A 34-year-old man comes to the emergency department with fatigue and lightheadedness. The patient had an upper respiratory infection last week, and since then his energy level has been low with shortness of breath on mild exertion. Otherwise, his medical history is insignificant. He is a lifetime nonsmoker. The patient's temperature is 37 C (98.6 F), blood pressure is 80/60 mm Hg, and pulse is 120/min and regular. His pulse becomes undetectable to palpation during inspiration. The lungs are clear to auscultation, but the jugular veins are distended. Which of the following is the most likely diagnosis?

Question

A 34-year-old man comes to the emergency department with fatigue and lightheadedness.  The patient had an upper respiratory infection last week, and since then his energy level has been low with shortness of breath on mild exertion.  Otherwise, his medical history is insignificant.  He is a lifetime nonsmoker.  The patient's temperature is 37 C (98.6 F), blood pressure is 80/60 mm Hg, and pulse is 120/min and regular.  His pulse becomes undetectable to palpation during inspiration.  The lungs are clear to auscultation, but the jugular veins are distended.  Which of the following is the most likely diagnosis?

Quizplus · Accepted Answer

11ec160b_3a81_0d1c_9249_4bf8a37e9708_MD0001_00 This presentation of hypotension, tachycardia, jugular venous distension with clear lungs, and pulsus paradoxus (manifesting as loss of palpable pulse during inspiration) is consistent with cardiac tamponade. This is most likely due to the patient's recent viral illness causing viral pericarditis with significant pericardial fluid accumulation. Normally there is a <10 mm Hg decrease in systolic blood pressure during inspiration. Pulsus paradoxus refers to an abnormal exaggerated decrease in systolic blood pressure >10 mm Hg on inspiration, a common finding in patients with large pericardial effusions causing tamponade. Inspiration causes an increase in systemic venous return, resulting in increased right heart volumes. Under normal conditions, this results in expansion of the right ventricle into the pericardial space with little impact on the left side of the heart. However, in conditions that impair expansion into the pericardial space (eg, cardiac tamponade), the increased right ventricular volume that occurs with inspiration leads to bowing of the interventricular septum toward the left ventricle. This leads to a decrease in left ventricular (LV) end-diastolic volume and forward stroke volume, with a resultant decrease in systolic pressure during inspiration. (Choice A) Acute myocardial infarction typically presents with sudden onset of substernal discomfort, diaphoresis, and/or dyspnea, and can progress to cardiogenic shock (hypotension, tachycardia, jugular venous distension, and pulmonary edema). Patients can have weak or undetectable peripheral pulses; however, pulsus paradoxus is typically not seen. (Choice B) Acute viral myocarditis can lead to severe LV systolic dysfunction and present with acute congestive heart failure and cardiogenic shock. Patients with severe LV failure can have pulsus alternans - a variation in pulse amplitude with alternate beats. Pulsus paradoxus is typically not seen in such patients. (Choice D) Pulsus paradoxus can also occur in patients with asthma, chronic obstructive pulmonary disease, and (less frequently) constrictive pericarditis. Constrictive pericarditis is caused by scarring and loss of elasticity of the normal pericardial sac; it takes several weeks to months to develop and only rarely occurs after recurrent episodes of acute pericarditis. (Choice E) The initial stage of septic shock is a hyperdynamic circulatory state with lowered systemic vascular resistance and increased cardiac output (warm shock). Weak pulses and pulsus paradoxus would not be expected in such patients. (Choice F) In tension pneumothorax, breath sounds are typically absent on the affected side with hyperresonance to percussion. Other features of tension pneumothorax include tachypnea, tachycardia, hypotension, distended neck veins, and tracheal deviation to the contralateral side. Educational objective: Cardiac tamponade typically presents with hypotension with pulsus paradoxus, elevated jugular venous pressure, and muffled heart sounds (Beck's triad). Pulsus paradoxus refers to an abnormal exaggerated decrease in systolic blood pressure >10 mm Hg on inspiration, and is a common finding in patients with pericardial effusion with cardiac tamponade.

A 34-Year-Old Man Comes to the Emergency Department with Fatigue