Right atrial volume is a major determinant of tricuspid annulus area in functional tricuspid regurgitation: A three-dimensional echocardiographic study

Aims: The aim of this study is to explore the relationships of tricuspid annulus area (TAA) with right atrial maximal volume (RAVmax) and right ventricular end-diastolic volume (RVEDV) in healthy subjects and patients with functional tricuspid regurgitation (FTR) of different aetiologies and severities. Methods and results: We enrolled 280 patients (median age 66 years, 59% women) with FTR due to left heart disease (LHD), pulmonary hypertension (PH), corrected tetralogy of Fallot (TOF), chronic atrial fibrillation (AF), and 210 healthy volunteers (45 years, 53% women). We measured TAA at mid-systole and end-diastole, tenting volume of tricuspid leaflets, RAVmax, and RVEDV by 3D echocardiography. Irrespective of TA measurement timing, TAA correlated more closely with RAVmax than with RVEDV in both controls and FTR patients. On multivariable analysis, RAVmax was the most important determinant of TAA, accounting for 41% (normals) and 56% (FTR) of TAA variance. In FTR patients, age, RVEDV, and left ventricular ejection fraction were also independently correlated with TAA. RAVmax (AUC = 0.81) and TAA (AUC = 0.78) had a greater ability than RVEDV (AUC = 0.72) to predict severe FTR (P < 0.05). Among FTR patients, those with AF had the largest RAVmax and smallest RVEDV. RAVmax and TA were significantly dilated in all FTR groups, except in TOF. PH and TOF had largest RVEDV, yet tenting volume was increased only in PH and LHD. Conclusion: RA volume is a major determinant of TAA, and RA enlargement is an important mechanism of TA dilation in FTR irrespective of cardiac rhythm and RV loading conditions.