A 65-year-old woman comes to the emergency department for transient weakness. She experienced muscle weakness in her right arm and leg this morning that lasted approximately 20 minutes and has since resolved completely. The patient has had no headache, vision loss, or vomiting. She has never before had similar symptoms. Medical history is significant for hypertension and diet-controlled type 2 diabetes mellitus. The patient underwent mitral valve replacement with a bioprosthetic valve 5 years ago due to mitral valve endocarditis. She is a life-long nonsmoker. Blood pressure is 131/70 mm Hg, and pulse is 65/min and regular. Chest examination is unremarkable. Neurologic examination reveals no muscle weakness or sensory loss. ECG, complete blood count, and renal function are within normal limits. In addition to a neuroimaging study, which of the following is the best next step in management of this patient?

Question

A 65-year-old woman comes to the emergency department for transient weakness.  She experienced muscle weakness in her right arm and leg this morning that lasted approximately 20 minutes and has since resolved completely.  The patient has had no headache, vision loss, or vomiting.  She has never before had similar symptoms.  Medical history is significant for hypertension and diet-controlled type 2 diabetes mellitus.  The patient underwent mitral valve replacement with a bioprosthetic valve 5 years ago due to mitral valve endocarditis.  She is a life-long nonsmoker.  Blood pressure is 131/70 mm Hg, and pulse is 65/min and regular.  Chest examination is unremarkable.  Neurologic examination reveals no muscle weakness or sensory loss.  ECG, complete blood count, and renal function are within normal limits.  In addition to a neuroimaging study, which of the following is the best next step in management of this patient?

Quizplus · Accepted Answer

Explanation: This patient with a recent episode of neurologic weakness likely experienced a transient ischemic attack (TIA). TIA represents interrupted cerebral flow and can be due to either ischemia or thrombus (eg, embolized clot). Given this patient's prosthetic valve, embolization in the setting of prosthetic valve thrombosis (PVT) should be strongly suspected. Prosthetic mitral (and tricuspid) valves are particularly susceptible to thrombus, at least in part due to lower blood flow rates through the valve. The most common presentations of PVT include: Thromboembolism: left-sided (ie, mitral or aortic) PVT (which embolize to the systemic circulation) can present as TIA, stroke, myocardial infarction, bowel ischemia, and limb ischemia; by contrast, right-sided (eg, tricuspid) PVT may cause pulmonary embolism. Prosthetic valve dysfunction: usually manifesting as obstruction (stenosis) or, rarely, regurgitation. Patients may have a new murmur or signs and symptoms of heart failure. Transthoracic echocardiography can confirm the diagnosis of PVT, assess the degree of thrombus, and evaluate for prosthetic valve dysfunction. To prevent PVT, patients with prosthetic valves are kept on antithrombotic therapy. Mechanical prosthetic valves are more thrombogenic and require anticoagulation. Bioprosthetic valves are less thrombogenic and typically require only aspirin therapy; however, PVT can still occur. (Choice B) An electroencephalogram (EEG) can be useful in diagnosing seizure activity. Focal seizures can sometimes result in persistent weakness lasting minutes or hours (ie, Todd paralysis); however, seizure is less likely in the absence of a history of involuntary movements or impaired consciousness. (Choice C) Hypercoagulability studies can help elucidate less likely causes of TIA in this patient (eg, antiphospholipid syndrome) and may be indicated if the initial workup fails to determine an etiology. However, a prosthetic valve should be considered the source of thromboembolism until proven otherwise. (Choice D) Prosthetic valve dysfunction can mechanically damage circulating erythrocytes, which can lead to hemolysis with schistocytes on peripheral smear. However, this complication is uncommon with bioprosthetic valves and is unlikely to explain this patient's TIA. (Choice E) Antinuclear antibody testing is useful in the initial diagnostic evaluation for systemic lupus erythematosus (SLE). Although SLE increases the risk of stroke and TIA, patients typically have other manifestations of the condition (eg, joint pain, rash); stroke and TIA are rare as the initial presentation. Educational objective: Prosthetic valve thrombosis (PVT) is a potential complication of both mechanical and bioprosthetic valves. Patients can have a new murmur, heart failure due to valvular obstruction (stenosis) or regurgitation, or a thromboembolic event (eg, transient ischemic attack). Suspected PVT should be promptly evaluated with echocardiography. References: Mechanical and surgical bioprosthetic valve thrombosis. (http://www.ncbi.nlm.nih.gov/pubmed/28780576)

A 65-Year-Old Woman Comes to the Emergency Department for Transient