Myocardial infarction (MI) in children is uncommon, but underdiagnosed. This is due to two main factors: the etiologies are varied; and the presenting symptoms are “atypical”.
Two main presentations of MI due to congenital lesions: novel and known. The novel presentation is at risk for underdiagnosis, due to its uncommonness and vague, atypical symptoms. There are usually some red flags with a careful H&P. The known presentation is a child with a history of congenital heart disease, addressed by corrective or palliative surgery. This child is at risk for expected complications, as well as overdiagnosis and iatrogenia. Risk stratify, collaborate with specialists.
Anomalous Left Coronary Artery from the Pulmonary Artery (ALCAPA) is an example of what can go wrong during fetal development: any abnormality in the number, origin, course, or morphology of the coronary arteries can present as a neonate with sweating during feeds (steal syndrome), an infant in CHF, or an older child with failure to thrive or poor exercise tolerance.
Normal coronary arteries run along the epicardial surface of the heart, with projections into the myocardium. If part of the artery’s course runs within the myocardium (i.e. the artery weaves into and/or out of the myocardium), then there is a myocardial bridge of the coronary artery. With every systolic contraction, the artery is occluded.
Although a myocardial bridge may not cause symptoms (especially at distal portions), the area it supplies is at risk.
With any minor trauma or exertion, demand may outpace supply, resulting in ischemia.
Diagnosis is made on coronary angiography.
The child with single ventricle physiology may have a Norwood procedure at birth (creation of a neoaorta, atrial septectomy, and Blalock-Taussig shunt), a Bidirectional Glenn procedure at 3-6 months (shunt removed, superior vena cava connected to pulmonary arteries), and a Fontan procedure at about 2-3 years of age (inferior vena cava blood flow is shunted into the pulmonary arteries).
These children depend on their preload to run blood passively into the pulmonary circuit; afterload reduction is also important to compensate for a poor left ejection fraction, as well as to avoid the development of pulmonary hypertension. They are typically on an anticoagulant (often aspirin), a diuretic (e.g. furosemide), and an afterload reduction agent (e.g. enalapril).
Any disturbance in volume status (hyper- or hypovolemia), anticoagulation, or afterload may cause myocardial strain or infarction. Take the child s/p Fontan seriously and involve his specialists early with any concerns.
The body’s inflammatory-mediated reaction to a real or perceived insult can cause short- and long-term cardiac sequelae. Find out how well the underlying disease is controlled, and what complications the child has had in the past.
The red, hot, crispy, flaky child: acute Kawasaki disease
Kawasaki disease (KD) is an acute systemic vasculitis, diagnosed by the presence of fever for five or more days accompanied by four or more criteria: bilateral conjunctival injection, mucositis, cervical lymphadenopathy, polymorphous rash, and palmar or sole desquamation. The criteria may occur (and disappear) at any time during the illness.
Infants are under double jeopardy with Kawasaki Disease. They are more likely to have incomplete KD (i.e. not fulfill strict criteria) and if they have KD, they are more likely to suffer the dangerous consequences of aneurysm formation (chiefly coronary arteries, but also brain, kidney). Have a low threshold for investigation.
Treatment includes 2 g/kg/day IVIG and high-dose aspirin (30-50 mg/kg/day) acutely, then low-dose aspirin (5 mg/kg/day) for weeks to months. Regular and long-term follow-up with Cardiology is required.
The family and child with a history of KD may have psychological trauma and continuous anxiety about the child’s risk of MI. Approximately 4.7% of children who were promptly diagnosed and correctly treated will go on to have cardiac sequelae.
Children who have no detected cardiac sequelae by 8 weeks, typically continue to be asymptomatic up to 20 years later.
Smaller aneurysms tend to regress over time, especially those < 6 mm.
Thrombi may calcify, or the lumen may become stenotic due to myofibroblast proliferation. Children with any coronary artery dilatation from KD should be followed indefinitely.
Giant aneurysms (≥8 mm) connote the highest risk for MI.
Parents often are concerned about recurrence, and any subsequent fever can be distressing. There is a low rate of recurrence for KD: approximately 2%. Infants who have coronary aneurysms are at the highest risk for recurrence.
Up to 15% of cases of SLE begin in childhood. Adult criteria are used, with the caveat that the diagnosis of SLE in children can be challenging; many children only manifest a few of the criteria initially before going on to develop further systemic involvement.
The Systemic Lupus International Collaborating Clinics (SLICC) revised the criteria in 2012. The patient should have ≥4/17 clinical and/or immunologic criteria. The clinical criteria are: acute cutaneous (malar); chronic cutaneous (discoid); oral; alopecia; synovitis; serositis; renal; neurologic; hemolytic anemia; leukopenia; or thrombocytopenia. The immunologic criteria are: ANA; anti-dsDNA; anti-Sm; antiphospholipid; low complement; and/or Direct Coombs (in absence of hemolytic anemia). At least one criterion should be clinical, and at least one should be immunologic.
Children with antiphospholipid syndrome (APS) may occur with or without SLE. Patients are at risk for venous and arterial thrombi formation. APS may also cause structural damage, such as valvular thickening and valvular nodes (Libman-Sacks endocarditis). Mitral and aortic valves are at the highest risk.
Although most children with chest pain will not have MI, those with comorbidities should be investigated carefully.
Direct, blunt trauma to the chest can cause myocardial stunning, dysrhythmias, or an asymptomatic rise in Troponin I. However, some children are at risk for disproportionate harm due to a previously unknown risk factor. Clinically significant cardiac injury occurs in up to 20% of patients with non-penetrating thoracic trauma.
The motor vehicle collision: blunt myocardial injury
Direct trauma (steering wheel, airbag, seatbelt), especially in fast acceleration-deceleration injury, may cause compression of the heart between the sternum and the thoracic spine.
Electrocardiography (ECG) should be performed on any patient with significant blunt chest injury. A negative ECG is highly consistent with no significant blunt myocardial injury.
Any patient with a new abnormality on ECG (dysrhythmia, heart block, or signs of ischemia) should be admitted for continuous ECG monitoring.
Elevation in troponin is common, but not predicted. A solitary elevated troponin without ECG abnormality is of unclear significance. Author’s advice: obtain troponin testing if there is an abnormal ECG, more than fleeting suspicion of BCI, and/or the child will be admitted for monitoring.
Hemodynamically labile children should be resuscitated and a stat transesophageal echocardiogram obtained.
Direct trauma (e.g. MVC, baseball, high-velocity soccer ball) may cause damage to the left anterior descending artery or left circumflex artery, at the highest risk due to their proximity to the chest wall. Thrombosis and/or dissection may result, often presenting in a focal pattern of ischemia on the ECG.
Echocardiography may reveal valvular damage related to the injury, as well as effusion and ejection fraction. Since there is often a need to investigate the coronary anatomy, percutaneous coronary intervention (PCI) is recommended.
As mentioned in the congenital section (above), a known variation of a coronary artery’s course involves weaving in and out of the myocardium, creating a baseline risk for ischemia. Even minor trauma in a child with a myocardial bridge may cause acute thrombus, or slow stenosis from resulting edema. Unfortunately, the presence of myocardial bridging is often unknown at the time of injury. Approximately 25% of the population may have myocardial bridging, based on autopsy studies. Take the child seriously who has disproportionate symptoms to what should be a minor injury.
Coagulopathic and thrombophilic states may predispose children to focal cardiac ischemia. The best documented cormorbidity is sickle cell disease, although other pro-thrombotic conditions also put the child at risk.
The child with sickle cell disease and chest pain: when it’s not acute chest syndrome
Sickle cell disease (SCD) can affect any organ system, although the heart is traditionally considered a lower-risk target organ for direct sickling and ischemia. The major cardiac morbidity in sickle cell is from strain, high-output failure and multiple, serial increases in myocardial demand, causing left ventricular hypertrophy and congestive heart failure.
However, there is mounting evidence that acute myocardial ischemia in sickle cell disease may be underappreciated and/or attributed to other causes of chest pain.
Other cardiac sequelae from SCD include pulmonary hypertension, left ventricular dysfunction, right ventricular dysfunction, and chronic iron overload.
Evidence of myocardial ischemia/infarction in children with SCD has been demonstrated on single-photon emission computed tomography (SPECT) scan.
Children who suffer from nephrotic syndrome lose proteins that contribute to the coagulation cascade. In addition, lipoprotein profiles are altered: there is a rise in the very low-density lipoproteins (LDL), contributing to accelerated atherosclerosis. Typically nephrotic patients have normal levels of high-density lipoproteins (HDL), unless there is profuse proteinuria.
Children with difficult-to-control nephrotic syndrome (typically steroid-resistant) may form accelerated plaques that rupture, causing focal MI, as early as school age.
Asymptomatic patent foramen ovale (PFO) is the cause of some cases of cryptogenic vascular disease, such as stroke and MI. However, the presence of PFO alone does not connote higher risk. When paired with an inherited or acquired thrombogenic condition, the venous thrombus may travel from the right-sided circulation to the left, causing distal ischemia. Many of these cases are unknown until a complication arises.
A family history of adult-onset hypercholesterolemia is not necessarily a risk factor for early complications in children, provided the child does not have the same acquired risk factors as adults (e.g. obesity, sedentary lifestyle, smoking, etc). Parents may seek help in the ED for children with chest pain and no risk factors, but adult parents who have poor cholesterol profiles.
The exception is the child with familial hypercholesterolemia, who is at risk for accelerated atherosclerosis and MI.
Myocarditis has varied etiologies, including infectious, medications (chemotherapy agents), immunologic (rheumatologic, transplant rejection), toxins (arsenic, carbon monoxide, heavy metals such as iron or copper), or physical stress (electrical injury, heat illness, radiation).
In children, the most common cause of myocarditis is infectious (viruses, protozoa, bacteria, fungal, parasites). Of these, viral causes are the most common (adenovirus, enterovirus, echovirus, rubella, HHV6).
The verbal child may complain of typical chest complaints, or may come in with flu-like illness and tachycardia or ill appearance out of proportion to presumed viral illness.
The most common presenting features in children with myocarditis are: shortness of breath, vomiting, poor feeding, hepatomegaly, respiratory distress, and fever.
Beware of the poor feeding, tachycardic, ill appearing infant who “has a cold” because everyone else around him has a ‘cold’. That may very well be true, but any virus can be invasive with myocardial involvement. Infants are only able to increase their cardiac output through increasing their heart rate; they cannot respond to increased demands through ionotropy. Look for signs of acute heart failure, such as hepatomegaly, respiratory distress, and sacral edema.
The child with tachycardia out of proportion to complaint: myocarditis
The previously healthy child with “a bad flu” may simply be very symptomatic from influenza-like illness, or he may be developing myocarditis. Look for chest pain and tachycardia out of proportion to presumed illness, and constant chest pain, not just associated with cough.
Acute heart failure may mimic viral pneumonia. Look for disproportionate signs and symptoms.
Younger children may get into others’ medications, be given dangerous home remedies, take drugs recreationally, have environmental exposures (heavy metals), suffer from a consequence of a comorbidity (iron or copper overload) or have adverse events from generally safe medications.
Attention deficit hyperactivity disorder (ADHD) is growing in rate of diagnosis and use of medications. As the only medical diagnosis based on self-reported criteria, many children are given stimulants regardless of actual neurologic disorder; with a higher proportion of children exposed to stimulants, adverse effects are seen more commonly.
Methylphenidate is related to amphetamine, and they both are dopaminergic drugs. Their mechanisms of action are different, however. Methylphenidate increases neuronal firing rate. Methamphetamine reduces neuronal firing rate; cardiovascular sequelae such as MI and CHF are more common in chronic methamphetamine use.
Although methylphenidate is typically well tolerated, risks include dysrhythmias such as ventricular tachycardia.
Some anti-epileptic agents, such as carbamazepine, promote a poor lipid profile, leading to atherosclerosis and early MI. Case reports include school-aged children on carbamazepine who have foamy cells in the coronary arteries, aorta, and vasa vasorum on autopsy. It is unclear whether this is a strong association.
The spice trader: synthetic cannabinoids
Synthetic cannabinoids are notoriously difficult to regulate and study, as the manufacturers label them as “not for human consumption”. Once reports surface of abuse of a certain compound, the formula is altered slightly and repackaged, often in a colorful or mysterious way that is attractive to teenagers.
The misperceptions are: are a) synthetics are related to marijuana and therefore safe and b) marijuana is inherently “safe”. Both tend to steer unwitting teens to take these unknown entities. Some suffer MI as a result.
Exposure to tetrahydrocannabinol (THC) in high-potency marijuana has been linked to myocardial ischemia, ventricular tachycardia, and ventricular fibrillation. Marijuana can increase the heart rate from 20-100%, depending on the amount ingested.
K2 (“kush 2.0”) or Spice (Zohai, Genie, K3, Bliss, Nice, Black Mamba, fake weed, etc) is a mixture of plant leaves doused in synthetic chemicals, including cannabinoids and fertilizer (JWH-108), none of which are tested or safe for human consumption.
Synthetic cannabinoids have a higher affinity to cannabinoid receptors, conferring higher potency, and therefore worse adverse effects. They are thought to be 100 to 800 times more potent as marijuana.
Bath salts (Purple Wave, Zoom, Cloud Nine, etc) can be ingested, snorted, or injected. They typically include some form of cathinone, such as mephedrone, similar to the substance found in the naturally occurring khat plant. Hallucinations, palpitations, tachycardia, MI, and dysrhythmias have been reported from their use as a recreational drug.
Chest pain with marijuana, synthetic cannabinoid, or bath salt ingestion should be investigated and/or monitored.
Riding that train: high on cocaine
Cocaine is a well-known cause of acute MI in young people. In addition to the direct stimulant causes acutely, such as hypertension, tachycardia, and impaired judgement (coingestions, risky behavior), chronic cocaine use has long-term sequelae. Cocaine causes accelerated atherosclerosis. That, in conjunction with arterial vasospasm and platelet activation, is a recipe for acute MI in the young.
Methamphetamine is a highly addictive stimulant that is relatively inexpensive and widely available. Repeated use causes multiple psychiatric, personality, and neurologic changes. Risky behavior, violence, and motor vehicle accidents are all linked to this drug.
Like cocaine, methamphetamine may cause fatal dysrhythmias, acute MI from demand ischemia, and long-term sequelae such as congestive heart failure.
Acute MI is a challenging presentation in children:
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This post and podcast are dedicated to Edwin Leap, MD for his sanity and humanity in the practice of Emergency Medicine. Thank you, Dr Leap for all that you do.