A Pericardial Effusion is when there is a collection of excess fluid within the pericardial cavity. When enough pressure builds up from a pericardial effusion, it can turn into Cardiac Tamponade.
Patients with Pericardial effusion will typically present with exercise intolerance, tachycardia, pleural friction rub, tachypnea, shortness of breath, and chest pain. The causes of a pericardial effusion can be from various causes including pericarditis, myopericarditis, uremia, malignancy, infections, rheumatologic, etc.
An important point you must remember about Pericardial effusions is that is it not just based on size, the deleterious effects of pericardial effusions are actually more dependent on how quickly a pericardial effusion accumulates rather than it’s size.
In the figure below, a rapidly accumulating pericardial effusion can increase the pericardial pressures significantly and lead to cardiac tamponade despite a relatively small size. Conversely, an end-stage renal disease patient can have a chronic pericardial effusion that slowly accumulates with over 200-400 ml with no hemodynamic consequences.
Ultrasound Findings of Pericardial Effusion:
- The parasternal long-axis and subcostal four-chamber views are typically favored for inspection of pericardial effusions
- The Descending aorta is a distinguishing landmark used to distinguish between a Pericardial Effusion and a pleural effusion
- A pericardial effusion will appear anterior to the descending aorta whereas a pleural effusion will appear posterior to the descending aorta.
The cardiac ultrasound image below shows both a pericardial effusion (anterior to the descending aorta) and a pleural effusion (posterior to the descending aorta).
Pericardial effusion vs Pericardial Fat Pad
Being able to determine the difference between a Pericardial Effusion and a Pericardial Fat Pad is important as they may have similar sonographic appearances.
- Pericardial fat pads are usually located anteriorly and can usually be seen on the Parasternal Long Axis view.
- Pericardial fat pads are usually not completely anechoic and can appear to have striations.
- Lastly, pericardial fat pads can usually be seen to move with the motion of the heart.
- If you are in doubt, ask another more experienced POCUS user to look at it or order a formal echo to clarify if needed.
