A 63-year-old woman with a long history of hypertension collapses in her church after experiencing the sudden onset of severe chest pain that radiated to her back. She is rushed to the emergency department. On arrival, she is confused and agitated. Her blood pressure is 90/50 mm Hg and heart rate is 110/min. The jugular veins are distended. The lungs are clear on auscultation. An intra-arterial catheter in the radial artery shows significant variation of systolic blood pressure related to the respiratory cycle. Chest x-ray reveals widening of the mediastinum. Which of the following is the most likely cause of this patient's syncope?

Question

A 63-year-old woman with a long history of hypertension collapses in her church after experiencing the sudden onset of severe chest pain that radiated to her back.  She is rushed to the emergency department.  On arrival, she is confused and agitated.  Her blood pressure is 90/50 mm Hg and heart rate is 110/min.  The jugular veins are distended.  The lungs are clear on auscultation.  An intra-arterial catheter in the radial artery shows significant variation of systolic blood pressure related to the respiratory cycle.  Chest x-ray reveals widening of the mediastinum.  Which of the following is the most likely cause of this patient's syncope?

Quizplus · Accepted Answer

This patient's clinical presentation is consistent with an acute aortic dissection complicated by cardiac tamponade. The sudden onset of severe chest pain radiating to the back and widened mediastinum on chest x-ray are suggestive of aortic dissection. The presence of hypotension, tachycardia, distended jugular veins, and respiratory variation in systolic blood pressure (ie, pulsus paradoxus) are all consistent with the presence of cardiac tamponade. Cardiac tamponade can occur as a complication of aortic dissection, with rupture of the aorta and rapid accumulation of blood in the pericardial space. An abrupt accumulation of even small amounts of blood can significantly raise the pressure inside the pericardial cavity. Increased pericardial pressure causes compression of cardiac chambers and limits diastolic filling of the right-sided chambers. This causes a decrease in preload and reduces cardiac output, resulting in hypotension and syncope. (Choice A) In aortic stenosis, syncope usually occurs with activity. Chest pain is also typically exertional, not as severe as with aortic dissection, and does not radiate to the back. Physical examination in patients with aortic stenosis shows pulsus parvus et tardus (slow-rising and low-amplitude pulse). Pulsus paradoxus or widened mediastinum on chest x-ray is also not present in aortic stenosis. (Choice B) Cardiac tachyarrhythmias, including atrial and ventricular arrhythmias (eg, atrial flutter, fibrillation, ventricular tachycardia or fibrillation), can cause syncope. They usually do not present with sudden onset of severe chest pain, pulsus paradoxus, or a widened mediastinum on chest x-ray. (Choice C) Hypovolemia or intravascular volume depletion typically occurs in the setting of acute blood loss and protracted vomiting and/or diarrhea. Patients have dizziness and postural hypotension or may present initially with hypovolemic shock. In patients with significant intravascular volume depletion leading to syncope, jugular venous pressure is typically reduced with flat neck veins. (Choice D) Papillary muscle dysfunction is a well-described complication of acute myocardial infarction. It causes acute mitral regurgitation and presents as sudden onset of pulmonary edema, hypotension, and progression to cardiogenic shock. Papillary muscle dysfunction is usually not a consequence of aortic dissection. (Choice F) Vagal hyperactivity is the underlying mechanism behind vasovagal syncope, a common cause of syncope in patients presenting to the emergency department. This disorder is characterized by prodromal symptoms, including dizziness, nausea, diaphoresis, pallor, and visual disturbances prior to syncope. Educational objective: Cardiac tamponade can occur as a catastrophic complication of acute aortic dissection. It should be suspected in patients with hypotension, tachycardia, distended neck veins, and pulsus paradoxus who have sudden onset of severe tearing chest pain radiating to the back.

A 63-Year-Old Woman with a Long History of Hypertension Collapses