What is the purpose and procedure of a cardiac angiogram for diagnosing coronary artery disease?

Cardiac Angiogram for Diagnosing Coronary Artery Disease

Coronary angiography is considered the "gold standard" for diagnosing coronary artery disease (CAD), providing detailed visualization of coronary anatomy and the severity of luminal obstruction, which is essential for determining appropriate treatment strategies and improving mortality and morbidity outcomes in patients with suspected CAD. 1

Purpose of Cardiac Angiogram

• Coronary angiography defines coronary anatomy, including the location, length, diameter, and contour of the epicardial coronary arteries; the presence and severity of coronary luminal obstructions; the nature of the obstruction; the presence of collateral flow; and coronary blood flow 1

• It helps identify patients who would benefit from revascularization procedures (percutaneous coronary intervention or coronary artery bypass grafting) to improve symptoms and outcomes 1

• It allows for assessment of the functional significance of coronary stenoses when combined with fractional flow reserve (FFR) measurements, which helps determine if a stenosis is hemodynamically significant 1

Procedure of Cardiac Angiogram

• Cardiac angiography is an invasive procedure performed in a cardiac catheterization laboratory 1

• The procedure involves inserting a catheter (typically via the radial or femoral artery) and advancing it to the coronary arteries under X-ray guidance 1

• Radial artery access is recommended as the preferred access site due to lower complication rates 1

• Contrast material is injected through the catheter into the coronary arteries, and X-ray images are taken to visualize blood flow and identify areas of narrowing or blockage 1

• The severity of stenosis is typically defined as significant when there is ≥70% diameter reduction (≥50% for left main disease) 1

Indications for Cardiac Angiogram

• Patients with presumed stable ischemic heart disease (SIHD) who have unacceptable ischemic symptoms despite guideline-directed medical therapy and who are candidates for coronary revascularization 1

• Patients whose clinical characteristics and results of noninvasive testing indicate a high likelihood of severe ischemic heart disease and who are candidates for revascularization 1

• Patients with suspected symptomatic SIHD who cannot undergo diagnostic stress testing or have indeterminate/nondiagnostic stress tests, when findings will likely change therapy 1

• Patients with stress test results that don't suggest CAD but clinical suspicion remains high and findings would likely change therapy 1

Limitations and Considerations

• Coronary angiography has inherent limitations in assessing stenosis severity, with significant interobserver variability in grading coronary stenoses 1

• Angiographic assessment relies on comparison to an adjacent, non-diseased reference segment, which may lead to underestimation of lesion severity in diffusely diseased arteries 1

• Visual assessment often overestimates stenosis severity when coronary stenosis is ≥50% 1

• It cannot reliably determine the physiological significance of lesions - many stenoses considered severe (≥70% narrowing) may not restrict coronary blood flow, while others considered "insignificant" (<70%) may be hemodynamically significant 1

• Coronary angiography cannot assess whether an atherosclerotic plaque is stable or "vulnerable" (likely to rupture and cause acute coronary syndrome) 1

Risks and Complications

• Invasive coronary angiography carries a 1.5% risk of procedural complications according to the ACC's National Cardiovascular Data Registry 1

• Potential complications include death, stroke, myocardial infarction, bleeding, infection, contrast allergic reactions, vascular damage, contrast-induced nephropathy, and arrhythmias 1

• Risk is higher in certain patient groups: advanced age (>70 years), marked functional impairment, severe left ventricular dysfunction, severe valvular disease, severe comorbidities, bleeding disorders, or history of contrast allergies 1

Adjunctive Techniques

• Fractional Flow Reserve (FFR) can assess the hemodynamic significance of angiographically "intermediate" or "indeterminate" lesions and guide decisions about revascularization 1, 2

• Intravascular ultrasound and optical coherence tomography provide more precise information about stenosis severity and plaque morphology than coronary angiography alone 1

• These adjunctive techniques can help overcome some limitations of conventional angiography and improve diagnostic accuracy 1

Alternative Diagnostic Approaches

• Non-invasive testing options include coronary CT angiography (CCTA), stress echocardiography, single-photon emission computed tomography (SPECT), positron emission tomography (PET), and cardiac MRI 3, 4

• CCTA has emerged as an alternative for initial diagnosis in patients with suspected CAD, particularly those with low to intermediate pretest probability 4, 5

• However, invasive coronary angiography remains superior for therapeutic decision-making in patients with high likelihood of CAD and for guiding revascularization procedures 5