293CHAPTER 30 Diagnostic and Therapeutic Cardiac Catheterization time of the initial pericardiocentesis 13 After placement, the peri cardial drain will remain until drainage decreases to a safe level[.]
CHAPTER 30 Diagnostic and Therapeutic Cardiac Catheterization time of the initial pericardiocentesis.13 After placement, the pericardial drain will remain until drainage decreases to a safe level and there is no evidence of reaccumulation of fluid Atrial Septostomy Balloon atrial septostomy (BAS) was first used in cyanotic newborns with transposition of the great arteries (TGA) to facilitate mixing of systemic and pulmonary venous return at the atrial level, leading to improved systemic oxygen saturations The survival of patients with certain types of congenital heart disease is dependent on minimal restriction to the communication between the right and left atria Therefore indications for BAS have expanded since its initial use in patients with TGA.14 The presence of an unrestrictive atrial shunt may also be needed to decompress the left atrium in patients with left-sided obstructive lesions such as hypoplastic left heart syndrome (HLHS) or left ventricular failure (with left atrial hypertension) requiring extracorporeal membrane oxygenation (ECMO) support Atrial septostomy may also be required to decompress the right side of the heart and augment cardiac output in patients with right ventricular failure in the postoperative setting or due to pulmonary vascular disease BAS is rarely required in infants with tricuspid or pulmonary atresia in order to augment cardiac output due to a restrictive foramen ovale A standard Rashkind BAS can be performed at the patient’s bedside with echocardiographic guidance in urgent cases15 (Fig 30.2) However, fluoroscopic guidance in the catheterization lab is preferred in patients with complex anatomy Standard Rashkind septostomy is usually performed via the femoral or umbilical vein A septostomy balloon catheter is advanced across the atrial defect from the right atrium to left atrium under echocardiographic and/or fluoroscopic guidance The balloon is then gently inflated in the left atrium and rapidly jerked back to the right atrium to tear the septum primum Although initial reports suggested that BAS may be associated with an increased risk for embolic neurologic injury,16 subsequent analyses have refuted these findings BAS prior to the arterial switch operation has been associated with reduced postoperative morbidity and mortality.17,18 Older pediatric patients and newborns with HLHS in need of a septostomy often have a more thickened atrial septum Techniques other than the Rashkind septostomy are often required Septostomy Balloon RA LA • Fig 30.2 Echocardiography-guided balloon atrial septostomy From the subcostal view, the septostomy balloon is easily seen as it inflates in the left atrium (LA) RA, Right atrium 293 for these patients, such as blade septostomy, cutting balloon dilation, or stenting of the atrial septum In some situations, transseptal puncture with a Brockenbrough needle or radiofrequency perforation is required to create a hole, followed by an atrial septoplasty using the aforementioned techniques Due to the urgency of septostomy in newborns with HLHS, a bedside hybrid approach with sternotomy and per-atrial approach may be required.19 Pulmonary Balloon Valvuloplasty Pulmonary balloon valvuloplasty was first performed in 198220 and remains the treatment of choice for valvar pulmonary stenosis Congenital pulmonary valve stenosis may present as a murmur heard in the newborn period If the obstruction is mild, intervention with balloon dilation can be deferred Newborns with critical pulmonary valve stenosis or pulmonary valve atresia have severe restriction or absence of antegrade flow across the right ventricular outflow; as a result, they have ductus arteriosus-dependent pulmonary blood flow requiring prostaglandin E1 (PGE1) infusion to maintain ductal patency There is typically some degree of cyanosis due to right-to-left shunt across the atrial septum Rarely, there can be signs of right heart failure if the atrial septal communication is restrictive There may be some degree of tricuspid valve hypoplasia and/or hypoplasia of the right ventricle Class I indications for pulmonary balloon valvuloplasty include ductal dependence (critical pulmonary valve stenosis) and/or a peak-topeak catheter gradient or echocardiographic peak instantaneous gradient of more than 40 mm Hg or clinically significant pulmonary valvar obstruction in the presence of right ventricular dysfunction dysfunction.7 When there is reduced transpulmonary valve flow due to right ventricular dysfunction or elevated pulmonary vascular resistance, Doppler gradients by echocardiogram are less reliable for evaluating the severity of obstruction A balloon pulmonary valvuloplasty is typically performed from a femoral venous approach A balloon catheter is passed over a guidewire antegrade across the pulmonary valve, and balloon dilation is typically performed with a balloon that is 120% the size of the pulmonary valve annulus, but can be repeated with a balloon up to 140% of the annulus diameter if the initial result is inadequate (Fig 30.3).21 When there is membranous atresia of the pulmonary valve, wire or radiofrequency perforation of the valve plate is required to cross the valve Acute complications from balloon valvuloplasty are rare Heart block and ventricular ectopy may occur with wire manipulation in the right ventricle but are usually transient Some degree of pulmonary insufficiency is typically seen after valvuloplasty but is usually well tolerated acutely Severe infundibular stenosis can occur immediately after valvuloplasty and is sometimes referred to as a suicide right ventricle when the infundibulum completely collapses upon itself This is not typically a problem when the ductus arteriosus is patent, but when there is no ductus, this can severely impair pulmonary blood flow Management includes fluid boluses to augment right ventricular filling with or without b-blockers, which decrease contractility and reduce severity of infundibular obstruction Antegrade flow across the pulmonary valve may not increase significantly after balloon dilation until right ventricular compliance improves In that case, continuation of PGE1 infusion to maintain patency of the ductus arteriosus for several days following balloon dilation may be necessary For some patients, longer-term supplemental pulmonary blood flow is necessary, which can be achieved with a PDA stent or surgical aortopulmonary shunt 294 S E C T I O N I V Pediatric Critical Care: Cardiovascular • Fig 30.3 Pulmonary valvuloplasty in a newborn with severe pulmonary valve stenosis Lateral view with balloon catheter centered across a stenotic pulmonary valve As the balloon is inflated, a “waist” representing the stenotic valve is seen Balloon Aortic Valvuloplasty Newborns with critical valvar aortic stenosis (AS) have ductaldependent systemic circulation These patients will develop signs of poor cardiac output, including hypotension and acidosis as the ductus arteriosus closes They require resuscitation with PGE1 to restore ductal patency and may require mechanical ventilation and inotropic support to achieve stabilization before an intervention is performed Balloon aortic valvuloplasty in the catheterization lab is the preferred intervention at most institutions (Fig 30.4),22 although surgical repair of the valve or neonatal Ross procedure are acceptable alternatives and may be preferred at some institutions.23 According to guidelines from the American Heart Association,7 class I indications for aortic valvuloplasty include (1) newborns with isolated ductaldependent critical valvar AS or isolated valvar AS in the presence of depressed left ventricular systolic function regardless of valve gradient; (2) resting peak systolic gradient across the valve of 50 mm Hg or more by catheterization measurement; and (3) children with resting gradient of 40 mm Hg or greater in the presence of symptoms of angina or ST changes on exercise testing.7 In practice, findings from echocardiography are typically used to determine whether intervention might be indicated The echocardiogram mean Doppler gradient typically correlates best with the peak-to-peak gradient measured in the catheterization laboratory At catheterization, a guidewire is passed either retrograde (via femoral/carotid artery) or antegrade (via femoral or umbilical vein) across the aortic valve A balloon catheter is passed over the wire, and dilations are performed up to 90% to 100% of the aortic valve annulus dimension The pressure gradient across the aortic valve is measured after each dilation, and an ascending aortogram is obtained to evaluate aortic valve regurgitation Successful balloon aortic valvuloplasty reduces the peak systolic gradient to less than 30 mm Hg, ideally with minimal insufficiency • Fig 30.4 Aortic valvuloplasty in a newborn with critical aortic stenosis Anteroposterior view with antegrade catheter course from the femoral vein The balloon, also with the “waist” apparent, is seen being inflated across the aortic valve Morbidity and mortality from aortic valvuloplasty are higher in neonates with critical AS than when performed in older children, but outcomes have improved with better technology and equipment as well as proper selection of patients better suited for singleventricle versus biventricular circulation Early reports indicated a procedure-related mortality up to 4.8%; however, a recent multicenter study from the C3PO registry reported no procedurerelated mortality.24,25 The most common and feared complication with aortic valvuloplasty is creating more than moderate aortic insufficiency, which has been reported in 14% to 22%24,26 of cases and is sometimes unavoidable due to the morphology of the aortic valve A unicommissural aortic valve and balloon-to-annulus ratio of greater than 0.9 have been associated with higher risk of insufficiency, but other studies have failed to show any definitive risk factors.27,28 Other procedural complications include possible mitral valve damage, ventricular fibrillation, and an acute low cardiac output state secondary to coronary ischemia in patients with a hypertrophied ventricle Balloon Dilation of Pulmonary Arteries PA balloon and stent angioplasty to relieve stenosis is a common procedure performed in the pediatric catheterization laboratory.29 PA stenosis may be congenital or acquired It is most often encountered postoperatively after repair of tetralogy of Fallot, truncus arteriosus, TGA, and other congenital heart lesions Primary stenosis is most commonly seen in syndromes such as Williams syndrome and Alagille syndrome Stenosis of the PAs may involve the main PA, proximal branch PAs, or multiple distal branches Discrete stenotic lesions with normal-size vessels distal to the stenosis respond best to intervention as opposed to diffusely hypoplastic PAs, as is often seen in both Williams and Alagille syndromes Balloon angioplasty is sometimes preferred to stent placement in younger children to avoid the need for serial stent CHAPTER 30 Diagnostic and Therapeutic Cardiac Catheterization dilations and due to the larger sheath sizes required for stent placement However, balloon angioplasty is rarely able to relieve obstruction to the same extent that stents can.7 Therefore stents are often preferred in older patients When balloon angioplasty is suboptimally effective and stent implantation must be considered in younger patients, sheath size limitations sometimes dictate the use of lower-profile premounted coronary, biliary, or peripheral vascular stents A major drawback to many of these stents is that they cannot be dilated to adult dimensions and must either be fractured (depending on the stent, this may or may not be feasible) or surgically removed when the patient has outgrown the stent From a critical care perspective, PA stenosis may lead to an increased right ventricular systolic pressure or, in the case of unilateral branch PA stenosis, flow discrepancy to the lungs with increased flow to the unaffected lung This is a particular concern in patients in whom right ventricular hypertension might be poorly tolerated (e.g., after tetralogy of Fallot or truncus repair) or in whom unobstructed pulmonary blood flow is essential (e.g., single-ventricle palliation) Noninvasive diagnosis of PA stenosis in these settings is usually based on the presence of a Dopplerdetected pressure gradient or evidence of narrowing by echocardiography Other features—including evidence of right ventricular hypertension (more than one-half to two-thirds of systemic right ventricular pressures), significant flow discrepancy (discrepancy of 35%/65% or worse) in branch PA, or obstruction identified by computed tomography (CT) angiography or cardiac MRI—may provide the impetus for proceeding to the cardiac catheterization laboratory Intraoperative hybrid branch PA stenting can be performed under direct vision during open heart surgery and may be preferred over percutaneous stent placement in the following situations: (1) the need for a concomitant surgical procedure, such as conduit replacement, VSD closure, and so on; (2) limited vascular access related to vascular occlusions; (3) low patient weight and/or age; and (4) as a rescue procedure for complications of percutaneous stent placement Complications after PA interventions are more commonly seen in younger patients and in the immediate postoperative setting Complications may include vessel dissection causing worse obstruction, vessel rupture causing bleeding into the chest, stent embolization or migration, stent obstruction of branches that must be crossed, and reperfusion injury.5 General anesthesia and controlled ventilation are recommended before intervention in this at-risk group of patients PA disruption is signaled by local extravasation of contrast in the lung parenchyma, sudden hemodynamic deterioration from cardiac tamponade, acute hemothorax, or sudden onset of hemoptysis.30 The tear in the PA may be either a confined or controlled tear or unconfined, resulting in hemodynamic collapse and the possible need for immediate surgical intervention In the presence of substantial hemoptysis, immediate endotracheal intubation is indicated for airway control and ventilation Hypertension and further airway stimulation should be avoided, the addition of positive end-expiratory pressure (PEEP) may be useful, and instillation of epinephrine via the endotracheal tube may help reduce immediate bleeding by causing vasoconstriction of mucosal vessels An immediate intervention by the interventionalist to tamponade the disrupted branch PA with a balloon catheter may be lifesaving Permanent occlusion of the vessel with a coil or covered stent may be necessary to prevent further hemorrhage Reperfusion injury following intervention to stenotic segmental PA branches results in transient unilateral or unilobar pulmonary edema This finding is related to sudden large increases in 295 pulmonary blood flow and distal PA pressure after dilation in a previously underperfused pulmonary vascular bed Pulmonary edema usually occurs immediately following balloon dilation but can be delayed for up to 24 hours and may result in frank blood or blood-tinged secretions in the airway Patients with this complication often must be managed with mechanical ventilation and increased PEEP until the edema and bloody secretions improve Occlusion Device Insertion Although device closures of intra- or extracardiac defects are commonly performed interventions in the catheterization laboratory, they are typically performed electively and are relatively less common procedures in pediatric intensive care patients Nonetheless, there are select scenarios for which device closure might be considered in critically ill patients, including: • When a persistent left-to-right shunt is contributing to right ventricular (e.g., ASD) or left ventricular (e.g., PDA or VSD) volume overload that impairs a patient’s ability to recover These lesions are often less well tolerated in critically ill patients and should be considered as potential contributors to delayed convalescence in the postoperative setting or in patients with systemic illness In particular, left-to-right shunts from a VSD or PDA can significantly impact a patient’s ability to wean from mechanical ventilatory or circulatory support.7 • Occasionally right-to-left shunts across an ASD or via venovenous collateral vessels can cause cyanosis The most common intensive care scenario occurs after stage II single-ventricle palliation when patients will sometimes develop desaturating venous collaterals When these contribute to clinically significant cyanosis, transcatheter coil or device occlusion may be indicated Less commonly, right-to-left shunting at an ASD may be maladaptive—for example, in patients with right ventricular diastolic dysfunction—and may warrant intervention to reduce risk of cyanosis or paradoxical embolism and cerebral vascular accident In these scenarios, test occlusion with hemodynamic assessment is typically warranted to ensure that permanent occlusion will be well tolerated.7 A number of different coils, devices, and even embolization particles can be used to occlude cardiac or vascular defects Specialized devices exist for ASD, VSD, or PDA closure while more generic vascular plugs and coils can be used to close any number of vascular defects Safety of these procedures depends on the size of the defect as well as size and stability of the patient ASDs are typically closed electively in patients at to years of age (12–15 kg) but can be closed in smaller children if needed Most commonly, earlier ASD closure is considered in infants with a history of prematurity-related bronchopulmonary dysplasia in which the intracardiac shunt is felt to be contributing to the patient’s underlying lung disease.31,32 PDAs with morphology amenable to device closure can typically be safely closed in patients greater than kg However, new devices are now approved for use in much smaller patients33 and interventionalists are increasingly performing PDA closure in smaller patients when the defect is hemodynamically significant Transcatheter PDA occlusion has been reported in children as small as 650 g.34 VSDs are the most challenging intracardiac defects for transcatheter closure The perimembranous VSD is the most common type of VSD but sits in close proximity to the atrioventricular nodal tissue; device closure has been complicated by device-related heart block Consequently, surgical intervention remains the preferred approach to closure of these defects at most institutions Muscular VSDs are 296 S E C T I O N I V Pediatric Critical Care: Cardiovascular more often amenable to device closure In smaller children, hybrid approaches can facilitate muscular VSD closure by overcoming some of the technical challenges of device delivery.35 Native and Recurrent Coarctation of the Aorta Native coarctation of the aorta can present at any age and with a wide spectrum of severity In the critical care setting, coarctation is most commonly seen in neonates, who often present with cardiovascular collapse as the ductus closes In this scenario, there is no doubt that relief of the aortic obstruction is required, but most centers prefer surgical coarctation repair to transcatheter approaches.36–39 Both surgical repair and balloon dilation of aortic coarctation are highly successful at acutely relieving the blood pressure gradient and heart failure produced by severe obstruction However, balloon dilation of native coarctation is associated with a relatively high rate of early (within 6–12 months) recurrence, and there is an associated long-term risk of aneurysm formation along the segment of the aorta that is dilated.40,41 Despite these concerns, the American Heart Association guidelines state that transcatheter balloon or stent angioplasty may be reasonable to consider in neonates who are deemed to be too critically ill or high risk for surgical intervention.7 In older patients (.8 years old) presenting with coarctation of the aorta and a peak systolic gradient greater than 20 mm Hg, stent placement is often the treatment of choice (Fig 30.5) Bare metal stents allow for relief of obstruction without the need to overdilate the aorta, thereby decreasing the risk of aortic wall injury, including the long-term risk of aneurysm formation.42,43 Covered stents are increasingly being used to treat severe coarctations when there is increased risk of aortic wall injury and to cover aneurysms or other aortic wall injuries created by previous catheter-based or surgical management Stents are less preferable in infants and neonates because they will require frequent dilation to accommodate for growth and because available stents that can be safely delivered in smaller children typically cannot be dilated to adult dimensions (.18–21 mm).39 A B In contrast to native coarctation, transcatheter approaches are the treatment of choice for recurrent coarctation In these patients, the risk of aneurysm formation is lower, presumably because the segment requiring dilation is protected by scar tissue A peak systolic catheter gradient more than 20 mm Hg is considered a class I indication for transcatheter balloon angioplasty in a patient with recoarctation, assuming favorable angiographic appearance.7 Recurrent coarctation is a particular concern in single-ventricle patients after Norwood arch reconstruction because arch obstruction is poorly tolerated by the tenuous single-ventricle circulation In the landmark Single Ventricle Reconstruction trial, recurrent coarctation occurred in 18% of survivors within the first year of life.44 Median age at reintervention was 4.9 months, with most interventions occurring at the time of stage II cardiac catheterization In these patients, Doppler echocardiography may underestimate severity of obstruction For this reason, cardiac catheterization should be considered in any single-ventricle patient with a history of arch repair and decreased systemic ventricular function and/or worsening tricuspid valve insufficiency to assess for recoarctation Due to the significant adverse consequences of arch obstruction, many interventionalists advocate for more aggressive thresholds for intervention in single-ventricle patients A catheter gradient more than 10 mm Hg is often considered as a reasonable threshold; lower gradients may also warrant intervention when systolic function is decreased or when there is angiographic evidence of significant obstruction Ductal Stenting Infants with cyanotic cardiac lesions that include severe right ventricular outflow tract obstruction, severe pulmonary stenosis, or pulmonary atresia often have ductal-dependent pulmonary blood flow Conventionally, patients with ductal-dependent pulmonary blood flow require a surgical systemic-to-pulmonary shunt (i.e., modified Blalock-Taussig shunt) to establish a source of stable pulmonary blood flow prior to future interventions In the early 1990s, cardiac interventionalists first described stenting C • Fig 30.5 Stent angioplasty in a patient with native aortic coarctation (A) Angiogram in the lateral view of the transverse aortic arch and proximal descending aorta demonstrating a moderate discrete coarctation distal to the left subclavian artery (B) Stable position of the stent across the coarctation with improvement in vessel caliber (C) Relief of coarctation without evidence of vessel injury or contrast extravasation CHAPTER 30 Diagnostic and Therapeutic Cardiac Catheterization A B 297 C • Fig 30.6 Patent ductus arteriosus stent placement (A) Three-dimensional model of the patent ductus arteriosus assists with preprocedural planning and anatomic definition (B) Angiogram in the lateral view demonstrating a highly tortuous reverse-angle patent ductus arteriosus accessed via the axillary artery (C) Successful stent placement within the ductus arteriosus resulting in relative straightening of the ductal anatomy of the ductus arteriosus to maintain ductal patency without a PGE1 infusion.45 Since that time, ductal stenting has been increasingly used as an alternative to a surgical shunt in infants with ductal-dependent pulmonary blood flow and confluent PAs In 2018, two large studies in the United Kingdom and United States used registries to compare outcomes between surgical modified Blalock-Taussig shunt and ductal stenting in this patient population.46,47 Bentham et al found a reduced risk of death prior to surgical repair in patients receiving a ductal stent, but with an increased risk of reintervention.47 Alternatively, Glatz et al found equivalent hazards for death or unplanned reintervention between the surgical and catheterization groups.46 However, the study did note larger and more symmetric branch PA size at last follow-up prior to surgical repair in patients with ductal stent placement From a technical perspective, patients with antegrade pulmonary blood flow can have ductal stents placed through sheaths in the femoral vein More commonly, however, a retrograde arterial approach is required In patients with usual ductal anatomy, access from the femoral artery is feasible Due to the orientation of the ductus and the aorta, patients with a reverse-oriented ductus arteriosus often require carotid or axillary artery access for procedural success Multimodality imaging, including echocardiogram and CT angiography with threedimensional reconstruction, can assist preprocedural planning (Fig 30.6 A and B) Depending on the size of the ductus arteriosus, the interventionalist may request discontinuation of the prostaglandin infusion several hours prior to the procedure to allow the ductus to contract and improve stent stability during placement In patients without any antegrade pulmonary blood flow, this may result in more hemodynamic instability and increase procedural risks Typically, premounted balloon expandable coronary stents are placed to cover the entire ductus (Fig 30.6C) Multiple telescoping stents may be required to avoid eventual stenosis as the ductus contracts If stenosis develops, a repeat catheterization procedure is required, as restarting a prostaglandin infusion may result in stent embolization Patients often require postprocedural monitoring in a critical care setting, but tend to have shorter ICU lengths of stay compared with patients with surgical shunts.47 Hybrid Stage I Palliation for Hypoplastic Left Heart Syndrome First described in 1993, the hybrid approach to stage I palliation in HLHS included a combination of initial surgical PA banding and subsequent percutaneous ductal stenting.48 Successful stage I palliation requires unobstructed systemic blood flow, restriction of pulmonary blood flow, and an unrestrictive ASD The goal of the hybrid procedure is to achieve successful stage I palliation without cardiopulmonary bypass From the American Heart Association scientific statement, the hybrid procedure is an indicated alternative approach in high-risk surgical candidates with HLHS/complex single-ventricle anatomy or as a bridge to transplantation (class IIb).7 In 2005, Galantowicz and Cheatham modified the approach with both bilateral PA banding and ductal stent placement performed through a median sternotomy This is followed by atrial septal intervention as a separate catheterization via the femoral venous approach.49 Nationally, there is institutional variability in both the technical aspects and patient selection for the hybrid stage I procedure—a few institutions now use the hybrid as the primary approach to all neonates with HLHS.50 The procedure has a significant learning curve, and complications remain an issue Given the risk of delayed and recurrent atrial restriction, reintervention to the atrial septum may be required after the hybrid procedure.45 Retrograde aortic arch obstruction is an important consideration and has been considered a contraindication to proceeding with the hybrid approach.7 Compared to a conventional surgical stage I palliation, the hybrid approach may carry an increased risk of necrotizing enterocolitis.51 For patients who continue through the staged palliation procedures, a comprehensive stage II procedure is performed between to months of age and includes removal of PA bands and the ductal stent; Norwood-type aortic arch reconstruction; atrial septectomy; and cavopulmonary anastomosis Transcatheter Pulmonary Valve Replacement The first transcatheter pulmonary valve implantation was performed in 2000 by Bonhoeffer et al.52 and transcatheter pulmonary valve replacement (TPVR) is now widely used throughout ... they cannot be dilated to adult dimensions and must either be fractured (depending on the stent, this may or may not be feasible) or surgically removed when the patient has outgrown the stent From... unilateral branch PA stenosis, flow discrepancy to the lungs with increased flow to the unaffected lung This is a particular concern in patients in whom right ventricular hypertension might be poorly... Other features—including evidence of right ventricular hypertension (more than one-half to two-thirds of systemic right ventricular pressures), significant flow discrepancy (discrepancy of 35%/65%