Double Orifice Mitral Valve

Article Author:
Rishard Abdul
Article Editor:
Yuvraj Chowdhury
Updated:
6/9/2020 1:10:32 AM
PubMed Link:
Double Orifice Mitral Valve

Introduction

Double orifice mitral valve (DOMV) is a rare anomaly, congenital, or acquired, that is characterized by a mitral valve with a single fibrous annulus resulting in 2 orifices.[1] It was first described by William Smith Greenfield, a British pathologist in 1876. Since then, the literature has been limited to case reports and small necropsy-based case series.[1] It is usually asymptomatic as the anomaly allows for normal blood flow between the two chambers of the left heart, however, symptoms may arise due to the development of mitral valve dysfunction such as stenosis or regurgitation.

Etiology

Double orifice mitral valve is rarely an isolated pathology as it is usually associated with other cardiac congenital anomalies such as coarctation of the aorta, patent ductus arteriosus, or even a bicuspid aortic valve suggesting that a defect in the endocardial cushion may be the underlying etiology.[2] In an autopsy case series, atrioventricular septal defects were considered to be the most common congenital cardiac defect associated with DOMV.[3] It is well known that the majority of cases are congenital; however, some authors have described cases of acquired DOMV after edge to edge mitral valve repair, whether surgical or percutaneous, as with transcatheter mitral valve repair.[4][5]

Based on echocardiographic features, there are three morphological types of congenital DOMV described in the literature; eccentric type, central type, or duplicate mitral valve type.[6] The eccentric type accounts for approximately 85% of all cases and is characterized by larger main orifice and a smaller accessory orifice located either at the posteromedial or anterolateral commissure.[6][7] The central or bridge type is seen in 15% of patients with DOMV and is characterized by a central bridge of fibrous tissue connecting the two leaflets of the mitral valve.[6] The two orifices may be of the same size or unequal. The third morphological type of congenital DOMV, the duplicate mitral valve type, is comprised of two mitral valve annuli and valves, each individually with its own set of leaflets, commissures, papillary muscles, and chordae.[6]

Epidemiology

Given its infrequency, actual epidemiological data regarding double orifice mitral valve is lacking. In a postmortem study conducted on 2733 autopsied cases from the Cardiac Registry of The Children’s Hospital in Boston, DOMV was found in 28 cases (1% of autopsied patients).[7] In the adult population, a retrospective study involving echocardiographic data revealed an estimated incidence of 0.06 %.[8] As with the United States, international data is deficient; however, one Polish retrospective study involving echocardiographic studies of 79,919 patients between 1993 and 2006 found the incidence to be 0.01%.[9] No current reports are suggesting a predilection to either gender.

Pathophysiology

Several classifications have been proposed based on either the etiology or the morphological appearance of double orifice mitral valve. For instance, congenital anomalies of the native valve account for the vast majority of cases however when mitral annular calcifications affect the second scallop of the anterior leaflet as well as the second scallop of the posterior leaflet, and the mitral valve orifice may split into two, resulting in an acquired form of DOMV.[10] Some iatrogenic interventions have been documented as the underlying cause of DOMV. Several authors have described edge to edge mitral repair, whether surgical (Alfieri stitch) or percutaneous, resulting in the development of DOMV.[4][5] As it pertains to congenital anomalies of the underlying native valve, DOMV occurs as a result of the abnormal fusion of the dorsal endocardial and the left lateral endocardial with the persistence of left part of the common atrioventricular canal.[1]

History and Physical

Double orifice mitral valve is usually an asymptomatic entity unless accompanied by mitral valve stenosis, regurgitation, or a concomitant congenital cardiac anomaly. In patients with an associated congenital heart defect, it is usual for that particular disorder to manifest on clinical examination as there are no signs specific to DOMV. In isolated DOMV, the extent of symptoms depends on the grade of left atrial pressure resulting in pulmonary congestion. Symptoms are primarily due to diminished cardiac output and can range from tachypnea, dyspnea, and wheezing to poor feeding and failure to thrive in the pediatric population. In asymptomatic patients, the physical examination may be completely unremarkable as isolated DOMV is benign, even to cardiac auscultation. However, if complicated by mitral valve stenosis (MS), one may appreciate the murmur of MS, a low pitched mid-diastolic murmur best heard at the apex. The same can be said for DOMV with mitral regurgitation (MR), a blowing pansystolic murmur is appreciated at the apical region. As patients develop symptoms, one may find clinical signs of heart failure such as increased work of breathing, peripheral cyanosis, increased jugular venous pressure, palpation of a parasternal heave, pulmonary crackles on auscultation as well as evidence of hypervolemia such as peripheral edema.

Evaluation

Transthoracic echocardiography (TTE), whether two dimensional (2D) or three dimensional (3D) remains the mainstay of assessing for double orifice mitral valve.[11] The double orifices of the DOMV are best assessed in the parasternal short-axis view; however, for adequate visualization of the sub-valvular apparatus, the apical and subcostal 4-chamber views are useful. 3D TTE is used as an adjunct to 2D TTE as it can provide a more vivid assessment of the mitral valve anatomy and function. 3D TTE can more accurately assess the size and spatial relationships of the mitral valve and intracardiac structures, allowing for closer inspection of the chordal attachments as well as abnormalities of the sub-valvular apparatus.[1]

With the addition of color Doppler, one can gain important information about flow through the mitral valve and can add valuable information regarding valve regurgitation or stenosis. Preoperative transesophageal echocardiography (TEE) is generally unnecessary; however, an intraoperative approach is routinely used to confirm preoperative echocardiographic findings.[12] Cardiac magnetic resonance imaging (MRI) adds little and generally not pursued.[13] Other nonspecific data can be acquired with the use of a chest X-ray and an electrocardiogram. For instance, a chest X-ray may reveal left atrial enlargement along with evidence of pulmonary congestion such as upper lobe diversion, increased interstitial markings, and Kerley B lines. It is important to understand that an electrocardiogram will be normal in isolated DOMV, however possible findings include P mitrale (if left atrial enlargement is present) as well as voltage criteria for left ventricular hypertrophy (if mitral incompetence is severe enough).

Treatment / Management

Management of a double orifice mitral valve is primarily based on whether patients are symptomatic or not, which in turn directly correlates to the degree of mitral valve dysfunction. For asymptomatic patients, interval TTE is recommended; however, there are no current guidelines specifically addressing how frequent. Management of symptomatic DOMV involves medical therapy, non-invasive intervention, or surgical approach.

The purpose of medical therapy is to treat symptoms of heart failure and pulmonary congestion until a more definitive treatment modality is sort for the mitral valve dysfunction. Medical therapy is especially important in the pediatric population as control of congestive heart failure symptoms is crucial until an infant becomes of age for specific valve intervention. In cases of DOMV with mitral valve stenosis, the use of percutaneous transcatheter balloon dilatation has been shown as an appropriate tool to relieve the obstruction. If balloon dilatation is not practicable or unsuccessful, surgical mitral valvuloplasty or valve replacement may have a role.[4]

All symptomatic patients with a regurgitant valve should be considered for surgical repair with leaflet plication and possible division of the bridging tissue.[14][15] As it pertains to DOMV, surgical closure of one of the orifices might lead to the acute diminution of the mitral valve area with a resultant stenotic flow.[16]

Differential Diagnosis

Double orifice mitral valve is a unique disorder; however, its symptomatology is very nonspecific. As stated above, the development of symptoms correlates to the degree of mitral valve dysfunction, the left atrial pressure, and the degree of pulmonary venous congestion. Therefore, in adults, it is important to consider other causes of mitral valve disease such as rheumatic heart disease, functional MR, myocardial ischemia, annular calcifications in the elderly, connective tissue disorders, myxomatous degeneration and infective endocarditis.[17] In the pediatric population, DOMV should be considered when another congenital heart disease is present. These include coarctation of the aorta, patent ductus arteriosus, or a bicuspid aortic valve as well as atrioventricular septal defect.

Prognosis

In asymptomatic patients without mitral valve dysfunction, the prognosis is reassuring. However, at the time of writing, there are no prospective studies done to aid in a timeline for progression from diagnosis of double orifice mitral valve to mitral valve dysfunction as some patients develop mitral valve dysfunction early in infancy and others, in adulthood.[15][18] With the advent of non-invasive techniques, the survival rate with intervention for mitral valve dysfunction is much higher than with surgical valve replacement.

Complications

Complications of double orifice mitral valve include mitral valve dysfunction (mitral stenosis/mitral valve regurgitation) with resulting pulmonary edema and congestive heart failure. There have been cases of atrial arrhythmias such as atrial fibrillation and atrial flutter as a direct result of DOMV, and as a result, patients may experience embolic strokes.[19]

Deterrence and Patient Education

Double orifice mitral valve is most commonly found incidentally while investigating other possible cardiac pathologies. This anomaly, by itself, is asymptomatic; however, it can lead to mitral valve dysfunction. It is at this juncture that intervention is pursued with medicines and some sort of valve intervention, whether noninvasive or surgical. At the time of diagnosis, patients should be referred to a cardiologist and a cardiothoracic surgeon and followed closely with interval TTE. For symptomatic patients, physical activity is restricted, and patients are advised to seek medical care if they develop signs of heart failure. This may include but is not limited to shortness of breath, cough, leg swelling, and weight gain. At this time, medications may be required to help with heart failure and serve as an interim measure until the dysfunctional mitral valve can be repaired.

Enhancing Healthcare Team Outcomes

To ensure appropriate patient care and improvement in outcomes, it is prudent to have a team approach when managing a patient with double orifice mitral valve. DOMV is predominantly an asymptomatic condition and given is low incidence rate, echocardiography technicians and cardiologists must be on high alert, especially when obtaining the parasternal short-axis views, scanning from the base to the apex to assess the sub-valvular structures. Early referral to a cardiologist and cardiothoracic surgeon is warranted. DOMV is usually a disorder that is managed as an outpatient with inpatient care designated for acutely decompensated heart failure and further investigative workup. At the time of writing, valve intervention is only recommended at the stage of valve dysfunction, and as such, it is imperative to have a thorough risk vs. benefit discussion with a cardiologist, cardiothoracic surgeon and of course, the patient, as to which form of valve intervention is best suited for the patient’s best outcome.


References

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