Abstract
Background:
Stenosis of the retroaortic pulmonary artery is common in patients with single ventricle heart disease. Intraoperative hybrid stenting at the bidirectional Glenn or Fontan operation can treat this lesion and avoid a complex surgical arterioplasty.
Methods:
Patients who underwent intraoperative stent implantation to the retroaortic pulmonary artery during the bidirectional Glenn or Fontan operation at our center between January 2005 and July 2014 were retrospectively identified.
Results:
Thirteen patients were included with a median weight of 8 kg (5.6-14.4 kg) and age of 6 months (4 months-3.8 years). All had undergone Norwood operation, and eight (62%) had hypoplastic left heart syndrome. Eight (62%) underwent stent placement during bidirectional Glenn and five (38%) during Fontan operation. Ten patients had one stent placed, and three had two overlapping stents. The median diameter of the stenotic vessel was 3 mm (2.0-5.5 mm) and diameter of the balloon used for stent expansion was 7 mm (5-10 mm). Two complications occurred including pulmonary hemorrhage from presumed wire perforation and left main stem bronchus compression requiring stent removal. No patient required stent intervention in the postoperative period, and all were discharged from the hospital. At a median follow-up of 1.3 years (2 months-7.1 years), six patients underwent interval dilation to account for somatic growth.
Conclusions:
Hybrid stenting of the retroaortic pulmonary artery at the bidirectional Glenn or Fontan operation is an effective treatment of pulmonary artery stenosis and prevents the need for a complex surgical arterioplasty.
Introduction
Percutaneous stent placement is an effective modality to treat branch pulmonary artery (PA) stenosis in patients with congenital heart disease. 1 Hybrid intraoperative PA stent placement can be advantageous in patients with challenging vascular access, with a potentially difficult percutaneous intervention, and in those who are having concomitant surgery with challenging surgical arterioplasty. 2 The hybrid approach has been widely reported in patients with repaired conotruncal lesions. 2 –7
Patients with single ventricle congenital heart disease who have undergone Norwood operation are at risk for stenosis of the retroaortic PA due to external compression by the dilated, neoascending aorta. 8 At our institution, we have used a hybrid approach at the time of the bidirectional Glenn (BDG) or Fontan operation to treat this lesion in these patients. This technique spares the need for complex surgical arterioplasty that can be ineffective and prolong operative times. This approach has not been extensively described and we report our experience.
Methods
Study approval was obtained from the institutional review board of Arnold Palmer Hospital for Children. Patients who underwent intraoperative stent placement to the retroaortic PA during the BDG or Fontan operation were retrospectively identified at our institution between January 2005 and July 2014. Records were reviewed and relevant demographic, anatomic, clinical, and procedural details extracted. The postoperative course was also reviewed and relevant details recorded. Catheterizations performed after hospital discharge were reviewed as was the most recent clinical follow-up. The data were summarized as mean ± standard deviation or median with range.
Procedural Details
All patients underwent a preoperative catheterization, at which time the PA stenosis was appreciated and relevant PA measurements made. As a catheter-assisted open surgical hybrid procedure, the BDG or Fontan operation was performed in a standard fashion using normothermic cardiopulmonary bypass including superior vena cava (SVC) cannulation. Usually, the operations were performed in our hybrid operating suite that is equipped with biplane fluoroscopy. After the patient was weaned from bypass and modified ultrafiltration was completed, the SVC cannula was replaced with a vascular sheath of appropriate size. The sheath was large enough in size to accommodate the largest possible stent to potentially be implanted. Angiography was undertaken by hand contrast injection performed via the SVC sheath. The relevant PA measurements were then made. Only balloon-expandable stents were used, and a stent was chosen whose diameter was slightly greater than the nonstenotic distal PA and whose length adequately covered the stenotic region without obstructing caval flow. If size allowed, we chose a Genesis XD stent (Johnson & Johnson-Cordis Corporation, Miami Lakes, Florida), which can eventually be dilated to adult size. A coronary catheter was then used to direct a floppy-tip wire of appropriate size into the left lower lobe branch of the PA. The catheter was removed and balloon catheter with stent then advanced over the wire into the intended position. If a Genesis XD stent (Johnson & Johnson-Cordis Corporation) was hand crimped onto a balloon, then the stent was formed into a slight “S shape” when on the balloon to limit stent migration (Figure 1). Sighting injections were performed and the stent expanded under fluoroscopic guidance. The balloon catheter was then removed and final angiogram performed. If results were acceptable, the cannula was removed. All patients underwent follow-up chest X-ray within 24 hours and echocardiogram prior to discharge to evaluate stent position and PA patency. Figures 2 and 3 show preoperative and intraoperative images in two patients.
Image of “S-shaped” configuration created to encourage stent stability after 1910B Genesis XD stent (Johnson & Johnson-Cordis Corporation, Miami Lakes, Florida) was hand crimped onto an 8-mm Opta Pro (Johnson & Johnson-Cordis Corporation) balloon prior to intraoperative pulmonary artery stenting during extracardiac Fontan operation.
A, Anterior–posterior view of conventional superior vena cava angiogram performed at pre-Fontan catheterization in a three-year-old female with hypoplastic left heart syndrome. Pulmonary artery stenosis leftward of the cavopulmonary connection is present but poorly profiled in this projection. B, Cranial view from rotational pulmonary angiogram performed at the same catheterization nicely profiling pulmonary artery stenosis from external compression in the anterior–posterior dimension, possibly from the dilated, reconstructed aorta. This cranial view cannot be obtained with conventional angiography. C, Anterior–posterior view of hand contrast injection via directly placed superior vena cava sheath following intraoperative hybrid placement of a Genesis XD 1910B stent (Johnson & Johnson-Cordis Corporation, Miami Lakes, Florida) mounted on a 9-mm balloon during extracardiac Fontan operation and showing relief of the stenosis.
A, Anterior–posterior view of aortogram during prestage 2 catheterization in a four-month with tricuspid atresia who had undergone Norwood operation with right modified Blalock-Taussig shunt. The angiogram shows long-segment pulmonary artery stenosis leftward of the shunt as the artery travels under the dilated, reconstructed aorta. B, Anterior–posterior view of hand contrast injection via directly placed superior vena cava sheath immediately prior to hybrid pulmonary artery stent placement at the time of right bidirectional Glenn operation, again demonstrating the stenotic pulmonary artery. C, Anterior–posterior view of hand contrast injection via directly placed superior vena cava sheath after intraoperative expansion of a Genesis XD 1910B stent (Johnson & Johnson-Cordis Corporation, Miami Lakes, Florida) with a 7-mm balloon demonstrating successful treatment of the stenosis.
Occasionally, a stent was placed under direct visualization while the patient was supported with cardiopulmonary bypass. After pulmonary arteriotomy, a floppy-tip wire was advanced into the distal left PA by the surgeon. The balloon catheter and stent were advanced over the wire and the stent expanded under direct vision.
Results
Thirteen patients were included and their characteristics described in Table 1. The median age was 6 months (4 months-3.8 years) and weight 8 kg (5.6-14.4 kg). Eight (62%) patients had hypoplastic left heart syndrome, three (23%) patients had double-inlet left ventricle {S, L, L}, one had tricuspid atresia with transposed great arteries {S, D, D}, and one patient had posterior malalignment ventricular septal defect with left ventricular hypoplasia. All patients had undergone prior Norwood operation, and only one patient had undergone prior transcatheter PA intervention.
Baseline Characteristics in 13 Patients Undergoing Stent Placement to Pulmonary Artery Leftward of Cavopulmonary Connection.
Abbreviations: CPS, cardiopulmonary support; DILV, double-inlet left ventricle; EC, extracardiac; HLHS, hypoplastic left heart syndrome; LV, left ventricle; R BDG, right bidirectional Glenn; TGA, transposition of great arteries; VSD, ventricular septal defect.
a Formula 418 biliary balloon expandable stent (Cook Medical, Bloomington, Indiana).
b Genesis premounted stent (Johnson & Johnson-Cordis Corporation, Miami Lakes, Florida).
c Genesis XD stent (Johnson & Johnson-Cordis Corporation).
All patients underwent cardiac catheterization prior to the operation, and in six patients, rotational angiography was used during that procedure. Eight (62%) patients underwent PA stent placement concomitant with right BDG and five (37%) during extracardiac Fontan operation. All had stent placed to PA leftward of cavopulmonary connection. Twelve (92%) patients underwent stent placement through an SVC sheath after weaning from cardiopulmonary bypass but before chest closure. In one patient, the stent was placed under direct visualization. This stent was placed too distally; after weaning from bypass, an SVC sheath was placed and a second overlapping, proximal stent delivered. The median sheath size was 8F (6-9F), and the median fluoroscopy time was 11.1 minutes (7.2-31.1 minutes). In ten (77%) patients, one stent was placed, whereas in three (23%), two overlapping stents were required. The median diameter of the stenotic PA segment was 3 mm (2-5.5 mm) and the median stent balloon diameter 7 mm (5-10 mm). In four (31%) patients, a premounted stent or stents were used, whereas Genesis XD stents (1910B, 2510B; Johnson & Johnson-Cordis Corporation) were placed in all others. Stent delivery was successful in all patients.
No procedural mortality occurred, but two major complications were encountered. First, a four-month-old infant with hypoplastic left heart syndrome underwent right BDG with intraoperative placement of a premounted stent to the PA leftward of the Glenn connection under direct visualization. The stent appeared too distal. After the operation was completed and the patient separated from cardiopulmonary bypass, a 6F sheath was placed in the SVC at the prior bypass cannulation site. A 0.018 floppy-tip wire was advanced into the lower lobe branch of the left PA. To treat residual proximal stenosis, another premounted stent was expanded proximal to the first stent in an overlapping fashion. Stent placement was excellent, but the patient developed significant left pulmonary hemorrhage. No extravasation of contrast was seen from the PA near the stent. The patient required an equivalent of extracorporeal membrane oxygenation; she successfully separated from support after five days and was discharged home after five weeks. The hemorrhage may have been due to wire perforation of the distal PA. Second, a 3.9-year-old female with double-inlet left ventricle and transposed great arteries {S, L, L} underwent extracardiac, fenestrated Fontan operation. The patient had a history of tracheobronchomalacia. After completion, a Genesis XD 2510B stent (Johnson & Johnson-Cordis Corporation) was expanded in the PA leftward of the cavopulmonary connection via a 9F SVC sheath. The patient’s ventilation acutely deteriorated, and contrast bronchography showed left main stem bronchus compression. Cardiopulmonary support was resumed and the stent removed. The patient was discharged two weeks after Fontan. At six months, the patient underwent simultaneous expansion of 7-mm balloon in PA and bronchoscopy showing dynamic left main stem bronchus compression. Therefore, the PA was not stented.
All patients were discharged home after operation, and no patient underwent stent reintervention in the postoperative period. At a median follow-up of 1.3 years (2 months-7.1 years), six patients underwent interval dilation of the PA stent to achieve a diameter commensurate with somatic growth.
Comment
We describe hybrid intraoperative stent placement to the retroaortic PA in 13 patients undergoing BDG or Fontan operation. All patients had undergone prior Norwood operation and exhibited external PA compression due to the dilated neoascending aorta making surgical arterioplasty difficult. In almost all patients, stent delivery was performed via SVC sheath after successful weaning from cardiopulmonary bypass. Stent deployment was successful in all patients, and two experienced important complications. No patient required reintervention on the stent in the postoperative period, and all were discharged home.
Hybrid intraoperative stent placement has been previously described, particularly in patients with repaired conotruncal lesions. 2 –7,9 The hybrid approach can prevent a complex arterioplasty in those undergoing surgery and/or can provide easier technical access to the stenotic lesion. In most published series, stents were placed under direct visualization while on cardiopulmonary bypass and without fluoroscopy. The use of a hybrid approach to treat retroaortic PA stenosis in patients undergoing BDG or Fontan has only been sparingly described. 2,4,6,10
Using the hybrid strategy to address retroaortic PA stenosis at the time of BDG or Fontan is valuable because it prevents the need for a complex surgical arterioplasty, particularly in patients who have undergone Norwood. Typically, augmentation of the branch PA leftward of the cavopulmonary connection is performed at BDG or Fontan operation. However, if the augmentation needs to extend leftward of the neoascending aorta near the left hilum, then this is considered complex as mobilization of the neoaortic root is required. We use the hybrid stent strategy to treat nearly all patients who had history of Norwood operation and needed a retroaortic PA plasty at the time of BDG or Fontan that extended significantly under the reconstructed aorta. The arterioplasty can involve hazardous, challenging dissection near the dilated neoascending aorta, may be ineffective, and can significantly prolong operative and support time. Even if an appropriate PA plasty is performed, the dilated neoascending aorta that is under systemic pressure may externally compress the retroaortic PA in the anterior–posterior dimension.
We prefer to deliver the stent after the patient has successfully weaned from cardiopulmonary bypass; the SVC bypass cannula is replaced with a vascular sheath and the stent is delivered using fluoroscopic guidance. This strategy has potential advantages over direct visualization including a reduction in cardiopulmonary support time and improved accuracy in stent placement given the use of angiography. It does involve exposure to radiation, but fluoroscopic times in our series were short. In the four patients who underwent stent placement during the BDG operation, no substantial challenges were encountered at the Fontan operation due to the presence of a PA stent. There are several points to consider when performing a Fontan operation on a patient with stented retroaortic PA. During the dissection of the PAs, the stented PA is not overtly denuded of the scar tissue overlying the adventitia, which helps in keeping the Fontan anastomosis hemostatic. Additionally, the back-bleeding through the left PA is controlled by inserting a Fogarty balloon catheter into the left PA via the PA arteriotomy. This strategy negates the need of placing an occlusive clamp over the stented PA.
A dilated neoascending aorta following Norwood operation is a known risk factor for PA compression. 8 All patients in our cohort underwent preoperative catheterization, and in many patients, rotational angiography was performed during the catheterization. Frequently, compression of the PA as it travels under the dilated arch occurs in an anterior–posterior dimension. 8 This compression can be missed on a conventional angiogram in the anterior–posterior view but is nicely outlined in an axial view that rotational angiography facilitates. Preoperative magnetic resonance imaging can also profile this lesion.
Retroaortic PA compression can be minimized or avoided if a neoascending aorta is created at the Norwood operation that is not significantly dilated or too short. The strategy to optimize arch reconstruction includes appropriately sizing the shield-shaped patch both at the base and at its communication with transverse arch. These adjustments are patient specific as the size of each aortic arch and ascending aorta varies. Despite the surgeon’s best effort, subsequent dilatation of the homograft patch can occur. Retroaortic PA compression from a dilated neoascending aorta is very common worldwide, illustrative of the challenge of creating an appropriate-sized neoascending aorta.
Our preference is to implant Genesis XD stents (Johnson & Johnson-Cordis Corporation) when possible as this stent can eventually be dilated to 18 mm. Due to small patient size, a premounted stent was placed in four patients, all undergoing BDG operation. The Formula 418 (Cook Medical, Bloomington, Indiana) and Genesis premounted stents (Johnson & Johnson-Cordis Corporation) can be maximally dilated to roughly 12 mm and can often be fractured if diameters beyond this are needed. 11 However, the use of premounted stents in infants with potential need for eventual stent fracture may be a limitation of this approach.
In the postoperative period, no patient required stent reintervention and all were discharged home. Untreated PA stenosis is associated with increased morbidity following the Fontan operation. 12 We believe that successfully treating the PA stenosis concomitant with BDG or Fontan maximizes the chance of uneventful postoperative recovery and, possibly, prevents the need for catheterization in this period. Additionally, mild, untreated PA stenosis may have negative long-term consequences for those with Fontan physiology. Chronically decreased left PA blood flow may lead to underdevelopment of the left lung vasculature and, thus, elevated pulmonary vascular resistance. Also, in those with Fontan circulation, the minimum PA area has been shown to correlate with cardiac index. 13
At a median follow-up of 1.3 years, six patients underwent further dilation of the implanted stent to achieve a diameter commensurate with somatic growth. The long-term rate of reintervention after hybrid PA stenting can be significant. 3 In any case, patients with single ventricle congenital heart disease will require frequent interval catheterizations throughout their life during which these stents can be further expanded. Studies have illustrated that PA stents placed in childhood and infancy can be dilated to appropriate adult size with an average of three interventions. 14,15
For stents that are not premounted, we found it useful to crimp the stent on the desired balloon and then place two small “bends” in the stent creating an “S” shape. This helps prevent stent migration on the balloon as the unit is being advanced without sheath coverage across the stenotic area.
Two significant complications were encountered. First, a patient developed pulmonary hemorrhage after stent placement via direct visualization and, then, second, overlapping stent placed from SVC sheath. In both approaches, a floppy tip guide wire was used and no extravasation of contrast was visualized in the area of stent placement. The etiology of hemorrhage was unclear but may have been due to wire perforation of distal pulmonary vessel despite the use of a floppy-tip wire. This patient required cardiopulmonary support for several days but survived to discharge. Another patient with tracheobronchomalacia developed acute left main stem bronchus compression after stent expansion, a known, very rare complication of PA stenting. 16 The stent was immediately removed surgically. The patient returned to the catheterization laboratory six months after operation and bronchoscopy performed with simultaneous balloon dilation of PA. Persistent bronchomalacia was appreciated and dynamic compression observed and, thus, a stent was not placed.
Limitations
Some centers may prefer to attempt surgical arterioplasty at the time of BDG or Fontan operations to treat retroaortic PA stenosis. This technique avoids stent placement with the need for stent redilation and risk of stenting procedure. We acknowledge the merit of this approach and present an alternative, not necessarily superior, method for treating this lesion. We prefer hybrid stent placement because surgical arterioplasty can be complex with risk of phrenic nerve injury and increased bleeding and, often, may incompletely treat the stenosis requiring later transcatheter stent placement. However, we did not directly compare patients undergoing surgical arterioplasty to patients undergoing hybrid stent placement to treat retroaortic PA stenosis and, thus, cannot make conclusions about the superiority of our strategy. Additionally, our follow-up was limited and stent reintervention was needed in the setting of ongoing somatic growth. Long-term follow-up is necessary prior to drawing definitive conclusions about our approach.
Conclusion
In conclusion, intraoperative hybrid stent placement is an effective strategy to treat retroaortic PA stenosis in patients undergoing BDG or Fontan operation, especially those who have undergone prior Norwood operation. The strategy prevents the need for complex surgical arterioplasty.
Footnotes
Declaration of Conflicting Interests
The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.
Funding
The author(s) received no financial support for the research, authorship, and/or publication of this article.