A 33-year-old, previously healthy woman comes to the emergency department due to sudden-onset shortness of breath and left-sided chest pain. The symptoms began an hour ago while she was doing yard work, and she nearly passed out at symptom onset. The patient takes no medications or supplements other than ibuprofen for occasional headaches. She does not use tobacco, alcohol, or illicit drugs. Temperature is 37.1 C (98.8 F), blood pressure is 84/58 mm Hg, pulse is 122/min, and respirations are 24/min. Pulse oximetry is 86% on room air. On physical examination, the patient is in moderate distress. The jugular veins are distended. Heart sounds are rapid and regular with no murmurs. Lungs are clear to auscultation bilaterally with no crackles or wheezes. Arterial blood gas results are pH 7.52, PaCO₂ 28 mm Hg, and PaO₂ 54 mm Hg. Which of the following is most likely to be seen on bedside echocardiography?

Question

Quizplus · Accepted Answer

11ec160b_38e4_73f7_9249_e159232dfac2_MD0001_00 This patient most likely has an acute pulmonary embolism (PE). The classic presentation is acute-onset chest pain and shortness of breath that may be accompanied by syncope or near-syncope. Patients usually have tachycardia, tachypnea, jugular venous distension, and clear lungs. Arterial blood gas typically show hypoxemia and acute respiratory alkalosis due to hyperventilation. Up to 30% of cases may present with no apparent risk factors (eg, hypercoagulability). Massive PE can lead to hypotension and obstructive shock. There is a rapid increase in pulmonary arterial resistance that leads to an increase in pulmonary arterial and right ventricular (RV) pressure. The rapid pressure increase causes RV cavity enlargement due to increased RV wall tension and cardiac muscle stretching. RV myocardial oxygen demand increases and coronary artery perfusion decreases, leading to a supply/demand mismatch and RV ischemia. Consequent RV dysfunction then leads to an inability to pump blood through the pulmonary circulation, resulting in decreased left-sided preload and decreased cardiac output. Such RV failure caused by an increase in pulmonary vascular resistance is sometimes called cor pulmonale. (Choice A) An enlarged left ventricular (LV) cavity usually results from eccentric hypertrophy in the setting of chronic volume overload, such as occurs in dilated cardiomyopathy or severe aortic or mitral valve regurgitation. In acute PE, the LV cavity is either normal or somewhat reduced in size due to reduced blood flow coming from the right side of the heart. (Choice C) Left atrial enlargement is typical of severe mitral stenosis, which usually occurs in the setting of rheumatic heart disease. Undiagnosed mitral stenosis can sometimes present acutely with decompensated heart failure; however, a rumbling diastolic murmur and evidence of pulmonary edema (eg, crackles on lung auscultation) are expected. (Choice D) LV wall thickening is expected with the concentric hypertrophy that occurs with prolonged systemic hypertension or severe aortic stenosis. (Choice E) RV wall thickening is seen with the concentric hypertrophy that occurs in patients with chronic pulmonary hypertension. In acute PE, there is no time for compensatory wall thickening to occur in response to the increased pressure load; the rapid increase in pressure causes RV dilation that may be accompanied by RV failure. Educational objective: A large, acute pulmonary embolism causes a rapid increase in right ventricular (RV) pressure that leads to RV cavity enlargement and RV dysfunction. Thickening of the RV wall is not seen in acute pulmonary embolism, as there is no time for compensatory hypertrophy to occur in response to the increased pressure load. __________ References: Pulmonary embolism, part I: Epidemiology, risk factors and stratification, pathophysiology, clinical presentation, diagnosis, and nonthrombotic pulmonary embolism. (http://www.ncbi.nlm.nih.gov/pubmed/23940438)

A 33-Year-Old, Previously Healthy Woman Comes to the Emergency Department