Pericardial effusion can be classified by: * Onset (acute or subacute vs. chronic [when lasting >3months]) * Distribution (circumferential or loculated) * Haemodynamic impact (cardiac tamponade or no cardiac tamponade) * Composition (serous fluid, blood, rarely air, or gas from bacterial infections) * Size based on a simple semi-quantitative echocardiographic assessment. The size of the effusion on ECHO. indicates the volume of pericardial fluid as follows: * Trivial (seen only in systole) * Small (<10 mm), which corresponds to 50-100 mL pericardial fluid * Moderate (10-20 mm), corresponding to 100-500 mL pericardial fluid * Large (>20 mm), corresponding to >500 mL pericardial fluid * Very large (>25 mm); usually indicates >700 mL pericardial fluid. 🏳️