Partial anomalous pulmonary venous drainage (PAPVD) occurs in around 1 in every 1000 people. Blood from part of the lung returns to the wrong side of the heart, causing the heart to stretch. This causes breathlessness and heart rhythm problems in later life. PAPVD can currently only be fixed by open heart surgery, and when the abnormality affects the right lung, even this can be impossible.

This study is designed to examine whether a new keyhole procedure to limit blood flow through the affected lung segments can be safely used to reduce the impact of PAPVD on the heart, reducing symptoms, protecting against heart rhythm problems, and avoiding the need for open heart surgery.

In this study, a flow limiting device will be positioned in the affected lung artery to reduce blood flow to this segment of lung. The procedure is performed under a general anaesthetic, and is done either as a day case or a single overnight stay in hospital. X-rays are used to guide the positioning of the stent. The procedure is performed as a keyhole procedure through a 3 mm cut in the groin.

The investigators will use heart ultrasound, heart MRI and exercise testing before and six months after the procedure to assess the safety and effect of the flow limiter.

The flow limitation device will either be a standard covered stent used in every day practice, but with a modified balloon for deployment, a vascular plug or similar vascular occlusion device which can be modified to restrict rather than occlude flow. If there is a problem with the flow limitation being too severe, the stent can be fully inflated returning the flow back to normal, and the vascular plug can be retrieved using another key hole procedure.

PAPVD has been reported in 0.2% of the population undergoing CT scans and in 0.4 - 0.7% of the population in autopsy studies. They can be associated with superior sinus venosus atrial septal defects or can be present in isolation.

PAPVD causes blood which should be draining from the lungs into the left hand side of the heart to drain into the right side of the heart. Thus PAPVD results in a left to right shunt of varying proportions dependent upon the number of lobes involved. Long term sequelae reflect the impact of the resultant volume loading of the right heart, which can lead to atrial arrhythmia and right heart failure in later life and these patients can develop pulmonary hypertension. Patients with significant left to right shunts often present with symptoms of breathlessness and poor exercise tolerance, which worsen as they age.

Historically, PAPVD has only been considered suitable for surgical repair. This requires an open heart procedure, including cardio-pulmonary bypass, and necessitates around a week in hospital, and a three month recovery period. Surgical repair is technically challenging due to anatomical considerations, particularly in right sided anomalous veins, and there is a relatively high risk of pulmonary venous thrombosis post operatively due to low velocity venous flow. Current European Society of Cardiology guidelines recommend that technical suitability for repair and operative risk must be weighed against the potential benefit of intervention. These guidelines also state that it is unusual for a single anomalous pulmonary venous connection of only one pulmonary lobe to result in a sufficient volume load to justify the risk of surgical repair.

Inclusion Criteria:

• Haemodynamically & Functionally significant PAPVD (all of the following)

  • Right heart dilated on trans thoracic echo
  • cardiac MRI Qp:Qs ≥ 1.3:1, and right ventricular to left ventricular volume (RV:LV) ratio ≥ 1.5:1
  • Maximal oxygen consumption (VO2 max) on cardiopulmonary exercise testing < 85% predicted
  • Normal pulmonary artery pressure

• No contra-indication to pulmonary artery intervention procedure under general anaesthetic

• Able to give informed consent

Exclusion Criteria:

• Contra-indication to cardiac MRI
• Not able to give informed consent
• Contra-indication to pulmonary artery intervention under general anaesthetic