine and exercise possible but limited |
• Not widely available • Vendor, field strength, sequence differences • No radiation • Devices affect image quality |
• Limited LV coverage (conventionally 3x short axis slices used) • Arrhythmia can be detrimental • Can identify peri-infarct ischaemia • Spatial resolution: 1 × 2 × 6–8 mm3 |
• Gold standard modality for volume assessment • Peri-infarct ischaemia assessment • Additional tissue characterization |
• Not performed routinely • Limited LV coverage |
• Altered contrast kinetics associated with complex graft-native vessel flow • Non-linearity between blood flow, contrast and signal intensity |
| SPECT | • Exercise or vasodilator | • Widely available • Radiation (significantly reduced with modern scanners) |
• Isotropic left ventricle coverage • Limited spatial resolution: 10 × 10 × 10 mm3 |
• Viability and function assessment possible • Limited temporal resolution |
• Hybrid imaging with CT possible | • Limited temporal resolution • New generation scanners offer quantitative analysis |
| PET | • Exercise or vasodilator | • Not widely available • Radiation |
• Isotropic left ventricle coverage • Endocardial- epicardial flow estimation possible • Spatial resolution 4 × 4 × 4 mm3 |
• Viability assessment possible • Lower spatial resolution than CMR |
• Hybrid imaging with CT possible | • Linear relationship between blood flow and 15O-water • Linear relationship between tracer and image signal |
| CT perfusion/ angiography | • Vasodilator | • Perfusion not widely available • Radiation |
• Spatial resolution (image analysis): 0.5 × 0.5 × 6–8 mm3
• Isotropic left ventricle coverage • Low CNR • Coronary and graft anatomy available |
• Viability and function assessment possible, but increased radiation dose | • Data on anatomy • Difficulties with anastomosis sites and natives. • CT-FFR not validated for patients post CABG |
• Non-linear relationship between blood flow and contrast |
SPECT, Single-Photon Emission Computed Tomography; CMR, Cardiac Magnetic Resonance; PET, Positron Emission Tomography; CNR, contrast to noise ratio; FFR, fractional flow reserve.