The condition where heart chambers are compressed by blood in the pericardial sac, reducing preload, is?

• A. Pulmonary embolism
• B. Myocardial infarction
• C. Aortic dissection
• D. Pericardial tamponade

Answer: (D)

When blood or fluid fills the pericardial sac, it raises the pressure around the heart and externally compresses the chambers, especially during diastole when they’re supposed to fill. This limits ventricular filling, reduces end-diastolic volume, and therefore lowers preload. With less preload, the stroke volume and cardiac output fall even if the heart muscle itself is healthy. This scenario is pericardial tamponade. Clinically, it leads to poor perfusion and can show signs of venous congestion; the emergency treatment is rapid relief of the pressure, typically by pericardiocentesis or surgery, and addressing the underlying cause. The other conditions involve different mechanisms (such as a blockage in the pulmonary circulation, myocardial tissue death, or tearing of the aorta) and do not describe external compression of the heart by fluid in the pericardial sac.