Supravalvular Ring Mitral Stenosis 

Updated: Feb 11, 2014
Author: Michael D Pettersen, MD; Chief Editor: Howard S Weber, MD, FSCAI 

Overview

Background

Supravalvar mitral ring is a rare congenital heart defect of surgical importance. The condition characterized by an abnormal ridge of connective tissue on the atrial side of the mitral valve. Often circumferential in shape, the supravalvar ring may encroach on the orifice of the mitral valve and may adhere to the leaflets of the valve and restrict their movements. Although a supravalvar mitral ring may allow for normal hemodynamic flow from the left atrium to the left ventricle (LV), it often substantially obstructs mitral valve inflow.

Two subtypes of this anomaly have been described, a "supramitral" variant and an "intramitral" variant. The supramitral type is a fibrous shelflike membrane located just above the mitral valve annulus but inferior to the left atrial appendage. The membrane is distinct from and not adherent to the mitral valve leaflets. This variant typically has an otherwise normal mitral valve apparatus. The intramitral variant is a membrane located within the mitral tunnel, closely adherent to the valve leaflets. This subtype is associated with a high incidence of mitral valve abnormalities, including restricted mobility of the mitral leaflets, reduced chordal length, reduced interpapillary muscle distance, single papillary muscle, or hypoplastic mitral annulus.

The intramitral type is also frequently part of the Shone complex, in which multiple levels of left heart obstruction are present, including aortic arch hypoplasia or coarctation, aortic valve stenosis, or subaortic stenosis.

Supravalvar mitral stenosis can develop as an acquired lesion late after mitral annuloplasty to repair mitral regurgitation.

Pathophysiology

The physiologic effect of a supravalvular mitral ring depends on the degree to which the membrane obstructs mitral valve inflow as well as the associated anatomic and functional impairment of the mitral valve. The supramitral ring may initially be incomplete and eccentric, allowing for unobstructed flow through the mitral valve. However, turbulence can cause a progressive increase in the supravalvar membrane or ridge, worsening mitral inflow obstruction. The same mechanism is responsible for the acquired variety of supravalvar mitral stenosis that occurs after mitral annuloplasty for repair of mitral regurgitation.

The intramitral variant may also be eccentric or circumferential in nature. This variety may be difficult to detect because the membrane often adheres to mitral valve leaflets. Adhesion to the valve may impair opening of the leaflets, and this impairment may be the main mechanism of mitral valve inflow obstruction in some patients.

Supravalvar mitral ring rarely occurs as an isolated defect; other congenital heart defects are also present in 90% of patients. The mitral valve itself is often abnormal and stenotic at the valvar or subvalvar level; fusion of leaflets, a small valve orifice, and abnormal papillary muscles are common abnormalities. Shone complex is a combination of 4 congenital heart defects: supravalvar mitral ring, parachute mitral valve, subvalvar aortic stenosis, and aortic coarctation. Other common associated lesions in patients with supravalvar mitral ring include ventricular septal defect (VSD), patent ductus arteriosus (PDA), atrioventricular (AV) canal defect, and tetralogy of Fallot.

Uncommonly associated defects include atrial septal defect, cor triatriatum, left superior vena cava, unroofed coronary sinus, partial anomalous pulmonary venous drainage, pulmonary venous obstruction, double-orifice mitral valve, and Wolff-Parkinson-White syndrome. Lesions such as transposition of the great arteries, AV discordance, and double outlet right ventricle are occasionally complicated by a supravalvar left AV valvular ring.

Obstruction to mitral inflow results from reduced area of the mitral valve orifice. When clinically significant, a diastolic pressure difference occurs between the left atrium and the LV. Left atrial and pulmonary venous pressures increase, leading to exudation of fluid into the pulmonary interstitium, which increases lung stiffness. Breathlessness and tachypnea are secondary to the interstitial edema and diminished pulmonary compliance. In severe cases, frank pulmonary edema can occur. An associated atrial septal defect may decompress the left atrium, reducing or masking the severity of the mitral-valve obstruction. Associated lesions, such as VSD or PDA, which increase LV output, exacerbate the manifestations of mitral-inflow obstruction. In the converse, a supravalvar mitral ring may be difficult to detect in conditions with diminished pulmonary blood flow, such as tetralogy of Fallot.

Persistently elevated pulmonary venous hypertension leads to pulmonary arterial hypertension, a rise in pulmonary vascular resistance, and eventual failure of the right ventricle. Tricuspid regurgitation commonly accompanies right heart failure from pulmonary hypertension.

Epidemiology

Frequency

International

In clinical series of patients with congenital heart disease (CHD), the reported incidence rate of supravalvar mitral ring is 0.2-0.4%, but it is as much as 8% in patients with congenital mitral valve disease. The incidence in autopsy series of patients with congenital heart disease is reported to be 0.6-1.5%. In most patients, the supravalvar mitral ring is detected during investigation for other CHD or mitral valve disease.

Race

No specific race predilection has been reported.

Sex

Supravalvular ring has no specific sex predilection.

Age

No specific age predilection is noted.

 

Presentation

History

Supravalvar mitral ring can be diagnosed in one of the following ways:

  • Supravalvar mitral ring is most commonly diagnosed as an associated finding in other congenital heart disease (CHD).

  • Supravalvar mitral ring is occasionally the cause of congenital mitral stenosis in symptomatic children with dyspnea or pulmonary hypertension. The severity of symptoms depends on the level of left atrial and pulmonary venous hypertension.

  • Most patients become symptomatic by age 2 years.

  • In rare cases, this condition may be detected as an incidental finding in asymptomatic patients undergoing echocardiography for some unrelated reason.

Symptoms of supravalvar mitral ring with mitral stenosis include one or more of the following:

  • Dyspnea, nocturnal cough, and tachypnea from pulmonary venous congestion and increased lung stiffness

  • Frequent respiratory infections and wheezing from pulmonary congestion, increased fluid exudation, and airway narrowing

  • Poor feeding, failure to thrive, fatigue, and sweating from heart failure and reduced cardiac output

  • Occasionally acute pulmonary edema or generalized edema

  • Hemoptysis and syncope in older patients

Physical

Physical signs in supravalvar mitral ring are usually related either to the associated CHD or to pulmonary arterial hypertension. Children with clinically significant mitral obstruction are often sick, with tachypnea and respiratory distress. Diminished cardiac output and poor perfusion lead to a low volume pulse and peripheral cyanosis. Systemic venous pressure may be elevated with the development of congestive heart failure (CHF). A prominent parasternal heave indicates right ventricular hypertrophy from pulmonary hypertension.

The pulmonary component of the second heart sound is accentuated. Unlike acquired mitral-valve stenosis, an opening snap of the mitral valve is not common in supravalvar mitral ring. An apical middiastolic murmur of mitral stenosis may be audible at the apex, especially in the left lateral decubitus, and it may exhibit presystolic accentuation. The murmur is prominent when supravalvar mitral ring is associated with ventricular septal defect (VSD) or patent ductus arteriosus (PDA), causing a large mitral inflow.[1]

Patients with chronic mitral obstruction develop signs of tricuspid regurgitation and CHF, such as hepatomegaly, engorged neck veins, large expansile CV waves in the jugular venous pulse, and a systolic murmur that accentuates in inspiration at the lower left sternal border.

 

DDx

Diagnostic Considerations

Important considerations

It is important that clinicians recognize supravalvar mitral ring as an associated defect in patients with coarctation or subaortic stenosis.

Clinicians should also recognize associated abnormalities of the mitral valve and left ventricular (LV) outflow tract in patients with supravalvar mitral ring.

Do not fail to identify the presence of a supravalvar mitral ring in patients with symptoms and signs of mitral stenosis.

Special concerns

Supravalvar mitral ring may not be easily detectable in children with congenital heart disease (CHD). Therefore, awareness of the problem and careful echocardiographic screening are important in all children with CHD.

Differential Diagnoses

 

Workup

Laboratory Studies

No specific laboratory blood tests are required for diagnosis of supravalvar mitral ring.

Electrocardiography

In cases of isolated supravalvar mitral ring, the electrocardiogram demonstrates left atrial enlargement, right ventricular hypertrophy, and right atrial enlargement in proportion to the degree of obstruction.

Additional defects influence the electrocardiogram accordingly.

Imaging Studies

Imaging studies are essential to define the anatomy of the ring and mitral valve, to assess the severity of obstruction, and to identify any associated defect before undertaking surgical treatment. Several examples of imaging studies are shown in the videos below.

Parasternal long axis echocardiographic image showing a supra mitral variant of supravalvular mitral stenosis. A discrete membrane is visualized superior to but distinct from the mitral valve. The mitral valve appears otherwise normal.
Parasternal long axis color flow image showing a supra mitral variant of supravalvular mitral stenosis. Turbulence is noted at the level of the supra mitral membrane. In this case, Doppler interrogation revealed only mild obstruction.
Apical 4-chamber echocardiographic image showing an intramitral variant of supravalvular mitral stenosis. A membrane is visualized that is closely adherent to the mitral valve leaflets, restricting leaflet mobility.
Apical 4-chamber color flow echocardiographic image showing an intramitral variant of supravalvular mitral stenosis. Color flow imaging demonstrates severe mitral valve stenosis.

Chest Radiography

Left atrial enlargement, the most common abnormality on chest radiographs in patients with mitral obstruction, is diagnosed on the basis of straightening of the left cardiac border (mitralization), widening of the tracheal carina, and elevation of the left bronchus. In older children, the enlarged left atrium may be seen as a double opacity near the right cardiac border.

The left atrium tends to enlarge in a posterior direction.

Prominent upper-lobe pulmonary veins, increased interstitial markings, and Kerley lines indicate pulmonary venous hypertension. In severe cases, alveolar edema produces a hazy appearance in the hilar regions of both lung fields.

The pulmonary trunk and its branches become dilated with the rise in pulmonary arterial pressure. The cardiac contour reflects right ventricular hypertrophy.

Echocardiography

Two-dimensional echocardiography with Doppler imaging is the most important tool for the diagnosis and detailed assessment of patients with supravalvar mitral ring. It depicts the lesion and helps in quantifying the severity of the obstruction.[2]

Detailed scanning of the mitral valve and left atrium should be performed using multiple transthoracic views and by paying particular attention to all components of the mitral valve apparatus. Use parasternal, apical, and subcostal views to visualize the mitral inflow region.

Using this technique allows visualization of the supravalvar mitral ring and definition of its exact position, size, and extent as well as assessment of the relationship of the ring to the mitral valve leaflets.

On occasion, a thin membrane may so closely adhere to the valve leaflets that it is difficult to visualize on 2-dimensional echocardiography. With an adherent membrane, the movements of mitral-valve leaflets may be impaired. The presence of supramitral flow acceleration identified with color Doppler imaging may help identify such a membrane.[3]

The mitral-valve chordae and papillary muscles should be carefully inspected for any associated abnormalities. Associated defects such as subaortic stenosis, ventricular septal defect (VSD), and coarctation of the aorta should be evaluated.

The pulmonary artery, right ventricle, and right atrium may be enlarged in patients with pulmonary arterial hypertension.

Use M-mode echocardiography of the pulmonary valve, which often shows such signs of pulmonary hypertension as an abbreviated A wave, midsystolic closure, and systolic flutter of pulmonary leaflets.

Real-time 3-dimensional echocardiography permits comprehensive assessment of the mitral valve and may compliment 2-dimensional transthoracic echocardiography.[4]

Doppler echocardiography

Doppler interrogation and color-flow mapping reveal the pattern of flow through the mitral valve, diagnose the presence and severity of obstruction, and demonstrate additional areas of abnormal flow in valvar or subvalvar mitral regions. The characteristic finding is turbulent flow with increased velocity across the supravalvar mitral ring into the mitral valve.

The severity of mitral obstruction may be assessed by measuring the mean velocity of diastolic flow through the mitral valve. The mean diastolic velocity and the pressure half-time (time for the peak diastolic velocity to decrease to half its initial value) are well correlated with the severity of obstruction.

The peak velocity of the tricuspid regurgitant jet in the right atrium can be measured to estimate the systolic right ventricular pressure.

Continuous wave Doppler interrogation is shown in the image below.

Continuous wave Doppler interrogation of the mitra Continuous wave Doppler interrogation of the mitral valve in a patient with supravalvular mitral stenosis demonstrates severe stenosis with a mean gradient of 25 mm Hg.

Transesophageal echocardiography

In children, transesophageal echocardiography is generally not necessary to assess a supravalvar mitral ring with obstruction because adequate information can be obtained from transthoracic windows.

In adults, transesophageal study can provide additional clear views to inspect all components of the supravalvar mitral ring and mitral valve.

Thrombi in the left atrium may be detected.

Intraoperative transesophageal echocardiography is useful for patients of all ages to assess adequacy of repair in the operating room.

Cardiac Catheterization

Cardiac catheterization is not necessary if echocardiography provides all of the necessary anatomic and hemodynamic data in patients with supravalvar mitral ring. However, it can provide additional information about the severity of mitral obstruction, especially in the presence of other associated congenital heart disease (CHD).

Proximal left atrial pressure and pulmonary venous pressure are both elevated. A diastolic pressure difference can be demonstrated between the left atrium and the left ventricle (LV). Because entry into the left atrium may be difficult and because transseptal puncture may be required, the pressure recorded in the pulmonary artery wedge position is usually a reliable indicator of left atrial pressure. Simultaneous recording of pressures in the pulmonary artery wedge position and the LV is shown in the image below.

Simultaneous recording of pressures in the pulmona Simultaneous recording of pressures in the pulmonary artery wedge position (PAW) and the left ventricle (LV) shows a large gradient in diastole across the mitral valve. PAW pressure is markedly elevated.

Pulmonary artery pressure is elevated in chronic mitral obstruction. Associated shunts and other obstructive lesions are also identified and quantified during cardiac catheterization.

Cardiac Angiography

With the availability of high-quality 2-dimensional and Doppler echocardiography, cardiac angiography has a limited role in the assessment of patients with supravalvar mitral ring. Echocardiography is superior to angiography in defining the anatomic and functional abnormality.

Left atrial angiography in the caudally angulated right anterior oblique view and the 4-chamber view may demonstrate the supravalvar mitral ring. However, a closely adherent ring may be difficult to visualize and differentiate from mitral valvar stenosis. The left atrium and appendage are enlarged, and clearance of contrast material from the left atrium into the LV is delayed.

An LV angiogram provides additional anatomic information about the mitral valve, ventricular septum, LV outflow tract, and aortic arch.

 

Treatment

Medical Care

Evaluation of patients with supravalvar mitral ring is generally performed on an outpatient basis.

Hospital admission may be indicated in order to perform cardiac catheterization, for treatment of severe heart failure or pulmonary edema, and for surgery. Therefore, transfer patients to a tertiary cardiac center for further diagnostic evaluation and surgical correction. Adjunctive therapeutic measures may be needed.

The goals of medical treatment include the following:

  • To relieve symptoms caused by pulmonary venous congestion and congestive heart failure (CHF)

  • To stabilize the patient's condition before undertaking detailed assessment and surgical repair

  • To serve as an adjunct to surgical repair in the postoperative period

  • To control heart failure in small infants, in whom it may be the only option (Controlling CHF may temporarily defer surgery.)

Note the following:

  • Administer potassium supplements to all patients receiving furosemide or thiazide diuretics.

  • Restrict physical activity of symptomatic patients.

  • Place patients with severe pulmonary venous congestion in the sitting or propped-up position.

  • Administer parenteral morphine in patients with pulmonary edema to help relieve anxiety and reduce pulmonary congestion.

  • Administer oxygen by a nasal catheter or mask to improve oxygenation in acute pulmonary edema.

  • Vigorously treat concurrent infections or other aggravating factors.

  • Correct anemia if present. Increase the oxygen carrying capacity by a packed-cell transfusion to give considerable relief in patients with severe symptoms of congestive heart failure (CHF).

Consultations

Consult a cardiologist and a cardiothoracic surgeon.

Surgical Care

Indications for and goals of surgical therapy

Note the following:

  • Surgical repair should be considered in all symptomatic patients with supravalvar mitral stenosis to relieve the obstruction.

  • Early operation to resect the supravalvar mitral ring should be considered in the presence of severe heart failure, pulmonary edema, or pulmonary arterial hypertension.[5]

  • The type of type of surgical intervention depends on the anatomy of the supravalvar ring and mitral valve apparatus, as well as any associated congenital heart defects. Every effort should be taken to define the anatomy in detail before undertaking surgery. In many patients, the supravalvar ring can be completely excised, while any associated mitral valve abnormality is simultaneously repaired.[6, 7, 8] If the supravalvar ring is strongly adherent to the mitral valve leaflet or if the mitral valve apparatus is grossly abnormal, replacement of the mitral valve may be necessary.[9, 10]

  • All associated defects should be repaired at the same time. In fact, surgery is often necessary for the associated heart defects even if the supravalvar mitral ring is not causing major hemodynamic disturbance.

  • The presence of a normal underlying mitral valve is associated with a surgical outcome better than that obtained with an abnormal valve apparatus, which may need replacement.

  • In patients who require surgery at an early age, the prognosis is poor. The mortality rate is high. Recurrent supravalvar mitral stenosis is a risk in as many as 15% of survivors, probably because of continuing turbulence across the small LV inflow tract.

  • Patients with Shone complex have a wide spectrum of anatomic abnormalities. Staged repair is usually necessary for coarctation treatment, the relief of left ventricular outflow tract obstruction, and reconstruction of the mitral valve. The results are encouraging. Bolling et al reported an actuarial survival rate of 89% 15 years after repair.[11] In a more recent series, Brown at al reported a 20-year survival of 82% and 20-year freedom from reoperation of 88%.[6] Operative mortality is increased by earlier age of repair, severe mitral valve disease, left ventricular hypoplasia, and the need for multiple operative procedures.

Percutaneous transcatheter balloon dilation

Percutaneous transcatheter balloon dilation has been used in selected cases of supravalvar mitral ring, but the results are less satisfactory than surgical outcomes. Surgical resection is considered the treatment of choice.

Diet

No special diet is required in asymptomatic patients with supravalvar mitral ring.

Advise patients with heart failure to avoid excess intake of salt or to reduce their salt intake. Prescribe salt restriction cautiously in infants.

Restrict fluid intake to approximately 60-80 mL/kg/d in infants with congestive heart failure (CHF).

Activity

Advise patients with pulmonary venous congestion or CHF to avoid strenuous exertion.

Symptomatic patients with supravalvar mitral ring should avoid sports and other strenuous activity that could aggravate pulmonary congestion and CHF.

Asymptomatic children without pulmonary hypertension may participate in normal activities.

 

Medication

Medication Summary

Medical therapy for supravalvar mitral ring consists of drugs to control pulmonary venous congestion and cardiac failure. The 2 main categories of drugs used are diuretics to promote excretion of excess water and positive inotropic drugs to improve myocardial function. Medical therapy helps to relieve symptoms of pulmonary edema and congestive heart failure (CHF) but does not correct the underlying anatomic problem of obstruction.

Antibiotics for endocarditis prophylaxis are no longer recommended for most patients with congenital heart disease. Some significant exceptions are noted, including patients who have previously had endocarditis or patients within 6 months of their surgical repair. Current American Heart Association guidelines also recommend subacute bacterial endocarditis (SBE) prophylaxis for patients who have undergone mitral valve replacement.[12] For more information, see Antibiotic Prophylactic Regimens for Endocarditis.

Diuretics

Class Summary

These agents are useful to remove excess water that accumulates in heart failure and to relieve symptoms associated with pulmonary edema and peripheral edema.

Furosemide (Lasix)

Drug of choice (DOC) for rapid relief of pulmonary congestion and edema caused by CHF. Useful for maintenance therapy for CHF in patients with supravalvar mitral ring. Promotes renal excretion of water by inhibiting electrolyte-transport system in ascending limb of loop of Henle. Can increase solute and water excretion, even with declining glomerular filtration rate.

Chlorothiazide (Diuril)

Thiazide that increases water excretion by inhibiting reabsorption of sodium chloride in distal renal tubule.

Less potent diuretic than furosemide.

Useful in maintenance therapy of CHF; in severe CHF or refractory edema, thiazides act synergistically with furosemide to promote diuresis.

Hydrochlorothiazide (Esidrix, HydroDIURIL)

Thiazide that increases water excretion by inhibiting reabsorption of sodium chloride in distal renal tubule.

Less potent diuretic than furosemide, useful in maintenance therapy of CHF; in severe CHF or refractory edema, thiazides act synergistically with furosemide to promote diuresis.

Spironolactone (Aldactone)

Counteracts secondary hyperaldosteronism that occurs in cardiac failure; inhibits sodium absorption in collecting duct and has a potassium-sparing diuretic effect. Used alone, produces relatively mild diuresis; however, it may be used with furosemide for synergistic action in severe CHF.

Inotropic agents

Class Summary

Positive inotropic agents increase the force of myocardial contraction and are used to treat acute and chronic CHF. Some may also provide vasodilatation, improve myocardial relaxation, or increase or decrease the heart rate (positive or negative chronotropic agents, respectively). These additional properties influence the choice of drug for specific circumstances.

Digoxin (Lanoxin)

DOC among inotropic agents. Improves CHF by positive effect on myocardial contraction. Also helps to control fast ventricular rate, especially in atrial arrhythmia. Preparations include elixir 0.05 mg/mL and tabs 0.125 or 0.25 mg.

 

Follow-up

Further Outpatient Care

Provide follow-up care on an outpatient basis for monitoring symptoms, compliance with treatment, dose requirements, and early recognition of adverse drug effects.

Periodically check serum electrolyte levels and renal function in patients taking diuretics.

Promptly treat any intercurrent infections, arrhythmia, or other complications helps to reduce morbidity and prevent worsening of CHF.

Inpatient & Outpatient Medications

Continue treatment with diuretics and digoxin in patients with supravalvar mitral ring and CHF.

Recommend use of a potassium supplement, especially in children receiving furosemide therapy.

Antibiotics are necessary for intercurrent bacterial infections and for prophylaxis of infective endocarditis during dental or surgical procedures.

Prognosis

Among patients with congenital mitral stenosis, those with supravalvar mitral ring have a relatively good prognosis. Complete surgical excision is feasible and usually provides lasting relief. The presence of a normal underlying mitral valve and absence of other major cardiac lesions are associated with a better surgical outcome.

The prognosis is poor in patients who require resection at an early age. The mortality rate is high. Recurrent supravalvar mitral stenosis is a risk in survivors, probably because of continuing turbulence across the small left ventricular (LV) inflow tract.

In patients with Shone complex, thickened mitral valve leaflets, shortened chordae, subvalvar abnormalities, left ventricular outflow obstruction, and aortic incompetence were associated with rapid progression of hemodynamic abnormalities and poor prognosis.[13]

Complications

Possible complications of supravalvar mitral ring include pulmonary edema, pulmonary arterial hypertension, atrial arrhythmia, left atrial thrombus, embolic episodes, recurrent pulmonary infections, and infective endocarditis.

Cerebral venous thrombosis has been described in infants with supravalvar mitral ring.

Patient Education

Educate the patient and family about the importance of regular medical treatment, of periodic medical review, of restricting heavy physical exertion, of the need for antibiotic prophylaxis during dental and surgical procedures, and of the need to promptly attend to all infections.