Double orifice mitral valve
Synonyms and keywords: DOMV

# Overview
A double orifice mitral valve (DOMV) is a rare congenital malformation characterized by two valve orifices with two separate subvalvular apparatus.  It is mostly associated with atrioventricular septal defect, but may also be associated with other congenital heart defects such as left-sided obstructive lesions, ventricular septal defects or cyanotic lesions.  Isolated DOMV have been rarely reported.

# Classification
Based on the size and location of the two orifices, various classifications for DOMV have been proposed.  Trowitz et al. described three different types of DOMV using the 2D echocardiographic findings
A fourth type of DOMV, duplicate mitral valve with two annuli and valves, each with its own set of leaflets, commissures, chordae, and papillary muscles have been described by some authors.

# Pathophysiology
While the normal mitral valve consists of a large central orifice located between the large anterior leaflet and the small posterior leaflet, in DOMV, an abnormal tissue divides the large central orifice into 2 parts.  This division of the large central orifice might reduce the total area of the mitral valve orifice, obstructing its inflow and causing mitral stenosis.  When the inflow obstruction is significant, the left atrial and pulmonary venous pressure rises, leading to exudation of fluid into the interstitium of the lung and frank pulmonary edema.  Persistent pulmonary venous hypertension leads to pulmonary arterial hypertension and eventually the failure of the right ventricle with tricuspid regurgitation. Mitral regurgitation is the commonest hemodynamic abnormality associated with DOMV.  Similar to mitral stenosis, mitral regurgitation causes left atrial and pulmonary venous hypertension.  Left ventricular outflow obstruction can aggravate the mitral regurgitation, leading to more severe clinical presentations like irreversible ventricular dysfunction, marked enlargement of left atrium with subsequent compression of left bronchus, and worsening pulmonary hypertension with right heart failure.

# Epidemiology and Demographics
DOMV was first described by Greenfield in 1876.  Although incidences of 0.01% to 1% have earlier been reported, the true incidence of DOMV is yet to be established.  To date, we have approximately 200 reported cases.

# History
DOMV without mitral regurgitation or mitral stenosis is asymptomatic.  It is symptomatic with physical findings only when mitral regurgitation or mitral stenosis coexist.  Although DOMV can be an isolated anomaly, it is detectable in most cases when it is associated with other congenital malformations such as AV canal defect, ventricular septal defect, coarctation of the aorta, interrupted aortic arch, subaortic stenosis and primum type ASD.  Occasionally, DOMV coexists with secundum type ASD, tetralogy of Fallot, hypoplastic left heart syndrome, Ebsteins anomaly or bicuspid aortic valve.

# Symptoms
DOMV becomes symptomatic based on the associated severity of mitral regurgitation or mitral stenosis.  Increased pulmonary venous pressure and the following pulmonary congestion and fluid exudation leads to dyspnea, tachypnea, nocturnal cough, and recurrent respiratory tract infections.  Acute pulmonary edema can occur in children and it presents with hemoptysis in elderly patients.  Poor feeding, failure to thrive, fatigue and sweating may occur because of heart failure and reduced cardiac output.

# Physical Examination
DOMV presents with the physical findings of coexisting mitral regurgitation or mitral stenosis.

# Other Imaging Findings
DOMV is usually detected during investigation of other congenital heart diseases using echocardiography and cardiac catheterization.

# Medical Therapy
Medical therapy is considered while managing mitral regurgitation or mitral stenosis complicated DOMV with pulmonary edema and congestive heart failure.

# Surgery
DOMV with mitral stenosis can be corrected using  percutaneous mitral balloon valvotomy.  Incomplete correction of mitral stenosis and symptomatic DOMV with mitral regurgitation can be managed with surgical corrections like mitral valve replacement and mitral valvuloplasty.