A 37-year-old woman is brought to the emergency department after developing sudden-onset right arm weakness and difficulty speaking. She has no significant medical history but takes oral contraceptives. Examination shows decreased right upper extremity strength and expressive aphasia. Cardiac auscultation is normal. MRI of the brain reveals acute infarction in the left frontal lobe. Further evaluation to determine an etiology is performed. During echocardiogram, agitated normal saline is injected into a peripheral vein and bubbles are seen passing into the left side of the heart. Which of the following is the most likely cause of the observed finding in this patient?

Question

A 37-year-old woman is brought to the emergency department after developing sudden-onset right arm weakness and difficulty speaking.  She has no significant medical history but takes oral contraceptives.  Examination shows decreased right upper extremity strength and expressive aphasia.  Cardiac auscultation is normal.  MRI of the brain reveals acute infarction in the left frontal lobe.  Further evaluation to determine an etiology is performed.  During echocardiogram, agitated normal saline is injected into a peripheral vein and bubbles are seen passing into the left side of the heart.  Which of the following is the most likely cause of the observed finding in this patient?

Quizplus · Accepted Answer

11ec160b_3735_168d_9249_c54f5da5f8eb_MD0001_00 This young patient had a cryptogenic stroke, which is evaluated with echocardiography with a "bubble study" to identify right-to-left intracardiac shunts. This study is performed by injecting agitated normal saline intravenously and observing for microbubbles in the left heart. Shunt detection is improved by having the patient release a sustained Valsalva maneuver, which increases right atrial pressure. Cryptogenic stroke is frequently associated with atrial septal abnormalities such as patent foramen ovale (PFO) and atrial septal defect (ASD). During fetal development, the foramen ovale shunts oxygenated fetal blood across from the right to the left atrium. After delivery, umbilical cord clamping and decreased pulmonary vascular resistance lower right atrial pressure and raise left atrial pressure. This pushes the septum primum against the septum secundum, closing the foramen ovale. Over time, fibrosis and tissue remodeling fuse the flap closed. Incomplete fusion occurs in approximately 25% of normal adults, resulting in a PFO. PFO usually remains functionally closed and asymptomatic after birth as left atrial pressure is greater than right atrial pressure. However, conditions that raise right atrial pressure above left atrial pressure (eg, Valsalva release) produce a transient right-to-left shunt across the PFO. This is particularly concerning in patients with hypercoagulability (eg, oral contraceptive use) as they are at increased risk for venous thrombosis and paradoxical brain embolism. Chronically elevated right heart pressure (eg, Eisenmenger syndrome) is not necessary for paradoxical embolism. (Choice A) ASD results from aplasia of the septum primum or septum secundum during development. Although ASD may lead to paradoxical embolism, it is much less common than PFO and characterized by fixed splitting of S2. Unrepaired ASDs may lead to heart failure, pulmonary hypertension, or Eisenmenger syndrome. (Choice B) Incomplete development of the aorticopulmonary septum results in truncus arteriosus, which causes cyanosis in newborns and requires early surgical repair. (Choice C) Incomplete closure of the interventricular foramen results in ventricular septal defect (VSD), which causes a holosystolic murmur at the lower left sternal border. Large VSDs can cause significant left-to-right shunting, leading to heart failure in infancy; however, VSDs infrequently lead to paradoxical embolism. (Choice E) The ductus arteriosus functionally closes within 24 hours after delivery. Persistent patent ductus arteriosus causes a continuous murmur and may eventually result in heart failure, pulmonary hypertension, or Eisenmenger syndrome. Educational objective: The foramen ovale is patent in approximately 25% of normal adults. Although the foramen ovale usually remains functionally closed, transient increases of right atrial pressure above left atrial pressure can produce a right-to-left shunt, leading to paradoxical embolism of venous clots into the arterial circulation. __________ References: Contemporary approach to paradoxical embolism. (http://www.ncbi.nlm.nih.gov/pubmed/24799505) Patent foramen ovale. (http://www.ncbi.nlm.nih.gov/pubmed/23931102)

A 37-Year-Old Woman Is Brought to the Emergency Department After