Cardiac tamponade has which effect on LV diastolic filling?

• A. Increased
• B. Decreased
• C. No change
• D. Increased afterload

Answer: (B)

In tamponade, the buildup of fluid in the pericardial sac raises the pressure around the heart, constraining diastolic expansion of the chambers. LV diastolic filling depends on the transmural pressure gradient driving expansion (the LV diastolic pressure minus the surrounding pericardial pressure). When pericardial pressure increases, that gradient falls, so the LV cannot fill as much, leading to decreased LV end-diastolic volume and preload. This reduced filling lowers stroke volume and cardiac output, even if systolic function is intact. It’s not about increased afterload; the external constraint mainly limits filling rather than increasing the resistance to ejection.