Hakan Akintuerk1, Dietmar Schranz1, 2, and Norbert Voelkel3 1Justus‐Liebig University Giessen, Germany 2University Clinic, Frankfurt, Germany 3Virginia Commonwealth University, School of Pharmacy, Richmond, VA, USA Over the last three decades tremendous progress has been made in the treatment of patients, particularly in newborns with congenital heart disease (CHD). Surgical and catheter‐based interventions have improved in parallel. Surgery remains the treatment of choice for the majority of children with complex heart disease. However, percutaneous transcatheter techniques have become the treatment of choice in a number of anatomically simpler conditions. Today modern treatment of children with cardiovascular malformations has improved to the point that almost 90% of these patients survive to adulthood [1, 2]. Increasing experience in surgical and catheter‐interventional procedures combined with technical innovations has led to a common platform for surgical and interventional experts developing complementary procedures. Combined surgical–interventional approaches have been developed and are now termed “hybrid” procedures. Typically, hybrid procedures reduce the number of interventions, decrease operative complexity, and avoid prolonged cardiopulmonary bypass (CPB) [3]. In complex CHD the aim of hybrid procedures is to reduce morbidity and mortality [4, 5]. If conventional treatment is rejected or judged to be high risk (e.g., cardiopulmonary bypass in premature infants), hybrid procedures facilitate or enable therapeutic options [6]. Gibbs and colleagues described the first hybrid approach in 1993 for the palliation of newborns with hypoplastic left heart syndrome (HLHS) [7]. Beyond stage I palliation for HLHS [8], multiple hybrid procedures were developed to treat single cardiac lesions or parts of complex CHD at any age. Within the last two decades, hybrid treatments were pioneered and became routine in many institutions worldwide. Multiple reviews and textbooks summarize the current experiences with hybrid procedures [9]. Some single institutions have reported an increased number of hybrid procedures to almost 10% of cases during the last decade [10]. This chapter will not address all hybrid procedures; instead we will focus on hybrid strategies to treat patients with HLHS, hypoplastic left heart complex (HLHC), and other congenital anomalies of the left heart. Additionally, we will review the lessons learned from experience dealing with neonatal univentricular as well as borderline left heart diseases. The treatment algorithm for neonates with HLHS follows the Norwood approach, a well‐established three‐step procedure performed in many institutions [11, 12]. As mentioned above, Gibbs and colleagues reported the first complete hybrid approach to HLHS consisting of arterial duct stenting, bilateral pulmonary artery banding (bPAB), and surgical or catheter‐based atrial septum manipulation (Figure 5.1) [7]. However, the initial results were disappointing. The approach, intended as an alternative to the Norwood operation, was not further recommended by the group from Leeds, UK [13]. A more successful collaborative surgical–interventional approach had been developed in the Pediatric Heart Center at Giessen in Germany [4] and the Nationwide Children’s Hospital in Columbus, Ohio [5]. In both centers, the hybrid approach has essentially replaced the conventional Norwood stage I procedure [14, 15]. In most institutions, a hybrid stage I procedure is currently in use in newborns with multiple comorbidities, low birth weight, or other high‐risk conditions, which can be aggravated by cardiopulmonary bypass. Under such circumstances, hybrid palliation is favored because it avoids cardiopulmonary bypass and its associated complications [6, 16]. However, restricting the hybrid approach to high‐risk cases may be a disadvantage in that the hybrid team might not become sufficiently familiar with all technical aspects of the procedure. The aim of hybrid stage 1 is to achieve a sufficient systemic blood flow via an unobstructed arterial duct, to protect the pulmonary circulation by balancing the pulmonary and systemic circuits, and to guarantee a laminar pulmonary vein flow, in most cases by achieving an unobstructed interatrial communication (Figure 5.1). The open‐chest approach is used to perform a surgical circumferential bPAB. Galantowicz [5, 15] improved bPAB by cutting a 3.5 or 3 mm polytetrafluoroethylene (PTFE) tube to a small 1–2 mm strip, which is used in neonates with body weight above or below 3 kg. Of great importance is that an overly wide band‐strip has caused hypoplasia of the main pulmonary branches. A small strip of 1–2 mm band applied to the pulmonary arteries may avoid migration by fixing the band to the adventitia. Transpulmonary duct stenting completes the hybrid approach if no atrial septum manipulation is necessary. Some patients develop retrograde arch obstruction and require placement of a “reverse” Blalock–Taussig–Thomas (BTT) shunt [16, 17]. Complications such as blood loss and circulatory instability can be associated with mortality rates between 10% and 25% [16, 17]. Figure 5.1 Bilateral pulmonary artery bands and a patent arterial duct stent via a median sternotomy followed by a balloon atrial septostomy several days later before discharge. Source: Galantowicz et al. 2008 / with permission of Elsevier. In Giessen, the surgical part of the hybrid procedure is reduced to bPAB with a very low mortality [8]. Duct stenting is performed in most patients following bPAB as an elective and separate percutaneous approach by the transfemoral vascular access. Three major aspects have contributed to the decision for percutaneous duct stenting as a separate approach. First, duct stenting is not an absolutely essential part of the hybrid stage 1, as long as prostaglandin‐E1 can be effectively administered at a low dosage of 0.05 μg/kg/min. Second, and most important, the anatomic junction of the duct and the descending aorta is variable and needs to be carefully delineated in order to achieve an exact duct stenting. Additionally, if necessary, any manipulation of the isthmus region must be carefully weighed. In a few patients with a narrowed isthmus, balloon dilatation needs to be considered before a stent is placed within the duct. If there exists a significant coarctation, a stent needs to be placed after duct stenting to guarantee a sufficient retrograde blood flow to the brain and coronary circulation. This prevents the need for a reverse BTT shunt. The third aspect is related to the stent technology in Europe. The self‐expanding stent design of the currently used Sinus‐SuperFlexDS (OptiMed, Karlsruhe, Germany) is available with widths from 4–9 mm and lengths between 12 and 24 mm. The deliverable system can be advanced through a 4F vascular sheath, which allows duct stenting by femoral vein or preferentially by femoral artery access. Hybrid ductal stenting with self‐expandable stents, when compared with balloon‐expandable stents, produced favorable results; stent‐related complications were reduced in London from 22% to 6% [18]. The reintervention rate for both stent types needs to be considered, which appears to be lower after placement of a self‐expandable stent [18]. Two important determinants to avoid reinterventions are duct and material related. The entire length of the duct needs to be covered by the stent; in case of an extremely long duct, telescope stenting with two or three stents may become necessary. The stent profile is designed for a rapid dilatation of an obstruction by ballooning. We use a Tyshak‐Mini 8 × 20 mm (PFM, Cologne, Germany) that can also be advanced through a 4F sheath placed in the femoral artery. The two‐step hybrid approach has a further advantage if manipulation of the atrial septum becomes necessary. An atrial septum obstruction is observed in a relatively high percentage of HLHS patients. An intervention is performed before the septum becomes significantly obstructed during the follow‐up. A Rashkind maneuver, static dilatation with or without utilizing a cutting balloon, or stenting of the atrial septum can and should be performed in most patients prior to duct stenting, during the same catheter session. Considering the three parts of the hybrid approach consisting of bPAB, duct stenting, and atrial septum manipulation, we are convinced that the HLHS‐related low cardiac output and associated multiorgan failure can be effectively improved by one or all parts of the hybrid procedure. It is necessary, especially in life‐threatening situations, that the hybrid team is familiar with all three parts of the procedure. The pulmonary run‐off, as a consequence of an unrestricted atrial communication, can be overcome easily by an immediate surgical bPAB. Duct‐dependent low systemic blood flow with associated metabolic acidosis and prostaglandin‐refractory duct obstruction can be efficiently dealt with by immediate percutaneous duct stenting. A hypoxemic HLHS newborn with severe restrictive or absent atrial left–right shunt is treatable by the percutaneous creation of a sufficient atrial communication, if there is no preformed severe lymphangioectasia. In general, an unrestrictive atrial left‐to‐right and duct‐dependent right‐to‐left shunt together with a protected pulmonary circulation are required for a successful comprehensive stage 2 surgery, which is usually performed between the ages of 4–6 months. Appropriate follow‐up monitoring with detailed counseling of the parents is mandatory in order to maintain the fragile interstage 1 period [12]. A combined parents/physician monitoring program can reduce the interstage morbidity and mortality comparable to the follow‐up of Norwood palliation [19]. The range of outcomes following the hybrid approach is comparable to that of a Norwood procedure. The mortality following the Norwood procedure varies from 7% to 39% across centers [12]. For Norwood stage 1, basic elements such as preoperative intubation, CPB times, route of feeding at discharge, and utilization of a home monitoring program exert an enormous influence on the outcome. It can be postulated that similar factors influence the outcomes for the hybrid approach. However, the Norwood surgery per se seems currently more uniform when compared to the technique of the hybrid procedures. Karamlou and colleagues recently evaluated the North American experience with contemporary multicenter hybrid use and institutional/patient factors associated with the hybrid use relative to the Norwood procedure [20]. They reported that currently only a few centers select the hybrid procedure for most infants with HLHS. Institutions with higher hybrid use have a lower HLHS case volume and higher Norwood mortality. Independent of the initial preference, hybrid palliation was preferentially used for higher‐risk patients as defined above. However, based on the two center experiences of Giessen [14] and Columbus [15], hybrid stage 1 can be performed with a mortality rate of less than 2–4% and with an interstage mortality of 5%. The comprehensive stage 2 consisting of bilateral pulmonary artery debanding, ductal stent removal, atrial septectomy, reconstruction of the aortic arch, and bidirectional cavopulmonary anastomosis has become routine and can be performed with a surgical mortality of less than 5%. A major cause of morbidity following surgical palliation of HLHS is left pulmonary artery stenosis or hypoplasia [21], particularly following comprehensive stage 2 [8]. However, stenting of the left pulmonary artery after hybrid, Norwood, or Fontan palliation is safe and effective [8, 21]. Stents can be redilated to match somatic growth. Refinements, such as intraoperative stenting, will likely improve the current surgical techniques [8, 14]. Following the comprehensive stage 2, a Fontan completion can be performed with an expected low mortality. At dedicated centers, an estimated 10‐year survival of 78% can currently be achieved following the hybrid stage 1 approach in an unselected population of neonates [14]. The circumvention of neonatal CPB surgery has not only improved survival [8], but it seems also the patient’s neurocognitive outcome [22]. The constellation of HLHC varies from a Shone complex with mitral, subaortic, aortic valve stenosis and coarctation to that of HLHS with an antegrade ascending aortic flow and duct‐dependent systemic circulation. The management of neonates with a borderline left ventricle continues to be a challenging area in CHD. The borderline left ventricle has been the subject of numerous studies to determine suitable candidates for a biventricular repair in the neonatal period [23–25]. Predictive scores have been developed for postnatal decision‐making for uni‐ or biventricular repair. However, no clear consensus exists on the surgical strategy in neonates with a borderline left ventricle. The Rhodes score [23] focuses on indexed aortic root, mitral valve, and left ventricle dimensions that are most reliable with aortic stenosis. Colan and associates [24] used body surface area and valve z‐scores to determinate the anatomical dimensions. A left ventricular volume greater than 30 mL/m2 and a left ventricular cavity reaching the apex in the four‐chamber view on echocardiography or magnetic resonance imaging are helpful for aiding the decision for biventricular neonatal repair. However, the range from a sufficient left chamber to a genuine hypoplastic left heart without growth potential is extremely variable. Here it is important to emphasize that borderline left ventricular structures are not determined at birth and that postnatal decision‐making has to be based on the cardiac regeneration potential [26]. Typically, in patients with inadequate formation and/or diastolic dysfunction of a subaortic ventricle, there is pulmonary vascular congestion and consequent pulmonary artery disease. Neonates with a similar structural constellation survive because of the persistence of an atrial and ductal communication that may be at the expense of cyanosis, but with adequate systemic oxygen delivery. Growth of borderline left heart structures occurs only under specific circumstances. Required are adequate left ventricular preload, sufficient diastolic blood flow through the cavity of the left chamber, and enough time for fluid forces to promote cardiac growth. Important is a restrictive atrial communication, which diminishes the incidence of pulmonary congestion and allows an adequate left ventricular preload. A calibrated fenestration can best and most precisely be performed by a surgical punched patch, but also by transcatheter techniques [27]. Based on our institutional experience, infants benefit from a 4 mm fenestration, where children and young adults need a communication of 6 to a maximum of 8–10 mm, respectively. In the near future, specifically designed atrial flow regulators with a defined hole between 4 and 10 mm will become available for percutaneous placement (Figure 5.2). A postnatal hybrid procedure can also be combined with techniques to redirect blood flow to the left ventricle, influencing the growth of the cavity (Figure 5.3). Figure 5.2 Computed tomography scan of an atrial flow regulator (AFR) (Occlutech® Atrial Flow Regulator, Occlutech, Helsingborg, Sweden) positioned in an atrial switch baffle of a Senning patient with transposition of the great arteries and failing systemic right ventricle. Considering the cardiac regenerative potential, biventricular reconstruction is best started during fetal life. Colleagues from São Paulo, Brazil, recently reported an exemplary case where a fetal aortic valvuloplasty prevented left ventricular degeneration to an HLHS, and a postnatal hybrid approach allowed biventricular repair when the child was a toddler [28]. Such an ideal therapeutic course underlines the relevance of pathophysiology‐based treatments when cohort studies are missing. Figure 5.3 (A) 7 mm AmplatzerTM
CHAPTER 5
Hybrid Procedures for Congenital Heart Disease
Hybrid Approach for Hypoplastic Left Heart Syndrome with the Objective of Generating a Fontan Circulation
Technical Considerations
Results
Hybrid Approach for Hypoplastic Left Heart Complex with the Objective of Biventricular Repair
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