Right ventricular volume and its relationship to functional tricuspid regurgitation

Background: Significant right ventricular (RV) dilatation has long been considered integral to the pathogenesis of functional tricuspid regurgitation (FTR). Objectives: To explore the relationship of RV dilatation and FTR in patients with 'pure' RV volume overload. Methods: Patients (>17yrs) with RV dilatation due to pre-tricuspid shunts (atrial septal defect; ASD and/or partial anomalous pulmonary venous drainage; PAPVD) referred to our service (2000-2019) were retrospectively identified. Those with pulmonary hypertension, primum ASD or left-heart disease were excluded. Using standard cardiac MRI protocols, RV, right atrial and TV parameters were measured and compared. Results: Of 52 consecutively eligible patients (42 +/- 15yrs, 25 males), 25 had ASDs, 13 had PAPVD and 14 had both conditions. All were in sinus rhythm and none had pulmonary regurgitation. Left and right ventricular ejection fractions were normal (LVEF 63 +/- 8%, RVEF 56 +/- 8%). Indexed RV end-diastolic volumes (RVEDVi) were moderately increased (males 148 +/- 33 mL/m(2) and females 141 +/- 42 mL/m(2), range 95-267 mL/m(2)). Despite substantial RV volume overload, no patients had severe tricuspid regurgitation (TR). Only two had > mild TR. There was a weak correlation between tricuspid annular diameter and both degree of RV dilatation (r = 0.37; p = 0.01) and degree of TR (r = 0.38; p = 0.006). There was a similarly poor correlation between right atrial dimensions and the degree of TR (r = 0.34; p = 0.02). Conclusion: When RV dilatation is simply due to volume overload, we find that significant TR is extremely rare. This gives an important and novel insight; that RV dilatation per se does not result in FTR.