Percutaneous Treatment of Ductal Origin of the Distal Pulmonary Artery in Low-Weight Newborns

Ductal origin of the distal pulmonary artery¹ is characterized by a patent ductus arteriosus in continuity with the proximal end of a pulmonary artery (either left or right, or both) with no continuity to the main pulmonary artery (PA). Progressive closure of the ductus arteriosus results in the loss of blood flow to the dependent PA. This malformation has been recognized in a variety of congenital heart diseases including ventricular septal defect (VSD), tetralogy of Fallot, and heterotaxy syndrome tetralogy of Fallot variants.^2-6
Surgical reconstruction of the disconnected pulmonary branches has been described.^2-4,7,8 In recent years, percutaneous techniques have been tremendously improved and they are increasingly selected as valuable alternatives to surgery. Here we report on a series of 5 infants weighing < 3 kg with ductal origin of the PA associated with other congenital heart disease, in which a percutaneous approach was used.

Patients and Methods

The patients’ procedural characteristics are reported in Table 1. In all subjects, the diagnosis of ductal origin of the pulmonary artery was suspected on echocardiographic evaluation. Prostaglandins were withdrawn 6 hours prior to the procedure in order to allow for partial constriction of the ductus arteriosus and to increase the stability of the stent during implantation. Parents of the patients signed an informed consent to the procedure.
The procedures were performed under general anesthesia and the patients were fully heparinized (100 UI/kg). Aortography, performed by using a 4 Fr sheath and a pigtail catheter from the right femoral artery, showed a significantly stenosed patent arterial duct giving origin to a pulmonary artery. A right carotid approach (surgical cutdown) using a 5 Fr sheath was performed in all patients. The arterial duct was cannulated using a 0.014 inch guidewire and subsequently stented with a premounted coronary stent. The diameter of the stent was chosen by following the same indications given for the surgical implantation of a modified Blalock-Taussig systemic-to-pulmonary shunt.⁸ In those cases in which the stent did not completely cover the duct, 2 partially overlapping stents were implanted. All technical details are reported in Table 1. All patients received cephalosporin for 24 hours and aspirin at a dose of 3-5 mg/kg once a day starting from the day of the procedure. Statistics. Data are expressed as a frequency or percentage for nominal variables, as the median (range) for categorical variables, and as the mean ± standard deviation or median (range) for continuous variables. The Statistix software, Version 8 (Analytical Software, Tallahassee, Florida), was used for statistical computations. The paired Student’s t-test was used to analyze modifications of oxygen saturations before and after the procedure. All tests were two-sided. A probability value of p < 0.05 was considered statistically significant.

Results

The median procedure and fluoroscopy times were 100 (range 90-120) and 8 (range 6-14) minutes, respectively. A total of 7 stents were used. In two cases, 2 partially overlapping stents were used. Stent diameter ranged between 3 and 3.5 mm. Oxygen saturation increased significantly in all patients (preprocedure: median 70% [range 60-70%] versus post procedure: 85 % [range 80-90%]; p = 0.0026). The postprocedural course was uneventful and patients were discharged 7-10 days after the procedure on aspirin (3-5 mg/kg/day).
All patients were followed up for a period of 4-12 months during which physical and echocardiographic examination revealed continued stent patency. The patients' oxygen saturations remained at their immediate postprocedural values. No abnormalities of carotid artery flow were found on either physical examination or Doppler evaluation during follow up.
Two patients underwent complete corrective surgery 6 months after stent implantation at a weight of 7-9 kg. Ductus arteriosus with the stent inside were completely removed by surgeons who did not report any difficulty. Three of our patients are still waiting for surgery.

Discussion

Ductal origin of a PA is the consequence of the involution of the proximal sixth aortic arch during embryological evolution. This results in the absence of the proximal PA and the persistent connection of the hilar PA to the distal sixth aortic arch that will become the ductus arteriosus. Various surgical approaches have been proposed to correct this including: ductal PA banding, palliation with a modified Blalock shunt, direct end-to-end anastomosis with or without patch augmentation or with the use of an interposition graft.¹⁰ However, these approaches may be highly challenging in neonates.^10,11 Due to the high risk of surgery in very low-weight newborn, an interventional approach may be extremely appealing. However, until now, very few cases have been described.^12-15
Here we report on the experience of a percutaneous approach in maintaining patency of the DA in 5 infants weighing < 3 kg with ductal origin of the pulmonary artery. The procedures were performed successfully and no major complications occurred. In all subjects, ductal patency was achieved and was stable during follow up. In our series, we utilized standard coronary stents. Recently, Koch et al¹⁵ successfully used sirolimus-eluting stents in a 7-week-old female; at 7-month follow up, the stent was perfectly patent. However, in our experience, the use of standard stents was not associated with the development of stenosis during follow up, therefore, we did not support the use of drug-eluting stents in small infants.
From a technical point of view, we decided to approach the DA from the right carotid artery due to its advantageous anatomy and straight course to reach the target. Furthermore, surgical cutdown may reduce the vascular risks of a percutaneous femoral artery approach in small infants. Stent length was chosen to cover the complete length of the DA, avoiding the use of longer stents in order to enable the surgeon to remove only the ductal tissue at the time of surgery.
The percutaneous approach has another advantage over surgery. In fact, it is easier to adapt the size of the prosthesis to the pulmonary artery; furthermore, the angulation of surgical conduits and the PA may cause distortion and stenosis.⁹ This problem does not occur with transcatheter techniques. Also, avoiding early surgery on the pulmonary arteries could reduce the risk of the occurrence of stenosis. Finally, in our strategy, the percutaneous approach was intended as an intermediary stage in a step-by-step approach to treatment. In fact, the patient may undergo stent implantation of the DA a few days after birth and complete surgical repair at a later stage when the patients’ weight will present a lower risk at surgery.
Study limitations. The main limitation of our study is the small number of patients treated. However, ductal origin of the distal pulmonary artery is a rare condition. Furthermore, there are only a few single case reports published in the literature on the percutaneous approach of such a clinical condition. To our knowledge, our case series is the largest yet reported.

Conclusion

In conclusion, percutaneous stent implantation is a promising approach to treat ductal origin of the pulmonary artery.

References

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