Figure 1: Transthoracic echocardiography. (a) Parasternal short axis view showing, a cleft in the right atrioventricular valve (Arrow). (b) Apical four chamber view showing a well coapted right atrioventricular valve with moderate regurgitation.

The right ventricular systolic pressure (RVSP) was 35 mmHg, showing normal biventricular function. The patient was taken up to surgery and the intraoperative findings showed the cardiomegaly in the left superior vena cava was draining into the dilated coronary sinus. Large primum ASD, complete cleft in left AV valve leaflet with moderate regurgitation, complete cleft in right AV valve with moderate regurgitation. The cleft in the left AV valve was sutured with interrupted 5-0 polypropylene sutures. The primum ASD was closed with an autologous untreated pericardial patch which keeping the coronary sinus on the right atrial side. The cleft in the right AV valve was repaired with 5-0 polypropylene suture (Figure 2). The posterior right AV valve annuloplasty was done using 4-0 polypropylene pledgeted suture.

Figure 2: Intraoperative pictures. (a) Complete cleft of a right atrioventricular valve. (b) A suture closed cleft.

The intraoperative transesophageal echocardiography revealed no residual shunt in the trivial left and right AV valve regurgitation and good biventricular function. The postoperative course was uneventful. The transthoracic echocardiography before discharge showed, there was not any residual ASD, trivial left and right AV valve regurgitation, RVSP 22 mmHg, mild right ventricular dysfunction, no pericardial effusion, and normal left ventricular function.

During the three-month follow-up appointment, the patient was in NYHA class I, and the echocardiography showed, no residual shunt or trivial left and right AV valve regurgitation. There was good ventricular function. A written informed consent was obtained from the patient.

The so-called ostium primum defect is an AV septal defect found in a common AV junction, but in which the fused bridging leaflets of the common AV valve are also fused to the scooped-out crest of the ventricular septum. As a result, shunting across the AV septal defect occurs only at atrial level.[4] These leaflets, irrespective of whether they guard a common AV orifice or separate orifices for the right and left ventricles, bear scant resemblance to the arrangement of the leaflets of the normal mitral and tricuspid valves.[4]

In the currently accepted definition of the cardiac morphology, it is true that the partial AV canal defect will have two separate AV valves although they will not always be well defined. The right AV valve can have three or four cusps depending on the degree of fusion between the anterior and posterior bridging leaflets. If these leaflets are completely fused we can observe a “right atrioventricular valve” made of three cusps namely the fused superior and inferior bridging leaflet, the right anterosuperior leaflet and the right mural leaflet.[4] Unlike with the cleft left AV valve, the cleft right AV valve does not produce severe symptoms because of the low pressure of the right ventricle and so this condition is often underdiagnosed and it can be associated with other congenital anomalies.[1-3]

Eichhorn et al.[1] first reported a 0.6% incidence of right AV valve cleft in patients with a diagnosis of congenital heart disease, and a 0.018% isolated cleft causing right AV valve regurgitation. Embryologically, the right AV valve develops from the inner wall of the right ventricle, by a process called undermining. Eichhorn et al.[1] described two theories. First, the right AV valve cleft, develops where the lateral endocardial cushion meets the right dorsal conus swelling. Therefore, the cleft might be the result of an anomalous fusion. Second, defective undermining process lead to variable anatomic structure of the right AV valve which may lead to the formation of cleft. Variability makes it difficult to differentiate a cleft from additional valves[1,2]

The anomalous fusion theory is the most widely accepted theory for complete cleft especially when a partial AV canal defect or endocardial cushion defect is present. The clinical features depend on the severity of tricuspid regurgitation and the associated congenital cardiac anomalies. Most patients commonly have right heart failure and supraventricular arrhythmias. At cardiac auscultation, a grade 2-3/6 holosystolic murmur is audible along with evidence of an associated cardiac malformation. The electrocardiography often demonstrates a right heart volume overload or right bundle branch block, or both. In most cases, the chest X-ray film shows marked enlargement of right-sided heart chambers without signs of pulmonary venous congestion. An echocardiography is the diagnostic tool used for this rare anomaly. Two and three dimensional transthoracic as well as transesophageal echocardiography can delineate this anomaly.[3]

The most common findings are a visible cleft in the right AV valve and a regurgitation jet in well aligned right AV valve leaflets. If the alignment deformity or prolapse is visible, it may be associated with a congenitally malformed valve and a cleft is very difficult to find in such a scenario. In this case, surgical closure of the cleft with or without a suture or a ring annuloplasty is the treatment of choice.[1,2] The ultimate decision depends on the severity of the right AV valve regurgitation and the associated congenital anomaly. Isolated mild AV valve regurgitation doesn't require any surgical treatment but the mild regurgitation associated with congenital cardiac anomaly requires correction of the anomaly with the closure of the cleft. For moderate or severe regurgitation some sort of annuloplasty technique will help in the long-term results.

In conclusion, the cleft of the right atrioventricular valve is a rare congenital anomaly. It is probably a result of a malformation of the right atrioventricular valve which occurred during embryologic morphogenesis. The diagnosis is easily made with an echocardiography. In most cases, the treatment of choice is surgical reconstruction of the deficient leaflet with or without suture or ring annuloplasty.

Declaration of conflicting interests
The authors declared no conflicts of interest with respect to the authorship and/or publication of this article.

Funding
The authors received no financial support for the research and/or authorship of this article.

1) Eichhorn P, Ritter M, Suetsch G, von Segesser LK, Turina M, Jenni R. Congenital cleft of the anterior tricuspid leaflet with severe tricuspid regurgitation in adults. J Am Coll Cardiol 1992;20:1175-9.

2) Motoyoshi N, Tofukuji M, Sakurai M, Ohmi M, Tabayashi K. Cleft on tricuspid anterior leaflet. Ann Thorac Surg 2001;71:1350-1.

3) Séguéla PE, Roubertie F, Tafer N, Thambo JB, Iriart X. Congenital isolated cleft of the tricuspid valve. Eur Heart J Cardiovasc Imaging 2014;15:1425.

4) Anderson RH, Baker EJ, Redington A, Rigby ML, Penny D, Wernovsky G, editors. Pediatric Cardiology. 3rd ed. Philadelphia: Churchill Livingstone; 2010.