Children with congenital heart disease (CHD) face a high risk of stroke, with causes ranging from differences in cardiac anatomy and blood composition to the risks inherent in mechanical support devices.
Pediatric neurologist Lori C. Jordan, M.D., of Monroe Carell Jr. Children’s Hospital at Vanderbilt, was the senior author on a review article on the epidemiology, mechanisms of injury, and challenges in the management of stroke in children with CHD.
“Incidence of ischemic stroke due to a blocked blood vessel or low blood flow to the brain is 100 times that of a typical child.”
“With this population, stroke is not rare,” she said. “Incidence of ischemic stroke due to a blocked blood vessel or low blood flow to the brain is 100 times that of a typical child and 10 times higher, still, in a child with single ventricle physiology – around one in 100. Awareness of this risk is important, so we are mindful of preventing stroke when possible, recognizing symptoms of stroke, and rapidly evaluating and treating those children who do have a stroke.”
Risk Factors and Types
Anatomical differences in the hearts of children with CHD put them at high risk of ischemic stroke. Ischemic strokes may also occur when clots form on mechanical devices they are using, or within the heart. Hemorrhagic strokes may be associated with anticoagulants or a rupture of an infected aneurysm due to bacterial endocarditis.
“Differences in blood flow and blood composition are major risk factors,” Jordan said. “The child’s heart defect leads to altered blood flow through the heart, sometimes promoting thrombus formation and impaired cerebral perfusion. Low oxygen-saturation levels result in higher hemoglobin concentrations, and the thickened blood is more prone to clotting.”
These children are also more vulnerable to bloodstream infections, Jordan added, with sepsis increasing clotting risks.
Corrective surgeries are necessary, but even with careful management clots may form at catheterization or repair sites. Mechanical circulatory support devices, like ventricular assist devices and extracorporeal membrane oxygenation machines, require anticoagulation and also create vulnerability to clot formation.
Clinicians must balance the need for and the risks of antithrombotic therapy, Jordan explained.
“Antithrombotic therapy is routinely given with the cardiac repair procedures to prevent blood clots –unless and until neuroimaging shows suspected hemorrhagic stroke.” she said.
After an ischemic stroke, tissue plasminogen activator (tPA), can be an option when the stroke is identified within 4.5 hours of symptom onset. Jordan says this classic option is confounded in children with CHD because tPA cannot be used adjacent to major surgery, plus stroke can be tough to recognize in children, especially those who are critically ill and heavily sedated.
In rare cases, she says, thrombectomy or clot retrieval is performed as an off-label therapy by highly specialized, experienced endovascular neurosurgeons.
She says key to neuroprotection and neurostabilization after stroke is optimizing the flow of blood and oxygenation to the brain, while monitoring for seizures and other secondary complications.
Suspicion and Rapid Evaluation
Jordan and her team promote awareness of stroke risks, checking closely for symptoms that are often harder to detect in babies and children than in adults, as well as prompt evaluation of any significant change in neurological status.
“Monroe Carell has had a pediatric acute stroke protocol since 2011. Our collaborative team has evaluated more than 500 children for stroke-like symptoms,” Jordan said. “Our protocol consists of rapid brain and blood-vessel imaging, rapid evaluation by a neurologist, and rapid supportive care. If a child has sudden weakness of their face, arm or leg, a sudden alteration speech or alertness, or persistent weakness after a new focal seizure, these are the kids that should be quickly evaluated for stroke.”
Registries as a Research Database
Jordan emphasizes the urgent need for more pediatric studies guiding acute management of children with intracerebral hemorrhage, including blood pressure targets, anticoagulation management, and surgical timing. She says future research should also include the role of biomarkers in children at high risk.
In the absence of large numbers to power studies, Monroe Carrell and Vanderbilt have a pediatric stroke registry that is incorporated into an international registry.
“We are trying to answer questions about what measures are really neuroprotective,” she said.
“We know getting fluids to the brain, trying to control temperature and not allowing children to have a fever if they’ve had a brain injury are important. There is some logic that would suggest cooling the body after a stroke may be beneficial. These and other promising strategies have just not been studied in kids with stroke or brain hemorrhage.”