Let’s Talk Tamponade (Physiology)

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The Pre-brief

Let’s talk about tamponade, but first…some abbreviations

RV – Right Ventricle 

RA – Right Atrium 

LA – Left Atrium 

LV – Left Ventricle 

IVC – Inferior vena cava 

Pericardial Effusion 

  • Mild less than 10 mm 
  • Moderate 10-20mm
  • Large > 20 mm 

Echocardiography can also be used for quantitative assessment of nonloculated pericardial effusions (1). 

Smaller effusion volumes can also cause tamponade in cases of acute accumulation due to lack of compensatory lymphatic drainage as compared to chronic long-standing effusions.

Cardiac Tamponade has been traditionally thought to be a clinical diagnosis but with point-of-care-ultrasound, tamponade physiology can be identified early and help with risk stratification. 

Echocardiographic features seen in a patient with cardiac tamponade 

Circumferential fluid accumulation (localized fluid can also cause tamponade, eg post-cardiac surgery cases)  

  • Post cardiac surgery or trauma may need TEE for better and timely visualization. 

RA late diastole/early systole collapse  

  • Very sensitive but not very specific
  • Duration of atrium collapse > 30 % per cardiac cycle makes this sign more specific. 
  • Image shows a 4 chamber apical view with pericardial effusion and right atrial inversion. 

RV diastolic collapse 

  • In early diastole (when intra-cardiac pressures in RV are low) 
  • More specific sign 
  • Image shows a sub-xyphoid view showing right ventricle collapse 

LA and LV collapse 

  • In early diastole 
  • Very specific sign
  • Mostly seen in loculated post cardiac surgery and in cases of severe pulmonary hypertension.
  • In severe pulmonary hypertension RA and RV collapse may be absent and patients may have ISOLATED LV collapse. 

Mitral and Tricuspid inflow velocity respiratory variation (Mitral E velocity > 25 %. Tricuspid E velocity 40 %) 

  • In tamponade, ventricular inter-dependence leading to an exaggerated response during ventricular filling 
  • inflow velocity is a surrogate for blood flow through the valves. 
  • Present with absent pulses paradoxus in case of tamponade in severe pulmonary hypertension.

Image shows mitral inflow velocities after placing a pulse wave Doppler over mitral valve:

Plethoric IVC 

  • Sensitive but not very Specific. 
  • No IVC plethora in tamponade with isolated loculated effusions in post-trauma and or surgery. 
  • Can also be absent in low-pressure tamponade 

Tamponade in patients with severe pulmonary hypertension 

  • Equalization of pressures may not be present. RV and RA collapse can be absent 
  • May only present with LV collapse 
  • Pulses-paradoxus may not be present 
  • Inflow velocities are key in this situation 
  • Drainage of the pericardial effusion may lead to further hemodynamic compromise 

Tamponade in a patient with significant pleural effusion

  • Large effusions can transmit intra-pleural pressure to the pericardial space and can lead to tamponade physiology 
  • Drainage of the effusion first, can lead to a reversal of tamponade physiology (2).

Tamponade in a patient with hypovolemia (Low-pressure tamponade) 

  • As tamponade is based on pressures and hemodynamics. A hypovolemic patient with a low intra-right-ventricle pressure can lead to a situation where the outside pericardial pressure (pericardial effusion) is higher than the RV pressure leading to RV collapse and thus tamponade physiology. 

The Debrief

  • Always use EKG leads to identify systole and diastole. 
  • Tamponade is a clinical diagnosis that depends on hemodynamics at a particular point in time. 
  • Severe pulmonary hypertension will protect from RV and RA collapse leading to atypical sings for tamponade. Drainage can lead to death. 
  • Significant pleural effusions can lead to tamponade which can reverse with effusion drainage.


  1. David Leibowitz,Gidon Perlman,David Planer,Dan Gilon,Philip Berman,Naama Bogot.Quantification of Pericardial Effusions by Echocardiography and Computed Tomography. The American Journal of Cardiology
  2. Adams JR, Tonelli AR, Rokadia HK, Duggal A. Cardiac tamponade in severe pulmonary hypertension. A therapeutic challenge revisited. Ann Am Thorac Soc. 2015;12(3):455-460. doi:10.1513/AnnalsATS.201410-453CC


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