Double Outlet Right Ventricle

Both great arteries arise entirely or mostly (more than 50% of each valve) from the right ventricle, with a ventricular septal defect as the only outlet of the left ventricle. About 1 to 1.5% of congenital heart disease, about 0.03 to 0.14 per 1000 live births. Associated with trisomies 13 and 18, 22q11.2 deletion, and maternal diabetes.

• Classification by the position of the ventricular septal defect: subaortic (about 50 to 60%), subpulmonary (the Taussig-Bing anomaly, about 20 to 30%), doubly committed (about 10 to 15%), and remote or non-committed (about 10%, often with an atrioventricular septal defect or single ventricle features). Pulmonary stenosis is present in about half of subaortic defects, producing a tetralogy of Fallot like picture. Coarctation or arch obstruction may coexist, especially in subpulmonary defects.
• Physiology depends on the defect position and the pulmonary outflow: ventricular septal defect like (subaortic, no stenosis; heart failure), tetralogy like (subaortic with pulmonary stenosis; cyanosis and spells), transposition like (subpulmonary; cyanosis with early pulmonary overcirculation), and single ventricle like (remote defect).
• Untreated, most affected infants die early from heart failure or cyanosis; outcomes after repair are good in most subtypes.

• Ventricular septal defect like: heart failure at 2 to 6 weeks, a loud pansystolic murmur, tachypnoea, poor feeding, and failure to thrive.
• Tetralogy like: progressive cyanosis, hypercyanotic spells (irritability, deep breathing, increased cyanosis, then limpness), clubbing, squatting in older children, ejection systolic murmur from outflow obstruction.
• Transposition like (Taussig-Bing): marked cyanosis from the first days with early heart failure and a loud second heart sound.
• Differential diagnosis: tetralogy of Fallot, transposition of the great arteries with ventricular septal defect, large ventricular septal defect, truncus arteriosus, atrioventricular septal defect, and single ventricle.
• Complications: heart failure, hypercyanotic spells, pulmonary vascular disease, stroke and brain abscess in cyanotic patients, endocarditis, polycythaemia, iron deficiency, left ventricular outflow tract obstruction after repair, conduit failure, and arrhythmia.

• ECG: right axis deviation and right ventricular hypertrophy, with superior axis in atrioventricular septal defect variants.
• Chest X-ray: increased pulmonary flow (ventricular septal defect or transposition like) or decreased flow with a boot shaped heart (tetralogy like).
• Echocardiography: both great arteries arising from the right ventricle, relationship of the great arteries, ventricular septal defect position, size and distance to the aortic and pulmonary valves, outflow obstruction, atrioventricular valve straddling, ventricular balance, coronary artery pattern, arch.
• CT or MR angiography and catheterisation for complex anatomy: ventricular septal defect position, intraventricular tunnel route, pulmonary artery size, coronary arteries, and pulmonary vascular resistance in late presenters.
• Laboratory: haemoglobin, haematocrit, ferritin, genetic testing for 22q11.2 deletion and aneuploidy.

• Initial stabilisation and medical therapy:
  • Heart failure: furosemide 1 to 2 mg/kg per dose orally 2 to 3 times daily, spironolactone 1 to 3 mg/kg/day, captopril 0.1 to 0.5 mg/kg per dose 8-hourly (avoid with severe outflow obstruction), and high calorie feeds of 120 to 150 kcal/kg/day.
  • Duct dependent circulation (severe pulmonary stenosis or atresia): alprostadil 0.05 to 0.1 micrograms/kg/min then 0.01 to 0.05 micrograms/kg/min, SpO2 target 75 to 85%.
  • Hypercyanotic spell:
    • Place the child in the knee chest position, calm the child, and give 100% oxygen.
    • Give morphine 0.1 mg/kg IV, IM or SC.
    • Give a fluid bolus of 10 mL/kg of 0.9% saline.
    • Give sodium bicarbonate 1 mmol/kg IV for acidosis.
    • Give phenylephrine 5 to 20 micrograms/kg IV bolus then 0.1 to 0.5 micrograms/kg/min, or ketamine 1 to 2 mg/kg IV.
    • Give propranolol 0.1 mg/kg IV slowly over 10 minutes (maximum 5 mg) or esmolol 0.5 mg/kg bolus then 50 to 200 micrograms/kg/min. Avoid beta blockers in heart failure.
    • Refractory spell: intubate, sedate, paralyse and ventilate, consider ECMO, and arrange urgent shunt or repair.
  • Prevention of spells and maintenance: propranolol 1 to 4 mg/kg/day orally in 3 to 4 divided doses, and treat iron deficiency with ferrous sulfate 3 to 6 mg/kg/day of elemental iron.
• Surgery depends on physiology:
  • Subaortic defect without pulmonary stenosis: patch closure creating an intraventricular tunnel from the left ventricle to the aorta at 3 to 6 months. Mortality about 2 to 5%.
  • Subaortic defect with pulmonary stenosis: shunt (Blalock-Taussig) first in a small or very cyanotic infant, then intracardiac repair at 6 to 12 months with outflow tract resection or patch, or a right ventricle to pulmonary artery conduit when the coronary pattern requires it. Alternative techniques include a Rastelli repair or the REV procedure when the tunnel is long.
  • Subpulmonary defect (Taussig-Bing): arterial switch operation and ventricular septal defect closure to the pulmonary artery, in the first weeks of life, with arch repair if coarctation is present. Mortality about 5 to 10%.
  • Doubly committed defect: tunnel to the aorta, or arterial switch if the tunnel is unsuitable.
  • Remote defect or hypoplastic ventricle: single ventricle palliation with shunt or banding, bidirectional cavopulmonary shunt at 3 to 6 months, and Fontan completion at 2 to 4 years.
  • Pulmonary artery banding is used as palliation for infants with excess pulmonary flow in whom repair is delayed.
• Postoperative and late issues:
  • Left ventricular outflow tract obstruction after tunnel repair (about 5 to 15%): resection or tunnel revision when the peak gradient is 50 mmHg or more or there is ventricular dysfunction.
  • Conduit or right ventricular outflow obstruction: balloon dilatation, stent, or replacement every 5 to 15 years; transcatheter pulmonary valve in suitable conduits.
  • Residual ventricular septal defect: closure when the shunt ratio is 1.5 to 1 or more.
  • Arrhythmias: atrial tachyarrhythmia and complete heart block (about 1 to 5%); bisoprolol 1.25 to 10 mg daily for rate control; amiodarone for refractory arrhythmia with thyroid, liver and lung monitoring; pacemaker for heart block.
  • Pulmonary hypertensive crisis after surgery: sedation and relaxation, oxygen, inhaled nitric oxide 20 ppm, sildenafil 0.5 to 1 mg/kg per dose 6 to 8-hourly.
• Endocarditis prophylaxis after prosthetic material or palliation: amoxicillin 50 mg/kg (maximum 2 g) orally 30 to 60 minutes before dental procedures.
• Special groups:
  • Genetic syndromes: surveillance for developmental, renal, immune and endocrine problems.
  • Pregnancy: tolerated after good repair with normal ventricular function and no outflow obstruction; high risk with cyanosis, pulmonary hypertension, or single ventricle circulation, so counsel before conception.
  • Adults: lifelong follow up for conduit failure, valve disease, heart failure and arrhythmia.
• Red flags: cyanotic spells, saturation less than 70%, poor feeding, tachypnoea at rest, syncope, fever with murmur.
• Follow up: after repair, review at 6 weeks, 6 months and 12 months, then yearly; echocardiography at each visit and periodic cardiac MRI or CT; lifelong specialist follow up.