BACKGROUND Little is known about the determinants and outcomes of significant atrial functional tricuspid regurgitation (AFTR).

OBJECTIVES The authors aimed to identify risk factors for significant TR in relation to atrial fibrillation-flutter (AF-AFL) and assess its prognostic implications.

METHODS The authors retrospectively studied patients with mild TR with follow-up echocardiography examinations. Significant TR was defined as greater than or equal to moderate TR. AFTR was defined as TR, attributed to right atrial (RA) remodeling or isolated tricuspid annular dilatation, without other primary or secondary etiology, except for AF-AFL. The Mantel-Byar test was used to compare clinical outcomes by progression of AFTR.

RESULTS Of 833 patients with mild TR, 291 (34.9%) had AF-AFL. During the median 4.6 years, significant TR developed in 35 patients, including 33 AFTRs. Significant AFTR occurred in patients with AF-AFL more predominantly than in those patients without AF-AFL (10.3% vs 0.6%; P < 0.001). In Cox analysis, AF-AFL was a strong risk factor for AFTR (adjusted HR: 8.33 [95% CI: 2.34-29.69]; P = 0.001). Among patients with AF-AFL, those who developed significant AFTR had larger baseline RA areas (23.8 vs 19.4 cm²; P < 0.001) and RA area-to-right ventricle end-systolic area ratio (3.0 vs 2.3; P < 0.001) than those who did not. These parameters were independent predictors of AFTR progression. The 10-year major adverse cardiovascular event was significantly higher after progression of AFTR than before or without progression (79.8% vs 8.6%; Mantel-Byar P < 0.001).

CONCLUSIONS In patients with mild TR, significant AFTR developed predominantly in patients with AF-AFL, conferring poor prognosis. RA enlargement, especially with increased RA area-to-right ventricle end-systolic area ratio, was a strong risk factor for progression of AFTR.