Clinical and imaging phenotypes.

Functional/Secondary tricuspid regurgitation (STR) accounts for over 85% of clinically significant tricuspid regurgitation (TR) and is associated with adverse prognosis and impaired quality of life. Advances in percutaneous tricuspid valve (TV) interventions underscore the need to differentiate TR aetiologies, mechanisms, and phenotypes. STR is subdivided into atrial (A-STR), caused by right atrial dilation and tricuspid annular enlargement without significant leaflet tethering, and ventricular (V-STR), resulting from right ventricular dilation/dysfunction with leaflet tethering. A-STR, increasingly prevalent with ageing and atrial fibrillation, typically presents with preserved right ventricular function, whereas V-STR reflects more advanced disease, is associated with RV dysfunction and, often, left ventricular systolic dysfunction and remodelling and/or left-sided valve disease, carrying higher mortality, compared with A-STR. Cardiac implantable electronic device (CIED) related TR is emerging as a distinct entity, while organic-TR arises from intrinsic structural abnormalities of the valve apparatus. Echocardiography, particularly three-dimensional imaging, is essential for accurate phenotyping and helps in procedural planning. Medical therapy remains primarily symptomatic, with diuretics as first-line therapy and targeted treatment of underlying cardiac pathology. In A-STR, rhythm control strategies, including catheter ablation for atrial fibrillation, may reverse annular remodelling. Surgical repair, preferably annuloplasty, is recommended in selected patients, often when concomitant left-sided surgery is needed. Transcatheter edge-to-edge repair offers a safe and increasingly used alternative, providing symptomatic improvement. The effects on outcomes are likely dependent on the time of intervention and the STR phenotype.