Tricuspid Valve Function

 
Introduction
 
The function of the tricuspid valve is to prevent back-flow from the right ventricle to the right atrium during systole. In the absence of disease, the tricuspid valve permits flow into the right ventricle during diastole.  The tricuspid valve is analogous to its left heart counterpart, the mitral valve.
Right Ventricular Filling
 
The factors determining right ventricular filling is the pressure gradient between the right atrium and right ventricle, right atrial function, tricuspid valve area, and right ventricular compliance.  The RA-RV pressure gradient is a consequence of intercavitary volume and compliance of the right ventricle.  Usually, the flow into the right ventricle is less than 0.8 m/sec.  Inadequate or excessive filling can occur by the alteration of one or more factors.
Right Ventricular Filling Factors
 RA-RV Pressure Gradient
 Right Atrial Function
 Tricuspid Valve Area
 Right Ventricular Compliance
 

Flow through the tricuspid valve has a pattern similar to the mitral valve except the systolic pressure gradients and diastolic flow velocities are much less.  Systole occurs from tricuspid valve closure (TVC) to pulmonary valve closure (PVC).  The four phases of diastole are:

  • Isovolumic Relaxation Time (IVRT) (Pulmonary Valve Closure (PVC) to Tricuspid Valve Opening (TVO))
  • Rapid Filling Phase
  • Diastasis
  • Atrial Contraction Phase

The initial systolic event is Isovolumic Contraction Time (IVCT) which occurs from Tricuspid Valve Closure (TVC) to Pulmonary Valve Opening (PVO).  The systolic ejection phase occurs from Pulmonary Valve Opening (PVO) to Pulmonary Valve Closure (PVC).

Right Ventricular Cardiac Cycle
Systole Diastole
IVCT IVRT 
Ejection Phase Rapid Filling
  Diastasis 
  Atrial Contraction
Preload
 
The right ventricle shows the same filling patterns as the left ventricle but with lower peak pressures.   As preload increases, filling of the right ventricle increases over a physiologic range.  Once a physiologic range has been exceeded, right ventricular filling may decrease because of an increase in right ventricular compliance.  The compliance of the right ventricle does not decrease until the right ventricle has dilated to the point where it is being restrained by the pericardium. 
 
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PWD of RVI PWD of RVI
Right Atrial Function
 
Right atrial function can also impact right ventricular filling.  Normally, right atrial contraction contributes little to right ventricular filling.  In normal physiologic conditions most of the filling of the right ventricle occurs in the initial phases of diastole.  However, in right ventricular failure (especially due to pulmonary hypertension), the right atrium may contribute significantly to right ventricular filling. If the right ventricle becomes hypertrophied, right atrial filling becomes increasingly important.  Loss of the atrial "kick" in hypertrophied ventricles can significantly reduce the end-diastolic volume of the right ventricle.  When the right ventricle is dilated, filling of the right ventricle is already maximal, so the loss of right atrial function is of lesser importance.  However, left atrial function becomes more important to deliver what little preload the right ventricle generates to the left ventricle. In the videos below the right ventricle can be seen to increase its end diastolic volume after the atrial kick in normal sinus rhythm.  The atrial fibrillation video does not exhibit an increase in end diastolic volume at the end of diastole.
 
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ME 4CV 2D ME 2CV 2D
Normal Atrial Fibrillation (No Kick)
Tricuspid Valve Area
 
Tricuspid stenosis will decrease right ventricular filling.  Tricuspid regurgitation, while it has some effect on filling, its main effect is a decrease in forward right ventricular output.
 
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Tricuspid Stenosis Tricuspid Regurgitation