A 45-year-old man comes to the emergency department after an episode of syncope. Medical history is unremarkable except for an upper respiratory infection one week ago. Temperature is 37.2 C (99 F), pulse is 90/min, blood pressure is 100/60 mm Hg, and respirations are 13/min. His neck veins are distended and his heart sounds are distant. His lungs are clear to auscultation bilaterally. Chest x-ray reveals small bilateral pleural effusions and an enlarged cardiac silhouette. Which of the following ECG findings is fairly specific for his condition?

Question

A 45-year-old man comes to the emergency department after an episode of syncope.  Medical history is unremarkable except for an upper respiratory infection one week ago.  Temperature is 37.2 C (99 F), pulse is 90/min, blood pressure is 100/60 mm Hg, and respirations are 13/min.  His neck veins are distended and his heart sounds are distant.  His lungs are clear to auscultation bilaterally.  Chest x-ray reveals small bilateral pleural effusions and an enlarged cardiac silhouette.  Which of the following ECG findings is fairly specific for his condition?

Quizplus · Accepted Answer

This patient has a pericardial effusion, which often causes electrical alternans on ECG. His recent upper respiratory infection is a clue towards the diagnosis, as pericardial effusions are often secondary to viral pericarditis. Accompanying pleural effusions may be found as well. electrical alternans Electrical alternans describes QRS complexes whose amplitudes vary from beat to beat on ECG. It is thought to result from the heart's swinging back and forth within an increased quantity of pericardial fluid. Jugular venous distension, muffled heart sounds, and borderline low blood pressure indicate developing cardiac tamponade. Echocardiography can confirm the presence of pericardial effusion. (Choice A) The PR interval is prolonged in first degree heart block, a condition that is usually asymptomatic and requires no treatment. (Choice B) The presence of F waves, or flutter waves, is diagnostic of atrial flutter. Jugular venous distension and hypotension can develop if the heart rate is rapid enough, but this patient's rate is only 90. (Choice D) A delta wave is an upsloping just before the QRS complex that occurs in patients with an accessory conduction pathway, as in Wolff-Parkinson-White syndrome. It is not associated with pericardial effusion. (Choice E) New-onset right bundle branch block can sometimes be seen in pulmonary embolism. Pulmonary emboli usually cause tachypnea and/or tachycardia. Educational objective: Electrical alternans is when the amplitudes of the QRS complexes vary from beat to beat. It is fairly specific for pericardial effusion. Enlargement of the cardiac silhouette can often be seen on chest x-ray as well. Echocardiogram can more definitely demonstrate a pericardial effusion.

A 45-Year-Old Man Comes to the Emergency Department After an Episode