Review Question - QID 106789

This patient presents with cardiac tamponade and examination reveals pulsus paradoxus, a decrease in systolic blood pressure by > 10 mmHg during inspiration. Tension pneumothorax is another disease that can present with pulsus paradoxus.

Cardiac tamponade is a frequent complication of penetrating or severe blunt thoracic trauma. It is caused by compression of the heart by fluid (most often blood in trauma cases) in the pericardium, which leads to a decrease in cardiac output. Typical findings include hypotension, increased jugular venous distention (Figure A), distant heart sounds, tachycardia, and pulsus paradoxus.

Goyle and Walling discuss pathophysiology of constrictive pericarditis and cardiac tamponade. To review, normal inspiration causes intrathoracic pressure to become negative. This causes ventricular chambers to dilate. In cardiac tamponade, the capacity to dilate is limited, particularly for the left ventricle. Notably, some blood still flows toward the right side of the heart during inspiration. The right ventricular inflow causes the intraventricular septum to shift to the left more than usual, decreasing left ventricular capacity and output. This results in the pulsus paradoxus phenomenon, which is present in 70 to 80% cases of cardiac tamponade.

Khasnis and Lokhandwala examine multiple diseases that can produce the pulsus paradoxus sign. They organize into three potential sources: cardiac, extracardiac pulmonary, and extracardiac nonpulmonary. Extracardiac pulmonary causes include asthma exacerbation and tension pneumothorax. Extracardiac nonpulmonary causes include anaphylaxis, diaphragmatic hernia, SVC obstruction, and extreme obesity. Briefly, tension pneumothorax can externally compress cardiac chambers, limiting cardiac output despite increased venous return during inspiration.

Figure A demonstrates jugular vein distention, which is typical of cardiac tamponade. Figure B demonstrate a normal chest radiograph that can be observed in cardiac tamponade and helps to rule out tension pneumothorax as a cause of this patient's presentation. Figure C is a transthoracic echocardiography image that demonstrates fluid in the pericardial space, which essentially confirms cardiac tamponade in this clinical setting.

Incorrect Answers:
Answers 1, 2, and 5: These are all conditions not associated with pulsus paradoxus.
Answer 4: Aortic dissection could cause cardiac tamponade to occur which would cause similar symptoms. However, the best, most direct answer to this question is a tension pneumothorax which would directly cause these symptoms itself.