Partial Anomalous Pulmonary Venous Return

One to three (but not all four) pulmonary veins drain into the right atrium or a systemic vein, giving a left to right shunt. Found in about 0.4 to 0.7% of the population at autopsy; more common in women, and a feature of Turner syndrome.

• Common patterns: right upper pulmonary vein to the superior vena cava with a sinus venosus atrial septal defect (most common); right pulmonary veins to the inferior vena cava in scimitar syndrome (hypoplastic right lung, abnormal arterial supply, dextroposition of the heart); left upper pulmonary vein to the innominate vein through a vertical vein; veins to the coronary sinus.
• Mechanism: the anomalous veins return oxygenated blood to the right heart, producing right atrial and ventricular volume overload proportional to the shunt. A single anomalous vein usually gives a shunt less than 1.5:1, which is haemodynamically small. Two or more veins can cause significant overload and, in a minority, pulmonary arterial hypertension.

• Single vein: usually asymptomatic and found incidentally.
• Larger shunts: exertional dyspnoea, fatigue, palpitations (atrial flutter or fibrillation), right heart failure, recurrent chest infections (scimitar syndrome), haemoptysis from systemic collaterals to the hypoplastic lung.
• Examination: fixed splitting of the second heart sound, soft systolic ejection murmur at the left upper sternal edge, right ventricular heave; signs of pulmonary hypertension when present.
• Differential diagnosis: atrial septal defect, pulmonary arterial hypertension, pulmonary stenosis, total anomalous pulmonary venous return, tricuspid regurgitation, Ebstein anomaly.
• Complications: right heart volume overload and dilatation, pulmonary hypertension, atrial arrhythmia, recurrent respiratory infection (scimitar syndrome), right heart failure, and paradoxical embolism.

• ECG: right axis deviation, right bundle branch block, atrial arrhythmia. Chest X-ray: scimitar sign (a curved vessel shadow along the right heart border), right heart enlargement.
• Echocardiography: right atrial and ventricular dilatation with no atrial septal defect, or a sinus venosus defect; the anomalous vein often needs transoesophageal echocardiography.
• CT or MR angiography confirms the anomalous veins and their number, and measures the shunt (Qp:Qs 1.5 or more with right ventricular dilatation is significant) and lung and aortic collateral anatomy.
• Right heart catheterisation when pulmonary hypertension is suspected: surgery is reasonable when pulmonary vascular resistance is less than 3 Wood units; with 5 Wood units or more, surgery is contraindicated.

• One anomalous vein, no right ventricular enlargement: no treatment; echocardiography every 3 to 5 years.
• Surgical repair indications: Qp:Qs of 1.5 or more with right ventricular dilatation, symptoms, or progressive right heart enlargement, provided pulmonary vascular resistance is less than 3 Wood units.
• Techniques:
  • Sinus venosus defect with right upper vein to the superior vena cava: intracardiac patch baffle redirecting the vein through the defect to the left atrium, with patch enlargement of the superior vena cava junction or a Warden procedure (superior vena cava transection and reattachment to the right atrial appendage) when stenosis risk is high.
  • Left upper vein through a vertical vein: reimplantation into the left atrial appendage or anastomosis to the left atrium.
  • Scimitar syndrome: intra atrial baffle through a created atrial septal defect or direct reimplantation into the left atrium; coil or plug embolisation of aortic collateral arteries to the hypoplastic lung; lobectomy or pneumonectomy only when lung is severely damaged by recurrent infection.
• Operative mortality is less than 1 to 2%. Complications: superior vena cava or pulmonary vein obstruction (about 5 to 10%), sinus node dysfunction (about 10 to 20% after Warden procedure), residual shunt, atrial arrhythmia.
• Symptom control: furosemide 20 to 40 mg daily for right heart failure; atrial flutter or fibrillation managed with bisoprolol 2.5 to 10 mg daily, anticoagulation (warfarin INR 2.0 to 3.0, or apixaban 5 mg twice daily, 2.5 mg twice daily if two of: age 80 or more, weight 60 kg or less, creatinine 133 micromol/L or more) and cavotricuspid isthmus ablation for typical flutter.
• Pulmonary arterial hypertension with high resistance: do not repair; specialist therapy with sildenafil 20 mg three times daily or bosentan 62.5 mg twice daily for 4 weeks then 125 mg twice daily.
• Recurrent chest infection in scimitar syndrome: amoxicillin clavulanate 625 mg orally 8-hourly for 7 to 10 days for exacerbations (adjust by sputum culture); chest physiotherapy.
• Endocarditis prophylaxis is needed only after repair with prosthetic material or for previous endocarditis: amoxicillin 2 g orally 30 to 60 minutes before dental procedures.
• Special groups: pregnancy (small shunts tolerated; with right heart failure or pulmonary hypertension pregnancy is high risk and surgery before conception is preferred); children (repair is usually delayed to 3 to 5 years unless symptomatic); elderly (repair still improves exercise capacity if pulmonary hypertension is mild).
• Red flags: haemoptysis, new right heart failure, syncope, sustained arrhythmia, stroke (paradoxical embolism).
• Follow up: after repair at 3 to 6 months, 12 months, then every 2 to 3 years with echocardiography for pulmonary vein or superior vena cava obstruction, and ECG or Holter monitoring for arrhythmia; yearly review in scimitar syndrome.