Systemic Arteriovenous Malformations
Systemic arteriovenous malformations in children result from errors in the formation and development of the normal arterial–capillary–venous connections that occur very early in gestation. They can arise anywhere in the body but are most commonly seen in the brain. Most arteriovenous malformations are clinically silent, with symptoms developing in adulthood. There are rare examples of arteriovenous malformations presenting at birth with life-threatening high output heart failure. A large arteriovenous malformation should be included in the differential diagnosis of an infant presenting with severe congestive heart failure.
Vein of Galen malformations are the most common form of symptomatic cerebrovascular malformation in neonates and infants. The clinical manifestations demonstrated early in life reflect both the large size and low resistance of the vascular malformation. There typically is torrential blood flow into the malformation, leading to increased cardiac output, increased cardiac chamber volumes, and congestive heart failure. Blood flow to the body is reduced and may result in ischemic multisystem organ failure, lactic acidosis, and death. Along with signs of severe congestive heart failure, unique physical findings include the presence of a cranial bruit, often heard over the posterior cranium, as well as bounding carotid pulses. The neonate who presents with a vein of Galen malformation may also be cyanotic, related to patency of the ductus arteriosus and elevated pulmonary vascular resistance.
The clinical signs and symptoms of a neonate or infant with a vein of Galen malformation mimic those of a patient with critical congenital heart disease, leading to the request for echocardiography. Although structural anatomy is typically normal, there are distinct anatomic and hemodynamic echocardiographic features that should lead the echocardiographer to suspect the diagnosis.
Cardiac output can be over twice normal in these patients, resulting in enlargement of all cardiac chambers. Increased blood flow into the vein of Galen malformation may lead to dilatation of the ascending aorta and carotid arteries (Fig. 26.1A). The left subclavian artery and descending aorta are typically of normal caliber but may appear relatively small, suggestive of aortic coarctation. Because coarctation of the aorta has been described with increased frequency in patients with vein of Galen malformations, careful two-dimensional imaging of the aortic arch is critical. Color Doppler interrogation of the descending thoracic aorta reveals marked holodiastolic retrograde flow into the cerebral circulation (Fig. 26.1B, Video 26.1); this is confirmed with pulsed Doppler examination of the descending aorta, which also reveals very limited antegrade systolic flow to the body (Fig. 26.1C). Increased systemic venous return from the malformation leads to dilatation of the superior vena cava (Fig. 26.2A, Video 26.2), with abnormal high-velocity continuous flow identified by pulsed and color Doppler (Fig. 26.2B). Increased frequency of sinus venosus atrial septal defects has also been reported, with some postulating the increased superior caval return in utero may interfere with absorption of the right horn of the sinus venosus into the right atrium.
The newborn with a vein of Galen malformation demonstrates unique hemodynamics secondary to elevation in pulmonary vascular resistance and the presence of a patent ductus arteriosus and patent foramen ovale. The elevated pulmonary resistance in combination with the low systemic resistance from the malformation promotes right-to-left ductal shunting. Decreased flow into the pulmonary arteries and left atrium combined with increased flow in the superior vena cava and right atrium promotes right-to-left atrial level shunting as well. The right heart structures are often markedly enlarged, with right ventricular dysfunction, tricuspid insufficiency, and Doppler evidence of systemic pulmonary artery hypertension.
Although much less common, the infant with a large hepatic arteriovenous malformation may present in a similar fashion. The echocardiographic findings are a bit different, as the site of the malformation in the lower body alters the distribution of blood flow. Increased blood flow into the liver may lead to dilatation of the descending aorta prior to the origin of the celiac axis. Doppler in the descending thoracic aorta will reveal augmented systolic antegrade flow, with persistence of antegrade flow throughout diastole. Increased systemic venous return from the malformation will lead to dilatation of the inferior vena cava. Again, because cardiac output is often twice normal, all of the cardiac chambers may appear dilated.
FIGURE 26.1. Suprasternal notch imaging in a newborn with a large vein of Galen malformation. A: Long-axis image reveals dilatation of the ascending aorta and brachiocephalic vessels, with mild distal transverse arch hypoplasia. There is no posterior shelf seen in the descending thoracic aorta. B:Color Doppler interrogation of the descending thoracic aorta demonstrates marked retrograde diastolic flow (red signal) into the cerebral circulation. C: Pulsed Doppler with the sample volume positioned in the descending aorta confirms dramatic retrograde flow from the aorta into the cerebral circulation, with little antegrade systolic flow to the body.
Before the advent of sophisticated imaging techniques and endovascular therapies, the mortality associated with a large systemic arteriovenous malformation in the newborn was extremely high, with some series quoting only 50% survival at 1 month of age. As interventional therapy has progressed with catheter-based occlusion of the malformation, survival has improved. Initial medical management of the congestive heart failure often helps alleviate symptoms, so that direct therapy of the malformation can be delayed until an older age.
Pulmonary Arteriovenous Malformations
Pulmonary arteriovenous malformations are caused by abnormal communications between pulmonary arteries and pulmonary veins. They are commonly congenital in nature, are often multiple, and have a tendency to involve the lower lobes. It is estimated that about 70% of pulmonary arteriovenous malformations occur in patients with hereditary hemorrhagic telangiectasia, also known as Rendu-Osler-Weber disease. Hereditary hemorrhagic telangiectasia is an autosomal dominant disorder characterized by arteriovenous malformations in the skin, mucous membranes and visceral organs. Pulmonary arteriovenous malformations are rarely identified in infancy or childhood, with a peak incidence in the fourth and fifth decades.
FIGURE 26.2. Subcostal sagittal view in a newborn with a large vein of Galen malformation. A: Aneurysmal dilatation of the superior vena cava is seen as it enters the right atrium. B: Pulsed Doppler with the sample volume positioned in the superior vena cava reveals abnormally high velocities with a continuous flow pattern.
Pulmonary arteriovenous malformations create a right-to-left shunt from the pulmonary arteries to the pulmonary veins, leading to systemic arterial desaturation. Because pulmonary vascular resistance is also low, flow into the malformation is not torrential; therefore cardiac output is typically normal or only mildly elevated. Most patients develop symptoms of dyspnea and cyanosis later in life, although life-threatening presentations including severe hemoptysis have been described. The intrapulmonary right-to-left shunt also may facilitate passage of emboli into the cerebral circulation, placing patients at risk for stroke and brain abscess. Presentation early in life is rare, but the classic triad of cyanosis, tachypnea, and an audible bruit over the lung fields in an infant should raise the question of a pulmonary arteriovenous malformation.
Pulmonary arteriovenous malformations can also be acquired. In the pediatric age group, acquired pulmonary arteriovenous malformations have been well described in the patient with single-ventricle physiology palliated with a cavopulmonary anastomosis. The development of pulmonary malformations appears to be related to exclusion of hepatic venous blood from the pulmonary circulation, supported by evidence that these malformations regress after completion of the Fontan operation when hepatic venous blood is again directed into the pulmonary circulation. Acquired pulmonary arteriovenous malformations also occur in the setting of mitral stenosis, chronic liver disease, schistosomiasis, trauma, and metastatic thyroid carcinoma.
Although the diagnosis of pulmonary arteriovenous malformations can be made with use of many different imaging modalities, contrast echocardiography has become the preferred tool for screening and diagnosis, as it is readily available and noninvasive. The technique involves injection of 5 to 10 mL of agitated saline into a peripheral vein, while simultaneously imaging the heart with two-dimensional echocardiography. The agitated saline contains microbubbles, which are easily visualized by echocardiography because of their echo-reflectivity. In the patient with normal intracardiac anatomy, no intracardiac or intrapulmonary shunt, and normal systemic venous drainage, the microbubbles quickly appear in the right heart, with gradual dissipation as the bubbles are cleared by the pulmonary capillary circulation, never appearing in the left heart (Video 26.3). In the patient with a patent foramen ovale or atrial level shunt, contrast can be visualized in the left atrium within one cardiac cycle of its appearance in the right atrium; the sensitivity of this procedure can be enhanced with the patient performing a Valsalva maneuver, which raises right atrial pressure to facilitate right-to-left atrial shunting. In the patient with a pulmonary arteriovenous malformation, contrast is also visualized in the left atrium, as the microbubbles bypass the pulmonary capillaries through the abnormal arteriovenous channels. However, as opposed to the atrial level shunt, there is a delay of about three to eight cardiac cycles before the contrast appears in the left atrium, because it takes time for the microbubbles to traverse the pulmonary vascular bed.
Contrast echocardiography in the patient with a cavopulmonary anastomosis is also helpful in the diagnosis of pulmonary arteriovenous malformations but is not diagnostic (Video 26.4). In this patient group, the superior vena cava is excluded from the atria and is directly connected to the pulmonary arteries. Therefore, injection of agitated saline into an upper extremity peripheral vein should not produce contrast echoes within the right or left atria, as they should be cleared by the pulmonary capillary bed. If contrast echoes are visualized within the heart, pulmonary arteriovenous malformations need to be considered; however, venovenous collaterals will also bypass the pulmonary vasculature, leading to return of microbubbles to the atria via the abnormal venous channels. It is critical to differentiate pulmonary arteriovenous malformations from venovenous collaterals in these patients, because both can result in marked cyanosis, yet treatment is completely different. Angiography is a better way to evaluate the venous collaterals and, if demonstrated, permits catheter-based interventional closure of the collaterals.
Pulmonary arteriovenous malformations can be treated with catheter embolization or surgical resection. Close observation may be reasonable in the asymptomatic patient with only mild desaturation. In the patient with acquired pulmonary arteriovenous malformations, treatment of the underlying disease process will often cause regression of the lesions. Incorporation of the hepatic circulation into the pulmonary vascular bed is the treatment of choice in the patient with pulmonary arteriovenous malformations after cavopulmonary anastomosis.
CORONARY ARTERY ABNORMALITIES
Isolated coronary artery anomalies have been described in approximately 1% to 5% of patients undergoing coronary angiography and approximately 0.3% of patients at autopsy. Many patients are asymptomatic, but signs of myocardial ischemia may present in childhood. Although visualization of coronary artery anatomy has traditionally been obtained using invasive procedures such as coronary angiography, transthoracic echocardiography has become the most important screening procedure for detection of these abnormalities in the pediatric population.
It is worthwhile considering coronary anomalies in children under three classifications: (a) anomalies involving obligatory ischemia, such as anomalous origin of the left coronary artery from the pulmonary artery, where clinical symptoms are frequent and presentation during childhood with evidence of myocardial dysfunction and injury is common; (b) anomalies involving exceptional ischemia, such as anomalous origin of a coronary artery from the opposite sinus of Valsalva, where ischemia can occur under severe clinical stress but there is no evidence of myocardial dysfunction at rest; and (c) anomalies involving absent ischemia, such as coronary artery fistulas, with minimal risk of myocardial dysfunction in childhood.
Transthoracic echocardiographic imaging of coronary artery origins is critical and should be a part of the routine complete examination in every child. This is usually best accomplished from parasternal short-axis imaging, where both origins can be visualized by scanning superior to the aortic valve with careful interrogation of the aortic sinuses. The left coronary generally rises at approximately 4 o’clock, if you consider the aortic root as a clock face, and the right coronary artery arises at approximately 12 o’clock (Fig. 26.3). Rotation of the transducer clockwise from the standard short-axis position frequently improves imaging of the length of the main coronary artery and its early branches, the left anterior descending coronary artery and the left circumflex coronary artery. In contrast, counterclockwise rotation from the standard short-axis view can facilitate imaging of the origin of the right coronary artery. Color Doppler flow interrogation of the left and right main coronaries is also important, as documentation of direction and timing of flow is also helpful in diagnosing anomalies (as described later). Normal coronary artery flow is predominantly diastolic, because that is the time that aortic pressure (and thus coronary pressure) exceeds ventricular pressure. To see these coronary flow signals, which are usually low-velocity, the Nyquist limit of the color Doppler map must be decreased to 20 to 40 cm/s. Many machines allow presets for coronary imaging to facilitate altering the setup to better identify coronary flow signals. Using the highest frequency transducer that allows adequate penetration is also important in coronary imaging, because fine-detail resolution is required to optimally image these small structures.
Anomalous Origin of a Coronary Artery from the Pulmonary Artery
Anomalous origin of the left coronary artery from the pulmonary artery (ALCAPA) is a rare congenital abnormality, occurring in approximately 1 in 300,000 children. The anomalous left coronary usually arises from the main pulmonary artery, although anomalous origin from the right pulmonary artery has also been described. The timing of presentation during childhood is quite variable and is related to adequacy of collateralization from the right coronary artery. In fetal life, the pressure in the pulmonary artery is high, allowing antegrade perfusion of the left coronary artery. However, shortly after birth, when pulmonary artery pressures fall, the left coronary artery system becomes dependent on the development of right coronary artery collaterals to supply the left ventricular myocardium. When few collaterals to supply left coronary flow are present, there is significant myocardial ischemia in infancy, leading to symptoms such as irritability, tachypnea, diaphoresis, and congestive heart failure. The clinical picture mimics the presentation of a patient with idiopathic dilated cardiomyopathy. In the patient with adequate right coronary collaterals, presentation is often delayed until adolescence or young adulthood, because myocardial function can be well preserved. Sudden cardiac death can occur in this age group, particularly with exercise, and is likely related to limited coronary reserve with development of pathologic ventricular arrhythmias during times of increased myocardial demands.
FIGURE 26.3. Short-axis images of the normal coronary origins from the aortic root (Ao). A: Normal origins of the left main coronary artery (LCA) from the left sinus of Valsalva and right coronary artery (RCA) from the right sinus of Valsalva are well visualized. With clockwise rotation of the probe from this position in B, a longer length of the left main coronary and its bifurcation into the left anterior descending and circumflex branches are visualized. Finally, color Doppler assessment of flow direction in the coronaries can obtained (C) by lowering the color Nyquist limit (in this case to 23 cm/s) to visualize the low-velocity diastolic antegrade flow in the left main coronary seen as a red flow signal coursing appropriately toward the transducer and away from the Ao.
Prospective identification of ALCAPA using echocardiography has been well described, and this technique should be diagnostic in most patients. Two-dimensional imaging may provide direct visualization of the anomalous coronary insertion into the pulmonary artery from parasternal long- and short-axis imaging, with the coronary usually inserting into the posterior and leftward aspect of the main pulmonary artery (Fig. 26.4, Video 26.5). The anomalous left coronary artery frequently courses close to its normal site of origin near the left sinus of Valsalva, so recognition of associated echo findings is often critical to the diagnosis (Table 26.1). The right coronary artery is dilated because of the obligate collateral circulation needed to perfuse the left ventricular myocardium, but this may not be striking in the infant with limited collateralization who presents early with a severe dilated cardiomyopathy (Video 26.6). Dramatic right coronary dilatation and tortuosity are characteristic of the older asymptomatic child (Fig. 26.5). In addition, the older patient is likely to have prominent coronary collaterals that can be identified using color Doppler flow mapping as abnormal diastolic flow signals within the myocardium of the ventricular septum (Fig. 26.6, Video 26.7A,B).
FIGURE 26.4. Two-dimensional image of anomalous insertion of the left main coronary artery into the posterior aspect of the proximal main PA from a parasternal short-axis view in a four-month-old infant with anomalous left coronary artery from the pulmonary artery (PA). The left anterior descending (LAD) and circumflex (Cx) arteries are both seen entering the PA through a short left main coronary segment, clearly a long distance from the normal entrance into the aortic root (Ao).
FIGURE 26.5. Short-axis image of the origin of the right coronary artery (RCA) in a 10-year-old child with anomalous origin of the left coronary from the pulmonary artery. The right coronary arises appropriately from the anterior aspect of the aorta (Ao) and is markedly dilated (arrows) because of the increased flow into that coronary, which measured 5.6 mm in diameter proximally.
Because the anomalous left coronary artery is perfused retrograde from the right coronary artery collaterals, identification of retrograde filling of the left coronary is critical for diagnosis (Fig. 26.7, Video 26.8). This can be accomplished by documenting direction of flow in the left main coronary artery using color or spectral Doppler, with the expectation that appropriate flow will progress away from the aortic root (usually seen as a red Doppler signal in the normal patient because the left coronary arises from the more posteriorly positioned left sinus and courses anteriorly toward the transducer from parasternal windows). Careful screening for diastolic flow signals in the main pulmonary artery by color Doppler is also important (Video 26.9). Mitral valve abnormalities are variable, but fibrotic changes of the chordae and papillary muscles secondary to chronic ischemia are common and can lead to the development of mitral valve prolapse and mitral insufficiency (Fig. 26.8, Video 26.10). Left ventricular dysfunction should always increase suspicion of ALCAPA, especially when endocardial fibrotic changes are also seen, but left ventricular function can be well preserved, particularly in older children with well-developed collaterals (Video 26.11).
FIGURE 26.6. Short-axis image of color Doppler interrogation of the ventricular septum shows septal coronary collateral flow in the same 10-year-old child as Figure 26.5. The child was initially referred for evaluation of a heart murmur and was found to have anomalous origin of the left coronary from the pulmonary artery. A low-velocity linear diastolic flow signal is seen in the ventricular septum (arrows). The color Doppler and spectral Doppler timing of flow in diastole help differentiate this septal collateral from a ventricular septal defect, which is generally characterized by a high-velocity systolicflow signal. The identification of this septal flow signal was the initial echo finding that led to the diagnosis of ALCAPA in this boy.
FIGURE 26.7. Short-axis image using color Doppler to identify retrograde flow in the left anterior descending coronary artery (LAD) in the same four-month-old infant with anomalous left coronary artery from the pulmonary artery shown in Figure 26.4. Flow in the LAD is blue as it moves away from the transducer towards the pulmonary artery (PA), which is abnormal because it should be flowing away from the aortic root (red Doppler signal) rather than towards it. A turbulent flow signal (arrows) is also seen in the pulmonary artery as the anomalous left coronary artery empties into the low-pressure pulmonary artery.
Surgery to reconnect the left coronary artery with the aortic root is indicated in all patients when this lesion is identified, even in the patient with good left ventricular function, to normalize perfusion to the left coronary bed. Initial surgical techniques involved ligation of the anomalous coronary to prevent continued “steal” of left coronary flow into the pulmonary artery, but this did not alter left ventricular dependence on right coronary collateral circulation for left coronary artery perfusion and resulted in significant surgical and late mortality. More recently, direct coronary reimplantation into the aorta or creation of an intrapulmonary tunnel that connected the aorta with the anomalous coronary have been used to provide antegrade flow from the aorta into the left coronary system. Imaging of the left main coronary origin and course after reimplantation should be obtained by postoperative echocardiography with documentation of laminar antegrade flow from the aortic root into the coronary bed by color Doppler. Serial evaluation of left ventricular function is important after surgery, because revascularization frequently results in dramatic remodeling of the left ventricle, with progressive normalization of function. Because mitral papillary muscle ischemia is common with ALCAPA, recovery of mitral function is variable after surgery and frequently does not correlate with recovery of left ventricular function. Late reoperation for mitral valve repair or replacement is required in a minority of patients with chronic severe insufficiency.
FIGURE 26.8. Apical four-chamber (A) and subcostal four-chamber (B) images of an infant with dilated cardiomyopathy and anomalous origin of left coronary artery from the pulmonary artery. These images demonstrate marked left atrial (LA) and left ventricular (LV) chamber dilatation with echo bright fibrotic changes of the mitral papillary muscles (arrows), consistent with chronic endocardial ischemia.
Anomalous Aortic Origin of a Coronary Artery from the Opposite Sinus of Valsalva
Anomalous origin of a coronary artery (AAOCA) from the opposite sinus of Valsalva has been associated with myocardial ischemia, ventricular arrhythmias, and sudden death, particularly when the anomalous coronary (left coronary from the right sinus or right coronary from the left sinus) courses in between the great arteries (Fig. 26.9).The anomalous coronary can arise from the opposite sinus and course anterior or posterior to the great arteries rather than between them, but the risk of coronary complications appears to be much lower. Although AAOCA from the noncoronary or posterior sinus of Valsalva has also been described, it is quite rare and not generally associated with myocardial ischemia or sudden death. When the anomalous coronary is interarterial, it can course within the myocardial sulcus between the great arteries (described as an “intramyocardial” or “intraconal” course between the great arteries) or within the anterior wall of the aorta between the great arteries (described as “intramural”).
Anomalous aortic origin of the left coronary artery from the right sinus of Valsalva with the anomalous coronary coursing in between the great arteries is quite rare (with an estimated incidence of 0.03% to 0.05%), but is clearly associated with sudden cardiac death. The majority of patients who died suddenly with this anomaly had the sudden death episode during or shortly after vigorous exertion. More important, the highest-risk groups for exercise-induced sudden cardiac death are children and adolescents, and the majority are asymptomatic without previous complaints of chest pain, palpitations, syncope, or an identified arrhythmia. Sudden death in older patients was much less common, and cardiac death in the older group is generally associated with atherosclerotic disease. The lower risk of sudden death in older patients with this anomaly is likely related to the fact that they rarely participate in high-intensity competitive sports. Anomalous aortic origin of the right coronary artery from the left sinus of Valsalva is more common (estimated incidence of 0.1%) and has also been associated with exercise-induced sudden cardiac death in children and young adults. Although anomalous aortic origin of either coronary artery from the opposite sinus with an interarterial course carries a risk of sudden cardiac death, particularly for the young athlete, assessment of that risk in an individual patient remains difficult and controversial, because symptoms are rare and provocative stress testing is typically normal. Finally, a subset of patients present with sudden death in infancy, related to severe coronary ostial stenosis at the origin of the anomalous coronary.
FIGURE 26.9. Schematic diagram of the two forms of anomalous aortic origin of a coronary from the wrong sinus associated with myocardial ischemia—anomalous origin of the left coronary artery from the right sinus of Valsalva (A) and anomalous origin of the right coronary artery (RCA) from the left sinus of Valsalva (B). In each case, the anomalous coronary can be seen coursing between the aorta and pulmonary artery (PA). With anomalous origin of the left coronary, the left main coronary artery (LMCA) arises from the right aortic sinus (R) and passes between the great arteries before dividing into its two usual branches—the left anterior descending (LAD) and left circumflex (LCx) coronary arteries. With anomalous origin of the right coronary, the right coronary artery (RCA) arises from the left aortic sinus (L) and passes between the great arteries before coursing in its usual distribution.
The mechanisms that lead to myocardial ischemia in the patient with AAOCA from the opposite sinus with an interarterial course between the pulmonary and aortic roots are unclear, but several theories have been proposed. The ostium of the anomalously arising coronary artery is frequently slitlike, likely compromising flow reserve. In addition, the anomalous coronary artery usually arises at an acute angle from the aorta, rather than perpendicularly, and this may alter flow patterns into that coronary artery bed. Finally, it has been hypothesized that the interarterial course places the anomalous coronary at risk of compression between the great arteries. This seems unlikely given the low pressure in the pulmonary artery in normal individuals, even during exercise. The ischemia is more likely due to deformation of the anomalous coronary within the aortic wall during periods of arterial hypertension with exercise, particularly in patients with an intramural course. Because wall tension is determined by the radius of a vessel, the aorta will have greater wall tension than the intramural coronary within its wall, resulting in deformation of the coronary and diminished cross-sectional area. As aortic wall tension increases with increasing aortic pressure during exercise, the anomalous coronary becomes flattened and coronary reserve is reduced to a point where myocardial oxygen requirements are not met.
Transthoracic echocardiography has become an important noninvasive tool for prospectively identifying anomalous aortic origin of the left coronary from the right sinus of Valsalva and anomalous aortic origin of the right coronary from the left sinus of Valsalva. Identification of either anomaly requires focused two-dimensional and color Doppler imaging of the coronary arteries. Intraconal anomalous coronary arteries from the opposite sinus can be seen running within the muscle immediately behind the right ventricular outflow tract between the great arteries, and they frequently stand out prominently within the muscle (Fig. 26.10, Video 26.12A,B). This form is very rare and appears to occur almost exclusively with anomalous origin of the left coronary from the right sinus. It is usually characterized by a single coronary ostia from the right sinus with early bifurcation into the left and right coronary branches (Fig. 26.11, Video 26.13). The intraconal course appears to carry less risk for coronary complications than the intramural course of anomalous left coronary from the right sinus.
FIGURE 26.10. Short-axis image through the aortic root in a patient with anomalous aortic origin of the left coronary artery from the right sinus of Valsalva and an intraconal course of the anomalous coronary. The anomalous left coronary artery can be seen coursing between the aorta (Ao) and right ventricular outflow tract (RVOT) within the myocardial wall before bifurcating into the left anterior descending (LAD) and circumflex (Cx) branches. No coronary artery is seen arising from the left coronary sinus.
The intramural course of an anomalous coronary from the opposite sinus is much more common but can be more difficult to detect, particularly because the coronary exits the aortic wall from the usual or appropriate sinus of Valsalva (Fig. 26.12, Videos 26.14A and 26.15A). Interestingly, the intramural segment in patients with anomalous origin of the left coronary from the right sinus is longer and usually traverses at least half of the right sinus before exiting the aortic wall from the left sinus (Fig. 26.13, Video 26.15A-C). In contrast, the intramural form of anomalous right coronary from the left sinus is usually characterized by a shorter (2 to 3 mm) intramural segment from the left sinus with the anomalous coronary ostia arising adjacent to the commissure between the right and left cusps (Fig. 26.14, Video 26.16A,B). Color Doppler imaging is critical in making this diagnosis, as it can help identify that intramural segment. In many cases, the intramural segment of the anomalous coronary is often only suspected after color Doppler interrogation of the aortic root identifies an abnormal color signal within the anterior aortic wall (Figs. 26.15 and 26.16, Videos 26.14B, 26.15C, and 26.16B). Color Doppler is also useful in diagnosing AAOCA from the opposite sinus with an intramural course, because the technique can give the additional information of direction of flow in the intramural segment. This helps in differentiating whether the anomalous coronary arises from the right or left sinus. When the left coronary arises anomalously from the right sinus, a blue Doppler signal will be seen in the intramural segment as flow moves away from the right sinus toward the more posteriorly positioned left sinus (Figs. 26.15C and 26.16B, Videos 26.14B and 26.15C). This is the opposite of anomalous origin of the right coronary from the left sinus, where a red Doppler signal will be seen in the intramural segment as flow moves toward the right sinus from its origin in the left sinus (Fig. 26.16C, Video 26.16B).
FIGURE 26.11. Short-axis image in a patient with anomalous aortic origin of the left coronary artery from the right sinus of Valsalva and an intraconal course of the anomalous coronary. There is a single coronary origin from aorta (Ao) arising from the right sinus of Valsalva and immediately bifurcating into the right and left main coronary arteries (arrows). Again, no coronary artery is seen arising from the left aortic sinus.
FIGURE 26.12. Short-axis image in a patient with anomalous aortic origin of the left coronary artery from the right sinus of Valsalva and an intramural course of the anomalous coronary. The left coronary artery appears to be exiting the aorta (Ao) appropriately from the left sinus of Valsalva (large arrow); however, on closer inspection, the anomalous intramural segment of the proximal left coronary can be appreciated coursing within the anterior aortic wall (small arrows).
FIGURE 26.13. Schematic diagram of anomalous aortic origin of the left coronary artery (LCA) from the right sinus of Valsalva with an intramural course between the great arteries. The left main coronary artery (LMCA) arises from the right aortic sinus (R) and passes between the great arteries through a long intramural segment before exiting the aortic wall from the left sinus. The exit site from the aortic wall in the left sinus is usually more anterior (nearer the commissure between the left and right cusps) than the normal or usual origin. It then divides into its two usual branches—the left anterior descending (LAD) and left circumflex (LCx) coronary arteries.
FIGURE 26.14. Schematic diagram of anomalous aortic origin of the right coronary artery (RCA) from the left sinus of Valsalva with an intramural course between the great arteries. The RCA arises from the left aortic sinus (R) and passes between the great arteries through an intramural segment before exiting the aortic wall from the right sinus. In contrast to anomalous origin of the left coronary from the right sinus with an intramural course, the origin of the anomalous right coronary is usually near the commissure between the left and right cusps (within 2 to 3 mm) with a clearly separate origin and short intramural course, and so it can sometimes be difficult to determine if the coronary is actually arising from the left or right sinus. It then courses through the anterior aortic wall to exit the aorta near its usual site of origin in the right sinus. N, noncoronary sinus.
Other transthoracic windows can also provide imaging evidence that a coronary has an anomalous origin from the aortic root. From the parasternal long-axis view, the anomalous coronary running between the great arteries can be seen as a discrete circle anterior to the aortic root as an initial clue (Fig. 26.17). In addition, in children who undergo high-quality subcostal imaging, scanning from the aortic root more anteriorly to the pulmonary root can identify a length of the anomalous coronary running between the great arteries (Fig. 26.18, Video 26.17).
FIGURE 26.15. Short-axis imaging in a patient with anomalous aortic origin of the left coronary artery from the right sinus of Valsalva and an intramural course of the anomalous coronary. A: Two-dimensional image shows the anomalous left main coronary artery running intramural within the anterior aortic wall (arrows) between the aorta (Ao) and pulmonary artery before exiting the wall in the left sinus of Valsalva. Note the long length of the left coronary within the anterior wall as it courses along the right sinus. B: Color Doppler imaging shows the linear diastolic flow of the anomalous coronary within the anterior aortic wall (arrows); the blue signal confirms anomalous coronary flow away from the transducer, consistent with the coronary originating from the right sinus and coursing towards the more posteriorly positioned left sinus. Note the low-velocity Nyquist limit (32 cm/s) needed to visualize the low-velocity coronary flow signal.
FIGURE 26.16. Short-axis imaging in a patient with anomalous aortic origin of the right coronary artery from the left sinus of Valsalva and an intramural course of the anomalous coronary. A: position of the aortic sinuses at the level of the aortic valve; the commissure between the right (R) and left (L) cusps is well visualized (arrow). The noncoronary sinus (N) is seen posteriorly. B: Angling the transducer more superiorly above the valve leaflets, the anomalous right coronary artery can be seen arising from the left sinus of Valsalva near the origin of the left main coronary artery (LCA) and coursing intramural within the anterior aortic wall (arrows) between the aorta and the right ventricular outflow tract towards the right sinus of Valsalva. Comparing A and B, it is easy to appreciate that the anomalous coronary originates close to the commissure but clearly from the left sinus. C: Color Doppler imaging shows the linear diastolic flow of the anomalous coronary within the anterior aortic wall (arrows) between the aorta (Ao) and pulmonary artery (PA); the red signal confirms anomalous coronary flow towards the transducer, consistent with the coronary originating from the left sinus and coursing towards the more anteriorly positioned right sinus. Again, note the low-velocity Nyquist limit (12 cm/s) needed to visualize the low-velocity coronary flow signal.
FIGURE 26.17. Parasternal long-axis image through the left ventricle (LV) in a patient with anomalous aortic origin of a coronary from the opposite sinus with an intraarterial course. The anomalous coronary is seen coursing anterior to the aorta (Ao) between the great arteries as a discreet circle (arrow); this may be the first clue that there is an anomalous coronary, as visualization of a coronary anterior to the aorta from this view is never seen with normal coronary origins.
Transesophageal echocardiography has also been very useful in identifying or confirming anomalous aortic origin of a coronary from the opposite sinus with an interarterial course, again particularly when that course is intramural. Imaging of the aortic root with the multiplane sector at 25 to 40 degrees in the standard transesophageal position frequently provides excellent imaging of the coronary anatomy, and the intramural segment is usually well delineated by both imaging and color Doppler interrogation (Fig. 26.19, Video 26.18). Intravascular ultrasound has documented both coronary hypoplasia and localized systolic lateral compression of the intramural segment of anomalous coronaries that run within the aortic wall. Not surprisingly, this degree of compression appears to have individual variations that likely explain the individual and unpredictable responses to exercise in this patient group. The coronary narrowing is exacerbated by pharmacologic challenge that likely mimics exercise conditions. In addition, the length of the intramural segment may play a role in development of ischemia, as longer segments may accentuate the degree of stenosis caused by luminal distortion during exercise (which may explain the perceived higher risk of anomalous origin of the left coronary from the right sinus). Finally, risk is almost certainly influenced by the precipitating conditions (usually vigorous exercise) at the time of the ischemic insult as well as the location/amount of myocardium supplied by the anomalous coronary. Again, there is currently no effective technique for quantifying these risks.
FIGURE 26.18. Subcostal image of a child with anomalous aortic origin of the left coronary from the right sinus of Valsalva and an interarterial course. This image demonstrates the anomalous coronary (arrows) immediately behind the pulmonary artery as the transducer is angled anteriorly from the left ventricle (LV) toward the right ventricular (RV) outflow. A coronary artery should never be imaged in this plane when there are normal origins.
FIGURE 26.19. Transesophageal echocardiographic image from a mid-esophageal short-axis window through the aortic root in a patient with anomalous aortic origin of the right coronary artery from the left sinus of Valsalva and an intramural course of the anomalous coronary. The anomalous right coronary artery can be seen arising from the left sinus of Valsalva (L) and coursing intramural within the anterior aortic wall (arrows) between the aorta and the right ventricular outflow tract towards the right sinus of Valsalva (R). The noncoronary cusp (N) is seen posteriorly.
Surgical repair of AAOCA has generally been reserved for patients with known symptoms of myocardial ischemia. Multiple surgical techniques have been used, including coronary bypass graft placement, patch enlargement of the anomalous coronary origin, reimplantation of the anomalous coronary to the appropriate sinus, and unroofing of the intramural segment of the anomalous coronary. The unroofing procedure has several advantages over other coronary repair techniques and is ideally suited for the patient with an intramural course of the anomalous coronary. The management of asymptomatic patients with AOCA remains controversial.
Coronary Artery Fistulas
Congenital coronary artery fistulas (CAFs) involve an abnormal communication between a coronary artery and a chamber of the heart or any segment of the systemic or pulmonary circulation. The origin of the coronary is normal; it is the termination or emptying segment of the coronary that is pathologic. The majority of fistulas arise from the right coronary artery (60%) and empty into the right side of the heart (90%). The most frequent sites of termination of a CAF are the right ventricle, right atrium, coronary sinus, and pulmonary vascular bed. Coronary fistulous communications can be seen in the context of other congenital cardiac anomalies, most frequently pulmonary atresia with intact ventricular septum. The pathophysiology of CAF is the steal of coronary blood flow related to runoff from the coronary fistula into a low-pressure receiving cavity; this puts the myocardium beyond the site of the fistula at risk for ischemia because blood will preferentially empty into the low-pressure chamber. Most patients with CAF are asymptomatic in childhood and present because of a continuous murmur appreciated along the precordium. This murmur can sound similar to a patent ductus arteriosus, although its parasternal location frequently suggests a different etiology. Late complications have been described in older adults and include bacterial endocarditis, congestive heart failure, and angina.
Two-dimensional echocardiographic findings are most striking for enlargement of the coronary that supplies the fistula; this coronary can be quite dilated and tortuous (Fig. 26.20, Video 26.19). Flow into the involved coronary is easily identified by color Doppler and is associated with high-volume shunts through the fistula. The entire course of the coronary fistula can sometimes be tracked using imaging and color Doppler (Fig. 26.21, Video 26.20A,B), and the site of drainage is best identified by color Doppler because a high-velocity continuous color signal is evident where the coronary empties into the lower-pressure receiving chamber (Fig. 26.22, Video 26.21). Cardiac chamber dilatation is unusual but may be present in the patient with a large left-to-right shunt. Large-volume fistulas can demonstrate retrograde steal from the aorta during diastole by color and spectral Doppler (Fig. 26.23).
FIGURE 26.20. Parasternal short-axis image of the dilated origin of the right coronary artery (RCA) in a child with a right coronary-to-right ventricular fistula. The coronary is markedly dilated, measuring 5 mm in diameter, and tortuous (arrows) as it arises from the aorta (Ao) because of the increased flow through the fistula.
Closure of the fistula is indicated in any child with symptoms, and this can be accomplished either surgically or with interventional devices that obstruct the fistulous opening placed in the cardiac catheterization laboratory. Most children are asymptomatic, and so timing and need for fistula closure depend on the size and location of the shunt. Because the natural history of larger fistulas is to continue to dilate over time with a progressively increasing risk of thrombosis, endocarditis, and/or rupture, all except small fistulas are generally recommended for closure. Transesophageal echo guidance during surgical or device intervention can be useful in confirming successful closure.
FIGURE 26.21. Subcostal images of a coronary fistula entering the right atrium in a child with a left coronary-to-right atrial fistula. A: Fistula courses posterior to the aorta (arrows) above the left ventricle (LV) with the terminal segment of the fistula emptying into the right atrium (RA). B: With color Doppler, the turbulent flow throughout the length of the fistula as it courses towards the right atrium is well visualized (arrows).
FIGURE 26.22. Subcostal image of the coronary fistula drainage site in a child with a left coronary–to–right atrial fistula. Color Doppler of the fistula shows a turbulent jet of flow where the fistula empties into the right atrium (RA), with the jet of flow striking the atrial wall (arrows).
Coronary Artery Aneurysms
Coronary artery aneurysms are uncommon and usually acquired, with an incidence that varies from 1.5% to 5% in postmortem series (likely reflecting varying criteria in defining a coronary aneurysm). They are usually defined as an area of dilatation that is 1.5 times the size of the adjacent normal coronary segment and can be classified as saccular (ball-like with nearly equal axial and lateral diameters) or fusiform (gradual tapering of a symmetrically dilated segment on either end of the aneurysm). Diffuse dilatation of a coronary without localized enlargement is described as “ectasia.” The possible causes of coronary aneurysms are summarized in Table 26.2, but the vast majority of aneurysms seen in pediatric patients are related to Kawasaki disease.
FIGURE 26.23. Pulsed Doppler tracing in the descending thoracic aorta in a child with a large left coronary–to–right atrial fistula. Because of significant diastolic steal of flow into the coronary as it empties into the low resistance right atrium, holodiastolic retrograde aortic flow (arrows) is appreciated from the Doppler signal; this would suggest a significant volume shunt through the fistula.
Kawasaki disease is an acute febrile vasculitis of unknown etiology with potential for serious morbidity and mortality attributable to the development of coronary artery aneurysms. Although the widespread use of intravenous immunoglobulin has improved outcome, Kawasaki disease remains the leading cause of acquired heart disease among children in the United States and Japan, surpassing acute rheumatic fever.
Because there is no specific diagnostic assay for Kawasaki disease, the diagnosis is based on clinical criteria that include fever for at least 5 days and four or more of the five major clinical features (conjunctival injection, cervical lymphadenopathy, oral mucosal changes, rash, and swelling/erythema of the extremities). Cardiovascular manifestations are prominent in the acute phase of the disease, and chronic changes in the coronary arteries continue to be the leading cause of morbidity and mortality. Two-dimensional and Doppler echocardiography remains the gold standard in the cardiac assessment of children with Kawasaki disease, because it is noninvasive and has a high sensitivity and specificity for detection of proximal coronary artery abnormalities.
Complete two-dimensional and Doppler echocardiography should be performed as soon as the diagnosis of Kawasaki disease is suspected. Although the echocardiographic examination of patients with Kawasaki disease is focused on the coronary arteries, histologic evidence suggests that myocarditis is universal in the acute phase of the disease. Measurement of left ventricular dimensions and ejection fraction should be a standard part of the initial examination and should be followed serially. Pericardial effusions can also be seen but typically are not hemodynamically important. Valvar insufficiency has also been reported, so all valves should be interrogated using color Doppler. The initial echocardiographic study will serve as a baseline for longitudinal follow-up of left ventricular function and coronary artery dimensions/morphology. Although the parasternal short-axis view provides ideal images of the proximal left and right coronary arteries (Fig. 26.24A, Video 26.22), multiple imaging planes and unique transducer positions are required when trying to image all major coronary artery segments. The apical four-chamber (Fig. 26.25, Video 26.23A) and subcostal (Fig. 26.26, Video 26.23B,C) views will often provide additional information, especially when trying to visualize the mid and distal right coronary artery. Transesophageal echocardiography may optimize coronary imaging in patients with limited transthoracic windows, and especially evaluation of the proximal right and left coronary arteries.
Coronary artery aneurysm formation rarely occurs before day 10 of the illness, but subtle changes in the coronary arteries can be seen at presentation. Coronary artery dilatation often occurs in the acute phase and may be a very early marker of coronary arteritis. Criteria for diagnosis of coronary artery ectasia have been characterized and vary with patient size; aneurysms have also been classified by size, with the largest ones clearly associated with late development of coronary insufficiency and myocardial ischemia. Individual measurements of the left main coronary artery, left anterior descending coronary artery, and proximal right coronary artery should be made. Measurements should be made from inner edge to inner edge and should exclude points of branching. In the setting of incomplete Kawasaki disease, it is suggested that the echocardiogram be considered “positive” if the z-score of the left anterior descending coronary artery or right coronary artery is equal to or exceeds 2.5. Other features suggestive of Kawasaki disease include perivascular brightness and lack of tapering of the coronary arteries (Fig. 26.27A,B).
FIGURE 26.24. Short-axis image (A) through the aortic root in a child with Kawasaki disease and aneurysms in both the proximal left and right coronary arteries with angiographic correlates (B, C). The left coronary artery (LCA) aneurysm is dramatic and extends into the left anterior descending coronary with a diameter of 8.7 mm; the extent of the aneurysm is well delineated (B) by the selective left coronary angiogram (arrows). The right coronary (RCA) aneurysm also is seen proximally and measured 6 mm in diameter. The proximal and more distal RCA saccular aneurysms are well delineated by selective right coronary angiography (C, arrows). The distal RCA aneurysms are imaged by echo from apical and subcostal imaging (Figs. 26.25 and 26.26).
FIGURE 26.25. Apical image in the same child with Kawasaki disease as shown in Figure 26.24, identifying multiple aneurysms in the posterior descending branch of the right coronary artery (arrows). The scanning plane has been angled posteriorly through the right heart to visualize the atrioventricular groove behind the tricuspid valve to image this distal coronary branch, which was important in characterizing the extent of the disease. The left atrium (LA) and left ventricle (LV) are also imaged, with a pericardial effusion posteriorly as well.
In the patient with detected coronary artery aneurysms, it is important to recognize the limitations of echocardiography. The detection of coronary artery stenosis and thrombosis is much more difficult using transthoracic echocardiography; other imaging modalities may be required if ischemic disease is suspected. Evaluation of the cardiovascular manifestations of Kawasaki disease requires serial echocardiography and should be performed using equipment with appropriate transducers. In the uncomplicated case of Kawasaki disease, echocardiographic assessment should be performed at the time of diagnosis, at 2 weeks, and at 6 to 8 weeks after disease onset. If the echocardiographic findings are normal at the 8-week evaluation, further studies are unlikely to reveal any coronary artery changes.
FIGURE 26.26. Subcostal transverse image in the same child with Kawasaki disease as shown in Figures 26.24 and 26.25. Image identifies aneurysmal dilation (arrows) of the proximal right coronary artery (RCA) as it courses down the anterior right ventricle (RV) adjacent to the aorta (Ao). A cross section of the proximal left coronary aneurysm is also seen (LCA).
FIGURE 26.27. Short-axis image through the aortic root (Ao) to visualize the proximal left coronary (A) and right coronary (B) arteries in a child with Kawasaki disease. Diffuse coronary dilatation (ectasia) of both proximal branches is appreciated with a lack of the normal tapering (arrows). Although subjective, there also appears to be perivascular brightness of the tissue around the vessels, and the walls of the coronaries appear prominent. No aneurysms are seen. PA, pulmonary artery.
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1.Where are systemic arteriovenous malformations most commonly found in children?
2.Which of the following conditions do the classic triad of cyanosis, tachypnea, and an audible bruit over the lung fields in an infant indicate?
A.Patent ductus arteriosus
B.Coronary artery fistula
C.Pulmonary arteriovenous malformation
D.Coarctation of the aorta
E.Branch pulmonary artery stenosis
3.How does normal coronary artery flow occur?
A.Predominantly during diastole
B.Predominantly during systole
C.Throughout the cardiac cycle
D.With atrial contraction
E.With ventricular contraction
4.With what is the anomalous origin of the left coronary from the pulmonary artery (ALCAPA) always associated?:
A.Aortic valve regurgitation
B.Left coronary artery dilatation
C.Right ventricular dysfunction
D.Right coronary artery dilatation
E.Retrograde flow in the right coronary artery
5.Anomalous origin of the left coronary artery from the pulmonary artery can present as:
A.arrhythmogenic right ventricular dysplasia.
6.What do diastolic flow signals seen by color Doppler in the ventricular septum of a patient with anomalous origin of the left coronary artery from the pulmonary artery usually represent?
A.Coronary collaterals from the right coronary artery
C.Muscular ventricular septal defects
D.Normal flow in the left coronary artery
7.Why is mitral regurgitation commonly seen with anomalous origin of the left coronary from the pulmonary artery?
A.An anterior leaflet cleft
B.Congenital mitral valve prolapse
C.Mitral papillary muscle ischemia
D.Mitral valve endocarditis
8.What does color Doppler imaging of anomalous aortic origin of the left coronary artery from the right sinus of Valsalva with an intramural course usually signify?
A.Blue flow signal in the anterior aortic wall
B.Continuous flow signal in the main pulmonary artery
C.Diastolic flow signals in the main pulmonary artery
D.Diastolic flow signals in the ventricular septum
E.Red flow signal in the anterior aortic wall
9.Sudden death is most commonly seen as a complication of anomalous origin of a coronary artery from the aortic root when the anomalous coronary courses:
A.anterior to the great arteries.
B.between the great arteries.
C.leftward of the great arteries.
D.posterior to the great arteries.
E.rightward of the great arteries.
10.What do coronary artery fistulas most likely empty into?
1.Answer: C. Vein of Galen malformations are the most common form of systemic arteriovenous malformation in children. This is followed in frequency by AVMs of the extremity, trunk, and viscera. Key echocardiographic features of CNS malformations include marked holodiastolic retrograde flow in the descending aorta by Doppler, as well as dilatation of the superior vena cava.
2.Answer: C. Pulmonary arteriovenous malformations create a right-to-left shunt from the pulmonary arteries to the pulmonary veins, leading to systemic hypoxemia. The diagnosis should be considered in any infant with cyanosis and heart failure. A high index of suspicion is required, because contrast echocardiography is required for diagnosis. Infants with a PDA, coronary fistula, coarctation of the aorta, and branch pulmonary stenosis can have audible murmurs over the lung fields, but will not be cyanotic.
3.Answer: A. Normal coronary artery flow is predominantly diastolic, because that is the time that aortic pressure (and thus coronary pressure) exceeds ventricular pressure.
4.Answer: D. The right coronary artery is dilated because of the obligate collateral circulation needed to perfuse the left ventricular myocardium since the left coronary is connected to the low-pressure pulmonary artery. As pulmonary artery pressures drop after birth, the left coronary artery system becomes dependent on the development of right coronary artery collaterals to supply blood flow to the left ventricle, and so the right coronary artery becomes the sole source of coronary blood flow for the entire heart muscle. The aortic valve is usually normal and competent with ALCAPA, and the left coronary is usually not dilated. Right ventricular function is generally well preserved (because of normal right coronary flow) and the flow pattern in the right coronary is always antegrade.
5.Answer: B. When few collaterals from the right coronary to supply left coronary flow are present in ALCAPA, there is significant left ventricular dysfunction secondary to myocardial ischemia, leading to symptoms such as irritability, tachypnea, diaphoresis, and congestive heart failure. The clinical picture mimics the presentation of a patient with idiopathic dilated cardiomyopathy, so careful assessment of coronary origins is a critical part of the echocardiographic assessment of any child who presents with dilated cardiomyopathy. Other forms of cardiomyopathy are not associated with anomalous origin of the left coronary artery from the pulmonary artery.
6.Answer: A. The timing of presentation for anomalous origin of the left coronary artery from the pulmonary artery during childhood is quite variable and is related to adequacy of collateralization from the right coronary artery. In the patient with adequate right coronary collaterals, presentation is often delayed until adolescence or young adulthood because myocardial function can be well preserved. These prominent coronary collaterals that can be identified using color Doppler flow mapping as abnormal diastolic flow signals within the myocardium of the ventricular septum. Mitral and tricuspid regurgitation and ventricular septal defect flow occur in systole, not diastole, and left coronary flow in ALCAPA is always abnormal and retrograde.
7.Answer: C. Mitral valve dysfunction is variable, but fibrotic changes of the chordae and papillary muscles secondary to chronic ischemia are common and can lead to the development of acquired (not congenital) mitral valve prolapse and mitral insufficiency. Congenital anomalies of the mitral valve are not associated with anomalous origin of the left coronary artery from the pulmonary artery, and pulmonary hypertension rarely affects mitral valve function.
8.Answer: A. Color Doppler is useful in diagnosing anomalous aortic origin of a coronary artery from the opposite sinus with an intramural course because the technique can give the additional information of flow direction in the intramural segment. This helps in differentiating whether the anomalous coronary arises from the right or left sinus. When the left coronary arises anomalously from the right sinus, a blue Doppler signal will be seen in the intramural segment as flow moves away from the right sinus toward the more posteriorly positioned left sinus. This is the opposite of anomalous origin of the right coronary from the left sinus, where a red Doppler signal will be seen in the intramural segment as flow moves toward the right sinus from its origin in the left sinus. Abnormal flow signals in the pulmonary artery and ventricular septum are not usually seen with anomalous aortic origin of a coronary artery.
9.Answer: B. Anomalous aortic origin of a coronary artery has been associated with myocardial ischemia, ventricular arrhythmias, and sudden death, particularly when the anomalous coronary courses in between the great arteries. A coronary can also arise anomalously from the wrong sinus and course anterior or posterior to the great arteries rather than between them, but the risk of coronary complications appears to be much lower. The terms “leftward” and “rightward” are not used to describe anomalous coronary origins or course.
10.Answer: E. The most frequent sites of termination of a coronary artery fistula are the right ventricle, right atrium, coronary sinus, and pulmonary vascular bed; fistulas that empty into left heart structures are much less common.