The following are 10 points to remember about this state-of-the-art review on functional tricuspid regurgitation (TR):

1. Background. Functional TR is primarily due to tricuspid annular dilation and right ventricular (RV) enlargement and dysfunction; it occurs most often secondary to left-sided heart disease, especially in the setting of mitral valve pathology.
2. Functional TR assessment. The authors propose that, in assessing functional TR, it is important to have a systematic approach that addresses its impact; which includes the severity of TR, tricuspid annular size, and the mode of tricuspid leaflet coaptation and extent of tricuspid leaflet tethering.
3. Tricuspid valve anatomy. The tricuspid valve has three leaflets (anterior, posterior, and septal). The anterior leaflet is largest in surface area and is almost always anchored by a single papillary muscle; affected most by annular dilation, functional TR occurs when annular dilation reduces coaptation of the anterior leaflet. RV enlargement can result in papillary muscle displacement, another mechanism of functional TR.
4. TR severity. TR severity is most often assessed on echocardiography using color-flow Doppler; assessment can be affected by factors including hemodynamics and instrument settings. The vena contracta and PISA assessment of regurgitant volume (RV) and effective regurgitant orifice area (EROA) also can be used to assess TR severity. A PISA radius >9 mm at a Nyquist limit of 28 cm/s, RV >45 ml, and EROA >40 mm² are associated with severe TR.
5. Categories of TR severity. The authors propose that TR should be assessed in one of three categories: none or mild, mild-to-moderate or moderate, or severe.
6. Tricuspid annular assessment. The tricuspid annulus can be measured in diastole from the apical four-chamber view; in this view, an annular diameter >40 mm (or >21 mm/m² body surface area) is considered to be dilated. Alternatively, intraoperative measurement of the diameter from the anterior-septal commissure to the anterior-posterior commissure >70 mm corresponds to an echocardiographic septal-lateral measurement >40 mm, and is considered dilated.
7. Leaflet coaptation. The surface of contact between the leaflets is the coaptation height. Normal coaptation occurs at the level of the annulus or just below it, with a coaptation length of 5-10 mm.
8. Tethering distance, tethering area. The distance of leaflet coaptation that forms the plane of the tricuspid annulus is the tethering distance (or tethering height). The distance between the leaflets and the annular plane is the tethering area. Leaflet tethering is thought to be significant if there is a tethering distance >8 mm or a tenting area >1.6 cm².
9. The authors propose three stages for the assessment of functional TR:
   • Stage 1. No or mild TR, the annulus is not dilated, and leaflet coaptation is normal.
   • Stage 2. Mild or moderate TR, the annulus is dilated, and leaflet coaptation is impaired (occurring only at the edges).
   • Stage 3. Severe TR, dilated annulus, and impaired coaptation (occurring only at the edges or not at all, with or without leaflet tethering).
10. The authors propose that stage 1 disease should be treated medically, stage 2 disease with tricuspid annuloplasty, and stage 3 disease with tricuspid annuloplasty plus leaflet augmentation if leaflet tethering is present.

Keywords: Body Surface Area, Cardiac Surgical Procedures, Diastole, Dilatation, Pathologic, Echocardiography, Heart Failure, Hemodynamics, Hypertrophy, Right Ventricular, Mitral Valve, Papillary Muscles, Radius, Ventricular Dysfunction, Right, Tricuspid Valve, Tricuspid Valve Insufficiency

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