Double Outlet Right Ventricle With Transposition

Double outlet right ventricle (DORV), as depicted in the image below, is a type of ventriculoarterial connection in which both the aorta (AO) and pulmonary artery (PA) arise entirely or predominantly from the right ventricle (RV). The only outlet from the left ventricle (LV) is a ventricular septal defect (VSD).

Double outlet right ventricle (DORV) with transposition of the great arteries accounts for 26% of cases of DORV. The aorta (AO) is anterior and to the right of the pulmonary artery (PA), and both arteries arise from the right ventricle (RV). The only outflow from the left ventricle (LV) is a ventricular septal defect (VSD), which diverts blood toward the RV. Pulmonary veins drain into the left atrium (LA) after blood has been oxygenated in the lungs (L). Systemic venous return is to the right atrium (RA).

DORV is usually associated with concordant atrioventricular (AV) connections (ie, the right atrium drains into the RV and the left atrium drains into the LV). Fibrous discontinuity is present between the mitral and semilunar valves. Conus is present beneath both the aortic and pulmonary valves (subpulmonic and subaortic conus).

DORV is virtually always associated with a VSD and, occasionally, with an atrial septal defect. Patients with DORV may also present with varying degrees of left ventricular hypoplasia and mitral valve anomalies such as stenosis or atresia. Straddling of the AV valves across the VSD may be present. The aortic valve may be stenosed, and the aortic arch may show coarctation or even interruption. Anomalies of the coronary arteries (CAs), such as those that occur in patients with dextro-transposition of the great arteries may be present. These include the left circumflex arising from the right main, a single right CA, a single left CA, and inverted origin of the CA.

The AV node and His-Purkinje fibers may be displaced in DORV because of the anatomic characteristics of these hearts.

In DORV, the great arteries may take different relationships as follows:

• In 64% of cases of DORV, the great arteries lie side by side with the AO to the right of the PA and both semilunar valves lying in the same transverse and coronal plane (physiologically similar to tetralogy of Fallot [TOF]).

• In 26% of cases of DORV, the AO is anterior and to the right of the PA, physiologically resembling transposition of the great arteries (ie, d-transposition of the great arteries), with a VSD.

• In 7% of cases of DORV, the AO is anterior and to the left of the PA (levo-transposition of the great arteries).

• Only 3% of cases of DORV have a normal great artery relationship with the AO arising posterior and to the right of the PA.

The pathophysiology of DORV varies, irrespective of the great arterial relationship (ie, side-by-side, d-transposition of the great arteries, l-transposition of the great arteries, normally related). Clinical manifestations may range from that of a large VSD to that of transposition of the great arteries and may mostly depend on the position of the VSD in relation to the great vessels (whether it is subpulmonary or subaortic) and the presence or absence of pulmonary valve stenosis (PS). Both of these factors contribute substantially to the hemodynamics of this congenital heart defect.

In cases of a subaortic VSD, which occurs in 60-70% of patients, the VSD is closer to the aortic valve, thus oxygenated blood from the LV is directed to the AO and desaturated blood from the right ventricle (RV) is directed primarily to the PA (see the image below).

Double outlet right ventricle (DORV) with transposition of the great arteries accounts for 26% of cases of DORV. The aorta (AO) is anterior and to the right of the pulmonary artery (PA), and both arteries arise from the right ventricle (RV). The only outflow from the left ventricle (LV) is a ventricular septal defect (VSD), which diverts blood toward the RV. Pulmonary veins drain into the left atrium (LA) after blood has been oxygenated in the lungs (L). Systemic venous return is to the right atrium (RA).

PS occurs commonly which forces some desaturated blood into the AO. Because of the large VSD, the RV and the LV as well as the AO handle equal systolic pressures. When PS is present, this poses a restriction to flow to the pulmonary circuit, and thus, systolic pressure in the pulmonary arteries is lower. This physiology resembles that of TOF with cyanosis and no congestive heart failure (CHF).

In cases of a subaortic VSD with no PS, systolic pressure in both great vessels as well as in both ventricles is equal; thus, blood follows the path of least resistance (ie, usually towards the lungs) and the clinical picture is that of a large VSD. The degree of blood oxygenation in the systemic as well as the pulmonary circuits is determined by degree of mixing in the systemic (ie, right) ventricle, which, in turn, depends on the degree of resistance upstream of the pulmonary valve.

All patients with increased pulmonary blood flow (PBF) at systemic or near systemic pressures are at increased risk of developing early pulmonary obstructive vascular disease regardless of their arterial oxygen saturation (ie, presence or absence of cyanosis).

With a subpulmonary VSD (Taussig-Bing anomaly), which occurs in 10% of patients, oxygenated blood from the LV is directed to the PA and desaturated blood from the RV is directed to the AO. This physiology resembles transposition of the great arteries with a VSD; thus, the patient presents with both cyanosis and CHF.

In cases of a doubly committed VSD, the left ventricular outflow is not committed preferentially to either semilunar valve. In the presence of PS, the physiology resembles that of TOF, and in the absence of PS, it is that of a large VSD.

In cases with remote VSD, the VSD is far from both semilunar valves. It is most commonly an AV canal-type VSD. Again, the physiology is that of TOF in cases involving PS and is that of a large VSD when flow through the pulmonary valve is not restricted (ie, absence of PS).

DORV is thought to be the result of a malformation in the outlet portion of the embryonic ventricular loop at 3-4 weeks' gestation. Although mostly sporadic, familial cases have been reported.

Fluorescence in situ hybridization (FISH) analysis has shown deletions in the 22q11.2 region in certain individuals with TOF, DORV, transposition of the great arteries, and VSD associated with other congenital heart disease (CHD).[1, 2, 3] As a matter of fact, DORV may be part of complex CHD in patients with DiGeorge syndrome, velocardiofacial syndrome, and conotruncal anomaly–face syndrome.

DORV has also been associated with trisomies 13 and 18 and tetrasomy 8p.

DORV has also been reported in patients with mutations in human cardiac transcription factor NKX2.5.

DORV, truncus arteriosus (TA), atrial septal defect (ASD), atrioventricular septal defect (AVSD), ventricular septal defect (VSD), transposition of the great arteries (TGA), and tetralogy of Fallot (TOF) occur with a higher incidence in the offspring of mothers with pregestational diabetes mellitus than in the general population. Teratogenic mechanisms involved are thought to be related to increased reactive oxygen species production, impaired cell proliferation, and altered Gata-4, Gata-5, and vascular endothelial growth factor (VEGF)–α expression. According to research studies in pregnant diabetic rats, antioxidant supplementation with vitamin E reduced the severity of malformations in their offspring[4] and supplementation of their drinking water with N -acetylcysteine eliminated the incidence of AVSD, TOF, and TGA and decreased the incidence of ASD and VSD.[5]

DORV has been reported to occur in mouse embryos homozygous for the JMJ mutation, which affects the nuclear protein jmj coded by chamber-specific genes.

Studies using animal models described a transcription factor that plays a critical role in directing cardiac asymmetric morphogenesis, known as Pitx2. Specifically, ectopic Pitx2c expression in the developing myocardium was found to correlate with the development of DORV. Whereas loss of function of the Pitx2 caused atrial isomerism, double inlet left ventricle, transposition of the great arteries, persistent truncus arteriosus, and abnormal aortic arch remodeling.

Most recently, hearts with persistent truncus arteriosus, DORV, and transposition of the great arteries, have been postulated to have rotation of the myocardial wall of the outflow tract that is arrested or fails to initiate. This is supported by the discovery that mutations in the NPHP4 gene involved in the formation of motile cilia in the Kupffer vesicle, which produce asymmetrical fluid flow necessary for normal left-to-right asymmetry, cause laterality defects such as dextrocardia, transposition of great arteries, DORV, and caval vein abnormalities.[6]

In summary, the pathogenesis of DORV is currently believed to include impairment of neural crest–derivative migration and impairment of normal cardiac situs and looping.[7]

United States data

Congenital heart disease (CHD) occurs in less than 1% of all newborns, and DORV is present in 0.5-1.5% of all patients with CHD. The estimated frequency of DORV is 1 case per 10,000 live births. A recent study showed a higher prevalence of DORV, tetralogy of Fallot, and truncus arteriosus, in addition to endocardial cushion defects and single ventricle, in certain regions of the country.[8]

Sex-related demographics

No sex predilection is reported.

Age-related demographics

The presentation is usually in the newborn period with this entity; however, in some circumstances (eg, subaortic VSD with mild-to-moderate PS), the diagnosis may not be made until later in infancy.

Improvement in surgical techniques in recent years has resulted in good outcomes for most patients born with congenital heart disease (CHD). Prognosis for infants born with DORV and transposition of the great arteries is generally good, although it is dependent on specific anatomy. For example, patients with DORV and transposition of the great arteries with a subaortic VSD and no other anatomic abnormalities (eg, left ventricular hypoplasia) are likely to do well after surgery. Patients with restrictive VSD may not do as well because this is a particularly difficult problem.[9] Enlargement of VSD is difficult and likely to result in complications, such as conduction abnormalities (atrioventricular [AV] block).

Morbidity/Mortality

Morbidity and mortality depend not only on the overall clinical condition of the patient at the time of presentation, but also on the type and severity of associated anomalies.

Irrespective of the great vessel relationship, the mortality rate is less than 5% for DORV cases with subaortic VSD and is somewhat higher for those with a doubly committed VSD.

In cases of subpulmonary VSD (Taussig-Bing anomaly), morbidity and mortality depend on whether the patient has already developed pulmonary vascular obstructive disease and also on the type of surgery that is required.[10] In cases of DORV with d-transposition of the great arteries, creation of an intraventricular tunnel between the VSD and the AO carries a mortality risk of 10-15%. In subpulmonary VSD with PS (ie, TOF-type physiology), an intraventricular tunnel between the VSD and the AO in addition to relief of PS by a patch graft also carries a mortality risk of 10-15%. In cases of remote VSD, the preferred surgical repair is creation of an interventricular tunnel between the VSD and the AO. However, it carries a mortality rate as high as 30-40%.

When the above surgical procedures cannot be performed (ie, hypoplastic LV, inadequate anatomy for an intracardiac conduit between the LV and the AO, hypoplastic AO, hypoplastic/atretic mitral valve), a Fontan-type operation is the choice; the mortality rate has decreased to approximately 5%.

For patient education resources, see Heart Health Center.

History of fetal bradycardia and heart block during the first trimester of pregnancy has been associated with double outlet right ventricle (DORV), as opposed to autoimmune causes of fetal heart block, which occur after the second and third trimesters. Fetal heart block can be diagnosed by fetal echocardiographic studies.

In patients with DORV and transposition of the great arteries, the clinical presentation depends on the location of the ventricular septal defect (VSD) and the presence and the degree of pulmonary valve stenosis (PS) or both. If the VSD is subpulmonic, the physiology resembles that of transposition of the great arteries with VSD. Patients with this anatomy usually present in the newborn period or within the first few weeks of life with cyanosis and signs of pulmonary overcirculation. If the VSD is subaortic, the patient may be only mildly cyanotic and may present primarily with pulmonary overcirculation at 3-6 weeks of life when pulmonary vascular resistance drops. If PS is present, which is often the case in DORV with subaortic VSD, the degree of PS greatly affects clinical presentation.

If PS is mild or moderate, the patient may present with mild cyanosis and little or no pulmonary overcirculation. If PS is severe, clinical presentation resembles that of tetralogy of Fallot (TOF). Cyanosis from diminished pulmonary blood flow (PBF) is likely to be the major clinical feature.

In patients with DORV and transposition of the great arteries (both uncommon lesions), the VSD may be doubly committed or remote from the great arteries. If the VSD is doubly committed, the conus septum is deficient and the VSD usually lies above the crista supraventricularis, closely related to both semilunar valves. Clinical presentation is often that of DORV with a subpulmonic VSD, although the patient may have slightly higher systemic oxygen saturation.

In DORV with transposition of the great arteries and remote VSD, many variables determine clinical presentation. If the VSD is remote from both semilunar valves, it is often part of an AV canal-type defect, in which case many other anomalies are likely.

Instead, multiple muscular VSDs may be remote from the semilunar valves. Clinical presentation depends on factors such as the location of the VSDs, the presence or absence of PS (right ventricular outflow tract obstruction), and the direction of streaming of blood flow through VSDs.

Physical findings vary, depending on the location of the VSD and the presence or absence of PS.

With a subaortic VSD and no PS, cyanosis is mild or absent. PBF is increased, thereby producing congestive heart failure (CHF). The precordium is hyperactive with a loud second heart sound, which may appear to be single. Harsh holosystolic murmur is heard as pulmonary vascular resistance decreases. Clinically, these patients resemble those with a large VSD.

In DORV with subaortic VSD and PS, physical findings depend on the degree of PS. If PS is mild, faint cyanosis and mild or no CHF may be present. These patients present with a murmur from PS (systolic ejection murmur), from the VSD (holomurmur), or both. If PS is moderate or severe, cyanosis is prominent because of decreased PBF (resembling TOF). If uncorrected, cyanosis leads to late findings such as polycythemia and digital clubbing.

In those patients with subpulmonic VSD (PS is rare in these patients), PBF increases as vascular resistance falls. These patients present similarly to those with transposition of the great arteries and VSD. Cyanosis is prominent early, and as pulmonary overcirculation develops, the cyanosis is less prominent. Failure to thrive is likely to develop if treatment is not instituted. The second heart sound is loud and possibly single, and a holosystolic murmur develops. If increased pulmonary vascular resistance occurs, signs of CHF diminish and the murmur decreases. An ejection click may appear along with a diastolic murmur of pulmonary valve insufficiency (late findings).

Patients with doubly committed VSD also present similarly to those with transposition of the great arteries and VSD. Cyanosis may be mild. Signs of CHF, including tachypnea, tachycardia, and hepatomegaly may be present, leading to failure to thrive.

Clinical laboratory studies (eg, hematologic analysis, urinalysis) are not likely to be of diagnostic help; late findings may include polycythemia, but this and other findings of chronic cyanosis are nonspecific.

Echocardiography is used to evaluate anatomy, hemodynamics, and function of the heart both prior to and after surgical repair or palliation, and it is the most important means of establishing diagnosis of double outlet right ventricle (DORV) with transposition of the great arteries. Four important findings are as follows:

• Both great arteries arise from the right ventricle (RV).

• The aorta (AO) is to the right of or anterior to the pulmonary artery (PA).

• No course of egress of blood from the left ventricle (LV) other than a ventricular septal defect (VSD) is present.

• Fibrous discontinuity of mitral and semilunar valves is present.

In experienced centers, the accuracy of the prenatal echocardiographic diagnosis (and prognosis) of fetuses with conotruncal anomalies in general is good (ie, correct diagnosis in 77% of cases in a major center).[13] However, defining the exact spatial relationship of the great arteries can be problematic in some fetuses (ie, 7 of 17 fetuses with DORV anatomy, of which 6 were thought to have a subpulmonary VSD, had incorrect prenatal assessment of the great artery relationships).[13]

Some authors have described real-time 3-dimensional echocardiography as a way to improve cardiac imaging and diagnosis of complex congenital heart disease (CHD) through a clear display of cardiac morphology using volumetric views combined with sequential segmental approach.[14] However, others have recently concluded that information provided by real-time 2-dimensional echocardiography in fetuses with and without CHD were consistent with that provided by real-time 3-dimensional echocardiography. Therefore, no clear advantage of real-time 3-dimensional echocardiography over real-time 2-dimensional echocardiography has been documented.

Sometimes chest radiography may provide valuable clues for the diagnosis of DORV with transposition of the great arteries. Chest radiography for patients with either subaortic or subpulmonary VSD without PS may show cardiomegaly with increased pulmonary vascular markings and the main PA segment may be prominent; however, these findings are not specific for DORV. If PS is present, chest radiography may show near normal heart size and normal-to-decreased pulmonary vascular markings.

CT has been described as an effective diagnostic modality, especially in identifying coronary artery anomalies prior to cardiac surgery to aid in adequate procedure planning.[15]

MRI may serve as an adjunct tool to echocardiography for determination of visceral and atrial situs as vasculo-vascular and vasculo-visceral relationships. In some patients with DORV with remote VSD, MRI may aid in defining the spatial relationship between VSD and the semilunar valves. A new modality in MRI is the 3-dimensional MRI, which is increasingly used as an adjuvant to echocardiography and angiography for such purposes.

Angiography (see images below) may add anatomic and physiologic details to information found by echocardiography.

This is an angiogram obtained during catheterization of a patient with double outlet right ventricle (DORV) with transposition of the great arteries. Injection of contrast though the catheter (arrow) into the left ventricle (LV) shows that blood is directed toward the right ventricle (RV) through a remote or doubly committed ventricular septal defect (VSD). The aorta (AO) is anterior to the pulmonary artery (PA) and both clearly arise from the RV.

This is an angiogram obtained during catheterization of a patient with double outlet right ventricle (DORV) with transposition of the great arteries (see Media file 2). Blood fills the aorta (AO) and pulmonary artery (PA) almost simultaneously, which is another indicator of a remote or doubly committed ventricular septal defect (VSD) (curved arrow). LV indicates the left ventricle, RV indicates the right ventricle, and the small arrow to the left indicates the catheter.

ECG in patients with DORV with transposition of the great arteries reveals no specific findings indicative of the diagnosis. Usually, normal sinus rhythm and possible prolonged PR interval are present. Right axis deviation and right ventricular hypertrophy (RVH) are present most often. Left axis deviation is present in patients with atrioventricular (AV) septal defect.

Some ECG variations may be noted, depending on the type of DORV with transposition of the great arteries. ECG in patients with subaortic VSD with no PS may show superior QRS axis (-30° to -170°) with either RVH or biventricular hypertrophy and left atrial enlargement. First-degree AV block may be present with this lesion. ECG in patients with subpulmonic VSD or in those with subaortic VSD and PS reveals right axis deviation, RVH, and often right atrial enlargement.

Echocardiography has mostly eliminated the need to perform cardiac catheterization in these patients; however, catheterization may still be necessary in certain circumstances.

Catheterization may be required for the following reasons:

• Need for further definition of coronary artery anatomy

• Need to determine coexistent conditions that cannot be elucidated by echocardiography

• Need to confirm restrictive VSD by measuring ventricular pressures

• Need to determine pulmonary vascular resistance (and reactivity) in patients suspected of having increased resistance

Medical treatment depends on the clinical presentation, which is determined by the differences in physiology of each type of double outlet right ventricle (DORV).

In DORV with no pulmonary valve stenosis (PS), medical management to control congestive heart failure (CHF) and improve the patient's condition prior to surgery should be instituted. Management of CHF requires medications such as loop diuretics (eg, furosemide), potassium-sparing diuretics (eg, spironolactone), after-load reducing agents, and digitalis. In addition, observe subacute bacterial endocarditis prophylaxis.

Infants with a subpulmonary ventricular septal defect (VSD) with a small or restrictive patent foramen ovale or atrial septal defect may require balloon atrial septostomy or blade atrial septostomy to improve interatrial mixing of saturated and desaturated blood and to decompress the left atrium.

In neonates with DORV and PS with marked cyanosis and hypoxemia, initial medical management consists of administration of intravenous prostaglandin E1 (PGE1) to open the ductus. The dosage used is 0.5 to 0.1 mcg/kg/min. The fraction of inspired oxygen (FIO2) should not exceed 0.4 (40%) unless there is associated pulmonary parenchymal pathology. Because of fixed intracardiac right-to-left shunting, higher FIO2 does not raise the O2 saturation.

Maintain patency of the ductus arteriosus with prostaglandin E1 in newborns with markedly diminished pulmonary blood flow (PBF) from severe pulmonary valve stenosis (PS). In newborns with double outlet right ventricle (DORV) and transposition of the great arteries who have subpulmonic ventricular septal defect (VSD), performing balloon atrial septostomy to enhance mixing of systemic and pulmonary circulations until surgery can be performed may be necessary.

The two surgical approaches to double outlet right ventricle (DORV) are palliative and corrective.

Because surgery in these patients often is technically demanding, strongly consider referring these patients to a center with a large pediatric cardiac surgical program.

Palliative surgery

Similar to medical management, palliative therapy helps improve the patient's clinical condition, allowing him or her to gain weight and achieve optimal conditions for definitive surgical repair.

Infants with no PS who have a subpulmonary VSD, subaortic VSD, or doubly committed VSD and who present with CHF may undergo pulmonary artery (PA) banding to normalize pulmonary blood flow (PBF) and PA pressures.

Patients with subaortic or subpulmonary VSD with PS are cyanotic and have decreased PBF; therefore, they should undergo a systemic-to-PA shunt, usually a modified Blalock-Taussig anastomosis, to increase PBF. Alternatively, balloon pulmonary valvuloplasty may be performed, provided there is significant pulmonary valvar stenois and there are multiple obstructions in pulmonary outflow tract.[16, 17]

Definitive surgery

The relationship of VSD to the great arteries and the distribution of coronary artery (CA) determine surgical strategies.

Biventricular repair can be achieved in most patients with DORV. If biventricular repair is not feasible (eg, in straddling or abnormal distribution of chordae tendineae of atrioventricular [AV] valves and/or severe underdevelopment of left ventricle [LV]), a Fontan-type operation is an option with redirection of systemic (deoxygenated) blood into the PA without traversing a ventricle.

If biventricular repair is feasible, the 2 basic surgical steps to follow according to certain authors are (1) creation of an intracardiac tunnel to connect the LV to usually the aorta or, less commonly, the main pulmonary artery, where the conal septum is resected and any abnormal AV valve insertion on such conal septum are preserved; and (2) creation of an intracardiac or an extracardiac reconstruction to connect the RV to the main pulmonary artery.[18]

Several surgical approaches are appropriate in subpulmonary VSD; surgery is usually completed by age 3-4 months to avoid development of increased pulmonary vascular resistance. The surgical approach with a mortality rate of approximately 10-15% is the arterial switch operation with creation of an interventricular tunnel directing LV outflow into the PA, which becomes a neo-aorta (AO).[19]

If the VSD is subaortic or doubly committed, the optimal approach is to create a tunnel between the VSD and the AO to direct oxygenated blood into systemic circulation and also to eliminate mixing of the 2 circulations. Timing for this surgery depends on the size and clinical condition of the patient, but it is generally completed by age 4-6 months.

Heart transplantation

If the anatomy of associated lesions is too complex to consider an anatomic repair or if a repair results in unsatisfactory hemodynamics and intractable symptoms, consider heart transplantation. According to a report from the Children's Hospital of Pittsburgh, 15.4% of patients undergoing transplant were born with some form of DORV.[20] These patients require lifelong immunosuppression and close follow-up care.

As with any other form of congenital heart disease (CHD), parents of patients born with DORV and transposition of the great arteries may meet with a geneticist to discuss the possibility of subsequent children having this or other forms of CHD. When CHD is detected, a detailed investigation for extracardiac malformation should be performed and vice versa. Also, issues such as preterm birth and stillbirth should be taken into account in risk assessment and risk stratification in patients born with CHD.

CHD belongs to the spectrum of birth defects and, despite technological advances, it significantly contributes to infant mortality. Because extracardiac anomalies occur in 15-45% of patients with CHD, these should always be investigated.

According to one study, the most prevalent extracardiac anomalies in general are the craniofacial malformations. However, the most prevalent associated with conotruncal heart defects are anomalies of the GI and genitourinary systems. Specifically, DORV may be associated with omphalocele, gastroschisis, facial clefting, and CHARGE (coloboma, heart disease, atresia choanae, retarded growth and retarded development and/or CNS anomalies, genital hypoplasia, and ear anomalies and/or deafness) syndrome.

Preterm infants have been shown to have more than twice as many cardiovascular malformations as do term infants, and 16% of all infants with cardiovascular malformations are preterm.

Prevalence of CHD is high among late stillbirths. In particular, a greater incidence of coarctation of the AO, double-inlet left ventricle, hypoplastic left heart, truncus arteriosus, DORV, and AV septal defect is noted among stillbirths.

Patients with DORV and transposition of the great arteries have no specific activity restrictions; their physiology may limit their exercise tolerance. After surgical intervention, some restrictions may be required depending on the hemodynamic result; however, these patients can usually participate in all age-appropriate activities.

Lifelong antibiotic prophylaxis is necessary prior to any potentially contaminated procedure, especially dental work.

Provide follow-up care every 6-12 months for the first few years after surgery to detect complications of surgery that may include arrhythmias (eg, persistent atrial tachycardias, complex ventricular ectopy) and stenosis or partial obstruction, or both, of the interventricular tunnel.

Because arrhythmias result in morbidity, mortality, or both, patients may require long-term antiarrhythmic medication or may be candidates for radiofrequency ablation of an arrhythmogenic focus or circuit.

Interventricular tunnel obstructions may occur without clinical manifestations. In patients with severe left ventricular outflow obstruction, patients with tunnel obstruction may present with left ventricular failure. As many as 20% of patients who have undergone surgery for DORV require reoperation.

Medical therapy is aimed at alleviating congestive heart failure (CHF), when present, to prepare patients for surgery. Antibiotics for endocarditis prophylaxis are required before performing procedures that may cause bacteremia. For more information, see Antibiotic Prophylactic Regimens for Endocarditis.

Class Summary

Furosemide is used to decrease pulmonary congestion in patients with pulmonary overcirculation.

Furosemide (Lasix)

Inhibits absorption of sodium and chloride in proximal and distal tubules of the loop of Henle, thereby promoting excretion of salt and water.

Class Summary

Potassium-sparing diuretics (eg, spironolactone) are weak diuretics usually prescribed with more potent loop diuretics to prevent potassium depletion with subsequent development of hypokalemic-hypochloremic metabolic alkalosis.

Spironolactone (Aldactone)

Inhibits aldosterone-dependent sodium-potassium exchanger in distal convoluted renal tubule, thereby retaining potassium and promoting excretion of sodium and water.

Class Summary

Positive inotropic agents increase the force of contraction of the myocardium and are used to treat acute and chronic CHF. Some may also increase or decrease the heart rate (ie, positive or negative chronotropic agents), provide vasodilatation, or improve myocardial relaxation. These additional properties influence the choice of drug for specific circumstances. Those used predominantly for their inotropic effects include cardiac glycosides. Digitalis glycosides are used for their inotropic properties in the presence of left ventricular failure.

Digoxin (Lanoxin, Lanoxicaps)

Digitalis glycoside. Enhances myocardial contractility by inhibition of Na+/K+ ATPase, a cell membrane enzyme that extrudes Na and brings K into the myocyte. Resulting increase in intracellular Na stimulates Na-Ca exchanger in the cell membrane, which extrudes Na and brings in Ca, therefore increasing contractility of myocyte (ie, positive inotropic effect).