This patient's presentation is consistent with a diagnosis of pericardial tamponade. Pulsus paradoxus is a sign commonly associated with cardiac tamponade and is defined as a decrease in systolic blood pressure of greater than 10 mmHg with inspiration.
Cardiac tamponade is classically associated with Beck's triad of signs: 1) hypotension, 2) jugular venous distension, and 3) muffled heart sounds. In addition, pulsus paradoxus is seen in acute cardiac tamponade, as well as in constrictive pericarditis, severe obstructive lung disease, or restrictive cardiomyopathy. In the absence of any pathology, there is normally a fall in blood pressure of less than 10 mmHg with inspiration. However, when this drop exceeds 10 mmHg in magnitude, it is referred to as pulsus paradoxus. In a normal heart, inspiration increases systemic venous return and leads to increases in right heart volumes; expansion of the wall of the right ventricle occurs into the pericardial space without impacting left ventricular volume. However, in cases of pulsus paradoxus, the fluid-filled pericardium prevents expansion of the right ventricular wall into the pericardial space. Instead, the interventricular septum bows into the left ventricle. In turn, this leads to a decrease in left ventricular diastolic volume, which results in decreased cardiac output and therefore a decreased systolic pressure during inspiration.
Goyle et al. discuss the presentation and diagnosis of pericarditis. They state that, in rare cases, the inflammation associated with pericarditis can lead to large pericardial effusions. These effusions can interfere with cardiac function and lead to cardiac tamponade, with pulsus paradoxus evident on examination.
Hamzaoui et al. discuss the pathophysiology and clinical implications of pulsus paradoxus. They state that the interdependence between the left and right ventricles plays an important role in the decrease in blood pressure with inspiration seen in pulsus paradoxus. They conclude that early recognition of pulsus paradoxus in the emergency department setting can lead to quicker diagnosis and treatment of cardiac tamponade. Additionally, serial measurements of pulsus paradoxus can be used to assess the severity of acute asthma exacerbations and their responses to therapy.
Illustration A summarizes the mechanism of pulsus paradoxus. Illustration B depicts a flow-chart highlighting the underlying pathophysiology behind several different causes of pulsus paradoxus.
Answer 1: Pulsus paradoxus is characterized by a decrease in blood pressure, not heart rate, with inspiration.
Answer 2: The presentation of cardiac tamponade is classically associated with hypotension, a component of Beck's triad that is due to a decreased cardiac stroke volume.
Answer 3: Reflex tachycardia is expected in the setting of hypotension and decreased perfusion secondary to decreased cardiac output.
Answer 5: Kussmaul's sign, a paradoxical increase in the central venous pressure, is expected in cardiac tamponade; this is apparent in the vignette with the finding of distended neck veins on examination.
Goyle KK, Walling AD. Diagnosing pericarditis. Am Fam Physician. 2002 Nov 1;66(9):1695-702.
PMID:12449268 (Link to Abstract)
Hamzaoui O, Monnet X, Teboul JL. Pulsus paradoxus. Eur Respir J. 2012 Dec 6.
PMID:23222878 (Link to Abstract)
USMLE World Step 1 QBank Question #2099. Copyright © USMLEWorld, LLC 2012