Which cardiac chambers are especially vulnerable to compression in tamponade, with abnormal filling appearing early?

The supplied material emphasizes that the **right heart is most vulnerable** to compression by pericardial effusion and that abnormal right-heart filling is the first sign of a haemodynamically significant effusion. This is consistent with the lecture's description of diastolic collapse involving the right atrium and right ventricle. The alternatives either identify the wrong side or claim equal early involvement, which is not what the material teaches. **Key takeaway:** Look for early impairment of right-sided filling in significant tamponade. **Glossary:** **Diastole**: the phase in which the heart relaxes and fills. **Compression**: pressure that deforms or restricts a structure.