Alterations associated with progression of tricuspid regurgitation

(A) Normal tricuspid valve and anatomy of the right side of the heart. The structure of the right heart enables efficient ejection of the same stroke volume as the left side of the heart with approximately 25% of the stroke work.

(B) Early adaptive changes associated with idiopathic functional tricuspid regurgitation or early pulmonary hypertension include right atrial dilation (green arrows) and basal RV dilation (white arrows) with progressive tricuspid annular dilation (yellow arrow) leading to malcoaptation of the tricuspid valve leaflets. Of note, the RV maintains its conical shape and there is no significant leaflet tethering.

(C) With increasing pulmonary impedance there is marked displacement of the anterior papillary muscle (green arrows), lateral RV wall (white arrows), and/or interventricular septum (black arrows), which results in marked tethering of the leaflets. This right-sided heart morphology is associated with more prominent mid-RV enlargement and relatively less annular and basal RV enlargement, resulting in a spherical-shaped RV.