A 76-year-old woman is hospitalized due to a fracture of her right proximal femur from an accidental nonsyncopal fall. Medical history is notable for breast cancer treated with a radical mastectomy 10 years ago, hypertension, and hyperlipidemia. She drinks a pint of vodka daily, but does not use tobacco or illicit drugs. The patient is started on thiamine and folic acid, and the next morning she undergoes orthopedic surgery for internal fixation of the right femur. She experiences mild agitation postoperatively, which is managed with as-needed, low-dose benzodiazepines. In addition, she is treated with low-molecular-weight heparin, opiates, and continued vitamin supplementation. On her third postoperative day, the nurse finds her agitated and in significant distress. The patient has an episode of nonbloody vomiting. On initial evaluation, she appears restless and confused but follows commands. Temperature is 36.7 C (98 F), blood pressure is 92/58 mm Hg, pulse is 122/min and regular, and respirations are 31/min. Pulse oximetry is 75% on room air and improves to 82% with supplemental oxygen by non-rebreather mask. Chest auscultation reveals no crackles or wheezes. Cardiac examination demonstrates tachycardia with a regular rhythm and normal S1 and S2. The abdomen is soft. Her pupils are equal and reactive to light, and she is moving all extremities. The patient is successfully intubated and put on mechanical ventilation. Initial settings include fraction of inspired oxygen set to 100% and positive end-expiratory pressure of 5 cm H₂O. Pulse oximetry shows 96%. Her blood pressure drops to 78/42 mm Hg and pulse is 120/min. ECG shows sinus tachycardia and a new right bundle branch block with no ST-segment or T-wave changes. Chest x-ray reveals a normal cardiac silhouette and no infiltrates. Which of the following is most likely to show on emergent bedside echocardiogram?

Question

Quizplus · Accepted Answer

Explanation: This patient's acute respiratory failure is most likely due to an acute massive pulmonary embolism (PE). Although administration of prophylactic low-molecular-weight heparin lowers the risk of PE, it is not completely preventive. Recent femur fracture, orthopedic surgery, and immobility all increase the risk of acute PE, and clinical presentation of hypotension and marked hypoxemia in the absence of pulmonary infiltrates are highly suggestive of the diagnosis. Sinus tachycardia is the most common arrhythmia found on ECG in patients with acute PE. Other consistent ECG findings that occur due to right ventricular (RV) strain include new right bundle branch block, atrial arrhythmias, and Q-waves or ST-segment changes in the inferior leads. In patients who are too hemodynamically unstable to undergo more definitive testing (eg, CT angiogram of the chest), bedside echocardiography is often performed and can strongly support the diagnosis of acute PE. Echocardiographic evidence of RV dysfunction, decreased RV contractility, and presence of RV thrombus are consistent findings. In addition, pulmonary hypertension caused by massive PE often leads to dilation of the tricuspid valve annulus and functional tricuspid valve regurgitation seen on echocardiogram. (Choice A) Massive PE is typically associated with global RV dysfunction. Less commonly, it may cause inferior-posterior wall hypokinesis affecting both the right and left ventricle, but this pattern is more typical of myocardial infarction. The lack of ischemic ECG findings and absence of pulmonary edema in this patient make this finding less likely. (Choice B) A large pericardial effusion would typically reveal cardiomegaly on chest X-ray and low-voltage QRS complexes, rather than right bundle branch block on ECG. (Choice C) Aortic valve insufficiency can occur in acute aortic dissection but is not associated with acute PE. Marked hypoxemia is not typical of acute aortic dissection. (Choice D) Severe, rather than moderate, mitral regurgitation can occur due to papillary muscle rupture in acute myocardial infarction. However, mitral regurgitation is not typically associated with acute PE. Educational objective: Massive pulmonary embolism causes pulmonary hypertension, which can lead to acute right ventricular dysfunction, tricuspid annulus dilation, and functional tricuspid valve regurgitation. Bedside echocardiography can aid in the diagnosis of acute, massive pulmonary embolism. References: Echocardiographic evaluation of pulmonary embolism and its response to therapeutic interventions. (http://www.ncbi.nlm.nih.gov/pubmed/1555480)

A 76-Year-Old Woman Is Hospitalized Due to a Fracture of Her