Double Orifice Mitral Valve


Background

Double orifice mitral valve (DOMV) is an uncommon anomaly that was first described by Greenfield in 1876. [1Since that time, more than 200 cases have been reported. [2This anomaly is characterized by a mitral valve with a single fibrous annulus with 2 orifices that open into the left ventricle (LV), as depicted in the image below.

Two-dimensional echocardiogram (apical view) in a Two-dimensional echocardiogram (apical view) in a patient with duplicate mitral valve. Two mitral valves can be seen opening into the left ventricle. Each valve has a separate annulus, and a separate set of mitral valve leaflets and subvalvar apparatus.

Subvalvular structures, especially the tensor apparatus, invariably show various degrees of abnormality. [3Although double orifice mitral valve may allow normal blood flow between the left atrium and LV, it can substantially obstruct mitral valve inflow or produce mitral valve incompetence.

Recognition of double orifice mitral valve and awareness of the anatomic variations are important to achieve good therapeutic results. Treatment is only necessary if significant mitral stenosis (MS) or mitral regurgitation (MR) is present.

Pathophysiology

The normal mitral valve consists of a large, central orifice located between a large sail-like anterior leaflet and a small, C-shaped posterior leaflet. In double orifice mitral valve, abnormal tissue divides the orifice into 2 parts.

Various classifications of double orifice mitral valve have been proposed on the basis of the size and location of the two orifices. [345]

Eccentric or hole type 

This is the most common type, accounting for about 85%, and was seen in the first case reported by Greenfield in 1876. [1It is characterized by a larger main orifice and a smaller accessory orifice situated at either the anterolateral or the posteromedial commissure. Other anomalies of the valve apparatus, such as cleft leaflets, accessory papillary muscles, fused papillary muscles, and crossing chordae tendineae, are commonly present. Abnormal chordal rings, with or without subjacent papillary musculature, are a constant finding in this classic type. When the accessory orifice is located at the posteromedial commissure, a common atrioventricular canal is usually present. By comparison, the atrioventricular canal is normally divided if the accessory orifice is located at the anterolateral commissure. [3]

Central or bridge type

In about 15% of patients with double orifice mitral valve, a central bridge of fibrous or abnormal leaflet tissue connects the 2 leaflets of the mitral valve, dividing the orifice into medial and lateral parts. These 2 openings may be equal or unequal, and the papillary muscles are usually normal, with chordae surrounding each orifice inserting into one papillary muscle. In this type of double orifice mitral valve, dilatation of the posteromedial orifice is feasible by means of balloon valvuloplasty.

Duplicate mitral valve type

This condition involves 2 mitral valve annuli and valves, each with its own set of leaflets, commissures, chordae, and papillary muscles. [6]

Associated congenital heart defects are common, although double orifice mitral valve can occur as an isolated anomaly. The most common associated lesion is atrioventricular (AV) septal defect (endocardial cushion defect), where it has been found in as many as 4.9-17.9% of cases in necropsy studies. [7]

In a postmortem series of 27 cases of double orifice mitral valve, Bano-Rodrigo et al concluded that 44% had an intact AV septum and 56% had an AV septal defect; 52% had mitral stenosis or mitral regurgitation. Double orifice mitral valve was always associated with an anomaly of the subvalvular apparatus because, by definition, a separate tensor apparatus is attached to each orifice.

Abnormal structures, including large bridging tissue, bulky abnormal leaflets, fused chordae, or abnormal papillary muscles reduce the effective area of the valve. Abnormalities in the leaflets include thickening, fusion, perforations, restricted movements, and ruptured chordae with flail cusps. Such valves can result in clinically significant degrees of mitral incompetence.

In another published clinical series of 18 patients with double orifice mitral valve and intact AV septum, Das et al found that double orifice mitral valve was most commonly associated with left sided obstructed lesions in 39% of the cases and with ventricular septal defects (VSDs) in 17% of the cases. [8In contrast to the above postmortem study, only 11% had significant mitral stenosis or mitral regurgitation. Higher incidence of mitral stenosis and mitral regurgitation noted in the postmortem study may be related to the selective bias because it was performed at a tertiary care specialized center.

Presence of atrial septal defects (ASD) may lead to underestimation of the frequency and the severity of mitral stenosis, which is revealed after the atrial septal defect closure. [9Tendinous attachments to both openings distinguishes double orifice mitral valve from acquired lesions, such as perforation or partial fusion of valve leaflets caused by inflammatory lesions, traumatic ruptures, and complications of interventional procedures. [8]

Other associated lesions include VSD, coarctation of the aortainterrupted aortic archsubaortic stenosispatent ductus arteriosus, and primum ASD.

On occasion, double orifice mitral valve is observed with tetralogy of Fallothypoplastic left heart syndrome, persistent left superior vena cava, unroofed coronary sinus, Ebstein anomaly of the tricuspid valve, dysplastic tricuspid valve, double-orifice tricuspid valve, Shone syndrome, parachute mitral valve, flail mitral-valve leaflet, truncus arteriosus, pulmonary stenosis, bicuspid aortic valve, left ventricular noncompaction (isolated and nonisolated types), tricuspid atresia, and corrected transposition. Double orifice mitral valve has also been reported in patients presenting with atrial tachycardia or congenital complete heart block. [910111213141516171819]

Double orifice mitral valve has also been reported in trisomy 21, de Lange syndrome, Astrom syndrome, Kabuki syndrome, and isovaleric academia.

In a published clinical series of 46 children with double orifice mitral valve, Zalzstein et al reported that mitral regurgitation was most frequent association and was detected by color Doppler in 43% of the patients. [9Double orifice mitral valve with normal flow was seen in 37% of the patients, and mitral stenosis was detected in 13% of the patients. Mitral stenosis and regurgitation were found together in 6.5% of the patients. However, only 16% of the patients had severe enough lesions to require surgical intervention.

Mitral stenosis

A reduction in the total area of the mitral valve orifice obstructs its inflow. When mitral stenosis is clinically significant, a diastolic pressure difference builds up between the left atrium and the LV. The rise in left atrial and pulmonary venous pressure leads to exudation of fluid into the interstitium of the lung and increased pulmonary stiffness (the main cause of breathlessness). In severe cases, frank pulmonary edema develops. Persistent pulmonary venous hypertension leads to pulmonary arterial hypertension, a rise in pulmonary vascular resistance and eventually, failure of the right ventricle (RV) with tricuspid regurgitation.

Mitral regurgitation

About 25% of patients with double orifice mitral valve present with mitral regurgitation as the dominant hemodynamic abnormality, especially when it is associated with an atrioventricular canal defect. Similar to mitral stenosis, mitral regurgitation causes left atrial and pulmonary venous hypertension. Clinical effects depend on the severity and duration of mitral regurgitation.

LV outflow obstruction from associated subaortic stenosis or coarctation can aggravate the mitral regurgitation. With increasing mitral regurgitation, cardiac output is maintained by increasing LV diastolic volume and hypertrophy. In chronic mitral regurgitation, LV function deteriorates, leading to further worsening of pulmonary venous congestion, pulmonary hypertension, and right heart failure. [20Ventricular dysfunction secondary to chronic dilatation is often irreversible even after the primary mitral lesion is corrected. The left atrium tends to markedly enlarge in mitral regurgitation and may compress the left bronchus.

When an ASD with a significant left to right atrial shunt is present, reduction of transmitral flow and left ventricular volume occurs, which may lead to underestimation of the mitral stenosis. [21]

Epidemiology

Frequency

United States

Double orifice mitral valve was found in 1% of autopsied cases of congenital heart disease (CHD) in the Cardiac Registry of the Children’s Hospital, Boston. [3]

International

To the author's' knowledge, no data are available on the incidence of double orifice mitral valve. More than 180 cases of double orifice mitral valve are reported in the literature. Approximately 50% of all cases of double orifice mitral valve are detected during investigation of other CHDs

CLINICAL PRESENTATION


History

Double orifice mitral valve (DOMV) without mitral regurgitation or mitral stenosis are asymptomatic. Physical findings may only exist if mitral regurgitation or mitral stenosis are present.

The severity of symptoms depends on the degree of left atrial hypertension. Dyspnea, nocturnal cough, and tachypnea occur, related to pulmonary venous congestion and increased lung stiffness. Frequent respiratory infections and wheezing occur, secondary to pulmonary congestion, increased fluid exudation, and airway narrowing. Poor feeding, failure to thrive, fatigue and sweating occur because of heart failure and reduced cardiac output. On occasion, a child with double orifice mitral valve presents with acute pulmonary edema or generalized edema. Hemoptysis and syncope can occur in older patients with double orifice mitral valve.

Double orifice mitral valve is detected in one of 3 ways. As an associated lesion with other congenital heart defects, especially in the presence of atrioventricular (AV) septal defect or left-sided obstructive lesions. The abnormal mitral valve aggravates the pulmonary congestion and heart failure that occurs in complete AV septal defect or ventricular septal defects (VSDs). In the converse, conditions such as large left-to-right atrial shunts and tetralogy of Fallot with reduced mitral valve flow may mask the presence of double orifice mitral valve. In patients with such conditions, double orifice mitral valve is not detected unless the clinician specifically looks for it.

Double orifice mitral valve may be sought as the anatomic explanation for symptomatic mitral valve disease or discovered as an incidental finding in asymptomatic patients who undergo echocardiography for any reason. [18]

Physical

Physical signs in DOMV with mitral stenosis

Respiratory distress, tachypnea, and subcostal retractions. Reduced pulse volume and peripheral cyanosis indicate diminished cardiac output and poor tissue perfusion. Central cyanosis can develop in the presence of severe pulmonary edema. Jugular venous pressure rises with the onset of right heart failure. Palpation reveals a parasternal heave from the hypertrophied RV and occasionally, a diastolic thrill at the apex.

The first heart sound may be normal or accentuated, while the pulmonary second sound generally is loud because of pulmonary hypertension. Unlike acquired mitral stenosis, an opening snap is not commonly heard.

A low-pitched mid-diastolic murmur of varying intensity is audible at the mitral area. It is often heard best with the patient in the left lateral decubitus position, and it is especially loud when mitral stenosis is associated with a VSD or mitral regurgitation.

In chronic, severe mitral stenosis, signs of tricuspid incompetence, such as systolic expansile pulsation in the jugular vein and liver and a pansystolic murmur at the lower sternal border, appear. This murmur is typically accentuated on inspiration.

Physical signs in DOMV with mitral regurgitation

The patient may present with respiratory distress and pulmonary edema. The pulse is often brisk. The apical impulse is displaced downward and outward and has a hyperdynamic quality because of LV dilatation and hypertrophy. The first and second heart sounds are usually normal in intensity, although the second heart sounds may be widely split. A third heart sound is commonly heard at the apex. A blowing pansystolic murmur is heard at or just inside the apex. It is often conducted toward the sternum rather than toward the axilla.

Severe mitral regurgitation can cause a low-pitched, apical diastolic murmur from large diastolic flow across the mitral valve. Diastolic murmur at apex of the heart (functional MS murmur). Pulmonary hypertension and tricuspid incompetence can occur in MR, though not as commonly or as severely as in MS.

DDX


Diagnostic Considerations

Other problems to be considered

Other conditions to consider in the differential diagnosis of double orifice mitral valve (DOMV) include the following:

  • Associated congenital heart disease - Atrioventricular (AV) septal defect, ventricular septal defect (VSD), left sided cardiac lesions

  • Syndromes and conditions - Trisomy 21, de Lange syndrome, Astrom syndrome, Kabuki syndrome, and isovaleric academia

Important considerations

It is important to identify double orifice mitral valve as the cause of mitral valve obstruction or regurgitation or as an associated defect in patients with atrioventricular-canal defect and other congenital heart diseases (CHDs).

Identify and recognize associated abnormalities of the mitral valve apparatus in patients with DOMV.

Special concerns

Double orifice mitral valve may not be detected easily in children with CHDs; therefore, awareness of the problem and careful echocardiographic screening are important in all children with mitral valve disease.

Differential Diagnoses

Workup

Laboratory Studies

The anatomy of the valve and also the hemodynamic abnormalities should be investigated by imaging studies and cardiac catheterization, as indicated.

No specific laboratory blood tests are required for diagnosis.

Imaging Studies

Chest radiography

A left atrial enlargement is suspected (the most common abnormality in double orifice mitral valve [DOMV]) if straightening of the left upper cardiac border (mitralization) and widening of the tracheal carinal angle secondary to the elevation of the left bronchus are present. In older children, the enlarged left atrium may be observed as a double opacity near the right atrial border that tends to enlarge in a posterior direction. Mitral incompetence, if severe, causes left ventricular (LV) enlargement.

Barium-swallow study in lateral projection shows a rounded indentation from the enlarged left atrium on the anterior wall of the esophagus.

Prominent upper-lobe 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.

Echocardiography

Two-dimensional echocardiography (2DE) with Doppler interrogation is the most important tool for the diagnosis and detailed assessment of double orifice mitral valve.

Systematic examination of the mitral valve by using multiple views for imaging and Doppler interrogation is important. Particular attention should be given to evaluate all components of the mitral valve apparatus. Refer to the image below.

Two-dimensional echocardiogram (apical view) in a Two-dimensional echocardiogram (apical view) in a patient with duplicate mitral valve. Two mitral valves can be seen opening into the left ventricle. Each valve has a separate annulus, and a separate set of mitral valve leaflets and subvalvar apparatus.

The 2 orifices in double orifice mitral valve are best demonstrated in a cross-sectional short axis view of the LV by scanning the ventricle from the apex to the base. Apical and subcostal 4-chamber views are also useful to visualize the subvalvular apparatus. See the images depicted below.

Two-dimensional echocardiogram (parasternal short-Two-dimensional echocardiogram (parasternal short-axis view) shows double-orifice mitral valve, the orifice being divided by a bridge of tissue.
Two-dimensional echocardiogram (parasternal short-Two-dimensional echocardiogram (parasternal short-axis view) in a patient with duplicate mitral valve. This diastolic frame shows two typical mitral valve orifices opening into the left ventricle. The two orifices are placed apart unlike the more common type of double-orifice mitral valve (see image above) where the orifice is divided by a bridge of tissue.

The relative positions of the 2 openings should be identified and the area should be measured. The nature and size of the bridging tissue and leaflets, as well as the movements of the valve cusps should be studied. Any associated congenital heart defect may also be identified and quantified.

Measuring the enlargement of the left atrium, LV, right ventricle (RV), and pulmonary artery on 2DE is important.

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

Real-time 3-dimensional echocardiography (3DE) allows comprehensive noninvasive assessment of the anatomical details in patients with double orifice mitral valve and provides incremental information to that obtained by 2DE as depicted in the images below. [22]

Real-time two-dimensional echocardiogram (apical view) in a patient with duplicate mitral valve. Two mitral valves can be seen opening into the left ventricle. Each valve has a separate annulus, and a separate set of mitral valve leaflets and subvalvar apparatus.
Two-dimensional echocardiogram (parasternal short-Two-dimensional echocardiogram (parasternal short-axis view) shows double-orifice mitral valve, the orifice being divided by a bridge of tissue.
Real-time two-dimensional echocardiogram (subcostal short-axis view) in a patient with duplicate mitral valve showing two typical mitral valves opening into the left ventricle. The two orifices are placed apart unlike the more common type of double-orifice mitral valve (see image above) where the orifice is divided by a bridge of tissue.

Doppler echocardiography

2DE with Doppler study and color flow mapping (as shown below) are useful to show the pattern of flow through the mitral valve and to identify the exact site of regurgitation.

Two-dimensional echocardiogram of a double-orificeTwo-dimensional echocardiogram of a double-orifice mitral valve (apical view) with color flow mapping, which shows diastolic flow through 2 separate orifices.

The severity of mitral regurgitation should be assessed in a semiquantitative manner by evaluation of the area of the regurgitant jet in the left atrium as well as jet width at its origin.

The severity of mitral obstruction can be quantified 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 mitral stenosis.

Estimating the systolic pressure in the pulmonary artery by measuring the peak velocity of the tricuspid regurgitant jet in the right atrium (only in the case of no right ventricular outflow obstruction) is crucial. The real-time 3DE can allow detailed and comprehensive assessment incremental to that obtained by 2DE. [223]

Transesophageal echocardiography

In children, transesophageal echocardiography is generally not necessary to assess double orifice mitral valve because adequate information can be obtained by using the transthoracic and subcostal windows.

In adults, transesophageal study may enable clear visualization of all valve components. A deep transgastric view with Doppler interrogation is often useful to show the 2 orifices and the precise origin of the regurgitant jet.

Thrombi in the left atrium can be detected.

In patients of all ages, intraoperative transesophageal echocardiography is extremely useful to assess the adequacy of mitral valve repair in the operating room.

Other Tests

Electrocardiography

The EKG findings may be normal, if no mitral stenosis, mitral regurgitation, or other associated cardiac pathology is found.

The mean frontal-plane QRS axis may be normal or shifted to the right.

Left atrial enlargement occurs in most patients with double orifice mitral valve and is diagnosed on the basis of wide bifid P waves (P mitrale pattern) in the limb leads and/or an increased P terminal force in lead V1.

Mitral incompetence is associated with LV hypertrophy. RV hypertrophy is common in stenotic double orifice mitral valve. Tall, peaked P waves in the inferior leads indicate right atrial hypertrophy because of pulmonary hypertension and tricuspid incompetence.

A sinus rhythm is commonly present. On occasion, atrial flutter or atrial fibrillation may develop in patients with double orifice mitral valve and chronic left atrial dilatation.

Associated congenital heart defects may modify electrocardiographic findings.

Procedures

Cardiac catheterization

Cardiac catheterization is often used to quantify the hemodynamic effects of abnormal mitral valve function.

Double orifice mitral valve with obstruction is characterized by elevation of left atrial pressure. Pressure tracings obtained from the pulmonary-artery wedge position reflect left atrial pressure and avoid the need to enter the left atrium by puncturing the interatrial septum. Simultaneous pressure recording from the pulmonary-artery wedge position and the LV shows that pulmonary-artery wedge pressure is substantially higher than LV pressure throughout diastole.

In patients with mitral regurgitation, the left atrial and pulmonary-artery wedge pressures are elevated, but no gradient can be demonstrated across the mitral valve at the end of diastole; LV diastolic pressure is often increased.

Cardiac output and pulmonary vascular resistance may be calculated. Associated shunts and other lesions, if any, may also be identified and quantified during cardiac catheterization.

Cardiac cineangiography

With the availability of high-quality echocardiography, cardiac angiography has a limited role in the assessment of double orifice mitral valve. Echocardiography is superior to angiography in defining anatomic and functional abnormalities of the valve.

LV angiography may be performed to confirm the severity of mitral regurgitation and to assess LV function.

Cardiac angiography is also helpful to assess other associated defects

TREATMENT AND MANAGEMENT


Medical Care

General principles

Patients with double orifice mitral valve (DOMV) are evaluated as outpatients. Patients should be admitted to the hospital for the treatment of severe heart failure, for pulmonary edema, for cardiac catheterization and for surgery.

Management depends on the type and severity of mitral valve dysfunction. Isolated double orifice mitral valve causing neither obstruction nor regurgitation needs no active intervention. This principle is important because the hemodynamics of a double orifice mitral valve at rest and during exercise do not differ from those of a normal mitral valve with a similar valvular area.

However, long-term follow-up and care are necessary to detect the onset of hemodynamic problems or complications.

All patients with clinically significant mitral stenosis or regurgitation require medical therapy and possibly transcatheter balloon or surgical treatment.

Roles of medical therapy

The roles of medical treatment include the following:

  • To initially stabilize the patient and to relieve pulmonary edema

  • To control congestive heart failure while detailed assessment and surgical repair is awaited

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

  • To treat small infants, in whom medical therapy may be the only option (Control of congestive heart failure may defer surgery until the child grows to an appropriate age and size.)

Adjunctive therapy

Physical activity restriction of symptomatic patients. Treat patients with severe pulmonary venous congestion in a 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 patients with acute pulmonary edema. Vigorously treat concurrent infections or other aggravating factors. Correcting anemia, if present, is important. Increasing the oxygen-carrying capacity by a packed-cell transfusion in patients with severe symptoms or heart failure may provide considerable relief.

According to the updated guidelines of the American Heart Association, patients with double orifice mitral valve do not need antibiotic prophylaxis against infective endocarditis. [24]

Percutaneous transcatheter balloon dilatation

Selected cases of double orifice mitral valve with mitral stenosis are amenable to percutaneous transcatheter balloon dilatation. This option offers a nonsurgical method of relieving obstruction. [25Successful dilatation has been reported in patients with the bridge type of double orifice mitral valve, especially if the bridge is incomplete. [26Stepwise dilatations by using an Inoue balloon are applied to the posteromedial orifice of the double orifice mitral valve. The results are best if the double orifice mitral valve is an isolated defect and if no major deformity of the subvalvular tensor apparatus is present.

Surgical standby is recommended to manage incomplete relief of obstruction or clinically significant disruption of the valve apparatus that causes mitral regurgitation.

Consultations

Obtain consultations with a cardiologist and a cardiothoracic surgeon.

Surgical Care

No surgery is necessary if the mitral valve is competent without mitral stenosis or mitral regurgitation.

This mitral anomaly can be difficult for even the most experienced surgeon to assess. The valve function should be tested to determine the cause of the regurgitation. If the regurgitation is due to a cleft in one orifice, then minor repair of the cleft may result in satisfactory function. Radical repair of the mitral valve has very poor outcome. The aim of surgical treatment of double orifice mitral valve is to correct abnormal mitral valve function and to repair all associated defects. A functionally normal double orifice mitral valve may be left intact even when the accompanying lesions are repaired. [19]

Surgical repair should be performed in all symptomatic patients with regurgitant double orifice mitral valve. It should also be performed in patients with stenotic double orifice mitral valve, if balloon dilation is not feasible or fails to relieve obstruction. Emergency surgical intervention is occasionally needed to manage severe mitral regurgitation resulting from balloon valvuloplasty for mitral stenosis.

Mitral valvuloplasty [27and valve replacement both have a place in the management of the double orifice mitral valve. [28]

Closure of one orifice might produce acute diminution of the mitral valve area leading to a stenotic condition. It may also cause deformity at the fibrous bridging tissue, leading to incompetence of another intact orifice. [29]

The type of operation should depend on the anatomic abnormality in the mitral valve apparatus. In many patients, the valve may be amenable to repair and reconstruction procedures, including resection of tissue, repair of defects and clefts, shortening of chordae, placement of artificial chordae, and annuloplasty. However, the delicate relationships among the various components of the valve and the subvalvar apparatus should be preserved. [30]

Replacement of the mitral valve is indicated, if the valvular mechanism is markedly abnormal.

For high-risk surgical patients, such as the elderly, percutaneous mitral valve therapies, including the MitraClip, are being developed for the treatment of severe mitral regurgitation. [3132]

Diet

Asymptomatic patients with double orifice mitral valve require no special diet. Counsel patients with heart failure to avoid excess intake of salt or to reduce their salt intake. Prescribe salt restriction cautiously in infants.

Activity

Patients with pulmonary venous congestion or congestive heart failure should avoid strenuous exertion

MEDICATION


Medication Summary

Medical therapy for double orifice mitral valve (DOMV) consists of the use of drugs to control of congestive heart failure (CHF). The 3 groups of drugs used are diuretics (to promote excretion of excess water), positive inotropic drugs (to improve myocardial contraction), and vasodilators (to reduce arterial resistance).

Antibiotics for endocarditis prophylaxis are administered to patients before procedures that may cause bacteremia are performed. For more information, see Antibiotic Prophylactic Regimens for Endocarditis.

Diuretics

Class Summary

These drugs promote the excretion of water and electrolytes by the kidneys and are used to treat heart failure or hepatic, renal, or pulmonary disease when sodium and water retention results in edema or ascites. They are useful to remove excess water that accumulates in patients with CHF. They also relieve symptoms associated with pulmonary congestion and reduce peripheral edema.

Furosemide (Lasix)

Drug of choice (DOC) for rapid relief of pulmonary congestion and edema from heart failure. Useful for maintenance therapy of CHF in patients with DOMV. Promotes renal excretion of water by inhibiting electrolyte-transport system in ascending limb of loop of Henle. Increases solute and water excretion, even with declining glomerular filtration rate.

Chlorothiazide (Diuril)

Increases water excretion by inhibiting reabsorption of sodium chloride in distal renal tubule. Less potent than furosemide, thiazide diuretics useful in maintenance therapy of CHF; in severe heart failure or refractory edema, act synergistically with furosemide to promote diuresis.

Hydrochlorothiazide (Esidrix, HydroDIURIL)

Increases water excretion by inhibiting reabsorption of sodium chloride in distal renal tubule. Less potent than furosemide. Useful in maintenance therapy of CHF; in severe heart failure or refractory edema, act synergistically with furosemide to promote diuresis.

Spironolactone (Aldactone)

Counteracts secondary hyperaldosteronism in cardiac failure. Inhibits sodium absorption in collecting duct. Potassium-sparing diuretic effect. Used alone, produces relatively mild diuresis. Can 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 to improve cardiac failure because of positive inotropic effect on myocardium. Helps control fast ventricular rate, especially in atrial arrhythmia.

Common preparations in children include tabs 0.125 or 0.25 mg and elixir 0.05 mg/mL. Caps and parenteral injection also available.

Vasodilators

Class Summary

Drugs that produce vasodilation include ACE inhibitors, nitrates, and direct vasodilators (eg, hydralazine). Of these drug classes, ACE inhibitors are frequently used because their adverse effects are the most tolerated. They reduce afterload on the LV by decreasing systemic arterial resistance. ACE inhibitors are particularly helpful in patients with mitral regurgitation, in whom decreased afterload reduces the severity of regurgitation and improves ventricular function. The DOC is captopril. Newer drugs from this category, such as enalapril and lisinopril, are also used for the treatment of CHF, but experience with their use in children is limited.

Captopril (Capoten)

Prevents conversion of angiotensin I to angiotensin II, potent vasoconstrictor. Lowers vascular resistance and aldosterone secretion.

Enalapril (Vasotec)

Competitive ACE inhibitor. Reduces angiotensin II level, potent vasoconstrictor. Lowers vascular resistance and aldosterone secretion.

Lisinopril (Zestril, Prinivil)

Prevents conversion of angiotensin I to angiotensin II, potent vasoconstrictor. Lowers vascular resistance and aldosterone secretion.