Cardiac ischemia in children is usually not an isolated disease in an otherwise normally formed coronary artery but is part of more complex congenital or acquired diseases. Although cardiac ischemia is not a frequent occurrence, it must be recognized as a serious, life-threatening event. This article lists and characterizes major causes of cardiac ischemia in children, describes signs and symptoms of each, and provides therapeutic considerations.
Children and teenagers are frequently brought to primary care physicians with complaints of chest pain. In the minds of the patients, their parents, and their physicians, thoughts of a cardiac event with an unpleasant outcome are often conjured up in such situations. If a child experiences chest pain while he or she is on the school grounds, the teachers and school officials may become alarmed, demanding an immediate medical consultation. There is prevailing fear of sudden death or cardiac disability among lay people as well as medical professionals. This fear of chest pain in a child is triggered by our vivid experience with an adult who suffered acute coronary syndrome or news reports of a high-profile case of sudden cardiac death in a young athlete. Atherosclerotic heart disease as a basis for myocardial ischemia in children is very rare. The great majority of chest pain experienced by children and teenagers are noncardiac in origin. Cardiac ischemia in children is usually not an isolated disease in an otherwise normally formed coronary artery, but is part of more complex congenital or acquired diseases. Myocardial infarction in a child is seldom manifested as classic pressure-like angina pectoris, but may take nonspecific symptoms such as unusual irritability, nausea and vomiting, abdominal pain, shocked state, syncope, seizure, or sudden unexpected cardiac arrest. Some patients may develop silent nonfatal infarction. Although cardiac ischemia is not a frequent occurrence, it must be recognized as a serious, life-threatening event. Pediatricians must be aware of these conditions, and stand ready to take prompt and appropriate actions to avoid irreversible consequences. This article lists and characterizes major causes of cardiac ischemia in children, describes signs and symptoms of each, and provides therapeutic considerations.
Definition and background
The word ischemia is derived from two Greek roots: ischō , to keep back, plus haima , blood. Myocardial ischemia implies inadequate perfusion of the myocardium usually as a result of coronary artery obstruction anywhere along the course of the epicardial artery from the ostium in the aorta to the minute intramyocardial branches. Obstruction may be due to intrinsic narrowing of the vessel lumen due to thickening of the wall, presence of thrombus within its lumen, extrinsic compression of the vessel from a nearby structure, kinking or stretching of the artery itself, or abnormal vasoreactivity or spasm.
Typically, in a normal subject, there are two coronary arteries arising from the right- and left-facing sinuses of Valsalva. The right coronary artery (RCA) typically courses along the right atrioventricular groove adjacent to the tricuspid valve ring and reaches the posterior crux of the heart. It gives off branches sequentially to the sinus node, right atrium, right ventricle (RV), atrioventricular node, and posteroinferior wall of the left ventricle (LV) in a majority of patients (so-called right dominant pattern). The main trunk of left coronary artery (LCA) tunnels under the main pulmonary artery and, as it resurfaces, bifurcates into the left anterior descending artery (LAD) and the left circumflex artery (LCX). The LAD courses on the anterior surface of the LV along the attachment of the ventricular septum to the free wall, supplying blood to the LV anterior wall and about two-thirds of the ventricular septum. The LCX courses along the left atrioventricular groove just outside the mitral valve ring, and gives off a large branch to the lateral wall of the LV. In a minority of patients the LCX crosses the posterior crux of the heart and extends into the posterior descending artery (so-called left dominant coronary pattern).
Embryologically, primordial coronary vessels are formed by endothelial precursor cells migrating from the liver and form networks of channels along the differentiating epicardium of the heart tube. These primitive vessels penetrate into the myocardium. These ingrowing vessels merge, acquire smooth muscle coats, and transform themselves into arteries. The main right and left arterial channels eventually connect to the aorta. In normal subjects, there are no well-developed connections (collateral arteries) linking the RCAs and LCAs. Intercoronary collaterals may develop rapidly, especially in young children, when one of the major arteries is blocked by disease process.
Coronary arteries provide oxygen and fuel (in the form of glucose and free fatty acid) to actively contracting myocardial cells. Because increased tension within the ventricular walls during systole impedes blood flow, most of the coronary blood flow occurs during diastole. Thus, the aortic diastolic pressure is an important determinant of coronary perfusion. Any pathologic condition that lowers the diastolic pressure, such as aortic insufficiency or presence of an abnormal run-off from the aorta (eg, patent ductus arteriosus or arterovenous fistula) tends to have a negative impact on coronary perfusion.
Classification
Coronary artery diseases which form the basis of myocardial ischemia in children may be classified in terms of cause. Major classes include (1) congenital anomalies of the coronary arteries, (2) coronary artery complications associated with congenital heart disease, (3) coronary artery sequelae of Kawasaki disease, and (4) myocardial ischemia associated with hypertrophic cardiomyopathy ( Box 1 ).
Congenital coronary artery anomalies
Anomalous origin of LCA from the pulmonary artery (ALCAPA; Bland-White-Garland syndrome)
Origin of a coronary artery from the wrong aortic sinus with its course between the aorta and the pulmonary artery
Coronary artery complications associated with congenital heart disease
Coronary artery obstruction after arterial switch operation for d -transposition of the great arteries
Coronary artery complication after repair of tetralogy of Fallot
Coronary artery ostial stenosis associated with supravalvar aortic stenosis (Williams syndrome)
Coronary artery obstruction associated with pulmonary atresia with intact ventricular septum
Coronary artery sequelae of Kawasaki disease
Thrombotic occlusion of large coronary artery aneurysm
Coronary artery stenosis at ends of large aneurysm
Obliterative coronary arteritis without large aneurysm (rare)
Myocardial ischemia associated with hypertrophic cardiomyopathy
Myocardial ischemia associated with cocaine use
Congenital anomalies of the coronary arteries
Anomalous Origin of the Left Coronary Artery from the Pulmonary Artery (ALCAPA) or Bland-White-Garland Syndrome
This particular anomaly is most likely come to the attention of a primary care physician in an infant between a few weeks to 12 months of age ( Fig. 1 ). There are a few patients with this anomaly who remain symptom-free and survive until adulthood. The prevalence of this anomaly is 1 in 300,000 live births. The predominant symptoms in infancy include pallor, sweatiness, rapid breathing, and episodes of extreme fussiness during feedings. Given early detection and prompt referral to a tertiary care facility, this rare congenital anomaly can be surgically corrected and the patient may survive with a good quality of life. Failure to diagnose this problem on a timely manner may result in early death due to congestive heart failure. Although this condition was known to pathologists as far back as the 19th century, its first rather graphic clinical description was published by Bland and colleagues in 1933. The LCA originates from the main pulmonary artery, and follows the usual distribution and branching pattern. During the fetal life and immediate neonatal period, blood flows into the LCA in a normal forward direction owing to relatively high pulmonary artery diastolic pressure. However, after the postnatal drop in pulmonary vascular resistance, the RV can no longer generate high enough pressure to drive blood forward into the myocardium. Thus, myocardial ischemia ensues over the LCA territory. Myocardial ischemia, in turn, stimulates development of collateral arteries bridging between the RCA and the LCA. In a few exceptional patients, intercoronary collaterals develop rapidly and adequately, so that the LV myocardium remains viable. However, in a majority of patients, the LV will suffer severe ischemic damage.
Physical examination may show tachypnea, tachycardia, and pale cool and sweaty skin. One may hear distant heart tones and systolic murmur over the cardiac apex due to mitral regurgitation. The chest radiograph may show cardiomegaly with or without signs of passive pulmonary congestion. The ECG may suggest ischemic change or infarction pattern over the left anterior wall. Echocardiogram may show dilated poorly contracting LV with dyskinetic or akinetic anterolateral wall and ventricular septum. Careful color Doppler flow mapping may reveal flow in the LCA directed toward the main pulmonary artery. Cineangiography with dye injection into the ascending aorta will demonstrate opacification of a dilated RCA, which will give off collateral arteries at various points along its route to the LCA ( Fig. 2 ). The direction of the flow in the LCA is retrograde and drains into the main pulmonary artery.
Differential diagnosis of ALCAPA includes acute myocarditis, cardiomyopathy, and severe forms of left heart obstruction such as congenital aortic stenosis or coarctation of the aorta.
Management
History of episodic respiratory distress with effort such as feeding, physical findings of pallor, wheezing, tachycardia, and ECG findings of ischemic changes and chest radiograph evidence of cardiomegaly with passive congestion raise an index of suspicion for this diagnosis. Definitive diagnosis relies on imaging studies such as echocardiography or cineangiography. A 2D-echocardiographic image of the LCA alone may be misleading, because there may be false continuity between the aorta and LCA. However, with color Doppler interrogation with Nyquist limit set to a low velocity, flow signal may detect retrograde direction of LCA flow with continuity to the main pulmonary artery, which is characteristic of this lesion. The life-threatening nature of this anomaly demands judicious medical stabilization and rapid transportation to a tertiary pediatric facility, so that surgery is performed. Currently, the preferred surgical approach is removal of the ALCAPA and reimplantation into the aorta. Because of ischemic myocardial injury, the postoperative course may be quite stormy due to hypotension and frequent arrhythmia. In some patients, extracorporeal membrane oxygenator support may be necessary until LV function recovers sufficiently. After a two coronary artery system is established and the patient survives the postoperative period, his or her myocardial function may improve steadily. However, depending on the size of infarcted fibrotic segment and surrounding peri-infarct ischemic area in the myocardium, the patient must be carefully monitored for recurrent ventricular arrhythmia. A patient with a large devitalized myocardial segment forming an aneurysm is particularly vulnerable to sudden onset of ventricular tachycardia or fibrillation months or years later. These patients may require Holter monitoring and, if indicated, an implantable defibrillator.
Origin of a Coronary Artery from the Wrong Aortic Sinus with its Course Between the Aorta and the Pulmonary Artery
Unfortunately, these cardiac anomalies seldom give warnings before a catastrophic event, frequently on an athletic field. They are often diagnosed postmortem after sudden unexpected cardiac death in athletes, and are the second most frequent cause of such death behind hypertrophic cardiomyopathy. Of the two types of anomalies depicted in Fig. 3 , the origin of the LCA from the right aortic sinus is more frequently lethal. The prevalence of sudden athletic field deaths due to all causes is estimated to be 0.5 per 100,000 per year among high school age athletes in the United States.
Postmortem examinations have shown an acute angle take-off of the anomalous coronary artery with a slit-like ostium located in the inappropriate aortic sinus. The proximal course of the anomalous artery lies between the aorta and pulmonary artery. It may be intramural (within the muscular layer of the aortic wall itself) or free in the space between the great arteries. Typically no atheromatous plaques have been found. Such an anomalous coronary artery may be able to provide adequate myocardial perfusion at rest such that the patients are asymptomatic. However, during strenuous activities, because of the narrow slit-like orifice, the intramural or interarterial course of the vessel, the aberrant coronary artery may be incapable of providing coronary blood flow commensurate with the subject’s demand for increased myocardial perfusion, thus producing sudden ischemia, which in turn may lead to onset of ventricular fibrillation or cardiac standstill. Systolic engorgement of the aorta and the pulmonary artery due to increased stroke volume may further compromise the coronary artery caliber.
Management
These anomalies are rarely suspected or diagnosed in life. ECG or stress tests may not yield abnormal results. Some of the athletes have noted syncope or chest pain in the preceding 24 months of the final catastrophic event. If healthy young patients complain of such symptoms, they should be explored carefully, including imaging studies for coronary arteries first with transthoracic echocardiography specifically focused on coronary artery origins. If the patient’s body habitus does not allow clear visualization of his or her coronary arteries, multidetector CT scan will demonstrate clear images albeit at the cost of added expense and radiation exposure. Also, it is highly recommended that when an echocardiogram is ordered for a young patient for any other clinical indications, the interpreting cardiologist and the sonographer verify origins and distributions of the RCAs and LCAs. This is not yet a uniformly established standard for sonographers, but every now and then an aberrant coronary artery is incidentally discovered.
Surgical “unroofing” of the intramural coronary artery segment to move coronary orifice to a more normal position and at the same time widen the orifice area has been done successfully.
Congenital anomalies of the coronary arteries
Anomalous Origin of the Left Coronary Artery from the Pulmonary Artery (ALCAPA) or Bland-White-Garland Syndrome
This particular anomaly is most likely come to the attention of a primary care physician in an infant between a few weeks to 12 months of age ( Fig. 1 ). There are a few patients with this anomaly who remain symptom-free and survive until adulthood. The prevalence of this anomaly is 1 in 300,000 live births. The predominant symptoms in infancy include pallor, sweatiness, rapid breathing, and episodes of extreme fussiness during feedings. Given early detection and prompt referral to a tertiary care facility, this rare congenital anomaly can be surgically corrected and the patient may survive with a good quality of life. Failure to diagnose this problem on a timely manner may result in early death due to congestive heart failure. Although this condition was known to pathologists as far back as the 19th century, its first rather graphic clinical description was published by Bland and colleagues in 1933. The LCA originates from the main pulmonary artery, and follows the usual distribution and branching pattern. During the fetal life and immediate neonatal period, blood flows into the LCA in a normal forward direction owing to relatively high pulmonary artery diastolic pressure. However, after the postnatal drop in pulmonary vascular resistance, the RV can no longer generate high enough pressure to drive blood forward into the myocardium. Thus, myocardial ischemia ensues over the LCA territory. Myocardial ischemia, in turn, stimulates development of collateral arteries bridging between the RCA and the LCA. In a few exceptional patients, intercoronary collaterals develop rapidly and adequately, so that the LV myocardium remains viable. However, in a majority of patients, the LV will suffer severe ischemic damage.
Physical examination may show tachypnea, tachycardia, and pale cool and sweaty skin. One may hear distant heart tones and systolic murmur over the cardiac apex due to mitral regurgitation. The chest radiograph may show cardiomegaly with or without signs of passive pulmonary congestion. The ECG may suggest ischemic change or infarction pattern over the left anterior wall. Echocardiogram may show dilated poorly contracting LV with dyskinetic or akinetic anterolateral wall and ventricular septum. Careful color Doppler flow mapping may reveal flow in the LCA directed toward the main pulmonary artery. Cineangiography with dye injection into the ascending aorta will demonstrate opacification of a dilated RCA, which will give off collateral arteries at various points along its route to the LCA ( Fig. 2 ). The direction of the flow in the LCA is retrograde and drains into the main pulmonary artery.
Differential diagnosis of ALCAPA includes acute myocarditis, cardiomyopathy, and severe forms of left heart obstruction such as congenital aortic stenosis or coarctation of the aorta.
Management
History of episodic respiratory distress with effort such as feeding, physical findings of pallor, wheezing, tachycardia, and ECG findings of ischemic changes and chest radiograph evidence of cardiomegaly with passive congestion raise an index of suspicion for this diagnosis. Definitive diagnosis relies on imaging studies such as echocardiography or cineangiography. A 2D-echocardiographic image of the LCA alone may be misleading, because there may be false continuity between the aorta and LCA. However, with color Doppler interrogation with Nyquist limit set to a low velocity, flow signal may detect retrograde direction of LCA flow with continuity to the main pulmonary artery, which is characteristic of this lesion. The life-threatening nature of this anomaly demands judicious medical stabilization and rapid transportation to a tertiary pediatric facility, so that surgery is performed. Currently, the preferred surgical approach is removal of the ALCAPA and reimplantation into the aorta. Because of ischemic myocardial injury, the postoperative course may be quite stormy due to hypotension and frequent arrhythmia. In some patients, extracorporeal membrane oxygenator support may be necessary until LV function recovers sufficiently. After a two coronary artery system is established and the patient survives the postoperative period, his or her myocardial function may improve steadily. However, depending on the size of infarcted fibrotic segment and surrounding peri-infarct ischemic area in the myocardium, the patient must be carefully monitored for recurrent ventricular arrhythmia. A patient with a large devitalized myocardial segment forming an aneurysm is particularly vulnerable to sudden onset of ventricular tachycardia or fibrillation months or years later. These patients may require Holter monitoring and, if indicated, an implantable defibrillator.
Origin of a Coronary Artery from the Wrong Aortic Sinus with its Course Between the Aorta and the Pulmonary Artery
Unfortunately, these cardiac anomalies seldom give warnings before a catastrophic event, frequently on an athletic field. They are often diagnosed postmortem after sudden unexpected cardiac death in athletes, and are the second most frequent cause of such death behind hypertrophic cardiomyopathy. Of the two types of anomalies depicted in Fig. 3 , the origin of the LCA from the right aortic sinus is more frequently lethal. The prevalence of sudden athletic field deaths due to all causes is estimated to be 0.5 per 100,000 per year among high school age athletes in the United States.
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