Intra-operative Stenting of a Prosthetic Left Pulmonary Artery Stenosis Under Fluoroscopy

Intraoperative stent placement under direct vision as a means of relieving pulmonary artery stenosis is an attractive alternative to complex surgical reconstruction or a valid option in patients with a limited vascular access.^1,2 We describe here the case of a complex congenital malformation in which the relief of a severe prosthetic left pulmonary artery (LPA) stenosis was judged to be essential for the good outcome of final surgical correction, but pre-operative stent dilation was impossible. Case report. The patient’s neonatal diagnosis was right atrial isomerism, left-sided venae cavae, mesocardia, a discordant atrio-ventricular connection, a single aortic outlet from the right ventricle (RV), pulmonary atresia (PA) with no true pulmonary arteries, and a wide inlet-type ventricular septal defect (VSD). The angiographically defined anatomy of the pulmonary circulation consisted of a single, long collateral from the left-sided descending aorta supplying the right hilum, with stenosis at the origin of each lobar branch and in two short collaterals (from the left subclavian artery and the distal thoracic aorta) supplying the upper and lower parts of the left lung. Three different palliative procedures were necessary to connect both lungs to each other and unifocalize the source of blood. Noteworthy, in the first operation, a bovine pericardial roll (diameter: 8 mm) was inserted in the left pleural cavity directly anastomosed to the upper and lower pulmonary branches, whereas, in the third procedure, a 12 mm hilum-to-hilum PTFE conduit (GORE-TEX^® Vascular Graft, Flagstaff, Arizona) was used to connect the right and left lung with a 6 mm PTFE central shunt implanted on it. On the left side, the anastomosis between the transverse conduit and the pericardial roll was extended inferiorly to the roll itself in order to enlarge a previously documented stenosis. At 7 years of age, the child was readmitted to our department because of cyanosis at rest and breathlessness on minimal effort. His hemoglobin level was 21.5 g/dl, hematocrit 61.5% and peripheral oxygen saturation was 70% on room air. An echocardiographic assessment revealed two normally functioning ventricles, an inlet-type VSD unconnected to the aorta and normally competent A-V valves. Color flow Doppler showed a good patency of the shunt and continuous wave Doppler demonstrated a velocity of about 3.9 m/sec across the shunt. The indication for final correction was established. A pre-operative angiographic study demonstrated good patency of the shunt and transverse conduit, good perfusion of the right lung and a recurrent, severe, 20 mm long stenosis in the proximal part of the left-sided pericardial roll. No attempt to measure pulmonary pressure was done because echo measurements were considered reliable. As any attempt to enter the shunt caused life-threatening hypoxia and thus prevented stent dilation, the intra-operative placement of an endovascular device was planned. Resternotomy was performed and the heart was freed from adhesions. A 6 Fr introducer sheath was positioned through a small stab incision in the transverse conduit between the ascending aorta and the left superior vena cava (LSVC) (Figure 1). Systolic pressure in the transverse conduit was 35 mmHg. Angioplasty was performed using a mobile image intensifier system (Stenoscop 2; General Electric Company, Milwaukee, Wisconsin). A 0.014 inch ACS high-torque Floppy II Extra support coronary guidewire (ACS-Guidant, Temecula, California) was advanced across the stenosis and predilation with a 6.0 mm balloon (Bypass Speedy; Scimed-Boston Scientific, Maple Grove, Minnesota) was performed up to 6 atm. Finally, two overlapping 18 mm long, 6.0 mm diameter Herkulink Plus stents (ACS-Guidant, Temecula, California) were implanted in the proximal and middle portions of the xenopericardial tube with an inflation pressure of 18 atm. Post-procedural quantitative angiography revealed good stent apposition and a residual stenosis of 10% (Figure 2). The stents implanted allow an overdilation to 7 mm in diameter. After establishing CPB, surgical correction was carried out by means of atrial and ventricular septation, and connection of the hilum-to-hilum conduit to the left ventricle (LV) through a 19 mm Freestyle^® stentless aortic root bioprosthesis (Medtronic Heart Valves, Minneapolis, Minnesota). The patient was easily weaned from CPB. The ratio between the subpulmonary LV and sub-aortic RV pressure was 0.8 at the end of CPB and decreased to 0.5 before chest closure. The post-operative course was uneventful, and after 12 days of hospitalization, the child was discharged with an echocardiographic estimate of 40 mmHg LV systolic pressure. A further angiographic study electively performed 15 months later revealed moderate intra-stent neointimal proliferation that was successfully dilated. Discussion. The intra-operative implantation of endovascular devices under direct vision in order to correct pulmonary artery stenosis has different indications: a difficult percutaneous vascular access,¹ or the need to perform a concomitant operative procedure.² However, caution has been recommended because of the high rate of complications probably related to the impossibility of seeing the distal end of the stent.³ Furthermore, the anatomical features of the lesion (such as its distal location, length and curvilinear course) require a perfect step-by-step evaluation of the dilating procedure that can only be obtained under repeated angiographic control. In our case, the early construction of a biological conduit to replace an absent main LPA led to a progressively worsening conduit stenosis which was not altered by surgical angioplasty during the third palliative operation. At the time of definite repair, pre-operative percutaneous treatment of the LPA stenosis was not feasible because of the impossibility of catheterising the shunt without seriously compromising lung perfusion. Successful endovascular stenting of peripheral pulmonary stenoses in the early post-operative period has been reported,⁴ but in our case may have led to an increased risk of post-CPB low output syndrome requiring VSD patch fenestration. We therefore chose to treat the stenosis intra-operatively. The direct insertion of the sheath into the transverse conduit did not interfere with patient oxygenation. Contrast angiography, wire advancement, balloon dilation and stenting were all performed under fluoroscopy and led to the very good resolution of a complex, long and bent stenosis. The successful outcome of the surgical correction and the absence of infective complications demonstrate the feasibility and safety of this strategy.

1. Mendelsohn AM, Bove EL, Lupinetti FM, et al. Intraoperative and percutaneous stenting of congenital pulmonary artery and vein stenosis. Circulation 1993;88:210–217. 2. Ungerleider RM, Johnston TA, O’Laughlin MP, et al. Intraoperative stents to rehabilitate severely stenotic pulmonary vessels. Ann Thorac Surg 2001;71:476–481. 3. Coles JG, Yemets I, Najm HK, et al. Experience with repair of congenital heart defects using adjunctive endovascular devices. J Thorac Cardiovasc Surg 1995;110:1513–1520. 4. Rosales AM, Lock JE, Perry SB, Geggel RL. Interventional catheterization management of perioperative peripheral pulmonary stenosis: Balloon angioplasty or endovascular stenting. Cathet Cardiovasc Intervent 2002;56:272–277.