Clinical Reasoning: Mechanical thrombectomy for acute ischemic stroke in the setting of atrial myxoma

Discussion

Incidence of AIS in young adults (18–49 years of age) has been increasing over the last decades, with improved survival of patients with predisposing conditions such as congenital heart disease and sickle cell anemia along with a rise in traditional stroke risk factors such as hypertension, hypercholesterolemia, and obesity in younger individuals. Stroke in young patients causes tremendous loss of work-years and incurs long-term health costs. A high index of suspicion for diagnosing stroke is required, as other more common and benign diagnoses like hemiplegic migraine may divert the clinician's approach and cause loss of valuable time. When treated promptly, disability can be mitigated and further investigation for the cause of stroke can be initiated.

Cardioembolism, often due to congenital or acquired heart disease, is the most common cause of stroke in children.³ With improved treatments for structural cardiac malformations of infancy, a larger fraction of these patients are now entering young adulthood and have an increased risk of stroke. In developing countries, rheumatic mitral valve disease most frequently predisposes young adults to cardioembolic stroke whereas patent foramen ovale and mitral valve prolapse are more common in the western world. Hemoglobinopathies, most notably sickle cell, are also associated with cerebral thrombosis, with exchange transfusion being the mainstay of treatment and limited evidence regarding the efficacy of tPA in this setting. In addition, migraines, illicit drug use, oral contraceptives, and pregnancy have been identified as independent risk factors for AIS in young adults.⁴

If a common cause of AIS is not apparent, rarer etiologies must be considered. Among these, arterial dissection resulting from cervical trauma or connective tissue disorders (Ehlers-Danlos, Marfan syndrome, osteogenesis imperfecta) has been found to account for approximately 20% of ischemic stroke in young adults.⁴ Other rare causes include infectious meningitis, vasculitis (inflammatory arteritis or induced by infectious hepatitis/HIV), cardiomyopathy, moyamoya, and prothrombotic states including antiphospholipid syndrome, factor V Leiden, antithrombin III deficiency, and protein C/S deficiency.³ Although these may be contributors to stroke throughout a human lifespan, the higher prevalence of traditional cardiovascular derangements such as hypertension, hypercholesterolemia, diabetes, obesity, and atrial fibrillation among older adults have made the aforementioned conditions more specific to young adults.

An uncommon etiology of cardioembolic stroke in the younger population is atrial myxoma, as seen in the present case. Myxomas are benign cardiac tumors arising from subendocardial mesenchymal cells and are most commonly found in the left atrium. Incidence of cardiac tumors has been reported to be between 0.001% and 0.3% in autopsy studies and 0.15% in major echocardiographic series with approximately 50% of identified tumors being myxomas.⁵ Myxomas often have a genetic origin and may be found in conditions such as tuberous sclerosis or the Carney complex.⁶ The natural history of these tumors is highly variable. While the majority of patients have cardiac complaints and approximately 10% of patients never experience symptoms, 29%–40% of cases present with an embolic episode.⁷

The embolic potential of a myxoma is expected to be influenced by tumor size, consistency, friability, and left atrial diameter. While the contribution of each of these attributes to embolization risk is incompletely understood, myxomas with irregular, villous, and friable surfaces are more frequently associated with production of emboli.⁷ The cerebral vasculature is the most common location for embolization from a myxoma and the prevalence of associated strokes has been reported to be 21%–29%.^7,–,9

Strokes secondary to atrial myxomas differ from strokes due to other etiologies in some key ways. These patients may be previously asymptomatic or without any known stroke risk factors and a few may have cardiac symptoms due to tumor causing mitral valve obstruction.⁷ Blurred vision has been identified as the most common neurologic symptom in this population and may present alone or in combination with more elaborate deficits such as hemiparesis/plegia. The blood vessels usually occluded are retinal vessels followed by medium-sized cerebral vessels such as M1.¹⁰ Of the approximately 22% of patients who may have embolization of a cardiac myxoma, multivessel infarction has been reported in up to 72.7% of patients.⁸

The response rate of patients to tPA from myxoma-induced AIS is lower than in stroke from other causes. This is primarily due to lysed tumor forming an integral part of the embolus. Therefore, mechanical thrombectomy may be a better option for treatment of these occluded segments, especially when large vessels vascularizing critical brain areas are involved. As demonstrated in the aforementioned case, recurrent strokes may occur unless the atrial myxoma is removed with surgical intervention. Hence patients not undergoing myxoma resection require follow-up for further neurologic episodes.

In the patient described above, an early diagnosis of stroke helped in timely administration of tPA. The large artery occlusion prompted a mechanical thrombectomy, which resulted in a dramatic improvement of her symptoms with minimal residual deficits. Further evaluation revealed an atrial myxoma and definitive treatment was done with surgical removal of the myxoma. Thus, having a high suspicion for cardiac myxoma in cases of AIS in young patients can facilitate a quick diagnosis allowing for initiation of focused management.

Atrial myxomas are an important etiology that should be included in the differential diagnoses of young patients with AIS. Early identification of the cause is of utmost importance as these patients may require IV tPA and mechanical thrombectomy to improve outcome and avoid residual disability. Definitive treatment involves surgical myxoma resection.