Isolated double-orifice tricuspid valve is an extremely rare congenital anomaly [10, 11], with less than 30 cases described in the literature [11]. More frequently, although still rare, it is associated with other congenital anomalies such as septal defects, Ebstein anomaly, TOF, mitral and pulmonary valve anomalies, and transposition of the great arteries [10, 12]. In 1876 Greenfild first described it for the mitral and tricuspid valves [13]. Also known as AV valve duplication, three different types are distinguished: type 1, with a simple fenestration in a leaflet; type 2, with fusion of leaflet tissue across the orifice dividing it in two but with normal AV valve papillary muscles; and type 3, with each orifice being supported by its own tension apparatus [10, 14].

Rarely, the valve may function normally, but more often it is insufficient, stenotic, or a combination of both [11]. Surgery, if at all indicated, will address the stenotic or insufficient components accordingly. In patients with associated defects, even with a correctly functioning double-orifice tricuspid valve, the detachment of the anterior and septal leaflets is often necessary to enhance visualization for repair of other defects, followed by reattachment at the annular level [12]. Results of repair are reported satisfactory in all case series [14, 15]. However, the correction of concomitant congenital cardiac anomalies is usually the indication for surgery and determines the outcome (Figs. 14.3 and 14.4) [12, 14, 15].

Uhl’s anomaly is an extremely rare congenital condition in which the RV myocardial tissue is lacking and replaced by fibroelastic tissue. The resulting RV is dilated and noncontractile, leading to various degrees of right heart failure and TI (Fig. 14.5) [16–20]. Pulmonary blood flow is dependent on right atrial contraction and paradoxical septal motion [18]. Surgical options are limited and include cardiac transplantation or conversion to single-ventricle physiology [16, 17]. In selected patients, this initially involves atrial septectomy, tricuspid valve exclusion, and a bidirectional Glenn anastomosis, with or without RV plication [16, 18–20]. These variants of one-and-a-half repair are often followed by total cavopulmonary connection [17, 18]. Historically, surgical results have been poor, albeit case reports in the more modern era have resulted in patient survival, with a more aggressive approach toward single-ventricle palliation and RV exclusion [18]. Occasionally, a patient may have moderate to severe RV dysfunction, which may allow for some RV developed pressure and therefore aid in cardiac output. Under these circumstances, tricuspid annuloplasty techniques can be employed to help with pressure-derived forward flow through the pulmonary artery circuit, which is clearly better than Fontan physiology. This is rare, however (Fig. 14.6).

In patients with AV canal, right-sided AV valve insufficiency may result from RV dilatation from massive left-to-right shunting and resultant annular dilatation, from technical error at the time of repair in judging the level of ventricular septation between the two future AV valves and/or insufficient availability of tissue to achieve adequate coaptation of leaflets, from clefts in the right-sided valve, or from straddling/overriding [21–28]. Furthermore, unbalanced AV canal with a right or dominant left ventricle may be associated with TI induced by pulmonary hypertension, insufficient RV contraction and functional TI, or overriding/straddling. Indications for surgery are unclear for isolated TI, as associated pulmonary valve and RV pathology are often confounding. However, they may include but are not limited to symptoms or reduced exercise intolerance, cyanosis (concomitant interatrial communication), progressive RV dilatation, progression of RV dysfunction, and onset/progression of arrhythmias [24]. Depending on the underlying mechanism, appropriate corresponding techniques may be used to achieve valvar competence, including De Vega annuloplasty, Kay-Wooler plasty, ring annuloplasty, surgical creation of a double-orifice valve, patch enlargement of a leaflet, and a one-and-half repair in the case of unbalanced ventricles with a bidirectional cavopulmonary anastomosis (Fig. 14.7) [5, 6, 21–28].

In single-ventricle physiology and an incompetent tricuspid valve, the majority of cases are represented by HLHS or unbalanced AV canal with a hypoplastic RV. Mechanisms are complex and multifactorial, including chronic volume overload, structural AV valve abnormalities, and myocardial damage from subendocardial ischemia and resulting papillary muscle dysfunction along with regional ventricular wall motion abnormality. Despite documented systemic ventricular dilatation from chronic volume overload leading to annular dilatation and TI from lack of leaflet coaptation, the vast majority of insufficient tricuspid valves in single ventricles have structural anomalies, including bileaflet or quadrileaflet valves, accessory orifices, and prolapsed leaflets. Hence, despite the myth or wishful thinking for volume unloading at stage II palliation for HLHS or other single-ventricle variants, valve insufficiency will often not improve by cavopulmonary anastomosis alone.

In single-ventricle physiology, TI occurs rarely at birth and therefore seems to be an acquired lesion. The rare neonates who present with severe valvar insufficiency are usually triaged to cardiac transplantation. With progressive and increasing AV valve insufficiency, the question of timing for an operation becomes crucial [17]. Insufficiency can develop after stage I palliation and, if severe enough, mandate an interstage operation prior to stage II. If mild to moderate, repair can be deferred and performed concomitantly at stage II palliation. Repairs are recommended at stage III Fontan completion only if a simple repair can be done (i.e., without unreasonable additional bypass or cross-clamp times) [17], as perioperative morbidity and surgical mortality may otherwise reach prohibitive levels. Finally, repair at Fontan conversion may be indicated if mild to moderate regurgitation exists [29].

Techniques of repair are variable and include Alfieri creation of a double-orifice valve or the Alfieri clover technique [23, 30], a Carpentier ring plasty, edge-to-edge repair [31], suture annuloplasty, cleft closure, patch augmentation of a leaflet, chordal repair, bridging annuloplasty [32, 33], and chordal replacement among others (Figs. 14.8, 14.9, 14.10, 14.11, and 14.12) [30, 31, 33, 34].