A 64-year-old man is brought to the emergency department with a 2-hour history of severe chest pain accompanied by nausea. The pain started suddenly, and the patient describes it as "tearing." He has a long-standing history of hypertension and type 2 diabetes mellitus. He has no history of coronary artery disease or stroke. The patient is a former smoker with a 35-pack-year history. He does not use illicit drugs. ECG shows sinus tachycardia without any significant ST-segment or T-wave changes. CT angiography is performed and confirms dissection of the ascending aorta extending up to the arch. While the patient is being prepared for urgent surgery, he develops increasing shortness of breath and refuses to lie flat. Chest auscultation reveals bibasilar crackles that were not present on initial evaluation. Which of the following is the most likely cause of this patient's shortness of breath?

Question

A 64-year-old man is brought to the emergency department with a 2-hour history of severe chest pain accompanied by nausea.  The pain started suddenly, and the patient describes it as "tearing."  He has a long-standing history of hypertension and type 2 diabetes mellitus.  He has no history of coronary artery disease or stroke.  The patient is a former smoker with a 35-pack-year history.  He does not use illicit drugs.  ECG shows sinus tachycardia without any significant ST-segment or T-wave changes.  CT angiography is performed and confirms dissection of the ascending aorta extending up to the arch.  While the patient is being prepared for urgent surgery, he develops increasing shortness of breath and refuses to lie flat.  Chest auscultation reveals bibasilar crackles that were not present on initial evaluation.  Which of the following is the most likely cause of this patient's shortness of breath?

Quizplus · Accepted Answer

11ec25c8_d178_1f2d_bc81_25bec3b73ee8_MD0003_00 Aortic dissection involving the ascending aorta (type A) is associated with a mortality rate of 1%-2% per hour following symptom onset, and emergency surgical repair is warranted to prevent complications and death. Retrograde extension of the intimal tear can involve the aortic valve and cause acute aortic regurgitation (AR) with rapid elevation in left ventricular end-diastolic pressure. As seen in this case, affected patients can develop sudden onset of worsening chest pain, hypotension, pulmonary edema, and orthopnea (suggested by refusal to lay flat), along with the early decrescendo diastolic murmur of AR. type A (Choice A) Acute respiratory distress syndrome (ARDS) refers to respiratory failure with dyspnea, hypoxemia, bilateral alveolar infiltrates, and crackles. ARDS is a diagnosis of exclusion; the pulmonary edema in this patient with acute aortic dissection is more likely due to acute AR (cardiogenic pulmonary edema). (Choice C) Aortic dissection involving the carotid or vertebral arteries can cause cerebral hypoperfusion, leading to stroke or transient ischemic attack. (Choice D) Ascending aortic dissection can propagate proximally into the pericardial space and lead to hemopericardium and cardiac tamponade. The elevated pressure in the pericardial space prevents filling of the heart chambers-primarily the low-pressure, right-sided chambers. This leads to a reduction in cardiac output, which can cause dyspnea as well as hypotension and jugular venous distension. However, because the right-sided heart chambers are principally affected, the lungs remain clear and there is usually no evidence of pulmonary edema (eg, orthopnea, crackles on lung auscultation). (Choice E) Pulmonary arterial hypertension describes elevated pulmonary arterial pressure that is caused directly by pathology in the pulmonary arteries/arterioles (ie, intimal thickening, vasoconstriction). Although acute AR transmits elevated hydrostatic pressure back to the pulmonary arteries, the pulmonary hypertension that is created is secondary and is not the principal cause of respiratory distress. Educational objective: Ascending aortic dissection can propagate proximally from the site of intimal tear to involve the aortic valve, causing acute aortic regurgitation and heart failure. Cardiac tamponade is another potential complication of ascending aortic dissection that can be differentiated from acute aortic regurgitation by an absence of pulmonary edema. References: Corrigendum to: 2014 ESC guidelines on the diagnosis and treatment of aortic diseases. (http://www.ncbi.nlm.nih.gov/pubmed/26129948) Aortic dissection: new frontiers in diagnosis and management: part I: from etiology to diagnostic strategies. (http://www.ncbi.nlm.nih.gov/pubmed/12900496)

A 64-Year-Old Man Is Brought to the Emergency Department with a 2-Hour