Clinical context and mechanism of functional tricuspid regurgitation in patients with and without pulmonary hypertension.

BACKGROUND Functional tricuspid regurgitation (FTR) with structurally normal valve is of poorly defined mechanisms. Prevalence and clinical context of idiopathic FTR (Id-FTR) (without overt TR cause) are unknown. METHODS AND RESULTS To investigate prevalence, clinical context, and mechanisms specific to FTR types, Id-FTR versus pulmonary hypertension-related (PHTN-FTR, systolic pulmonary pressure ≥50 mm Hg), we analyzed 1161 patients with prospectively quantified TR. Id-FTR (prevalence 12%) was associated with aging and atrial fibrillation. For mechanistic purposes, we measured valvular and right ventricular (RV) remodeling in 141 Id-FTR matched to 140 PHTN-FTR and to 99 controls with trivial TR for age, sex, atrial fibrillation, and ejection fraction. PHTN-FTR and Id-FTR were also matched for TR effective-regurgitant-orifice (ERO). Id-FTR valvular alterations (versus controls) were largest annular area (3.53±0.6 versus 2.74±0.4 cm(2), P<0.0001) and lowest valvular/annular coverage ratio (1.06±0.1 versus 1.45±0.2, P<0.0001) but normal valve tenting height. PHTN-FTR had mild annular enlargement but excessive valve tenting height (0.8±0.3 versus 0.35±0.1 cm, P<0.0001). Valvular changes were linked to specific RV changes, largest basal dilatation, and normal length (RV conical deformation) in Id-FTR versus longest RV with elliptical/spherical deformation in PHTN-FTR. With increasing FTR severity (ERO ≥40 mm(2)), changes specific to each FTR type were accentuated, and RV function (index of myocardial performance) was consistently reduced. CONCLUSIONS Id-FTR is frequent, linked to aging and atrial fibrillation, can be severe, and is of unique mechanism. In Id-FTR, excess annular and RV-basal enlargement exhausts valvular/annular coverage reserve, and RV conical deformation does not cause notable valvular tenting. Conversely, PHTN-FTR is determined by valvular tethering with tenting linked to RV elongation and elliptical/spherical deformation. These specific FTR-mechanisms may be important in considering surgical correction in FTR.