A 34-year-old woman comes to the emergency department with difficulty breathing and dizziness. An arterial line is placed and her blood pressure tracing is shown below. Which of the following diagnoses is most consistent with these findings?

Question

A 34-year-old woman comes to the emergency department with difficulty breathing and dizziness.  An arterial line is placed and her blood pressure tracing is shown below.  Which of the following diagnoses is most consistent with these findings?

Quizplus · Accepted Answer

Systemic arterial pressure normally falls <10 mm Hg during inspiration. However, this patient's arterial blood pressure tracing shows a fall in systolic pressure >10 mm Hg during inspiration. This exaggerated drop in blood pressure is referred to as pulsus paradoxus. It is most commonly seen in patients with cardiac tamponade, which causes increased pressure within the pericardial sac. As a result, the right and left ventricles are forced to compete with each other for space as they fill with blood (ventricular interdependence). During inspiration, increased systemic venous return to the right heart causes the interventricular septum to shift into the left ventricular cavity, reducing left ventricular end diastolic volume. This leads to decreased stroke volume and, consequently, reduced systolic blood pressure. Pulsus paradoxus can also be caused by other conditions such as asthma and chronic obstructive pulmonary disease (COPD). Normally, there is a small variation in intrathoracic pressure with respiration, which drops 2-5 mm Hg below atmospheric pressure during inspiration. In patients with severe asthma or COPD, the drop in intrathoracic pressure is greatly exaggerated (up to 40 mm Hg). This negative pressure causes pooling of blood in the pulmonary vasculature decreasing left ventricular preload. Marked expansion of the lungs in asthma and COPD can also impinge upon the outward expansion of the heart. Together, these factors lead to an excessive drop in blood pressure that is detected as pulsus paradoxus. (Choice A) Significant aortic regurgitation causes a large increase in left ventricular end-diastolic pressure that precludes the interventricular septum from shifting toward the left ventricular cavity during inspiration. This prevents development of pulsus paradoxus even in the presence of pericardial effusion and cardiac tamponade. (Choices B, C, and D) Lobar pneumonia, mitral stenosis, and panic attack are not associated with the finding of pulsus paradoxus on physical examination or arterial tracings. Educational objective: Pulsus paradoxus is defined as an exaggerated fall in systemic blood pressure >10 mm Hg during inspiration. It is a frequent finding in cardiac tamponade but can also occur in conditions without pericardial effusion such as severe asthma or chronic obstructive pulmonary disease.

A 34-Year-Old Woman Comes to the Emergency Department with Difficulty