Though graded balloon-atrial-septostomy (BAS) has been accepted as an effective palliative therapy for severe pulmonary arterial hypertension, spontaneous closure of septostomy is not uncommon. Radiofrequency-catheter-ablation (RFA), which has the potential to cause irreversible damage around the rim of created inter-atrial communication, might contribute to prevent the spontaneous closure. In patients with severe pulmonary arterial hypertension, the combined use of RFA and BAS (CURB) is investigated to create a stable inter-atrial communication.

Balloon atrial septostomy (BAS) is an important palliative therapy in patients with refractory pulmonary arterial hypertension. However, the incidence of spontaneous closure is higher, which limits the clinical utilization of this procedure. Radiofrequency catheter ablation (RFA) has the potential to cause irreversible damage around the rim of fenestration created with BAS, which might prevent the re-adhesion of the septal remnants. In addition, RFA on fossae ovalis might reduce the elastic recoil of local tissue and contribute to create larger inter-atrial fenestration with same BAS procedure. In this study, the patients between 18 and 60 years of age who have severe pulmonary arterial hypertension associated with right heart failure refractory to medical therapy or severe syncopal symptoms may be eligible for this study (idiopathic severe pulmonary arterial hypertension or severe pulmonary arterial hypertension associated with repaired congenital heart disease). These patients will be randomized 1:1:1 to control group, single-RFA group and double-RFA group:

1. In control group: only BAS is carried out.
2. In single-RFA group: after BAS procedure identical to control group, RFA is performed immediately around the rim of created inter-atrial fenestration.
3. In double-RFA group: the first step is RFA on fossae ovalis; and then the other two steps are identical to the single-RFA group (BAS and RFA around the rim of fenestration).

The immediate size of created fenestration will be determined with intra-cardiac echocardiography, and the patency and size of fenestration will be followed up for 12 months. During the period of follow up, the other evaluations will include the exercise tolerance, cardiac index, systemic arterial oxygen saturation and so on.

Inclusion Criteria:

1. Idiopathic severe pulmonary arterial hypertension;
2. Severe pulmonary arterial hypertension associated with repaired congenital heart disease;
3. World Health Organization functional class III or IV with right heart failure refractory to medical therapy;
4. Severe syncopal symptoms;

Exclusion Criteria:

1. Mean right atrial pressure >20 mm Hg;
2. Room-air resting arterial oxygen saturation <85%;
3. Left ventricular end diastolic pressure (LVEDP) >18mm Hg;
4. Pulmonary vascular resistance >55 wood units/m2.
5. Severe right ventricular failure on cardio-respiratory support
6. The predicted one-year survival <40%;