Are coronary arteries visible on two-dimensional transthoracic echocardiography?

Visualization of Coronary Arteries on 2D Transthoracic Echocardiography

Yes, coronary arteries are visible on 2D transthoracic echocardiography, but visualization is limited to the proximal segments of the major epicardial vessels. 1, 2

What Can Be Visualized

Proximal coronary segments are routinely imaged during standard 2D echocardiography, particularly in specialized protocols such as Kawasaki disease evaluation. 1 The following vessels can be visualized:

• Left main coronary artery (LMCA): Visible in approximately 86% of adults using parasternal short-axis views at the aortic valve level and precordial long-axis views 1, 2

• Left anterior descending (LAD) artery: Visualized in approximately 86% of patients, with mean visualized length of 3.9 cm (maximum up to 7.5 cm) and average luminal diameter of 4.9 mm in the proximal segment 2

• Right coronary artery (RCA): Seen in approximately 91% of patients, with mean visualized length of 5.6 cm (maximum up to 12 cm) and average proximal diameter of 3.1 mm 2

• Left circumflex artery: Visible in only 31% of patients with limited visualization (mean length 1.1 cm) 2

Technical Requirements for Optimal Visualization

High-frequency transducers (3.5-5.0 MHz) are essential for adequate coronary artery imaging, even in older children and adults. 1 Key technical factors include:

• Multiple imaging planes: Parasternal short-axis at aortic valve level, parasternal long-axis (superior and inferior tangential), apical four-chamber, and subcostal views are required to visualize different coronary segments 1

• Digital processing and cine loop review: Dynamic video format enables detailed frame-by-frame analysis of coronary anatomy 1, 2

• Color Doppler enhancement: Transthoracic color Doppler significantly improves visualization of coronary flow, particularly in peripheral branches 3

Clinical Applications

2D echocardiography is the primary imaging modality for detecting proximal coronary artery abnormalities in Kawasaki disease, with high sensitivity and specificity. 1 Additional clinical uses include:

• Detection of coronary artery aneurysms: Most commonly in proximal LAD and proximal RCA, followed by LMCA 1

• Assessment of anomalous coronary origins: Particularly anomalous origin from the pulmonary artery 1

• Evaluation of coronary ostia: Distance from aortic annulus to coronary ostia can be measured, particularly important before transcatheter aortic valve procedures 1

Important Limitations

Distal coronary segments and peripheral branches are not reliably visualized with standard 2D transthoracic echocardiography. 4, 2 Critical limitations include:

• Acoustic window dependency: Poor visualization occurs with abnormal chest wall configuration, narrow intercostal spaces, obesity, pulmonary emphysema, and mechanical ventilation 1

• Limited distal vessel imaging: Mid and distal LAD segments are seen in only 31% of patients, with average visualized length of only 1.9 cm 2

• Inability to assess atherosclerotic plaque: 2D echocardiography cannot visualize atherosclerotic plaques or vulnerable plaque characteristics that are visible on invasive angiography 1

• No assessment of coronary stenosis: Standard 2D imaging cannot reliably detect or quantify coronary artery stenoses 4, 5

When Alternative Imaging Is Required

For comprehensive coronary artery evaluation including stenosis detection, CT coronary angiography or invasive coronary angiography is required. 1, 6 Specific indications for alternative imaging include:

• Suspected coronary artery disease: Stress echocardiography with wall motion analysis is used rather than direct coronary visualization 1, 5

• Detailed coronary anatomy: CT angiography or invasive angiography provides complete visualization of all coronary segments and branches 1, 6

• Assessment of coronary stenosis: Functional testing (stress echo, nuclear imaging, cardiac MRI) or anatomic imaging (CT, invasive angiography) is necessary 1, 6

Common Pitfalls to Avoid

• Overestimating diagnostic capability: Do not rely on 2D echo for excluding coronary artery disease or detecting stenoses in symptomatic patients 4, 5

• Inadequate sedation in children: Poor-quality studies in uncooperative children under 3 years should be repeated with sedation within 48 hours 1

• Missing the bifurcation: The LMCA bifurcation is visible in only 43% of patients and requires specific imaging planes 2

• Confusing artifacts with pathology: Reverberation artifacts in the ascending aorta can mimic intimal flaps or other abnormalities 1