PARADOXICAL EMBOLI: AN UNCOMMON BUT CLINICALLY SIGNIFICANT CAUSE OF STROKE

Objectives: Introduction
Cerebrovascular embolic ischemic strokes are responsible for approximately 139,000 deaths annually within the United States. 40% of strokes have no inciting cause found on diagnostic workup and are subsequently termed cryptogenic strokes. The most common cause of cryptogenic stroke is hypothesized to be paradoxical embolism (PDE) which results from venous thromboemboli passing into the arterial system by way of an intra-cardiac or pulmonary vascular defect. The ambiguous nature of PDEs make them a diagnosis of exclusion in patients presenting with acute ischemic infarcts. We present two cases of PDEs resulting in acute ischemic events.

Case Report
A 63-year-old female was brought to the emergency department for evaluation of left upper extremity numbness. Magnetic resonance imaging (MRI) on admission demonstrated an acute ischemic infarct of the right middle cerebral artery and occlusion of the right internal carotid artery. Computed tomographic angiography (CTA) of the neck and chest was obtained and demonstrated a large saddle pulmonary embolus and extensive thrombi in bilateral common carotid arteries. Emergent mechanical thrombectomy was performed with subsequent stabilization of the patient. Transesophageal echocardiography (TEE) performed demonstrated a patent foramen ovale (PFO). Standard hypercoagulability tests revealed protein S deficiency. The patient’s stroke was postulated to have been caused by a PDE given the presence of the interatrial shunt combined with a proven hypercoagulable state.

An 87-year-old male was brought to the emergency department for evaluation of chest pain. The patient subsequently underwent three-vessel coronary artery bypass grafting with placement of an intra-aortic balloon pump (IABP) at the conclusion of the procedure. On post-operative day 12, the patient became hemodynamically unstable and required endotracheal intubation. Transthoracic echocardiogram followed by confirmatory TEE demonstrated a biatrial thrombus traversing a PFO. The patient was taken back to the OR for thrombectomy and PFO closure. The patient stabilized following the procedure, but experienced an acute left hemispheric stroke, likely caused by the clot seen pre-operatively traversing the PFO.

Discussion
CVAs are a common cause of morbidity and mortality in the United States. While the true prevalence and incidence of PDEs is unknown, a high index of suspicion must be maintained to ensure timely diagnosis and treatment of patients presenting with cryptogenic stroke. Management of patients who present with a PDE is multi-disciplinary and includes anticoagulation and potential thrombectomy. The prompt diagnosis and management of patients presenting with a PDE is paramount to preventing the morbidity and mortality associated with repeat ischemic events.

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