Double Outlet Right Ventricle, Normally Related Great Arteries |
INTRODUCTION
Background: Double outlet right ventricle (DORV) was first described pathologically in the late 19th century as partial transposition. The term double outlet right ventricle was first used in 1957 by Witham to describe a partial transposition of the great arteries. He described 4 hearts with 2 varieties of "complete aortic transposition with the pulmonary artery in normal position."
DORV is defined as a form of ventriculoarterial connection in which both great arteries arise completely or predominantly from the morphologically right ventricle. Controversies still exist regarding this definition. For example, some researchers require that the aorta and pulmonary artery arise from the right ventricle entirely. Alternatively, the 50% rule states that more than half of both arterial trunks must arise from the morphologically right ventricle. Finally, some require only the presence of fibrous discontinuity between mitral and semilunar valves. This is present in most specimens and is referred to as subpulmonic and subaortic conus.
Pathophysiology: DORV, with a large variability in anatomy, represents a continuum of congenital heart defects (CHD) that ranges from ventricular septal defect (VSD) with significant override of the aorta to origin of both great arteries from the right ventricle to transposition of the great arteries with pulmonary override of the VSD. A common arterial trunk may also arise completely from the right ventricle. This is actually a type of Truncus Arteriosus.
Pathophysiologic description and classification is accomplished by relating the location of the VSD to the arrangement of the great vessels. Each combination results in a physiologic behavior similar to that of other congenital heart defects. The VSD in DORV can be subaortic, subpulmonary, noncommitted, or doubly committed. Most ventricular septal defects are nonrestrictive, but up to 17% of patients may require VSD enlargement during repair to allow unrestricted systemic blood flow.
The most common type of VSD found in DORV is a subaortic type. The aortic orifice is usually posterior and to the right of the pulmonary orifice, with a spiral arterial relationship. Since the great arteries are normally related, the left ventricular outflow is directed toward the aorta, resulting in aortic oxygen saturations exceeding pulmonary saturations. In up to 50% of patients with DORV, associated pulmonary stenosis is present. The resulting physiology is similar to tetralogy of Fallot, in which the aorta is completely overriding the right ventricle. Systolic pressures are equal in both ventricles and in the aorta. In the absence of pulmonary stenosis, the physiology resembles that of a large isolated VSD in which the ratio of pulmonary to systemic blood flow is determined by the pulmonary vascular resistance. Systemic and pulmonary saturations are also affected by the degree of mixing in the right ventricle. This anatomy may result in congestive heart failure (CHF) and pulmonary vascular disease.
In DORV with subpulmonary VSD (Taussig-Bing anomaly), the left ventricular outflow is directed toward the pulmonary artery. This preferential streaming results in pulmonary artery saturations greater than aortic saturations. The aortic and pulmonary orifices are usually positioned side by side but are described as transposed or malposed. The rare presence of pulmonary stenosis results in physiology similar to tetralogy of Fallot. However, in the absence of pulmonary obstruction or stenosis, patients with DORV and subpulmonary VSD have physiology similar to transposition of the great arteries and VSD. In this case, pulmonary vascular resistance (PVR) determines pulmonary blood flow. Early-onset pulmonary obstructive vascular disease commonly occurs because of increased pulmonary blood flow and pressures, yet cyanosis may be absent with high pulmonary blood flow. This type of DORV is frequently associated with subaortic stenosis and arch obstruction.
DORV with noncommitted or remote VSD has anatomy and physiology similar to those of an isolated VSD or atrioventricular canal defect. To meet the criteria for DORV with noncommitted VSD, some have suggested that the distance between the VSD and the aortic and pulmonary outflow tracts should be at least equal to the aortic valve diameter. Most commonly, the great arteries are normally related in this type of DORV. Pulmonary and systemic blood flow and saturations are determined by the ratio of pulmonary to systemic vascular resistance and by the degree of right ventricular mixing.
Finally, DORV with doubly committed VSD displays physiology in which the left ventricular outflow is shared equally by the aorta and pulmonary artery. The systemic and pulmonary vascular resistances determine the ratio of pulmonary to systemic blood flow. This is a relatively rare form of DORV that typically has normally related great arteries. Right ventricular mixing affects oxygen saturations.
Since DORV is the only defect in fewer than 50% of patients with DORV, classification and description also may take into consideration obstruction of the systemic circulation, ventricular anomalies, coronary artery anomalies, and conduction system abnormalities. On further investigation, findings of additional ventricular septal defects, anomalies of ventricular rotation, and anomalies of insertion of the subvalvar apparatus of atrioventricular valves are not uncommon.
Systemic circulation may be obstructed at the aortic valve or subaortic; subaortic obstruction occurs in approximately 10% of patients. Aortic valve anomalies are usually associated with mitral valve anomalies that also may be present in the form of a restrictive VSD. Coarctation of the aorta is the most common associated lesion, and interrupted aortic arch also may be present.
Patients with DORV can have coexisting ventricular anomalies. Left ventricular inflow anomalies are less frequent yet can be severe. Mitral stenosis or atresia often is associated with a hypoplastic left ventricle as well as intact ventricular septum. Left ventricular hypoplasia will be present if decreased pulmonary venous return, restrictive VSD, and large atrial septal defect (ASD) are present. Also visible is misalignment of atrioventricular valves. This is very important for surgical correction and must be investigated. Finally, straddling of the atrioventricular valve annuli or straddling of the chordae may be present. Right ventricular abnormalities including tricuspid regurgitation, tricuspid stenosis, and Ebstein malformation may occur.
Coronary artery abnormalities are related to the relationship of the great arteries with several variations, including anomalous origin of the right coronary artery (RCA) from the left main coronary artery (LMCA), duplication of left anterior descending (LAD), anomalous origin of LAD from RCA (associated with a subaortic VSD and pulmonary stenosis), anterior origin of LAD, RCA immediately beneath pulmonary annulus (seen with l-malposed aorta), and RCA from the posterior sinus of Valsalva/LMCA from the left sinus, which is seen with an anterior aorta and subpulmonary VSD and is similar to transposition of the great arteries.
Conduction system abnormalities occur because of alterations in anatomy. Anatomy of the atrioventricular node and His-Purkinje system is similar to that in an isolated perimembranous VSD. In subaortic, subpulmonary, and doubly committed VSD, conduction tissues are displaced from the superior margin of the VSD.
Other abnormalities and associations are rare and can include dextrocardia and atrioventricular discordance, superior and inferior ventricles, and single atrioventricular valve connection.
Frequency:
- In the US: DORV accounts for 1-1.5% of all CHDs, with an incidence of 1 per 10,000 live births.
- Internationally: Incidence is the same internationally as in the United States.
Mortality/Morbidity:
- A recent review found early in-hospital mortality after operation to be 4.8%. The rate was significantly higher in patients with complex lesions. Late mortality was 3.2% with a mean follow-up time of 5.3 years. Overall 15-year survival ranged from 89.5-95.8%, with more complex lesions exhibiting higher mortality rates.
- Reoperation was required in 11.2% of surviving patients. This occurred a mean of 4.1 years after the original definitive repair. The most likely cause of reoperation was right ventricular outflow tract obstruction. Fifteen-year freedom from reoperation rates in surviving patients ranged from 72-100%. The reoperation rate was higher for patients with subpulmonary VSDs.
Race: No race predilection exists.
Sex: No sex predilection exists.
Age: Most cases of DORV are diagnosed in the first month of life.
CLINICAL
History: History of DORV varies with type of anatomy.
- Subaortic or subpulmonary VSD with pulmonary stenosis
- These children present with histories similar to those of children with tetralogy of Fallot.
- If pulmonary oligemia is present, severe cyanosis is seen in the newborn period and the condition is recognized early.
- Beyond the newborn period, cyanosis may be accompanied by hypercyanotic spells polycythemia, and failure to thrive.
- These children are less likely to develop pulmonary obstructive vascular disease from limitation of blood flow and pressure by pulmonary stenosis.
- Subaortic VSD without pulmonary stenosis
- These children present with histories similar to those of children with a large VSD and pulmonary hypertension.
- Oxygenation is relatively normal, and patients usually present with CHF and failure to thrive.
- Referral usually occurs later unless associated left heart lesions are present.
- These children may have associated chromosomal abnormalities such as trisomy 13 or trisomy 18.
- These children are likely to acquire pulmonary obstructive vascular disease without surgical repair, especially if the VSD is large.
- Subpulmonary VSD without pulmonary stenosis
- These children present with histories similar to those of children with transposition of the great arteries.
- Cyanosis varies, with oxygen saturations ranging from 40-80%.
- If associated coarctation or interruption of the aorta is present, earlier onset of CHF can be expected to result in earlier referral.
Physical: Physical examination findings vary with the anatomy.
- Subaortic or subpulmonary VSD with pulmonary stenosis: Physical examination reveals prominent right ventricular impulse, systolic thrill at left upper sternal border, harsh systolic murmur, and a single second heart sound.
- Subaortic VSD without pulmonary stenosis
- Physical examination reveals hyperdynamic precordial impulse, a grade III-IV/VI holosystolic murmur, a loud pulmonary component of the second heart sound, an apical diastolic rumble, and sometimes a palpable thrill.
- Once these children acquire pulmonary obstructive vascular disease, they exhibit decreased pulmonary blood flow with subsequent loss of the diastolic rumble and attenuation of systolic murmur. They also may develop a loud second heart sound and a diastolic decrescendo murmur of pulmonary insufficiency.
- Subpulmonary VSD without pulmonary stenosis
- Physical examination reveals cyanosis, tachypnea, grunting, and signs of CHF.
- Examination also reveals a loud pulmonary component of the second heart sound, a III/VI systolic murmur, and an apical diastolic rumble.
- If coarctation of aorta is present, the examination also reveals diminished femoral pulses.
Causes: As with other conotruncal heart defects, the cause of DORV may be of neural crest origin. The neural crest is involved in the development of the cardiac septum. Studies indicate removal of the neural crest during development results in outflow tract malformations, while total removal of cardiac neural crest usually results in truncus arteriosus abnormality. Deletions of smaller parts of the cardiac neural crest result in malformations such as DORV, tetralogy of Fallot, and Eisenmenger complex. Interestingly, neural crest ablation rarely results in transposition of the great arteries. Most changes in heart morphology occur while the heart is still in the looped tube stage.
In addition to formation of cardiac structures, this area of neural crest cells participates in formation of the thymus and the thyroid and parathyroid glands, serving as the basis for association of CHDs with DiGeorge syndrome. The combination of velocardiofacial syndrome, DiGeorge syndrome (facial anomalies and parathyroid/thymus aplasia or hypoplasia), and a chromosome band 22q11 deletion is known as CATCH 22.
The most common types of CHD associated with the band 22q11 deletion are tetralogy of Fallot, truncus arteriosus, VSDs, and aortic arch abnormalities. In a recent study, only 1 of 20 patients with DORV had the deletion; DORV was defined only by lack of fibrous continuity between mitral and aortic valves along with an aorta arising more than 50% over the right ventricle. Since DORV encompasses such a large spectrum of anomalies, however, recommendations are to test patients for the 22q11 deletion when they display other features of velocardiofacial syndrome.
DIFFERENTIALS
Transposition of the Great Arteries
Truncus Arteriosus
Ventricular Septal Defect, General Concepts
Lab Studies:
- Routine laboratory studies are not required for the initial diagnosis and management of children with DORV.
- Obtain a hemoglobin and hematocrit assessment if children are thought to have polycythemia.
- Monitor serum electrolytes after treating children with diuretics, glycosides, and afterload-reducing agents.
Imaging Studies:
- Chest radiography
- Findings on chest radiographs usually correlate with clinical presentation.
- Chest radiographs cannot be used to differentiate DORV from other forms of CHD.
- Presence or absence of pulmonary stenosis and pulmonary vascular resistance determines if cardiomegaly and increased pulmonary vascularity are present.
- Patients with subaortic VSD and severe pulmonary stenosis demonstrate diminished pulmonary vascularity and concave left heart border (similar to appearance associated with tetralogy of Fallot).
- If pulmonary obstructive vascular disease exists, peripheral pulmonary vascularity may be reduced and proximal pulmonary arteries may be dilated.
- The appearance in patients with subpulmonary VSD is similar to that in patients with transposition of the great arteries, revealing increased pulmonary vascularity and cardiomegaly.
- In patients in whom the aorta is anterior and to the left, radiographs may depict the leftward position of the aorta.
- Echocardiography
- Echocardiography is the imaging technique most often used to diagnose DORV.
- The principle diagnostic feature is appearance of both great arteries primarily committed to the right ventricle.
- Parasternal long and short axis views reveal degree of commitment to the right ventricle.
- Subcostal and apical 4-chamber views depict the separation between semilunar and atrioventricular valves (ventriculoinfundibular fold).
- Use multiple views to determine the relationship between the ventricular septum and the outlet septum.
- Features that must be established using echocardiography include primary commitment of both great arteries to the right ventricle, spatial relationship of both great arteries, location of the VSD and its relationship to semilunar valves, and the presence of associated anomalies such as coarctation, straddle/override of atrioventricular valve in relation to VSD, and presence of restrictive VSD.
- MRI
- MRI can help clarify ambiguities remaining after echocardiogram.
- MRI demonstrates the relationship between the great arteries, the anatomy of the outlet septum relative to the ventricular septum, and the relationship of the VSD to great arteries.
- A recent study found that, in patients with doubly committed or noncommitted VSDs, MRI more reliably predicted the feasibility of a biventricular repair than did echocardiography.
- Limitations include the need for prolonged evaluation, deeper sedation, and incomplete atrioventricular valve definition. MRI may also fail to demonstrate the presence of aberrant chordae tendineae.
Other Tests:
- Electrocardiography
- Abnormalities are often present on the electrocardiogram (ECG) but are not diagnostic of DORV.
- If performed after the newborn period, ECG reveals right ventricular hypertrophy.
- Left ventricular hypertrophy may occur in the presence of a restrictive VSD leading to left ventricular pressure overload or an increased pulmonary venous return leading to left ventricular volume overload.
- Right atrial enlargement is common.
- Left atrial enlargement may be present if pulmonary venous return or mitral stenosis/atresia is increased.
- Usually, left axis deviation of the frontal plane QRS exists because of displacement of the bundle of His posterior to VSD.
Procedures:
- Cardiac catheterization may delineate anatomy and hemodynamics. Objectives of catheterization include the following:
- Evaluation of right and left ventricular volumes
- Evaluation for possible gradient across VSD and PVR
- Evaluation of relationship between VSD and great arteries
- Evaluation of coronary artery and aortic arch anatomy
- Assessment of degree of mixing of the two circulations
- If a restrictive ASD is present, increased pulmonary blood flow with aortic saturations below 70% or 10% less than pulmonary saturations indicates the possibility of improvement with atrial septostomy (termed transposition physiology).
- Diagnostic angiographic features of DORV include the following:
- Opacification of both great arteries following right ventriculography
- Similarity of aortic and pulmonary valve horizontal planes
- Frequent anterior malposition of the aorta
- Presence of a filling defect dividing the two outflow tracts
TREATMENT
Medical Care:
- Initial evaluation and treatment are usually performed in the outpatient setting. Treatment varies, depending on anatomy of the lesion. Direct medical treatment of infants with DORV at control of CHF. Hospitalize children who present with severe heart failure, and treat them with fluid restriction and reduction of physical stress. Monitor children to ensure adequate weight gain since CHF can decrease oral intake and increase caloric expenditure. Other therapies include the following:
- Oxygen therapy may be required if pulmonary edema is present.
- Use oxygen only to relieve hypoxemia, since it is a pulmonary vasodilator and can exacerbate left-to-right shunt and CHF.
- Promptly initiate diuretic therapy with furosemide.
- Glycoside therapy with digoxin can be initiated in a maintenance dose if severe CHF is not present.
- Systemic afterload reduction is important in treating infants with CHF. Angiotensin-converting enzyme (ACE) inhibitors (ie, captopril, enalapril) are the most commonly used afterload-reduction agents.
Surgical Care: In 1957, Kirkland reported the first surgical repair of DORV using an intraventricular tunnel to establish left ventricular-aortic continuity via subaortic VSD. Surgical repair usually requires cardiopulmonary bypass with moderate hypothermia. Many DORVs have been repaired with a period of circulatory arrest.
Most transpositions are repaired using a biventricular approach with placement of an intraventricular baffle; this is more difficult without two well-developed ventricles or if the anatomy precludes a biventricular repair. An alternative repair is a Fontan procedure, which deteriorates with time.
In general, procedures depend on the location of the VSD. A significant proportion of patients undergo palliative procedures prior to definitive repair. These procedures include pulmonary artery banding, Blalock-Taussig shunt, coarctation repair, or stage one Norwood operation.
- DORV with subaortic VSD is repaired by VSD closure to baffle the left ventricular outflow to the aorta. It is typically repaired in patients younger than 6 months to prevent pulmonary vascular disease. If severe pulmonary stenosis is present, the condition and repair are similar to those of tetralogy of Fallot. Pulmonary stenosis often coexists with hypoplasia of the pulmonary arteries and coronary artery anomalies, making repair more difficult. Historically, this condition often was treated with initial shunting and definitive repair in patients aged 4-5 years.
- DORV with subpulmonary VSD can be repaired in 3 ways.
- The first procedure involves construction of a left ventricle–to–subpulmonary outflow tract tunnel with a subsequent arterial switch. This is the preferred method when the aorta is malposed anteriorly. Coronary artery transfer is similar to that in transposition of the great arteries.
- The second method consists of construction of a long intraventricular tunnel to establish continuity between the left ventricle and the aorta and between the right ventricle and pulmonary artery.
- The third method involves closure of the VSD with baffling of the left ventricular outflow to the pulmonary artery with a subsequent atrial baffle (eg, Senning procedure, Mustard procedure). This method is associated with high operative and late mortality rates.
- Doubly committed or noncommitted VSDs often require a complex repair with a Fontan procedure and possibly reoperation for secondary subaortic stenosis. For example, a patient with DORV, complete atrioventricular septal defect (AVSD), and valvar pulmonary stenosis underwent repair involving patching the ventricular portion of the AVSD and translocating it into a subaortic position. A left ventricular–to–aortic tunnel was then created. Nine years after primary repair, the patient required right ventricle–to–pulmonary artery conduit replacement.
Consultations:
- Refer patients with heart murmurs and physical findings suggestive of DORV to a pediatric cardiologist.
- Consult a pediatric cardiac surgeon for possible repair following diagnosis of DORV.
- Consult pediatric critical care personnel. Following surgical repair, postoperative care normally occurs in the pediatric intensive care unit.
- Involve a geneticist in the care of patients diagnosed with DORV who may have coexisting genetic syndromes, including velocardiofacial syndrome and DiGeorge syndrome.
Diet: Children with CHF from DORV often require increased caloric intake supplemented by the addition of medium-chain triglyceride or carbohydrate preparations to conventional infant formulas. Some children may require overnight, bolus, or continuous feeds by nasogastric tubes.
Activity: Activity is not
limited for infants initially diagnosed with DORV, unless they have CHF.
For patients with CHF, reduce physical stress until the heart failure can
be controlled. Advance the activity of patients in the postoperative
period as tolerated, until a normal level of activity is achieved.
MEDICATION
The overall goal of medical therapy in patients
with DORV is to prevent or control CHF.
Drug Category: Diuretic agents -- Promote excretion of water and electrolytes by the kidneys. Used to treat heart failure or hepatic, renal, or pulmonary disease when sodium and water retention has resulted in edema or ascites. Used to reduce plasma volume and, thus, improve CHF.
| Drug Name |
Furosemide
(Lasix) -- Titrate treatment dose to produce initial diuresis and
subsequently to control symptoms. Increases excretion of water by interfering with chloride-binding cotransport system, which, in turn, inhibits sodium and chloride reabsorption in ascending loop of Henle and distal renal tubule. |
|---|---|
| Adult Dose | 20-80 mg/d PO/IV/IM in divided doses q6-12h; not to exceed 600 mg/d |
| Pediatric Dose | 1-6
mg/kg/d PO divided q6-12h 1-2 mg/kg/dose IV/IM q6-12h |
| Contraindications | Documented hypersensitivity; hepatic coma, anuria, state of severe electrolyte depletion |
| Interactions | Metformin decreases furosemide concentrations; furosemide interferes with hypoglycemic effect of antidiabetic agents and antagonizes muscle relaxing effect of tubocurarine; auditory toxicity appears to be increased with coadministration of aminoglycosides and furosemide; hearing loss of varying degrees may occur; anticoagulant activity of warfarin may be enhanced when taken concurrently with this medication; increased plasma lithium levels and toxicity are possible when taken concurrently with this medication |
| Pregnancy | C - Safety for use during pregnancy has not been established. |
| Precautions | Hepatic cirrhosis (rapid alterations in fluid/electrolytes may precipitate coma) |
| Drug Name |
Digoxin (Lanoxin) -- Used to increase contractility of the left ventricle. Inhibits Na/K-ATPase, which causes intracellular calcium in the sarcoplasmic reticulum of cardiac cells to increase. This leads to a sustained but modest positive inotropic effect on the heart. Some question the inotropic effect of these medications on immature myocardium, while others have demonstrated improved left ventricular contractility without symptomatic improvement. |
|---|---|
| Adult Dose | Total
digitalizing dose (TDD): 0.75-1.5 mg PO Divide TDD: Initially give 50% and then give the remaining two 25% portions at 6- to 12-h intervals (1/2, 1/4, 1/4) Maintenance dose: 0.125-0.5 mg PO qd |
| Pediatric Dose | TDD: Preterm infants: 20-30 mcg/kg PO Term infants: 25-35 mcg/kg PO 1 month to 2 years: 35-60 mcg/kg PO 2-5 years: 30-40 mcg/kg PO 5-10 years: 20-35 mcg/kg PO >10 years: Administer as in adults Divide TDD: Initially give 50% and then give the remaining two 25% portions at 6- to 12-h intervals (1/2, 1/4, 1/4) Maintenance dose: Preterm infant: 5-7.5 mcg/kg/d PO divided bid Term infant: 6-10 mcg/kg/d PO divided bid 1 mo-2 years: 10-15 mcg/kg/d PO divided bid 2-5 years: 7.5-10 mcg/kg/d PO divided bid 5-10 years: 5-10 mcg/kg/d PO divided bid >10 years: Administer as in adults |
| Contraindications | Documented hypersensitivity; beriberi heart disease, idiopathic hypertrophic subaortic stenosis, constrictive pericarditis, carotid sinus syndrome |
| Interactions | Medications
that may increase digoxin levels include alprazolam,
benzodiazepines, bepridil, captopril, cyclosporine, propafenone,
propantheline, quinidine, diltiazem, aminoglycosides, oral
amiodarone, anticholinergics, diphenoxylate, erythromycin,
felodipine, flecainide, hydroxychloroquine, itraconazole,
nifedipine, omeprazole, quinine, ibuprofen, indomethacin, esmolol,
tetracycline, tolbutamide, and verapamil Medications that may decrease serum digoxin levels include aminoglutethimide, antihistamines, cholestyramine, neomycin, penicillamine, aminoglycosides, oral colestipol, hydantoins, hypoglycemic agents, antineoplastic treatment combinations (including carmustine, bleomycin, methotrexate, cytarabine, doxorubicin, cyclophosphamide, vincristine, procarbazine), aluminum or magnesium antacids, rifampin, sucralfate, sulfasalazine, barbiturates, kaolin/pectin, and aminosalicylic acid |
| Pregnancy | C - Safety for use during pregnancy has not been established. |
| Precautions | Hypokalemia may reduce positive inotropic effect of digitalis; IV calcium may produce arrhythmias in digitalized patients; hypercalcemia predisposes patient to digitalis toxicity, and hypocalcemia can make digoxin ineffective until serum calcium levels are normal; magnesium replacement therapy must be instituted in patients with hypomagnesemia to prevent digitalis toxicity; patients diagnosed with incomplete AV block may progress to complete block when treated with digoxin; exercise caution in hypothyroidism, hypoxia, and acute myocarditis |
| Drug Name |
Captopril (Capoten) -- Prevents conversion of angiotensin I to angiotensin II, a potent vasoconstrictor, resulting in increased levels of plasma renin and a reduction in aldosterone secretion. Shown to increase systemic flow by reducing left-to-right shunting in patients with relatively low pulmonary vascular resistance. |
|---|---|
| Adult Dose | 12.5-25 mg/dose PO q8-12h, increase by 25 mg/dose; not to exceed 450 mg/d |
| Pediatric Dose | Infants:
0.15-0.3 mg/kg/dose PO, titrate upward; not to exceed 6 mg/kg qd
or divided qid Children: 0.3-0.5 mg/kg/dose PO, titrate upward; not to exceed 6 mg/kg/d divided bid/qid |
| Contraindications | Documented hypersensitivity; renal impairment |
| Interactions | NSAIDs may reduce hypotensive effects of captopril; ACE inhibitors may increase digoxin, lithium, and allopurinol levels; rifampin decreases captopril levels; probenecid may increase captopril levels; the hypotensive effects of ACE inhibitors may be enhanced when given concurrently with diuretics |
| Pregnancy | C - Safety for use during pregnancy has not been established. |
| Precautions | Pregnancy category D in second and third trimesters; caution in renal impairment, valvular stenosis, or severe congestive heart failure |
| Drug Name |
Enalapril (Vasotec) -- Decreases pulmonary-to-systemic flow ratio in the catheterization laboratory and increases systemic blood flow in patients with relatively low pulmonary vascular resistance. It has a favorable clinical effect when administered over a long period. |
|---|---|
| Adult Dose | 2.5-5 mg/d PO; may gradually increase prn, not to exceed 40 mg/kg/d |
| Pediatric Dose | Limited data exist; suggested dose is 0.1 mg/kg PO qd or divided bid; increase prn over 2 wk; not to exceed 0.5 mg/kg/d |
| Contraindications | Documented hypersensitivity |
| Interactions | NSAIDs may reduce hypotensive effects of enalapril; ACE inhibitors may increase digoxin, lithium, and allopurinol levels; rifampin decreases enalapril levels; probenecid may increase enalapril levels; the hypotensive effects of ACE inhibitors may be enhanced when given concurrently with diuretics |
| Pregnancy | C - Safety for use during pregnancy has not been established. |
| Precautions | Pregnancy category D in second and third trimesters; use with caution and modify dosage in patients with renal impairment (especially renal artery stenosis), hyponatremia, hypovolemia, severe CHF, or with coadministered diuretic therapy; severe hypotension may occur in patients who are sodium and/or volume depleted; initiate lower doses and monitor closely when starting therapy in these patients; experience in children is limited; use with caution in neonates |
FOLLOW-UP
Further Inpatient Care:
- Provide inpatient care if CHF is severe. Treat patients initially with fluid restriction and alleviation of temperature and physical stress. Sedation may be required with opioids.
- Observe and manage ventricular function for patients in immediate postoperative period. Arrhythmias may develop after repair and may require medical intervention.
Further Outpatient Care:
- After repair, children with DORV often are treated with systemic afterload reduction using ACE inhibitors for several months to assist in cardiac remodeling.
In/Out Patient Meds:
- Commonly used medications are listed above, including furosemide, digoxin, captopril, and enalapril.
Transfer:
- Transfer may be required for further diagnostic testing as well as medical/surgical treatment.
Complications:
- If patients undergo surgery for repair at an older age, they often develop ventricular dysfunction and elevation of pulmonary artery pressures.
- Operative and postoperative complications depend on anatomy of lesion as well as type of repair.
- Some patients develop restrictive VSD and require reoperation.
- In patients with subaortic and subpulmonary VSD, the VSD diameter can decrease by 20% in the immediate postoperative period. These patients can sometimes develop subaortic obstruction.
- Patients, especially those undergoing complex repair, can develop postoperative ventricular dysfunction associated with residual VSD, aortic insufficiency, atrioventricular valve insufficiency, and prolonged circulatory arrest at repair.
- Some patients are at risk for late postoperative arrhythmias and sudden death.
- Patients may develop persistent atrial tachycardia, complex ventricular ectopy, or syncope requiring electrophysiologic studies.
Prognosis:
- The long-term survival rate for children who undergo repair for a subaortic VSD type of DORV is 80-95%.
Patient Education:
- Educate parents regarding anatomic defect, surgical repair, and postoperative course. Prior to repair, parents should learn about medical therapy and signs and symptoms of CHF.
- Institute a specific nutritional program to attain adequate weight gain.
MISCELLANEOUS
Medical/Legal Pitfalls:
- Failure to make the correct diagnosis
- Failure to prepare for and treat surgical complications
PICTURES
| Caption: Picture 1. Neonate with double outlet right ventricle. Chest radiograph shows a mildly enlarged heart with symmetrically slightly increased pulmonary vasculature. |
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| Caption: Picture 2. Double outlet right ventricle with subaortic ventricular septal defect. Arrow shows flow of oxygenated blood from left ventricle to aorta. |
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| Caption: Picture 3. Repair of double outlet right ventricle with subaortic ventricular septal defect. |
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| Caption: Picture 4. Double outlet right ventricle with subpulmonary ventricular septal defect (Taussig-Bing anomaly). |
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| Caption: Picture 5. Complex repair of double outlet right ventricle with subpulmonary ventricular septal defect. |
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| Caption: Picture 6. Double outlet right ventricle with doubly committed ventricular septal defect. |
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| Caption: Picture 7. Repair of double outlet right ventricle with doubly committed ventricular septal defect showing VSD patch and intraventricular baffle. |
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| Caption: Picture 8. Double outlet right ventricle with noncommitted ventricular septal defect. |
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| Caption: Picture 9. Repair of double outlet right ventricle with noncommitted ventricular septal defect using a long ventricular septal defect patch. |
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| Picture Type: Image |