Epidemiology, anatomy, pathophysiology and clinical evaluation of functional tricuspid regurgitation.

Tricuspid regurgitation (TR) is commonly encountered in the management of patients with a variety of cardiovascular diseases. Primary TR is the result of structural abnormalities of the valve or chordal attachments whereas functional TR results from alterations in right ventricular (RV) or right atrial (RA) size, shape or function. The vast majority of TR cases seen in practice are functional in nature and usually results from left-sided heart disease (e.g., mitral valve disease, left ventricular (LV) systolic dysfunction) and/or pulmonary vascular disease, though it also manifests in the presence of isolated chronic atrial fibrillation (AF). The relationships among the tricuspid leaflets, annulus, chordal attachments and papillary muscles are critical to normal valve function. Disruption of these interactions through annular dilation and apical displacement of the papillary muscles underlies the pathophysiology of functional TR. Two-dimensional transthoracic echocardiography (2D-TTE) is the primary modality used to assess TR. In situations where 2D-TEE is limited, 3D-TTE and transesophageal echocardiography (TEE), multidetector computed tomography (CT) and cardiac magnetic resonance imaging (MRI) can provide additional information. Classification schemes have been proposed that focus not only on the severity of TR, but also on annular dilation and the mode of leaflet coaptation. Despite often being referred to as the "forgotten valve," there is increasing evidence that functional TR is prognostically significant and may warrant intervention. Appropriate patient selection for and timing of intervention are important clinical tasks that require a comprehensive understanding of the pathophysiology and natural history of functional TR.