Tamponade

Acute or subacute, occurs when fluid or blood builds up in the pericardial space

Typically, the pericardial space can accommodate shifts in intracardiac volume. However, as fluid accumulates in the pericardial space, the capacity to accommodate reaches an inflection point and the pressure rapidly rises, reducing cardiac filling

Physiology: Ventricular interdependence, meaning as the RV fills with inspiration, because the free wall is restricted due to the pericardial fluid, the only direction for filling to occur is towards the septal wall, thereby inhibiting LV filling and subsequent stroke volume and pulse pressure 

Clinical Signs: Classically described Beck's Triad (Muffled heart sounds due to effusion, jugular venous distension, and hypotension due to impaired filling) seen in a minority of cases

Tachycardia may be the only sign in many patients before more significant decompensation

May also see pulsus paradoxus

Echo findings: Pericardial fluid, can also see RA and RV collapse on echocardiography but important to note that cardiac tamponade is a clinical diagnosis, not an echocardiographic diagnosis

Guide to the TTE 

Treatment: pericardial drainage via pericardiocentesis, potentially with placement of a pericardial drainage catheter