What is the primary cause of pulsus paradoxus?

Pulsus paradoxus is a clinical finding characterized by an exaggeration of the normal decrease in systolic blood pressure that occurs during inspiration. It is defined as a drop in blood pressure of more than 10 mm Hg during inspiration. The primary cause of pulsus paradoxus is cardiac tamponade, which is the accumulation of fluid in the pericardial space leading to impaired cardiac filling, particularly during diastole.

In cardiac tamponade, the pressure within the pericardial sac rises, restricting the heart's ability to expand fully during each cycle. During inspiration, negative intrathoracic pressure increases venous return to the right side of the heart. However, because of the restricted filling of the right ventricle due to the fluid around the heart, the left ventricle receives less blood during this phase, leading to a significant drop in stroke volume and, consequently, systolic blood pressure. This physiological response distinctly manifests as pulsus paradoxus.

In contrast, conditions like heart failure and aortic dissection can also lead to changes in blood pressure and other cardiovascular symptoms but are not characterized by pulsus paradoxus specifically. An atrial septal defect may present with other signs of volume overload but does not directly cause puls