Coronary Arteries: Imaging, Anomalies, and Kawasaki Disease

The coronary arteries are small, mobile, and easy to overlook — and missing an anomaly can have major consequences: unexplained heart failure in an infant, sudden death in a young athlete, or myocardial ischemia on weaning from bypass after an operation that put a coronary artery in harm’s way. Every initial echocardiogram should include a deliberate look at the origin and proximal course of each major coronary artery. This page covers how to image the coronary arteries, the congenital anomalies worth recognizing and how to diagnose each, and — although it is an acquired disease — Kawasaki disease, where the coronary arteries are the target organ.

Normal Coronary Anatomy: What Matters for Imaging

• Two arteries, from the two “facing” sinuses. The right and left coronary arteries arise from the aortic sinuses that face the pulmonary artery. The third, posterior sinus is the noncoronary sinus. Sinuses are named after the ventricle they supply rather than the artery that arises from them — in an L-looped heart, the artery supplying the L-looped right ventricle normally arises from the left sinus. See Congenitally Corrected Transposition.
• Left main artery. It arises from the left sinus, runs a short distance, and divides into the left anterior descending (LAD) and left circumflex (LCx) arteries. It may trifurcate with a ramus intermedius — and the ramus should never be presumed to be the LAD or the LCx, which would lead to an incomplete or inaccurate diagnosis of “normal” anatomy. A dual LAD is a benign variant.
• Right coronary artery (RCA). It arises from the right sinus, passes behind the main pulmonary artery, beneath the right atrial appendage, and along the right AV groove. Its first branch is the conus artery in about half of people; in the rest the conus artery arises from the right sinus through a separate ostium, which is a normal variant.
• Dominance. Around 90% of people have a right-dominant system, meaning the posterior descending artery arises from the RCA. “Dominance” refers only to the origin of the posterior descending artery — the majority of the myocardium is supplied by the left coronary artery regardless.
• Flow timing. Left ventricular systolic wall tension compresses the intramyocardial vessels so heavily that most left coronary flow occurs in diastole. Right coronary flow occurs in both systole and diastole, because right ventricular compressive forces are lower — although RV hypertension can interrupt systolic flow.
• Ischemia shows up first in the subendocardium, and regional wall motion is the echo readout of it. The anterolateral papillary muscle is supplied by the LAD and a diagonal or marginal branch of the LCx; the posteromedial papillary muscle by the LCx or RCA, depending on dominance.
• Embryology explains the anomalies. The coronary circulation forms at about 32 to 45 days of gestation from an endothelial plexus that grows into the aortic sinuses rather than out from the aortic root — a concept that gives a rational basis for the myriad patterns of anomalous origin. Coronary abnormalities also occur in genetic syndromes: diffuse or ostial stenosis and dilation in Williams syndrome (with supravalvar aortic stenosis), and ectasia and aneurysms in Noonan and Marfan syndromes.

How to Image the Coronary Arteries by Echocardiography

Two-dimensional echocardiography with color Doppler is an established tool for diagnosing coronary anomalies in infants and children. Its temporal and spatial resolution are good enough to image the origins and proximal courses even in small patients with fast heart rates. Quality depends heavily on probe choice, patient habitus, instrument settings, and — above all — operator skill.

Set-Up

• Use the highest-frequency probe that still penetrates adequately. This is often a higher frequency than you would normally choose for the view, because the proximal coronary arteries lie on the epicardium in the near field of the sector.
• Optimize the signal-to-noise and contrast-to-noise ratios. Reducing 2D gain and dynamic range (compression) often improves demonstration of the vessel lumen, and imaging at a shallower depth improves visualization.
• Know the limits. Transthoracic and transesophageal echocardiography can reliably image the proximal coronary arteries; the mid and distal branches are typically not well delineated.
• Use TEE where it counts. It is seldom the first study in children, but a careful coronary assessment belongs in a complete intraoperative study, given how strongly coronary anomalies are associated with congenital heart defects and how dramatically a new coronary diagnosis can change the operative plan.

Key Elements of a Coronary Study

• Identify the origin of each major artery (LAD, LCx, RCA) by 2D imaging and color flow mapping.
• Identify the proximal course of each artery and the branching of the left main artery.
• Show flow into the proximal artery from the aortic sinus, and the direction of flow in each major artery by color Doppler.
• Evaluate global and regional LV function (2D, 3D, and strain).
• Evaluate myocardial echogenicity for endocardial fibroelastosis and regional scar.
• Evaluate for mitral regurgitation, and identify associated defects.

The Views

The proximal arteries are best imaged in the parasternal long- and short-axis planes and, in infants and young children, from the subxiphoid coronal (long-axis) view. Together, these views show the origins and proximal courses in both horizontal and vertical relation to the aortic root.

Window	What it shows	Technique
Parasternal short-axis, base of the heart	Both coronary origins (often seen together) arising from their sinuses; the left main artery and its bifurcation into LAD and LCx; the proximal LAD and LCx; the proximal RCA	Clockwise rotation improves the left main bifurcation and a longer length of LAD and LCx; clockwise or counterclockwise rotation may be needed for the RCA. The movements are subtle. Use color to exclude the edge of the left atrial appendage or fluid in the left anterior AV sulcus
Parasternal long-axis, leftward angulation	The left main bifurcation and a long section of the LAD along the anterior interventricular septum	Sweep the plane between the aorta and pulmonary artery from right to left to bring up the proximal left coronary artery, LAD, and LCx
Subxiphoid coronal (long-axis) at the aortic root	Both proximal arteries relative to the sinotubular junction; the RCA rises first, then turns inferiorly and laterally into the right anterior AV groove	Especially valuable in infants and young children
Subxiphoid sagittal (short-axis)	The LCx in the left AV groove (particularly with aneurysms); the RCA in the lateral right AV groove	Angle rightward for the lateral right AV groove
Apical five-chamber or four-chamber, anterior angulation	The proximal RCA in the right anterior AV groove; the LCx in the left anterior AV groove	Tilted slightly anteriorly between the AV valves and the aortic valve, it shows a retro-aortic circumflex artery
Apical four-chamber, posterior tilt	The distal RCA in the posterior right AV groove; the distal LCx in the posterior left AV groove; the posterior descending artery	The posterior descending artery is also often seen from an inferiorly angled parasternal long-axis view
Parasternal long-axis toward the tricuspid valve	The mid RCA in cross-section in the lateral right AV groove	Angle toward the tricuspid valve and lateral AV groove
Leftward-angled parasternal long-axis, and modified apical	The coronary course beneath the pulmonary annulus (intraconal); the “hammock sign”	Use with and without color Doppler

Color and Spectral Doppler

• Show flow into the artery, not just the artery. Antegrade flow from the aortic root into the proximal coronary artery is what confirms a normal origin. Color Doppler of the origins from the parasternal short-axis view can be challenging, because the artery lies perpendicular to the beam — take great care to demonstrate antegrade flow unambiguously.
• Follow the direction of flow in every major artery. This can supply critical information about anomalous origin from the pulmonary artery.
• Beware of coronary veins. Direction of color flow also matters to avoid confusing an artery with a coronary vein, especially in the distal segments.
• Normal flow patterns. Right coronary flow is seen in both systole and diastole; left coronary flow is predominantly diastolic. Pulsed-wave Doppler is possible but easier to perform by TEE.

Pitfalls in Coronary Imaging

• Never rely on still frames. With an anomalous origin from the pulmonary trunk or aorta, the proximal coronary artery often approaches the appropriate sinus, and resolving the thin tissue between the coronary and aortic lumens on a single frame can be misleading. It is easy to be falsely assured of a normal origin when the artery actually arises from somewhere else.
• Dropout. Limited lateral resolution — worst in the parasternal short-axis view — can make the wall between an anomalous left main artery and the aortic root appear to be missing, suggesting a normal origin.
• Linear mimics. The transverse sinus of the pericardium, the left atrial appendage, and fluid in the left anterior AV groove can produce linear echoes running parallel to a coronary artery. Color Doppler resolves them.
• A high RCA origin can mimic ARCAPA. A high clockwise origin of the RCA from the ascending aorta can sometimes look like an origin from the pulmonary artery on transthoracic echo.
• Assuming the ramus intermedius is the LAD or LCx. Identify all major proximal branches.
• Variation in ostial position. Ostia are normally just below the sinotubular junction, but positions above or below it occur in up to 40% of people undergoing coronary angiography and appear benign. The relationship to the sinotubular junction still matters when the origin is anomalous.
• Pulmonary hypertension can confound flow direction. With ALCAPA and coexisting pulmonary hypertension, flow in the anomalous artery can appear bidirectional or mainly antegrade.

Setting-Specific Considerations

• Fetus. The coronary arteries are rarely imaged well. The exceptions are anomalies that dilate them or send abnormal flow into a chamber or vessel: coronary–cameral fistulae, and pulmonary atresia with intact ventricular septum or hypoplastic left heart syndrome with sinusoidal connections to the ventricular myocardium. Very large fistulae can steal from the fetal cerebral circulation. Prominent coronary flow on routine fetal echo is often seen with growth restriction, fetal anemia, or ductal constriction, and — together with absent or reduced diastolic flow in the umbilical artery — coincides with worse fetal outcomes.
• Operating room. Accurate coronary delineation is required before any congenital heart surgery, because an anomaly can place a major epicardial artery in the field of repair. See the associations below.
• Older patients. CT — or, less often, MRI — is frequently obtained for further anatomic delineation in older patients with slower heart rates.

When Echo Isn’t Enough

• Catheter angiography remains the gold standard for distal coronary disease.
• Cardiac CT is superior for anomalies of coronary origin and proximal course. Its role in children is growing with beta blockade for heart rate control, nitroglycerin for vasodilation, and refined protocols that limit radiation.
• Cardiac MRI offers radiation-free assessment of perfusion (with adenosine or dobutamine stress) and viability (with delayed enhancement).
• Nuclear perfusion imaging is rarely used in children because of relatively low sensitivity and specificity and radiation exposure; PET-CT is emerging for older children and young adults.
• Intravascular ultrasound, fractional flow reserve, and optical coherence tomography are rarely used in children but are occasionally applied to Kawasaki disease, anomalous aortic origin, and myocardial bridges.

Congenital Coronary Artery Anomalies

Classification

Group	Anomalies
I. Origin	Origin of one or more coronary arteries from the pulmonary artery (left main, RCA, LCx, accessory, both, single, or from a branch pulmonary artery); origin from the aorta from the wrong sinus, the posterior sinus, or the ascending aorta or a brachiocephalic artery; a single coronary ostium; ostial anomalies (abnormal number or position, ostial stenosis, ostial atresia)
II. Course, distribution, or intrinsic to the artery	Intramural or interarterial course; intramyocardial, intraconal, or intraseptal course; congenital stenosis, atresia, occlusion, or interruption; hypoplasia; coronary loops; myocardial bridges
III. Termination	Coronary arteriovenous or arterio-cameral fistulae
IV. Associated with congenital heart disease	Tetralogy of Fallot, transposition of the great arteries, and others
V. Luminal	Ectasia and aneurysms — physiologic (anemia, ventricular hypertrophy), acquired (Kawasaki disease), genetic (Noonan, Marfan), and congenital hypoplasia

Minor Variants Worth Recognizing

Minor variants are hemodynamically insignificant and not associated with an increased risk of sudden death — but they must be recognized to interpret angiograms and echocardiograms correctly, to avoid inadequate myocardial protection when cardioplegia is given selectively into the coronary orifices, and to avoid coronary injury during surgery.

• Absent left main artery with separate origins of the LAD and LCx from the left sinus — reported in about 0.4% of people, and associated with left coronary dominance and myocardial bridging.
• LCx from the right sinus or proximal RCA — about 0.5% of people undergoing coronary angiography, and compatible with normal life. The artery courses posterior to the aorta to reach the left AV groove. On echo it is recognized as a horizontal linear lucency posterior to the aorta on an apical four-chamber view tilted slightly anteriorly.
• Variation in the number of ostia — a separate conus artery ostium in the right sinus (about half of people) or a separate LCx ostium in the left sinus (about 1%); rarely both, producing four ostia.
• Origin from the posterior (noncoronary) sinus — exceedingly rare (RCA about 0.003%, left coronary about 0.0008%) and generally considered benign as long as the ostium is normal and the proximal course is not intramural. Case reports do link an origin of the left coronary artery from the noncoronary sinus to sudden cardiac death.

ALCAPA: Anomalous Left Coronary Artery from the Pulmonary Artery

Anomalous origin of the left main coronary artery from the pulmonary artery (ALCAPA, also called Bland-White-Garland syndrome) is one of the most important congenital coronary anomalies, because it offers a rare opportunity to cure what looks like dilated cardiomyopathy. It occurs in about 1 in 300,000 live births and accounts for 0.5% of congenital heart disease. It is usually isolated but can accompany PDA, VSD, AV canal defects, tetralogy of Fallot, coarctation, hypoplastic left heart syndrome, and truncus arteriosus.

The left main artery usually arises from the left or posterior sinus of the pulmonary artery — occasionally more distally, even from the undersurface of the proximal right pulmonary artery — and then branches normally. Only the origin is abnormal.

Physiology. Four hemodynamic phases are described, and patients may overlap between them:

1. Fetus and newborn: pulmonary pressure is high, so the anomalous artery is perfused from the pulmonary artery and there is no ischemia.
2. Transition: as pulmonary vascular resistance falls, flow into the left coronary artery falls or reverses before collaterals from the RCA have developed. Perfusion pressure and flow drop and ischemia results. Most patients present in infancy during this phase.
3. Adult phase: a rich collateral network has developed between the right and left coronary systems, and myocardial perfusion is adequate.
4. Steal: the left coronary artery has become a conduit from the RCA to the pulmonary artery, and oxygenated blood is stolen from the left coronary capillary bed, producing ischemia again.

Presentation. Most infants present with failure to thrive, tachypnea, dyspnea, wheezing, diaphoresis, or angina-like episodes — classically with feeding (“infantile angina”). Male infants outnumber females 2 to 1. There may be no murmur, or only a short one; mitral regurgitation, from papillary muscle ischemia and annular dilation, is sometimes the only sign. Patients with extensive collaterals may remain asymptomatic and present in childhood or adulthood with murmurs, arrhythmia, heart failure, sudden death, or an incidental finding (in one large adult series the mean age at diagnosis was 41 years and the oldest patient was 83). Patients whose ALCAPA is accompanied by another lesion that keeps pulmonary pressure high, or who have left main ostial stenosis limiting the steal, may present with severe LV dysfunction after the associated lesion is repaired if the anomalous artery is missed.

Echo findings. The typical picture is a dilated, hypocontractile LV, a dilated left atrium, and moderate or greater mitral regurgitation — with eccentric LV hypertrophy (increased LV mass index, normal or reduced mass-to-volume ratio) and global dysfunction with regional wall motion abnormalities. All of this also occurs in myocarditis and dilated cardiomyopathy, so the coronary arteries must be evaluated diligently in any patient with this presentation.

ALCAPA: echo findings in an infant
The left main origin from the main pulmonary artery (or, rarely, a branch pulmonary artery), with a retrograde flow jet into the main pulmonary artery
Retrograde flow in at least two of the three left coronary segments, including the left main artery
A dilated right coronary artery (larger in older infants and children)
Prominent collateral flow in the septal perforators (more prominent in older infants and children)
LV dilation with global and regional systolic dysfunction, often severe, and abnormal diastolic indices
Echobright papillary muscles and patchy areas of echobright endocardium
A structurally normal mitral valve with moderate or severe regurgitation

• 2D imaging of the arteries alone cannot distinguish ALCAPA from other conditions. The left artery lies so close to the left sinus that dropout can produce a false appearance of normal origin, and linear echoes from the transverse sinus or left atrial appendage can mimic a coronary course.
• Color flow mapping is crucial. The direction of flow in each left coronary segment is the key differentiating feature. An abnormal jet into the pulmonary artery combined with retrograde flow in at least two of the three segments is highly reliable for diagnosing ALCAPA.
• A dilated RCA — one study found an RCA to aortic root ratio above 0.2 highly specific — and prominent color flow in the myocardium, particularly the septal perforator region, indicate collateral circulation.
• Antegrade flow in one segment is useful but not enough to exclude ALCAPA, particularly with coexisting pulmonary hypertension.
• When color is inconclusive, a brief (10-minute) trial of supplemental oxygen, with or without agitated saline contrast, can transiently increase retrograde flow in the left coronary system and improve visualization of the shunt into the main pulmonary artery without compromising the patient.
• Echo rules the diagnosis in far better than out. When these findings are combined with mitral regurgitation, LV systolic dysfunction, and echobright papillary muscles, transthoracic echo can be adequate as the only imaging study before surgery. But echo has high specificity, so additional imaging should be considered to rule out ALCAPA in dilated cardiomyopathy with equivocal or nondiagnostic echo findings.

Intraoperative and postoperative imaging. TEE evaluates LV function and mitral regurgitation, confirms the anatomy and coronary origin, and shows the direction of coronary flow. Afterwards, antegrade flow from the aorta into the left main artery should be confirmed, along with a check for baffle leaks after a Takeuchi repair. Early recovery may be minimal and mechanical support is rarely needed; reported freedom from death, transplant, or reoperation is 87% at 1 year and 84% at 5 and 10 years. Recovery of LV size and ejection fraction does not mean recovery of subtle dysfunction: longitudinal strain abnormalities, diastolic abnormalities, and even RV dysfunction may persist, and stress perfusion, exercise testing, and stress MRI with delayed enhancement can detect residual scar or coronary stenosis. See Mitral Regurgitation and LV Systolic Function.

ARCAPA: Anomalous Right Coronary Artery from the Pulmonary Artery

Anomalous origin of the RCA from the pulmonary artery is much less common — about 0.002% of people — but is clinically important. It is associated with other congenital heart disease in 25 to 30% of cases — including aortopulmonary window (in which ARCAPA is the most common associated coronary abnormality), tetralogy of Fallot, septal defects, double-outlet right ventricle, coarctation, and PDA. Presentation in infancy is uncommon; when there is no other defect, a murmur in childhood is the usual finding, and almost half of patients are asymptomatic. Sudden death has been reported at any age.

• Echo approach. It is the same as for ALCAPA and hinges on a high index of suspicion plus meticulous imaging of the RCA origin and direction of flow.
• Findings. The RCA is typically dilated with reversed flow. Additional clues are abnormal flow signals in the RV free wall myocardium or the main pulmonary artery.
• Contrast with ALCAPA. In ARCAPA there is prominent RV collateral flow with preserved LV systolic function, unlike the severely reduced function seen with ALCAPA.
• Mimic. A high clockwise origin of the RCA from the ascending aorta can look like ARCAPA on TTE.

Left Main Ostial Atresia (and Stenosis)

Rarely, the left main artery and its branches have a normal epicardial course but atresia of the ostium at the aortic sinus. The physiology resembles ALCAPA — collateral supply from the RCA — but with no egress into the pulmonary artery. Presentation and course are similar: angina, heart failure, infarction, arrhythmias, and sudden death.

• This lesion shows why 2D and color Doppler must be combined. The left system can look normal by 2D up to the aortic sinus, with enough dropout to falsely suggest a patent ostium, yet show paradoxical retrograde flow in the left anterior descending or circumflex arteries.
• The RCA may be dilated with normal antegrade flow and prominent septal collateral flow.
• Unlike ALCAPA, there is no separate diastolic jet entering the pulmonary artery.
• Echo can suspect the diagnosis, but angiography or cardiac CT is needed to confirm it. It has been associated with VSDs, supravalvar aortic stenosis, and LV noncompaction.
• Ostial stenosis (rather than atresia) is even rarer and can have a malignant course, possibly because collaterals fail to develop while native antegrade flow is limited and demands rise after birth.

Other Origins from the Pulmonary Artery

• LAD or LCx from the pulmonary artery. Extremely rare but can cause ischemia. The RCA is often dilated with collateral flow and retrograde flow into the pulmonary artery.
• An accessory coronary artery (most commonly the conus artery) arising from the pulmonary artery usually has no functional significance, but it shows why every major proximal branch must be identified.
• Both coronary arteries from the pulmonary artery (separate ostia, or a single coronary artery). Infants usually present in the early neonatal period with profound heart failure and cardiac arrest as pulmonary pressures fall. Mortality is high, but prompt diagnosis allows surgical reimplantation.
• A coronary artery from a branch pulmonary artery. A diagnostic challenge on echo, seen in both normal and univentricular hearts.
• A cautionary case. In a single coronary artery arising from the main pulmonary artery, 2D imaging falsely suggested a normal left main origin, and both color and pulsed Doppler appeared to show antegrade flow in it — an aortogram then showed no coronary connections. When the story doesn’t fit, don’t stop at echo.

Anomalous Aortic Origin of a Coronary Artery (AAOCA)

AAOCA covers an anatomic spectrum: origin from the wrong or inappropriate sinus, both arteries from the same sinus, or a high origin from the ascending aorta above the inappropriate sinus or commissure — each with an interarterial, intramural, intramyocardial, or other abnormal course. Its reported incidence is up to 2%.

• Origin of the left main from the right sinus (AAOLCA-R) carries a higher incidence of sudden cardiac death and ischemia, but is less common than origin of the RCA from the left sinus.
• Origin of the RCA from the left sinus (AAORCA-L) is estimated to be three to six times more prevalent, but with a substantially lower rate of major complications. Autopsy series still suggest that up to one in four people found to have an anomalous RCA died suddenly, and whether to operate in asymptomatic patients is controversial.
• Origin of the left coronary artery from the noncoronary sinus has also been implicated in adverse events.
• Ischemia is common in AAOLCA-R — 17% of 560 patients in a Congenital Heart Surgeons’ Society registry — and sudden death is twice as prevalent as with AAORCA-L. Familial clustering has been reported, and screening of first-degree relatives has been suggested.

Why sudden death occurs. The proposed mechanism is myocardial ischemia, with or without lethal arrhythmia, from reduced coronary flow due to a combination of anatomic and physiologic factors: a slit-like ostial stenosis, an oblique or tangential take-off from the aorta, compression of the intramural or interarterial segment, an ostial ridge next to the intercoronary pillar, vessel spasm, and a noncompliant pericommissural area. CT studies show that patients with ischemia have a more elliptical ostium and proximal lumen, with a height-to-width ratio above 2.

The routes the anomalous left main artery can take after its origin from the right sinus:

• Between the aorta and pulmonary artery (interarterial), with or without an intramural course;
• In the ventricular septum beneath the RV infundibulum (intraconal);
• Anterior to the pulmonary artery; or
• Posterior to the aorta.

Echo Protocol for Anomalous Aortic Origin of a Coronary Artery

Excellent definition of origin and proximal course is often possible by echo. The parasternal short-axis view at the base is the best view for the relationship of the left coronary origin to the intercoronary commissure, its often-intramural course, and its relationship to the RV outflow tract. Optimizing color Doppler is integral to diagnosing an interarterial course and suspecting an intramural one — an abnormal jet in diastole over the space between the aorta and the pulmonary trunk is often the first indication of an abnormal coronary course. A protocol that increases diagnostic yield:

1. Origin: show the origin of the artery from the sinus of Valsalva by 2D, confirmed by color Doppler with multiple-beat capture showing flow from the sinus into the origin and proximal course.
2. Branching: delineate the left main bifurcation into LAD and LCx.
3. Commissure: show where the ostium sits relative to the intercoronary commissure.
4. Sinotubular junction: show the origin relative to the sinotubular junction in long-axis — within the sinus or above it.
5. Ostium: characterize a single ostium versus two separate ostia, from which sinus, and the ostial shape (ellipticity, best measured by CT — a superior-inferior length twice the anterior-posterior width is associated with a slit-like ostium and ischemia).
6. Proximal course, with careful color flow mapping to confirm flow:
   • Interarterial — between the aorta and pulmonary artery above the level of the pulmonary valve, without meeting the criteria for an intramural course.
   • Intramural — within the aortic wall. This is a surgical diagnosis, but it can be suspected when the artery arises at an acute angle from the aorta with linear diastolic color flow following the curve of the aortic wall, or on CT by absent pericardial fat.
   • Intraconal — through the conal (infundibular) septal muscle below the level of the pulmonary valve.
   • Anterior to the pulmonary artery, or posterior to the aorta.
7. Associated anomalies of the aortic valve and ascending aorta.

Intraconal (intraseptal) course of the left main or LAD is rare and generally benign, but recognizing it avoids unnecessary intervention. The key feature is seeing the myocardium surrounding the proximal coronary artery, from parasternal short- and long-axis views. A leftward-angled parasternal long-axis view, with and without color Doppler, shows the course beneath the pulmonary annulus and allows a check for stenosis in the intraconal segment; the “hammock sign” can be seen from a modified apical view. CT or MRI confirms that the course is within the conus rather than epicardial.

AAORCA-L is most often diagnosed incidentally by echo, or during evaluation of chest pain or exercise-induced syncope. The sinus of origin and location relative to the commissure are seen in the parasternal short-axis view, and location relative to the sinotubular junction in the parasternal long-axis view. The RCA in this anomaly often has a high origin at or above the sinotubular junction. When the origin is above the commissural post, sweep superiorly from a short-axis view showing the intercoronary commissure to a view showing the coronary origin to demonstrate the sinus of origin. A circular echolucency at the anterosuperior aspect of the aortic sinus on a standard parasternal long-axis view is a useful clue to the possibility of an anomalous RCA from the left sinus.

Risk stratification and surgical planning need more than echo. Ostial characterization, the angle of the proximal course, distal branching, dominance, and confirmation of the diagnosis require CT or MRI. CT findings that correlate with an intramural course are an acutely angled origin, an elliptical lumen, and no epicardial fat between the aortic wall and the artery. Stress MRI may be falsely reassuring if the obstruction is dynamic rather than fixed, TEE can confirm the diagnosis when TTE is equivocal, and intravascular ultrasound and coronary flow reserve help when narrowing is significant or dynamic. If surgery is needed, unroofing is generally performed for an intramural course; the relationship of the origin and course to the commissure determines whether commissuroplasty is also needed; and dense pericommissural tissue must be addressed to prevent neo-ostial stenosis.

After repair, echo evaluates for aortic regurgitation from distortion of the aortic valve and confirms flow from the appropriate sinus into the coronary artery. See Aortic Regurgitation.

Single Coronary Artery

A single coronary artery arises through one ostium in one of the aortic sinuses and then supplies the distribution of both the right and left arteries, or an abnormal distribution. In isolation it is very rare (about 0.024%), and it is usually an incidental finding in an otherwise normal heart. Classification schemes describe the sinus of origin, whether an aberrantly coursing artery is present, and its course.

• Distinguish a single coronary artery from left main atresia. A single artery with normal antegrade flow to all three major branches is a very different lesion from atresia of the left main, which has collateral flow to the left coronary circulation and much greater risk of LV ischemia.
• Most patients with a single RCA are asymptomatic, and the anomaly is compatible with a normal life. But a single RCA with an aberrant left coronary artery (or branch) coursing between the great vessels seems to carry a particular risk of sudden death — probably by the same mechanism as AAOLCA-R.
• When a single coronary artery is suspected, confirm the origin and proximal course of each of the three major arteries in multiple views.

Anomalies of Course and Intrinsic Anomalies

Intramural and interarterial courses and intraconal courses are covered above. The remaining anomalies — congenital stenosis, atresia, occlusion or interruption, hypoplasia, coronary loops, and myocardial bridges — are each rare. Myocardial bridging is worth knowing about because the narrowing is dynamic, and intravascular ultrasound and coronary flow reserve can aid assessment.

Coronary Fistulae

A coronary–cameral fistula connects a coronary artery to a cardiac chamber; a coronary–arteriovenous fistula connects it to a cardiac vein; a coronary-to-pulmonary-artery fistula behaves the same way. Together they are simply called coronary fistulae.

• Frequency. They account for about 0.2 to 0.4% of congenital cardiac anomalies and roughly half of congenital coronary anomalies. In adults with cardiac symptoms undergoing CT, they are found in up to 0.7 to 0.9%, mostly draining to the pulmonary arteries.
• Origin. Recent CT-based data indicate the left main artery and LAD are the most common sources, followed by the RCA and, lastly, the LCx. Multiple fistulae may be more common than single ones.
• Termination. About 90% terminate on the right side of the heart — most often the pulmonary artery, RV, and right atrium, followed by the coronary sinus, left atrium, and LV. About 20% coexist with other congenital heart defects.
• Acquired forms occur after cardiac surgery, in inflammatory states, and after penetrating chest trauma — including coronary–RV fistulae after RV outflow muscle resection in tetralogy of Fallot.

Physiology depends on where the fistula ends. A fistula to the right atrium behaves like a pretricuspid left-to-right shunt; to the RV or pulmonary artery, like a post-tricuspid left-to-right shunt; to the left atrium, like mitral regurgitation; and to the LV, like aortic regurgitation. Every fistula can also steal blood from the coronary bed beyond its insertion, causing ischemia or, rarely, infarction.

Presentation. Large fistulae can cause chamber enlargement in fetal life and heart failure in infants. Most, however, don’t present until adulthood (murmur, dyspnea, fatigue), and many are found incidentally. Long-term consequences include chronic volume loading, premature coronary disease, endocarditis, and pulmonary hypertension.

Echo findings.

• Dilation of the proximal coronary artery feeding the fistula, and chamber dilation matching the fistula’s physiology. Proximal ectasia accompanies significant fistulae and persists after closure.
• The fistulous connection itself is occasionally seen, but color Doppler greatly aids detection.
• Small fistulae are often first detected by abnormal diastolic flow into a right heart chamber or the main or branch pulmonary arteries — an unexpected finding in an asymptomatic patient with no murmur and no chamber or proximal coronary dilation.
• Fetal echo may show prominent flow in a dilated coronary artery, and a large fistula can cause retrograde flow in the aortic arch.
• CT or MRI, and stress imaging, are typically needed to confirm hemodynamic significance and define the anatomy before intervention.

Management. Guidelines recommend closing large fistulae regardless of presentation, and small or medium-sized ones if there are cardiac symptoms, abnormal testing, or endocarditis; there are no formal closure guidelines for children, although most pediatric cardiologists agree it is indicated for large fistulae, signs of hemodynamic effect or heart failure, or other evidence of ischemia. Residual connections are found in up to 30% after closure. TEE or intracardiac echo can document occlusion and check for new wall motion abnormalities during or after transcatheter closure, and long-term anticoagulation is recommended to reduce thrombotic occlusion, particularly in older patients and those with aneurysmal dilation.

Coronary Aneurysm and Ectasia

Coronary aneurysms are present in 1 to 5% of adults at angiography or autopsy, most often in the RCA. Causes include atherosclerosis (the presumed commonest in adults), Kawasaki disease, other vasculitides (polyarteritis nodosa, Takayasu arteritis, lupus), connective tissue disease (Marfan and Ehlers-Danlos syndromes), infection, cocaine, dilation from a distal fistula, and trauma or iatrogenic injury. A congenital aneurysm is a diagnosis of exclusion made after these are ruled out; one pathologic study attributed 17% of all coronary aneurysms to congenital causes, thought to reflect deficient elastic elements in the arterial media. Complications include rupture, myocardial infarction from embolization of thrombus, and endocarditis. Echo evaluation is the same as for Kawasaki disease (below); definitive diagnosis is by angiography, CT, or MRI.

Coronary Anomalies Associated with Congenital Heart Disease

Coronary anomalies are important in many congenital lesions — see Tetralogy of Fallot (LAD from the RCA crossing the RV outflow tract), Transposition of the Great Arteries (Leiden patterns and the intramural and single-artery risks for the arterial switch), and Truncus Arteriosus (ostia above the sinotubular junction). The general rule is that accurate coronary delineation is required in any patient undergoing surgery for congenital heart disease, and it remains important on later examinations. Some examples of why:

• An anomaly may put a major epicardial artery in the region of a surgical repair or catheter intervention — coronary assessment before transcatheter pulmonary valve replacement is one example.
• Unrecognized origin of a coronary artery from the pulmonary artery can cause ischemia on weaning from cardiopulmonary bypass, from changing hemodynamics and reduced coronary perfusion pressure.
• Unrecognized high origin from the ascending aorta above the sinotubular junction can lead to inadvertent clamping of the artery when the aortic cross-clamp is placed.

Since these tasks are performed against the confounders of complex defects, variable pulmonary pressures, and the stress of the operating room, meticulous coronary imaging belongs in every preoperative echocardiogram.

How to Diagnose Coronary Anomalies by Echo: A Practical Sequence

1. Look at every study. Identify the origin of the LAD, LCx, and RCA, the proximal course of each, and the branching of the left main artery, by 2D and color Doppler. Add global and regional LV function, myocardial echogenicity, mitral regurgitation, and associated defects.
2. Use cine loops and multiple views — never still frames. Rotate and angle deliberately; the movements are subtle.
3. Prove antegrade flow from the aortic sinus into every proximal artery. An artery that can’t be confidently traced to an aortic sinus, or that shows retrograde flow, points to an origin from the pulmonary artery.
4. Look for indirect signs when the arteries themselves are hard to see: a dilated, hypocontractile LV with mitral regurgitation; echobright papillary muscles or endocardium; a dilated RCA; color flow in the septal perforators; abnormal diastolic flow into the pulmonary artery, RV, or right atrium.
5. Check the sinus of origin against the intercoronary commissure and the sinotubular junction on parasternal short- and long-axis views, and look for a diastolic jet between the aorta and pulmonary trunk.
6. Work out the proximal course. Interarterial, intramural, intraconal, anterior, or posterior — and look for the myocardium surrounding the artery if an intraconal course is possible.
7. Count the arteries. A single coronary artery with normal antegrade flow is not the same as an absent left main artery with collateral flow.
8. Think about the clinical setting (table below).
9. Escalate when the story doesn’t fit. Echo rules ALCAPA in better than it rules it out; risk stratification of AAOCA needs CT or MRI; the significance of a fistula needs advanced or stress imaging; and confirmation of ostial atresia needs angiography or CT.
10. Before any surgery or catheter intervention, define the coronary anatomy — and document it again afterwards.

Pattern Recognition

Presentation	Think of	Key echo clues	Confirm with
Infant with heart failure, dilated hypocontractile LV, mitral regurgitation	ALCAPA	Retrograde flow in at least two of three left coronary segments; jet into the main pulmonary artery; dilated RCA; septal collateral flow; echobright papillary muscles	Echo may suffice if findings are complete; additional imaging if equivocal
Same picture, but the left main looks normal to the sinus and there is no jet into the pulmonary artery	Left main ostial atresia	Paradoxical retrograde flow in the LAD or LCx; dilated RCA with septal collaterals	Angiography or CT
Dilated RCA with reversed flow and abnormal signals in the RV free wall or pulmonary artery, LV function preserved	ARCAPA	RCA origin from the pulmonary artery; prominent RV collateral flow	Angiography or CT
Young athlete or teenager with exertional syncope or chest pain, or a family history of sudden death	AAOCA	Sinus of origin and commissure on short-axis; diastolic jet between the aorta and pulmonary trunk; acute-angle or slit-like origin; high origin above the sinotubular junction	CT or MRI for ostial shape, course, and risk
Murmur or incidental finding with a dilated proximal coronary artery, or abnormal diastolic flow into a right heart chamber or pulmonary artery	Coronary fistula	Dilated feeding artery; chamber dilation matching the drainage site; color flow at the entry point	CT or MRI; stress imaging
Fever of 5 or more days with the classic clinical features	Kawasaki disease	Coronary dimensions by z-score; pericardial effusion; mitral regurgitation; LV dysfunction	Serial echo (see below)
Congenital heart defect awaiting surgery or transcatheter intervention	Coronary anomaly associated with the defect	Origin and course of each artery relative to the planned repair	Per the defect (CT or angiography if unclear)

What to Put in the Report

• The origin of each major artery: which sinus, position relative to the intercoronary commissure and sinotubular junction, and single versus separate ostia.
• The proximal course, and whether it is interarterial, intramural, intraconal, anterior, or posterior.
• Flow direction in each artery, and whether antegrade flow from the aorta was demonstrated.
• The branching pattern of the left main artery.
• Dimensions and z-scores where dilation is a question (essential in Kawasaki disease), with location, number, and morphology of any aneurysm.
• Any indirect signs — LV function, wall motion, mitral regurgitation, collateral flow, and abnormal flow into a cardiac chamber or vessel.

See TTE Reporting for the broader structure of an echocardiography report.

Kawasaki Disease: Looking for Coronary Involvement

Kawasaki disease (KD) is an acquired condition — an acute systemic vasculitis of unknown cause — rather than a congenital one, but it is included here because the coronary arteries are its most important target and echocardiography is the central modality for following them.

Why the Coronary Arteries Matter

• Definition. KD is a clinical diagnosis. Complete criteria are fever for 5 or more days and at least four of five principal features: changes in the extremities, polymorphous rash, nonexudative conjunctivitis, changes in the lips and oral mucosa, and cervical lymphadenopathy. Incomplete KD can be diagnosed with persistent fever and two or three clinical criteria plus laboratory or echocardiographic findings that support it — which is one reason the echo matters.
• Who. Eighty percent of cases are under 5 years old and 90% under 8. Boys are affected 1.5 times as often as girls, and prevalence is highest in children of Asian descent. It is the most common form of acquired pediatric heart disease in the developed world.
• What happens to the arteries. The acute febrile phase is a diffuse vasculitis of medium-sized arteries, with a predilection for the coronary arteries. Three linked processes drive the vasculopathy: necrotizing arteritis (complete by about 2 weeks), subacute chronic vasculitis (which can persist for months to years), and luminal myofibroblastic proliferation (which can persist for months or years and cause progressive coronary obstruction). Later phases can show scarring, stenosis, and calcification.
• Thrombosis is most common in the subacute and early convalescent phase, between days 15 and 45 of illness.
• Regression is not normalization. About 60 to 70% of aneurysms show normalization of internal lumen diameter, typically over the first 2 years. But the mechanism can involve myointimal proliferation and layered thrombus that leave abnormal vessel architecture and sometimes stenosis, and even regressed segments have reduced coronary flow reserve and abnormal vascular reactivity.

KD Is a Pancarditis: Look Beyond the Arteries

Echo should assess the endocardium, myocardium, and pericardium as well as the coronary arteries.

• Pericardial effusion. Modest effusions are common in the acute phase and rarely significant hemodynamically, although tamponade has been reported in severe acute KD.
• Mitral and tricuspid regurgitation. Usually mild and transient in acute KD (valvulitis or myocarditis). Mitral regurgitation has been associated with a lower LV ejection fraction in the acute phase, and can rarely be severe. Persistent mitral regurgitation is rare and linked to ischemia and papillary muscle dysfunction.
• Aortic regurgitation and aortic root dilation. Aortic regurgitation is typically mild and transient (valvulitis or aortitis); it can persist and, extremely rarely, need surgery.
• Myocardial function. Myocarditis is present histologically in virtually all acute cases, so assess global function (shortening fraction or ejection fraction) and regional wall motion. Tissue Doppler has shown diastolic abnormalities even without systolic dysfunction — subclinical myocardial inflammation.
• Why these findings matter for the arteries. Pericardial effusion, mitral regurgitation, or myocardial dysfunction is more common in Kawasaki shock syndrome and is associated with a higher risk of coronary changes. It can also raise suspicion of KD when the clinical criteria are incomplete.
• With large or giant aneurysms, the focus shifts to thrombus, stenosis, regional and global function, and ischemia-related AV valve dysfunction.

See Mitral Regurgitation and Aortic Regurgitation.

When to Image

Coronary changes typically appear within the first 2 weeks of illness, and most patients who go on to develop aneurysms have changes by the first 10 days. The first 6 to 8 weeks is also when transient dilation and ectasia often resolve — and when aneurysms reach their maximum size.

Situation	Echocardiogram timing (AHA 2017)
Normal coronary arteries at diagnosis	At diagnosis; 1 to 2 weeks after diagnosis; 6 to 8 weeks after diagnosis
Coronary changes at baseline	Every 2 to 4 days until dimensions stabilize, noting acute changes in valves, myocardium, effusion, and coronary arteries
Complex cases (aneurysms or thrombosis, significant regurgitation, effusion, or myocardial dysfunction)	During the acute and subacute phases as clinical circumstances dictate
Chronic coronary changes	Annually

How to Image the Coronary Arteries in KD

• Highest feasible transducer frequency. Reducing 2D gain and dynamic range often improves demonstration of the lumen, and imaging at a shallower depth helps.
• Image every segment of both coronary systems. The most common sites for aneurysms are the proximal LAD and proximal RCA, followed by the left main artery, LCx, distal RCA, and proximal posterior descending artery. Distal aneurysms are uncommon without proximal ones, and involvement of both the right and left systems (particularly LAD, RCA, and left main) is more common than a single lesion.

Segment	Best views	Technique
Left main artery	Parasternal short-axis at the aortic root	The most readily imaged left-sided segment
LAD and proximal LCx	Parasternal short-axis; parasternal long-axis	Slight clockwise rotation from the standard short-axis view shows a greater length of both. In long-axis, sweep the plane between the aorta and pulmonary artery from right to left to show the proximal left coronary artery, LAD, and LCx
Distal LCx	Apical five-chamber with anterior angulation; subxiphoid sagittal	LCx in the left anterior AV groove; the subxiphoid view at the left AV groove is particularly useful when aneurysms are present
Proximal RCA	Parasternal short-axis at the aortic root; apical (anterior angulation); subxiphoid coronal	Slight clockwise rotation in short-axis shows a greater length of proximal and mid RCA; in the anterior right AV groove on apical or subxiphoid long-axis views
Mid RCA	Parasternal long-axis angled toward the tricuspid valve; subxiphoid sagittal	Cross-section in the lateral AV groove; angle rightward into the lateral AV groove from the sagittal view
Distal RCA and junction with the posterior descending artery	Apical four-chamber or parasternal long-axis with posterior angulation; subxiphoid long-axis with posterior angulation	Posterior right AV groove

Measuring and Grading

• Measure internal diameter, inner edge to inner edge, at standard sites: the left main artery distal to its ostium and before its bifurcation; the RCA after its initial turn rightward from the aortic sinus; and the LAD distal to its bifurcation from the left main artery and before the first diagonal branch.
• Express the result as a z-score normalized to body surface area. Published normal values exist only for the RCA, left main artery, and LAD. For other segments, compare with the adjacent segment.
• Fixed cutoffs under-recognize disease. The Japanese Ministry of Health criteria define dilation as an internal diameter over 3 mm in children under 5 years, over 4 mm in children 5 or older, at least 1.5 times an adjacent segment, or a clearly irregular lumen. These miss abnormalities that z-scores catch — so use z-scores, and a dimension that looks normal by absolute size may still be abnormal for the patient.
• Note the subtler acute changes. Mild diffuse enlargement can occur in the acute phase, but perivascular echogenicity does not discriminate from normal controls and is not a reproducible finding.

AHA 2017 classification and follow-up:

Risk level	Coronary findings (maximum z-score)	Imaging follow-up	Invasive testing
I	No changes at any stage	None	None
II	Dilation only (z-score 2.0 to 2.49)	None	None
III	Small aneurysm (2.5 to 4.9)	Echo and ECG yearly; inducible ischemia assessment every 2 to 5 years	Angiography if noninvasive imaging suggests ischemia
IV	Moderate aneurysm (5.0 to 9.9)	Echo and ECG twice yearly; inducible ischemia assessment every 1 to 3 years	May consider angiography 6 to 12 months after diagnosis or as clinically indicated; repeat if noninvasive testing suggests ischemia
V	Large or giant aneurysm (z-score 10 or more, and/or absolute dimension over 8 mm)	Echo and ECG twice yearly; yearly inducible ischemia assessment	Baseline angiography within 12 months, then surveillance every 1 to 5 years depending on clinical status

Describe Every Aneurysm

• Shape. Saccular aneurysms have nearly equal axial and longitudinal dimensions; fusiform aneurysms have an axial dimension smaller than the longitudinal one and taper at their ends. Fusiform aneurysms are more likely to regress over time.
• Location, number, and distribution. Larger size, bilateral involvement, and multiple aneurysms in one or more arteries carry a higher risk of adverse cardiac outcomes and should prompt more aggressive medical therapy and further testing, such as angiography and perfusion assessment.
• Thrombus. Look for it in every aneurysm, particularly large or giant ones. An echogenic mass within the lumen — sometimes with spontaneous contrast (smoke) from sluggish flow — is the finding.
• Stenosis or obstruction. This can come from thrombosis in the acute phase, or myointimal proliferation and layered mural thrombus in the chronic phase. It can be difficult to see by 2D alone; functional assessment of perfusion improves its detection, and angiography or CT angiography can confirm it.

Regional Wall Motion and Ischemia

• Regional wall motion is assessed in the parasternal long- and short-axis and apical four- and two-chamber views, segment by segment, and assigned to the responsible artery. (The Kawasaki chapter uses a 16-segment model; the coronary chapter favors the 17-segment AHA model.) It matters most in large or giant aneurysms, which are at risk of thrombosis or stenosis.
• Long-term imaging in severe coronary involvement can show myocardial dysfunction, scarring, and mitral regurgitation from ischemia or infarction.
• A dramatic example: a giant LAD aneurysm with a nearly occlusive thrombus presenting with myocardial infarction shows the thrombus in the aneurysm on short-axis and regional LV dysfunction on the four-chamber view.

Stress Echocardiography in KD

Anatomy alone doesn’t tell you whether the myocardium is ischemic. Stress echocardiography looks for inducible regional wall motion abnormalities — which appear earlier in ischemia than ECG changes or elevated cardiac enzymes — in segments supplied by a stenotic artery. See Stress Echocardiography for the technique in general.

• Exercise is limited in the young: children under about 7 to 8 years usually can’t exercise adequately, and imaging during or right after exercise is technically challenging. It has nonetheless demonstrated angiographically confirmed stenoses after KD.
• Dobutamine avoids these problems and is generally safe. Side effects (headache, nausea, hypertension, atrial or ventricular ectopy) generally resolve quickly when the infusion stops; serious arrhythmias and hypotension are rare in children.
• Protocol as described for KD. Obtain baseline images in the parasternal long- and short-axis and apical four- and two-chamber views so that all 16 segments can be assessed. Give dobutamine in 3- to 5-minute stages at 10, 20, 30, 40, and 50 µg/kg/min, with continuous ECG and vital-sign monitoring and images at the end of each stage. Compare rest, low-dose, high-dose, and recovery images (quad-screen display allows side-by-side comparison). The maximum dose (30 to 50 µg/kg/min) is reached at the target heart rate or the top of the range.
• Accuracy. In the largest study, dobutamine stress echo identified coronary stenoses with 90% sensitivity and 100% specificity.
• Alternatives. Cardiac MRI and CT have increasingly supplanted angiography for anatomy in long-term follow-up, particularly with high-risk abnormalities or limited echo windows, and stress nuclear perfusion or stress MRI with perfusion can assess perfusion. The choice depends on local experience and resources. Angiography still shows the distal vessels best but is invasive.

A Practical KD Echo Protocol

1. Time it: at diagnosis, 1 to 2 weeks, and 6 to 8 weeks (every 2 to 4 days if changes are already present); annually with chronic changes.
2. Optimize the image: highest frequency, lower gain and compression, shallow depth.
3. Image every coronary segment with the views in the table above, rotating to lengthen each segment.
4. Measure inner edge to inner edge at the standard sites, and convert to z-scores — not just millimeters.
5. Grade by the AHA categories, and describe each aneurysm’s shape, location, number, and distribution.
6. Look for thrombus and stenosis in every aneurysm.
7. Examine the whole heart: pericardial effusion, mitral, tricuspid, and aortic regurgitation, aortic root, and global and regional function.
8. Escalate as the category rises: stress imaging for inducible ischemia, and angiography, CT, or MRI per the AHA table.

Pitfalls in KD

• A “normal-sized” artery can still be abnormal. Absolute-dimension criteria under-recognize disease compared with z-scores.
• Perivascular brightness is not a diagnostic sign.
• Regression is not recovery — luminal normalization can coexist with abnormal vessel wall, reduced flow reserve, and stenosis.
• Distal segments are seldom seen well. When high-risk abnormalities are present, or windows are limited, use CT, MRI, or angiography.
• The first echo isn’t the last. Aneurysms can appear and reach their maximum size after a normal baseline study, which is why the 1 to 2 week and 6 to 8 week studies matter.

Clinical Importance

The coronary arteries are a small target with large consequences. In the congenital setting, the decisive skill is disciplined technique — high-frequency imaging, cine loops, several views, and color Doppler proof of antegrade flow from the aortic sinus into each artery — because 2D imaging alone can be falsely reassuring. In Kawasaki disease, the decisive skill is structure: measure the same segments in the same places, convert to z-scores, and repeat the study on schedule. Both depend on remembering that echo can rule some diagnoses in with confidence and others out only provisionally, and that CT, MRI, angiography, and stress imaging have a defined role beyond it.