|Year : 2006 | Volume
| Issue : 3 | Page : 105-110
The hybrid stage 1 operation in hypoplastic left heart syndrome: A new alternative
Associate Professor of Surgery, Harvard Medical School, Senior Associate in Cardiac Surgery, Children's Hospital, Boston, MA, USA
|Date of Web Publication||17-Jun-2010|
Children's Hospital Boston, 300 Longwood Ave. Bader 273, Boston, MA 02115
Source of Support: None, Conflict of Interest: None
| Abstract|| |
Hospital survival after the Norwood stage I palliation for hypoplastic left heart syndrome (HLHS) or related anomalies has remarkably improved over the last decade. However, results remain suboptimal. In recent years, hybrid techniques (interventional cardiologists and surgeons working together) have been developed and refined for problems (such as multiple muscular ventricular septal defects) that had no satisfactory solutions with either discipline. The hybrid stage I is a less invasive hybrid approach that allows for a non-pump 1st stage palliation, followed by a comprehensive second stage. The hybrid stage I is typically performed in a hybrid room. Via a median sternotomy, both branch pulmonary arteries (PA) are banded and a ductal stent is delivered via a main PA puncture and positioned under fluoroscopic guidance.
Despite the learning curve, hospital survival has been > 80%. The second stage operation consist of aortic arch reconstruction, atrial septectomy and cavopulmonary shunt. Several patients have undergone the last palliative step in the form of a Fontan procedure. The most acute problem after the hybrid stage I has been the development of a so-called retrograde coarctation from ductal tissue in patients with aortic atresia. In conclusion, primary experience with this new off-pump palliation has been satisfactory. This approach can be employed in selected patients.
|How to cite this article:|
Bacha E. The hybrid stage 1 operation in hypoplastic left heart syndrome: A new alternative. Heart Views 2006;7:105-10
| Introduction|| |
Despite undeniable recent improvement in survival rates, the Norwood Stage I operation for hypoplastic left heart syndrome (HLHS) and related anomalies remains a high-risk endeavor. Neonates undergoing a stage I Norwood operation face a mortality of 10-20%, depending on the risk factors and the experience of the cardiac team1. Current significant risk factors include birth weight < 2.5 kg, prematurity < 34 weeks gestational age, intact or restrictive atrial septum, additional cardiac anomalies and non-cardiac genetic malformations , .
Even a perfectly executed operation requires prolonged cardiopulmonary bypass (CPB) usually associated with deep hypothermic circulatory arrest, multiple blood transfusions, and delayed sternal closure. Furthermore, survivors of the Norwood procedure are showing suboptimal neurological development.
Prolonged neonatal CPB and prolonged hospitalization, especially in combination with hypoxemia and low diastolic pressures, has been linked to poor neurological development , . Other studies have also linked intrinsic genetic factors, pre-operative management, or post-operative management to those undesirable outcomes  .
What can be stated with certainty is that the current outcomes are far from ideal. With the initial success of ductal stenting, a new paradigm started to emerge. Some groups , began using percutaneous ductal stenting followed by surgical band placement for initial palliation of HLHS. Branch PA banding had been used during the 1980's by Norwood and others early on for stabilization of babies with HLHS  . The approach of percutaneous stenting and open PA banding was then modified to become a single procedure, performing ductal stenting and PA banding via a sternotomy [Figure 1], thus avoiding issues of percutaneous access, arrhythmias and valvar regurgitation associated with percutaneous procedures  .
The present article reviews the development of this new strategy, the current technique employed, as well as its advantages and disadvantages.
| Technique|| |
Ideally, the hybrid stage I, as all hybrid procedures, should be performed in a "hybrid suite", which is specially equipped to handle cardiopulmonary bypass machine as well as imaging technology (mobile fluoroscopy or fixed biplane catheterization). The room is set up as an operating room  .
A transesophageal echocardiography probe is placed if the atrial septum is to be approached. Under usual monitoring, chest, abdomen and groins are prepped and draped. A median sternotomy is performed. The chest retractor is placed in such a way as to be able to remove it when fluoroscopy is performed. 1.5mm wide rings are cut off a standard 3.5mm Goretex tube graft (W.L. Gore & Associates, Inc., Flagstaff, Az) and cut open. A 5-0 polypropelene mattress suture is placed through one end of the cut ring. The right PA is encircled to the right of the ascending aorta and the band is secured. A clip is placed over the sutured portion and further clips can be used to tighten further, if necessary. The left PA is similarly banded at its origin. Next a 5-0 polypropelene purse-string is placed at the sino-tubular junction of the main PA. 50 IU/kg Heparin is given. The main pulmonary artery is punctured using a 21G needle (Cook Inc., Bloomington, IN) and a 0.018" short guide wire is passed into the descending aorta via the ductus. A short 6Fr sheath is then advanced over the guide wire, positioned with the tip inside the vessel by 2-3mm only and secured.
An angiogram is performed using the sheath in the main PA in a 45° LAO angulation to profile the aortic arch and ascending aorta, measure the ductal diameter and to assess the position and appropriateness of the bands [Figure 1]. The proper size self-expandable stent (usually a 7 or 8 mm x 20 mm) is then advanced over the guide wire. The stent is placed so that the distal end of it is just protruding into the descending aorta and the proximal part is just above the branch PA openings. We have used either the Precise (Cordis, Johnson & Johnson, Warren, NJ) or Protege(ev3 Inc, Plymouth, MN) stents. Balloon-deployable stents can also be used. Once the stent is deployed, repeat angiogram is performed to assess the position of the stent, the pulmonary artery bands and the aortic arch. It is important to cover the entire ductal length, as it will constrict otherwise.
A second stent can be used if necessary. The pulmonary artery bands can be adjusted accordingly. The bands are adjusted by using the combined data from the arterial saturation, blood pressure, and the measured (by angiogram) diameter of the banded portion relative to the proximal branch PA. If the bands cannot be profiled adequately, a Judkins Right catheter can be used to cannulate the branch PA's directly and perform selective branch PA angiograms [Figure 2]. If the atrial septum is restrictive, the atrial communication can be enlarged using a self-expandable stent placed via a per-atrial approach under TEE guidance. An intracardiac common atrial monitoring line is placed prior to chest closure.
| Results|| |
Hospital survival has ranged from 70 to 90%  . More than 90% of patients can have primary closure of the sternum. Because pulmonary blood flow is controlled by banding the PA's while maintaining the same systemic outflow, the patients typically are more hemodynamically stable after the hybrid stage I than they are before. Several adverse outcomes such as ductal stent migration into the descending aorta or PA band migration occurred mostly because of inexperience with this strategy. Some of the specific complications encountered with the hybrid stage I are listed in [Table 1].
| Current Protocol|| |
Our current protocol is to proceed with the hybrid stage I as soon as possible after birth. Post-operative management is routine. We perform echocardiograms at least weekly, even after discharge. At 6 weeks, consideration is given to a cardiac catheterization to check the position of the stent(s) and bands. If the atrial septum is restrictive, it is stented or dilated at that time. The stage II is performed at 12-24 weeks of age. We choose to perform the stage II early so that we do not have to rely on an imperfectly opened (or stented) atrial septum, and the chances of significant PA distortion from the bands are less. Indications are listed in [Table 2].
| Advantages and Disadvantages|| |
Traditional Norwood palliation for HLHS relies on the establishment of an unobstructed systemic outflow with reliable coronary blood flow, a non restrictive atrial septal defect and a controlled source of pulmonary blood flow.
The main advantage includes complete avoidance of neonatal CPB. Palliation is achieved with 2 "pump runs" instead of 3, and early neonatal trauma due to prolonged hospitalization and multiple blood transfusions is avoided. On the other hand, the stage II reconstruction, which in the traditional approach is the least difficult, becomes a very challenging redo-operation, involving stent removal, arch reconstruction and cavopulmonary shunt. Despite that, the patient recovers with a circulation in series and not in parallel as after the Norwood stage I. Early palliation with a circulation in parallel as in the Norwood operation requires that ventricular output must be maintained at a level that is 2-3 times normal  . Right ventricular function has been shown to be better after CPS operations than after volume-loading procedures  . Finally, there is evidence that myocardial damage after heart surgery is greater in neonates as opposed to infants  .
The aortic arch is an area of concern with this approach. Recent data has shown that neonates with complex congenital heart disease have decreased pre-operative cerebral blood flow  . In aortic atresia patients (and thus no antegrade flow across the aortic valve), the development of a retrograde coarctation from a ductal shelf with subsequent coronary ischemia was the likely cause of demise in at least one patient, and caused us to proceed emergently to stage II in another [Figure 3].
The ductal stent by necessity covers the isthmic opening into the transverse arch since it has to cover the entire duct to prevent ductal constriction [Figure 4]. Ductal tissue is often circumferential at the level of the isthmus in HLHS patients  , and will constrict once prostaglandins are stopped. This problem has no clear solution at the present time. Caldarone et al  have suggested creating a "reverse" goretex shunt from the main PA to the innominate artery. This would help with cerebral blood flow but not necessarily with coronary blood supply since the junction between ascending aorta and transverse arch can be significantly narrowed as well. In aortic atresia patients, we now specifically image the entire aortic arch and ascending aorta during the initial angiogram [Figure 5] and[Figure 6] to exclude any significant stenoses, which, if present, would preclude us from proceeding with hybrid stage I palliation.
We have also learned to oversize the ductal stent by 1mm from the angiographically measured ductal width. Balloon-expandable stents may be better suited for ductal stenting.
Pulmonary artery distortion is obviously a dreaded complication from PA banding. Single ventricle patients do not tolerate any kind of pulmonary outflow problems. We have learned to secure the bands to the PA's just as it is done traditionally for main PA banding. Branch PA banding does not seem to result in significant PA distortion if the bands are taken down early, i.e. 3-4 months after placement. However, some patients have required left PA stenting at mid-term.
The reliable creation of an unrestrictive atrial septum by non-invasive means (i.e. without actually cutting out atrial septum primum) remains difficult. Peratrial stenting can be performed at the time of the hybrid stage I via an atrial purse-string. Some groups address the atrial septum percutaneously (usually via umbilical venous access) at the time of the hybrid stage I, and others routinely catheterize the baby at 4-6 weeks post-op to relieve any atrial gradient. Patients with a restrictive or intact atrial septum are taken to the catheterization laboratory immediately after birth for balloon atrial septostomy and stenting, followed by a hybrid stage I procedure once they are stable.
| The Future|| |
The strategy described in this article could potentially lead to a percutaneous Fontan completion  , with one major on-pump reconstruction sandwiched between 2 interventional procedures.
Development of new technologies will undoubtedly improve outcomes and widen the indications of lesser invasive hybrid strategies. Absorbable stents for temporary ductal stenting or a stable oral prostaglandin E analog would be of great benefit. Ultrasound tissue erosion  for percutaneous creation of an unrestrictive ASD is currently under animal investigation. Improved percutaneous flow occluders could help surmount some of the early problems seen in this study. Safer techniques for direct cardiac access delivery of devices through the unopened chest would render the sternotomy obsolete.
| Conclusion|| |
For the practitioner dealing with HLHS and related anomalies, the hybrid stage I palliation has, at the very least, created a new avenue that can be used in selected patients. Initial set-backs should not deter us from continuing to explore less invasive methods to treat single ventricle patients.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6]
[Table 1], [Table 2]