Transcatheter Palliation of Tetralogy of Fallot with Pulmonary Artery Discontinuity

Adiscontinuous pulmonary artery is one that is disconnected from the main pulmonary trunk and arises from a patent ductus arteriosus. This anomaly is not often found in conjunction with tetralogy of Fallot (ToF) and pulmonary stenosis. We treated an infant who had such an anomaly with impending closure of a patent ductus arteriosus (PDA). Herein, we describe the treatment of this challenging case.

Case Report

In April 2003, a 2-day-old male neonate (premature, low-weight [2.1-kg], non-syndromic) was referred to our division, due to a cardiac murmur and moderate-to-severe cyanosis detected at birth (percutaneous oxygen saturation, 70%–75%). With use of echocardiographic sequential analysis, we were able to make a diagnosis of ToF with suspected left pulmonary artery (LPA) discontinuity and a PDA with impending closure (transductal peak pressure gradient of 50 mmHg with diastolic run-off). To confirm the diagnosis, we performed cardiac catheterization via the femoral vein using general anesthesia and tracheal intubation. Angiography showed that the LPA arose from a left-sided PDA, which in turn originated from a quite unusual site—the mid-segment of the transverse aortic arch. There was moderate stenosis at the PDA–LPA junction (Fig. 1).

Fig. 1 A) Right ventricular (RV) angiography in the right anterior oblique view shows the aorta (Ao) and the RV outflow tract, which is severely stenotic due to anterosuperior deviation of the infundibular septum and pulmonary valve dysplasia (arrow). Note that the left pulmonary artery (LPA) is not visible. B) Ascending aortography in the posteroanterior view before stent deployment shows the origin of the LPA from a left-sided patent ductus arteriosus, with moderate stenosis at the PDA–LPA junction (arrow).

The asterisk (*) indicates the crista supraventricularis; RPA = right pulmonary artery

In order to improve oxygenation and prevent the expected PDA closure, a 3 × 9-mm coronary artery stent (Driver™, Medtronic, Inc.; Minneapolis, Minn), dilated at 9 atm to 3.0 mm, was placed inside the PDA. Due to its advantageous anatomy, the PDA was approached by cut-down of the right carotid artery (Fig. 2).

Fig. 2 The stent positioning inside the patent ductus arteriosus is angiographically guided through the 4F introducer sheath, without the need for a guiding catheter.

The asterisk (*) indicates the pre-mounted coronary artery stent; Ao = aorta

The stent length was chosen to cover the PDA exactly, which prevented ductal constriction and enabled the surgeon to resect only the ductal tissue at the time of corrective surgery. The stent was sized slightly larger than the diameter of the LPA to accommodate pulmonary artery growth (Fig. 3A).

Fig. 3 A) The final angiographic result is shown after the patent ductus arteriosus stenting. Note that the stent is slightly oversized. B) Angiogram shows the appearance of the stented patient ductus arteriosus 6 months after implantation. There was a moderate aortic–LPA pressure gradient (aortic pressure, 60/22 mmHg; LPA pressure, 25/10 mmHg).

The asterisk (*) and the arrow both indicate the stented patent ductus arteriosus; Ao = aorta; LPA = left pulmonary artery

After stent placement, a significant improvement in oxygen saturation was observed (final result, 85%), and the transductal echocardiographic peak pressure gradient was abolished. The infant was given antiplatelet therapy (dipyridamole, 3 mg/kg per day). We did not worry about the onset of hypertension of the LPA vascular bed, because this condition is usually prevented by the occurrence of some in-stent restenosis, as well as the patient's pulmonary artery growth (Fig. 3B).

At the 6-month follow-up visit, the patient's oxygen saturation remained at about 85%. The following month, when the infant weighed 6.6 kg, he underwent corrective surgery consisting of resection of the stented PDA and direct end-to-side anastomosis of the LPA to the main pulmonary trunk. When last seen in March 2004, he was in good clinical condition, showing only mild-to-moderate pulmonary valve regurgitation and nearly normal right ventricular pressures (right ventricular/left ventricular pressure ratio, <0.4).

Discussion

The term “discontinuous pulmonary arteries” identifies a rare cardiovascular malformation in which 1 pulmonary artery is disconnected from the main pulmonary trunk and arises from a PDA. This anatomic arrangement is found infrequently in ToF with pulmonary stenosis; it was reported in less than 1.5% of cases in a large surgical series in 1993.¹ This condi-tion is clearly different from the ToF with a hemitruncus, in which 1 pulmonary artery arises from the ascending aorta.² The LPA is most frequently involved, originating from a normally situated PDA and proceeding to the pulmonary hilum without entering the pericardium. If the PDA closes, the clinical diagnosis of congenital absence of the left pulmonary artery is usually made later in life.

Surgical management is challenging in neonates that have complex intracardiac anomalies and lack the intrapericardial portion of a pulmonary artery.³ In fact, traditional palliation by a systemic-to-pulmonary artery shunt may result in an uneven distribution of the pulmonary blood flow due to the difficulty in matching the size of the prosthetic conduit to the pulmonary artery. In addition, the angulation between the surgical conduit and the discontinuous pulmonary artery may cause distortion, limiting further flow-mediated growth of the dependent pulmonary vascular bed. One-step corrective surgery with unifocalization of the anomalous pulmonary artery has been suggested.³ In low-weight patients, percutaneous PDA stenting has been proposed as an alternative to a higher risk surgical shunt or primary repair.^4–11 This palliative approach is less invasive than surgery and allows matching of the stent prosthesis to the size and angulation of the pulmonary artery, thus avoiding lung perfusion imbalance and pulmonary artery distortion. In addition, stent angioplasty enables the adaptation of shunt size to pulmonary artery growth by serial stent dilations, which offers an advantage over surgery. In small series, this procedure was well tolerated even in premature and low-weight neonates, which constitute the subgroup at highest surgical risk.^8–11