Incidental Finding of an Isolated Double-orifice Mitral Valve in an Asymptomatic Man.

Double-orifice mitral valve (DOMV) is a very rare congenital anomaly that usually presents as mitral regurgitation. We present the case of a 39-year-old asymptomatic, healthy man with no previous medical history who was affected by isolated complete bridge type DOMV, incidentally detected by two-dimensional echocardiographic examination in the parasternal short-axis view. The mitral valve of the patient was normally functioning without any other coexistent cardiac abnormalities. Isolated DOMV was also confirmed by cardiac magnetic resonance imaging. The patient is now followed up to detect possible complications.

INTRODUCTION

Isolated double-orifice mitral valve (DOMV) is an extremely rare congenital anomaly whose exact incidence has not been conclusively determined.[1] Interestingly, this cardiac abnormality rarely presents as an isolated finding, preferentially associated with valvular regurgitation rather than stenosis.[1] The etiology of DOMV has been recognized in the abnormal fusion of the endocardial cushions and abnormal development of the mitral valve during the delamination process.[2] Transthoracic echocardiography is the modality of choice for the characterization of this anomaly; in this respect, the parasternal short-axis view allows a full morphologic characterization of the anomaly and should always be performed in the case of a meaningful clinical suspect.[1]

We present the case of an asymptomatic patient with isolated DOMV who was referred for cardiac evaluation to achieve a certificate of fitness for competitive sports.

CASE REPORT

A 39-year-old asymptomatic and healthy man was referred to our outpatients’ clinic for cardiac evaluation to achieve a certificate of fitness for competitive sports. He had no previous medical history, but presented a strong family history of early coronary artery disease. The clinical examination and resting electrocardiogram were normal. Accordingly, a complete transthoracic two-dimensional echocardiography with color Doppler examination was performed with a Philips iE33 ultrasound machine (Philips Healthcare, Leiden, The Netherlands). The echocardiographic examination in the parasternal short-axis view showed a distinctive morphology of an isolated DOMV [Figure 1]. The two mitral orifices were located in the posteromedial and posterolateral positions and their estimated areas were 2.20 cm2 and 1.98 cm2, respectively [Figure 2]. There was a single mitral annulus with the two valvular orifices separated by a central fibrous bridge [Figure 1]. The echocardiographic examination seemed to show separated subvalvular structures for each of the two orifices [Figure 3]. A normal function of both the anterior and posterior leaflets of each orifice was present without evidence of either systolic mitral regurgitation jets or diastolic turbulence [Figure 4]. Moreover, the two peak and the mean transmitral gradients were normal. Similarly, a normally functioning mitral valve (i.e. without stenosis or insufficiency) was evident also in the four-chamber view.

Figure 1

Parasternal short-axis view at the level of the mitral valve in diastole showing the bridge of tissue dividing the mitral valve into two orifices

Figure 2

Parasternal short-axis view at the level of the mitral valve in diastole showing the areas of the orifices of the double-orifice mitral valve

Figure 3

Apical four-chamber view seems to show the two separate subvalvular structures of the double-orifice mitral valve

Figure 4

Apical four-chamber view with color Doppler demonstrating the absence of mitral regurgitation

The resting echocardiographic examination excluded the presence of any sign of either congenital or acquired morphological cardiac abnormalities.

To definitively exclude the presence of any other cardiac or vascular anomaly, a cardiac magnetic resonance imaging evaluation was performed, which confirmed the findings of two-dimensional echocardiography as it showed DOMV and each of the two orifices with its own chordal apparatus [Figures 5–7]. The patient is now followed up on a yearly basis for the early recognition of any valvular alteration.

Figure 5

Cardiac magnetic resonance imaging demonstrating normal left ventricular volumes, apex hypertrabeculation, and absence of atrioventricular/ventricular septal defects

Figure 7

Cardiac magnetic resonance imaging demonstrating the two orifices of the double-orifice mitral valve in the absence of other cardiac abnormalities

DISCUSSION

DOMV was first described by Greenfield in 1876. This anomaly is characterized by the presence of a single mitral annulus with two orifices, each having independent subvalvular apparatus and papillary muscles.[134] DOMV is an extremely rare condition, usually associated with other congenital heart anomalies (above all, atrioventricular septal defect, coarctation of aorta, interrupted aortic arch, patent ductus arteriosus, and ventricular septal defect).[1] It generally presents with symptoms related to mitral regurgitation or stenosis, but it can also present as an incidental finding.[15] Three specific types of DOMV can be described at two-dimensional echocardiography: (1) Complete bridge type (about 15% of DOMVs), in which both openings are visible from the leaflet edge and both orifices appear circular (equal or unequal in size) with normal subvalvular apparatus and papillary muscles; (2) incomplete bridge type, in which the connection is seen only at the leaflet edge; and (3) hole type (the most frequent) characterized by a small accessory orifice situated at either the posteromedial or anterolateral commissure and identifiable only at the mid-leaflet level.[2] Accordingly, our patient presented the rarest form of the anomaly, as represented by the complete bridge type DOMV. Transesophageal echocardiography (TEE) defines the anatomy of mitral valve better than transthoracic echocardiography and may help to differentiate DOMV from other conditions such as lesions of valvular leaflets provoked by endocarditis.[6] However, despite these theoretical advantages, TEE was not performed in the diagnostic work-up of the patient because of its invasiveness. On the other hand, once DOMV is nearly assured by two-dimensional echocardiography, cardiac magnetic resonance imaging evaluation becomes a mandatory step to confirm the clinical suspicion, and above all, to exclude any concurrent cardiac and vascular abnormalities. Moreover, three-dimensional echocardiography is generally useful to add anatomical details to that obtained by two-dimensional echocardiography. However, it should be performed only in case of uncertain findings at the two-dimensional echocardiography, which is considered the screening test for DOMV.

The management of DOMV is related to the type and severity of mitral valve dysfunction. Asymptomatic DOMV usually requires no active intervention; in case of severe mitral regurgitation, stenosis, or associated cardiac anomalies, surgical repair is needed.[7] In all cases of DOMV, a long-term follow-up is required for the early detection of complications.[7]

Thus, DOMV is a very rare anomaly which is usually detected by transthoracic two-dimensional echocardiographic examination in short-axis parasternal views. Nevertheless, it can be rarely diagnosed in asymptomatic middle-aged and elderly patients. In any case, the presence of other coexistent cardiovascular abnormalities should be excluded.

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Conflicts of interest

There are no conflicts of interest.