Pathogenic structural heart changes in early tricuspid regurgitation

ObjectiveSevere, late functional tricuspid regurgitation is characterized by annulus dilation, right ventricular enlargement, and papillary muscle displacement with leaflet tethering. However, the early stages of mild tricuspid regurgitation and its progression are poorly understood. This study examined structural heart changes in mild, early tricuspid regurgitation.MethodsSequential patients undergoing cardiac computed tomography and transthoracic echocardiography with tricuspid regurgitation were identified and evaluated. The tricuspid annulus area and chamber volumes were measured by computed tomography angiography and categorized by tricuspid regurgitation severity.ResultsPatients (n = 622) were divided into 3 groups by tricuspid regurgitation severity: no/trace (n = 386), mild (n = 178), and moderate/severe tricuspid regurgitation (n = 58). Annulus area was highly dependent on and proportional to regurgitation severity and correlated with both right/left atrial enlargement. Annulus area most strongly correlated with right and left atrial volume, and the annulus shape changed from elliptical to circular in moderate/severe tricuspid regurgitation. Mild tricuspid regurgitation was associated with less right/left atrial enlargement than significant tricuspid regurgitation, normal right ventricular size, and annular dilation. Significant tricuspid regurgitation was associated with annular dilation, circularization, and right ventricular enlargement. Mild and significant tricuspid regurgitation were differentiated by annulus area and indexed right ventricular volume.ConclusionsTricuspid annular dilation and right/left atrial enlargement comprise early events in mild functional tricuspid regurgitation. Atrial enlargement occurs before right ventricular dilation, which occurs late, when tricuspid regurgitation is severe. Atrial volume and tricuspid annular dilation are early and sensitive indicators of tricuspid regurgitation significance.