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Pacing and Defibrillation Use in Pediatric Patients


Permanent cardiac pacemakers and implantable cardioverter defibrillators have been used in children for over half a century. There are several important differences in device usage between children and adults. Children are not only physically smaller than adults, but they also have different underlying cardiac diseases and face a longer lifetime of therapy. Therefore differences exist not only in selection of the optimal pacing system, but also in implantation techniques, programming considerations, and follow-up methods. This chapter will review these issues. With advances in medical and surgical therapy for structural heart disease, longevity is increasing, and patients with congenital heart disease are reaching adulthood. This chapter, although focused on pediatric pacing, can also pertain to adults with congenital heart disease (CHD).

Indications for Permanent Pacemaker Implantation

The most common indication for pacemaker implantation in children is third-degree atrioventricular (AV) block, either congenital or postsurgical. The American College of Cardiology Foundation (ACCF), the American Heart Association (AHA), and the Heart Rhythm Society (HRS) published updated guidelines in 2012 for implanting pacing systems in children, which will be reviewed in the following sections. The recommendations are divided into several classes reflecting the strength (or the absence) of the indication as well as levels of evidence ( Table 19-1 ).

TABLE 19-1
Class of Recommendations and Level of Evidence
Adapted from Epstein AE, DiMarco JP, Ellenbogen KA, et al: 2012 ACCF/AHA/HRS focused update incorporated into the ACCF/AHA/HRS 2008 guidelines for device-based therapy of cardiac rhythm abnormalities: a report of the American College of Cardiology Foundation/American Heart Association Task Force on Practice Guidelines and the Heart Rhythm Society. Circulation 127(3):e283-e352, 2013.
Class of Recommendations
Class Definition
I Evidence and/or general agreement that a given procedure or treatment is beneficial, useful or effective.
IIa Conflicting evidence and/or divergence of opinion that a given procedure or treatment is beneficial, useful or effective. However, the weight of evidence is in favor of usefulness/effectiveness and therefore it is reasonable to perform the given procedure/treatment.
IIb Conflicting evidence and/or divergence of opinion that a given procedure or treatment is beneficial, useful or effective. The weight of evidence is less well established but the given procedure/treatment may be considered.
III Evidence or weight of opinion that a procedure or treatment may be ineffective or potentially harmful.
Level of Evidence
Level Definition
A Data obtained from multiple randomized trials or meta-analyses
B Data derived from a single randomized study or large nonrandomized studies
C Only consensus opinion of experts based on small retrospective studies or registry data

Atrioventricular Node Dysfunction

Congenital Complete Atrioventricular Block

Congenital complete atrioventricular block (CCAVB) is often related to an in utero autoimmune mechanism, with clinical or laboratory evidence of connective tissue disease in the mother. CCAVB is also associated with specific forms of CHD, particularly those involving abnormal ventricular looping, such as levo-transposition of the great arteries ( L -TGA). The age at presentation with heart block in these patients can vary from fetus to adulthood and can occur with or without surgery. Patients who present prenatally with CHD and complete heart block have a higher morbidity and mortality.

For children with structurally normal hearts and CCAVB, the incidence of pacemaker implantation is lower in younger children but increases with age, reaching 75% by age 20 years. The need for permanent pacing results from the development of syncope, ventricular dysfunction, exercise intolerance or increasing ventricular ectopy, often associated with prolongation of the corrected QT interval (QTc). Death is rare in children without structural cardiac disease (only 5% by age 20) but can occur suddenly.

Asymptomatic children with CCAVB and narrow complex ventricular rates >50 beats per minute (bpm) should be evaluated periodically with Holter monitors for assessment of heart rate and ventricular ectopy and with echocardiography for assessment of ventricular function. Exercise testing can be a useful objective measure of the child's exercise capacity as symptoms of exercise intolerance can often be difficult to elicit by history alone. The presence of exercise intolerance or symptoms of dizziness or syncope should be considered an indication for permanent pacemaker placement.

Controversy surrounds the need for pacing in symptom-free older adolescents with heart rates <50 bpm while asleep with normal ventricular function and normal exercise tests. The natural history of CCAVB consists of the progressive decline of ventricular rates over time, with median ventricular rate 60 bpm in the neonatal period, 50 bpm between 6 to 10 years of age, 45 bpm between 16 to 20 years of age, and 38 bpm over 40 years of age. A prospective natural history study of adults with CCAVB showed that 8% of patients had sudden cardiac death, with a considerable proportion of those being their first symptom. Therefore it is reasonable to consider pacemaker implantation in asymptomatic adolescents who are close to their projected adult height. Several studies have demonstrated that pacemaker implantation is associated with both improved long-term survival and prevention of syncopal episodes in asymptomatic patients with CCAVB.

CCAVB can be associated with the development of a dilated cardiomyopathy with or without ventricular pacing and can be as high as 10%. Maternal anti-Ro/La antibodies have been implicated in the pathogenesis of dilated cardiomyopathy in CCAVB. In addition, chronic pacemaker-associated dyssynchrony may result in ventricular dysfunction. Therefore periodic evaluation of ventricular function with echocardiography is warranted after pacemaker implantation. The use of biventricular pacing in this group is discussed later with the indications for cardiac resynchronization therapy in children.

Current ACCF/AHA/HRS recommendations for pacemaker implantation for congenital AV node dysfunction are listed in Table 19-2 .

TABLE 19-2
Current American College of Cardiology Foundation/American Heart Association/Heart Rhythm Society Recommendations for Pacemaker Implantation for Congenital AV Node Dysfunction in Pediatric and Congenital Heart Disease Patients
Data from Epstein AE, DiMarco JP, Ellenbogen KA, et al: 2012 ACCF/AHA/HRS focused update incorporated into the ACCF/AHA/HRS 2008 guidelines for device-based therapy of cardiac rhythm abnormalities: a report of the American College of Cardiology Foundation/American Heart Association Task Force on Practice Guidelines and the Heart Rhythm Society. Circulation 127(3):e283-e352, 2013.
Class I Indications
  • 1.

    Advanced second- or third-degree AV block associated with symptomatic bradycardia, ventricular dysfunction, OR low cardiac output (LOE: C)

  • 2.

    CCAVB with a wide QRS escape rhythm, complex ventricular ectopy, OR ventricular dysfunction (LOE: B)

  • 3.

    CCAVB in infant with ventricular rate <55 bpm or with congenital heart disease and a ventricular rate <70 bpm. (LOE: C)

Class IIa Indications
  • 1.

    CCAVB beyond the first year of life with an average heart rate <50 bpm, abrupt pauses in ventricular rate that are 2-3 times the basic cycle length, OR associated with symptoms because of chronotropic incompetence. (LOE: B)

Class IIb Indications
  • 1.

    CCAVB in asymptomatic children or adolescents with an acceptable rate, a narrow QRS complex, and normal ventricular function. (LOE: B)

Class III Indications
  • 1.

    Permanent pacemaker implantation is not indicated for asymptomatic type I second-degree AV block (LOE: C)

AV, Atrioventricular; CCAVB, congenital complete atrioventricular block; LOE, level of evidence.

Surgically Induced Heart Block

Surgically induced heart block after repair of CHD initially accounted for 30% to 40% of children undergoing pacemaker implantation. Improved understanding of the anatomy of the AV nodal conduction system, as well as refinements in surgical techniques, have led to a significant reduction in the incidence of surgically induced heart block. The overall incidence of surgical heart block after repair of ventricular septal defect, atrioventricular canal defect, and tetralogy of Fallot (TOF) in the United States was approximately 5% from 2000 to 2009 but has been reported to be as low as 1% to 3% at individual major CHD surgical centers.

Surgical heart block is often transient in the immediate postoperative period, secondary to inflammation or temporary physical injury to the conduction system that resolves with time. Patients are routinely supported with external pacing through temporary epicardial pacing wires until consistent AV nodal conduction returns. Approximately 60% to 75% of patients with postoperative heart block will recover AV nodal conduction, and 97% of these patients recover conduction by postoperative day 9. Late AV nodal conduction recovery is also well recognized and can occur as long as a month or even several years after surgery in up to 10% to 20% of patients with postoperative heart block persisting beyond 14 days postoperatively.

A very poor prognosis with mortality rates ranging from 28% to 100% has been established for patients with permanent surgically induced heart block who are left unpaced. Thus postoperative AV nodal conduction block is a class I indication for permanent pacing, and these patients routinely receive permanent pacing systems before discharge from the hospital.

Transient surgical heart block also raises the risk of long-term conduction abnormalities. Studies have demonstrated a small but definite risk of late onset complete heart block and sudden death years or decades after surgery in patients with a history of transient postoperative heart block. In a study by Aziz et al, the risk of late onset complete heart block was 13 times higher in patients with transient complete heart block that recovered ≥7 days after surgery compared with those with recovery within 7 days. In addition, a substantial portion of patients who recover conduction often demonstrate residual conduction abnormalities. A meta-analysis by Krongrad et al demonstrated that 29% of patients who recovered from transient postoperative heart block with a residual bifascicular block experienced either late onset complete heart block or sudden cardiac death. Therefore the degree of residual conduction system injury and timing of conduction recovery likely do carry some prognostic significance in patients with transient postoperative heart block.

The current ACCF/AHA/HRS recommendations for pacemaker implantation for surgically induced heart block are listed in Table 19-3 .

TABLE 19-3
Current American College of Cardiology Foundation/American Heart Association/Heart Rhythm Society Recommendations for Pacemaker Implantation for Surgically Induced Heart Block in Pediatric and Congenital Heart Disease Patients
Data from Epstein AE, DiMarco JP, Ellenbogen KA, et al: 2012 ACCF/AHA/HRS focused update incorporated into the ACCF/AHA/HRS 2008 guidelines for device-based therapy of cardiac rhythm abnormalities: a report of the American College of Cardiology Foundation/American Heart Association Task Force on Practice Guidelines and the Heart Rhythm Society. Circulation 127(3):e283-e352, 2013.
Class I Indications
  • 1.

    Permanent pacemaker implantation is indicated for postoperative advanced second- or third-degree AV block that is not expected to resolve or that persists at least 7 days after cardiac surgery (LOE: B)

Class IIa Indications
  • 1.

    Permanent pacemaker implantation is reasonable for unexplained syncope in the patient with prior congenital heart surgery complicated by transient complete heart block with residual fascicular block after careful evaluation to exclude other causes of syncope (LOE: B)

Class IIb Indications
  • 1.

    Permanent pacemaker implantation may be considered for transient postoperative third-degree AV block that reverts to sinus rhythm with residual bifascicular block (LOE: C)

Class III Indications
Permanent pacemaker implantation is not indicated for:

  • 1.

    transient postoperative AV block with return of normal AV conduction in the otherwise asymptomatic patient (LOE: B)

  • 2.

    asymptomatic bifascicular block with or without first-degree AV block after surgery for congenital heart disease in the absence of prior transient complete AV block (LOE: C)

AV, Atrioventricular; LOE, level of evidence.

Sinus Node Dysfunction

Sinus node dysfunction (SND) is rarely seen in pediatric patients with structurally normal hearts and may be associated with specific channelopathies. Pacemaker implantation is only indicated in the presence of symptoms (such as dizziness or syncope) associated with bradycardia (heart rate <40 bpm or asystole for >3 seconds). In general, correlation of symptoms with bradycardia can be determined by ambulatory electrocardiogram (ECG) monitoring or an implantable loop recorder. Other causes for bradycardia should be excluded, such as apnea, seizures, medication effects, and neurocardiogenic mechanisms.

SND is more commonly seen in pediatric patients following CHD surgery such as the atrial switch operation for TGA. Patients undergoing staged palliation for single ventricle physiology with the Fontan procedure are also prone to developing SND. These patients may develop symptoms or sequelae of SND due to bradycardia or loss of AV synchrony at heart rates that do not produce symptoms in individuals with normal cardiovascular physiology. Atrial contraction contributes as much as 15% to diastolic ventricular filling, the loss of which may have significant hemodynamic effects in patients with single ventricle physiology and/or depressed ventricular function. As such, the indications for pacemaker implantation in these patients need to be based on the correlation of symptoms with relative bradycardia rather than an absolute heart rate criteria.

Intra-atrial reentry tachycardia (IART) has also been associated with SND in patients with CHD (tachy-brady syndrome). The loss of sinus rhythm is an independent risk factor for the subsequent development of IART with substantial morbidity and mortality in these patients. The use of long-term atrial pacing at physiologic rates and atrial antitachycardia pacing (ATP) have been reported as potential treatments for sinus bradycardia and the prevention or termination of recurrent episodes of IART. In other patients, pharmacologic therapy with agents such as sotalol or amiodarone may be effective in controlling IART but also results in symptomatic bradycardia or AV node dysfunction requiring pacemaker placement.

Current ACCF/AHA/HRS recommendations for pacemaker implantation for SND in pediatric patients and patients with CHD are listed in Table 19-4 .

TABLE 19-4
Current American College of Cardiology Foundation/American Heart Association/Heart Rhythm Society Recommendations for Pacemaker Implantation for Sinus Node Dysfunction in Pediatric and Congenital Heart Disease Patients
Data from Epstein AE, DiMarco JP, Ellenbogen KA, et al: 2012 ACCF/AHA/HRS focused update incorporated into the ACCF/AHA/HRS 2008 guidelines for device-based therapy of cardiac rhythm abnormalities: a report of the American College of Cardiology Foundation/American Heart Association Task Force on Practice Guidelines and the Heart Rhythm Society. Circulation 127(3):e283-e352, 2013.
Class I Indications
  • 1.

    Permanent pacemaker implantation is indicated for SND with correlation of symptoms during age-inappropriate bradycardia. The definition of bradycardia varies with the patient's age and expected heart rate (LOE: B)

Class IIa Indications
Permanent pacemaker implantation is reasonable for:

  • 1.

    patients with CHD and sinus bradycardia for the prevention of recurrent episodes of IART; SND may be intrinsic or secondary to antiarrhythmic treatment (LOE: C)

  • 2.

    sinus bradycardia with complex CHD with a resting heart rate less than 40 bpm or pauses in ventricular rate longer than 3 seconds (LOE: C)

  • 3.

    patients with CHD and impaired hemodynamics because of sinus bradycardia or loss of AV synchrony (LOE: C)

Class IIb Indications
  • 1.

    Permanent pacemaker implantation may be considered for asymptomatic sinus bradycardia after biventricular repair of CHD with a resting heart rate less than 40 bpm or pauses in ventricular rate longer than 3 seconds (LOE: C)

Class III Indications
  • 1.

    Permanent pacemaker implantation is not indicated for asymptomatic sinus bradycardia with the longest R-R interval less than 2 seconds and a minimum heart rate more than 40 bpm (LOE: C)

CHD, Congenital heart disease; IART, intra-atrial reentrant tachycardia; LOE, level of evidence; SND, sinus node dysfunction.

Other Indications

Patients with congenital long QT syndrome (LQTS) and recurrent ventricular tachycardia (VT), sinus bradycardia, and/or advanced AV block may also benefit from cardiac pacing in addition to beta blockade. A chronic increase in heart rate can shorten the QT interval, as well as prevent initiation of pause-dependent ventricular arrhythmias. These patients may often require a dual-chamber implantable cardioverter-defibrillator (ICD) to provide both pacing and rescue therapy as pacing alone may reduce the incidence of ventricular arrhythmias, but the long-term survival benefit remains to be determined.

A relatively controversial indication for pacemaker placement is symptomatic hypertrophic cardiomyopathy (HCM) with significant outflow tract obstruction. Although cardiac pacing is not effective in all children with this disorder, both hemodynamic and symptomatic improvements have been observed. Generators used for this indication must allow programming of relatively short AV intervals and rate adaptive AV intervals to maximize the QRS width and degree of ventricular preexcitation. Younger patients with more rapid heart rates and brisk AV node conduction may exhaust the programming parameters of the pacemaker generator making it difficult to maintain ventricular preexcitation with pacing. There are currently no data available to demonstrate that pacing alters the clinical course of the disease or improves survival or long-term quality of life (QOL) in pediatric patients with HCM. Therefore when pacing is employed in this setting, a dual-chamber ICD should be strongly considered.

Indications for Permanent Implantable Cardioverter-Defibrillator Implantation

Early reports have shown a high rate of appropriate shocks in pediatric patients with ICDs, suggesting a potential lifesaving benefit of ICDs in children. The cumulative lifetime risk of sudden cardiac death in high-risk patients and the need for decades of antiarrhythmic therapy make the ICD an important treatment option for pediatric patients and patients with CHD.

The use of ICDs in children, however, is limited by several factors, the most notable being risk stratification of sudden death. Children have a low incidence of sudden cardiac death (SCD), which limits the ability to evaluate risk stratification for primary prevention strategies. The majority of existing studies on ICDs in children are retrospective, containing small patient numbers at single institutions. Prospective randomized controlled trials (RCTs) are lacking, as fewer than 1% of all ICDs are implanted in pediatric patients or patients with CHD, making it difficult to determine which patients are at highest risk and would receive the greatest benefit from ICD placement. Therefore the indications for ICD implantation in pediatric patients and patients with CHD are derived primarily from adult RCTs. With additional experience in the adult population and the development of smaller devices and electrodes, both epicardial and endocardial, the pediatric use of ICDs has increased steadily over the last two decades ( Fig. 19-1 ).

Figure 19-1, Trends in visits involving implantable cardioverter-defibrillator (ICD) implantation based on data from the Kids' Inpatient Database from 1997 to 2006 in the United States.

Primary Prevention

Prospective identification and treatment of patients at risk for SCD are crucial because a very low percentage of children with out-of-hospital sudden cardiac arrests (SCA) are successfully resuscitated and survive to hospital discharge. SCA in pediatric patients and patients with CHD is primarily associated with cardiomyopathies (hypertrophic or dilated), genetic arrhythmia syndromes (such as LQTS), or sequelae from CHD.

Many individuals with HCM are asymptomatic, and the first manifestation of the condition may be SCD. The annual mortality from HCM has been estimated to be as high as 6%. Risk factors for SCD in HCM have been derived from multiple observational studies and registries and include history of a prior SCA, spontaneous sustained or nonsustained VT, family history of SCD, syncope, LV thickness ≥30 mm, and an abnormal blood pressure response to exercise. More recently, the presence of late gadolinium enhancement on cardiac MRI has also been associated with increased mortality in HCM. Studies by Maron et al demonstrated an ~5% per year rate of appropriate ICD discharges in high risk patients with HCM who received primary prevention ICDs. They found that a single risk factor was sufficient justification for placement of a primary prevention ICD, with 35% of patients receiving appropriate discharges having only a single risk factor for SCD.

Risk stratification of patients with LQTS has become increasingly dependent on genetic etiology. Although most patients have an excellent long-term prognosis with effective medical treatment, a subset will be refractory and require ICD implantation. Noncompliance with medical therapy or a strong family history of SCD may be considered as indication for ICD placement.

The marked heterogeneity of defects in patients with CHD precludes generalization of risk stratification for primary prevention of SCD in this population. Nevertheless, almost half of the pediatric patients undergoing ICD implantation have CHD. Unexpected sudden death is reported in 1.2% to 3% of patients per decade after surgical treatment of TOF, with risk factors including ventricular dysfunction, QRS duration, and atrial and ventricular arrhythmias ( Case Study 19-1 ). Patients with TGA or aortic stenosis are also at an increased risk of sudden death with most cases presumed to be due to ventricular arrhythmias associated with ischemia, ventricular dysfunction, or a rapid ventricular response to atrial flutter or fibrillation. These patients must be evaluated on an individual basis, taking into consideration the natural history of their particular CHD and individual arrhythmia history.

Case Study 19-1
Multiple Uses of an Implantable Cardioverter-Defibrillator for Right Heart Failure in Tetralogy of Fallot

History

A 14-year-old girl with a history of tetralogy of Fallot (TOF) underwent initial neonatal Blalock-Taussig (BT) shunt placement followed by complete repair with a ventricular septal defect closure (VSD), pulmonary valvotomy, and takedown of the BT shunt at 3 years of age. She subsequently had a pulmonary valve replacement with a 31-mm Hancock bioprosthesis at 13 years of age due to severe pulmonary valve regurgitation and progressive right ventricular (RV) dilation with RV dysfunction. Following her pulmonary valve replacement, she initially felt better with improved exercise tolerance, but at 15 years old, she presented to the emergency department with progressive exercise intolerance and palpitations. She was admitted to the hospital for further work-up. Initially, she was in sinus rhythm with frequent single premature ventricular contractions (PVCs), but on the first day of admission, she developed ventricular tachycardia (VT) requiring lidocaine and amiodarone boluses and infusions for control.

Medications

The patient was taking furosemide (Lasix) 20 mg twice daily and atenolol 25 mg twice daily for a history of frequent PVCs.

Current Symptoms

The patient had noted palpitations for the last month, but they seemed to increase in frequency within the last 2 days prior to presentation. She also noted significant shortness of breath with just mild physical exertion and could not go up a flight of stairs without significant symptoms.

Physical Examination

  • HR 68 bpm, BP 114/60 mm Hg, RR 24, oxygen saturation 97% on room air

  • Weight 48 kg, height 153 cm

  • Neck veins: not distended

  • Lungs/chest: clear

  • Heart: normal S1 and single S2. 2/6 systolic ejection murmur at the left upper sternal border

  • Abdomen: soft, nontender, nondistended. Mild hepatomegaly with liver edge palpable 1-2 cm below the right costal margin.

  • Extremities: normal

Laboratory Data

  • Hemoglobin: 9.7 g/dL

  • Platelet count: 209 × 10 3 /µL

  • Sodium: 141 mmol/L

  • Potassium: 4.1 mmol/L

  • Magnesium: 2.1 mg/dL

  • Calcium: 9.9 mg/dL

  • Creatinine: 0.6 mg/dL

  • Blood urea nitrogen: 12 mg/dL

Electrocardiogram

Sinus rhythm with a right bundle branch block (RBBB) and a QRS duration of 190 msec ( Fig. E19-1 ).

Figure E19-1, Baseline electrocardiogram with right bundle branch block and QRS duration 190 msec.

Echocardiogram

Dilated right ventricle with moderate RV dysfunction ( Fig. E19-2 ). No pulmonary stenosis or regurgitation. Normal left ventricular (LV) size and function. Mild tricuspid valve regurgitation.

Figure E19-2, Echocardiogram demonstrating right ventricular enlargement.

Cardiac MRI

  • LV end diastolic volume 105 mL/m 2 , LV ejection fraction (LVEF) 62.4%

  • RV end diastolic volume 200 mL/m 2 , RV ejection fraction (RVEF) 24%

Cardiopulmonary Exercise Test

  • V o 2 max 15 mL/kg/min (43% predicted)

  • V o 2 at anaerobic threshold 30% of predicted V o 2 max

  • Peak heart rate: 140 bpm

  • Peak blood pressure: 160/85 mm Hg

Focused Clinical Questions and Discussion Points

Question: What is the appropriate treatment for this patient with TOF and VT?

Discussion: Patients with repaired TOF are known to be at risk for sudden cardiac death due to arrhythmias. Risk factors for sudden death in this population include ventricular dysfunction, QRS duration >180 msec, late age at TOF repair, and history of arrhythmias. 1-3 This patient has significant RV dilation with severe RV dysfunction (RVEF 24%), a QRS duration of 190 msec, and now presents with VT, placing her at high risk for sudden cardiac death. She does not have any residual cardiac lesions, and therefore she meets a class I indication for implantable cardioverter-defibrillator (ICD) placement according to the American College of Cardiology Foundation/American Heart Association/Heart Rhythm Society recommendations for ICD implantation in pediatric and congenital heart disease patients. 4 Antiarrhythmic therapy is also indicated given her history of VT to help minimize her arrhythmia burden. This patient was continued on amiodarone oral therapy.

Question: Are there any treatment options available for her right heart failure?

Discussion: This patient has significant symptoms and exercise limitations due to her right heart failure. This is not uncommon in patients with TOF because they often have electrical and mechanical dyssynchrony with a RBBB, as well as myocardial scar formation after surgical repair. In addition, chronic RV volume and/or pressure overload secondary to pulmonary regurgitation and/or stenosis can further exacerbate RV or even biventricular failure. When isolated RV failure is present with preserved LV function, cardiac resynchronization can be achieved with RV pacing 5-7 RV pacing in the setting of a RBBB can create an activation wavefront that moves in the opposite direction of the spontaneously occurring activation wavefront. With appropriate manipulation of the programmed atrioventricular (AV) interval, the electrical wavefront created from the RV pacing lead can be merged with the wavefront created from intrinsic activation originating from the native left bundle, resulting in narrowing of the QRSd and more synchronous electrical activation. 8 Given that this patient already meets criteria for ICD placement for prevention of sudden death, the ICD can also be used for RV resynchronization with a dual chamber device configuration.

Figure E19-3, Chest radiograph demonstrating placement of the transvenous dual chamber implantable cardioverter defibrillator.

Final Diagnosis

The final diagnosis for this patient is RV failure and ventricular tachycardia.

Plan of Action

The plan for this patient was implantation of a transvenous dual chamber ICD for prevention of sudden cardiac death and RV resynchronization therapy.

Intervention

Under general anesthesia, a transvenous dual chamber ICD was implanted with the generator placed in a prepectoral pocket in the left upper chest (see Fig. E19-3 ). Optimization of the AV interval was performed with electrocardiograms (ECGs) to achieve the narrowest QRS duration with fusion between RV pacing and the patient's native AV nodal conduction ( Fig. E19-4 ).

Figure E19-4, Electrocardiogram with atrial synchronous right ventricular pacing via the implantable cardioverter defibrillator. The optimal programmed atrioventricular interval is 140 msec which gives the narrowest QRS duration of 150 msec.

Outcome

The patient was discharged from the hospital on oral amiodarone therapy after ICD placement. Follow-up cardiac computed tomography (CT) scan 2 months later demonstrated a significant decrease in her RVEDV to 173 mL/m 2 and an increase in her RVEF to 34%. Her symptoms were improved as demonstrated by her repeat cardiopulmonary exercise testing with an improved V o 2 max of 60% predicted. She did not have any significant ventricular arrhythmias, and she has not received any inappropriate or appropriate ICD discharges after nearly 8 years of follow-up.

References

  • 1.

    Silka MJ, Hardy BG, Menashe VD, Morris CD: A population-based prospective evaluation of risk of sudden cardiac death after operation for common congenital heart defects. J Am Coll Cardiol 32:245–251, 1998.

  • 2.

    Gatzoulis MA, Balaji S, Webber SA, et al: Risk factors for arrhythmia and sudden cardiac death late after repair of tetralogy of Fallot: a multicentre study. Lancet 356:975–981, 2000.

  • 3.

    Khairy P, Harris L, Landzberg MJ, et al: Implantable cardioverter-defibrillators in tetralogy of Fallot. Circulation 117:363–370, 2008.

  • 4.

    Epstein AE, DiMarco JP, Ellenbogen KA, et al: 2012 ACCF/AHA/HRS focused update incorporated into the ACCF/AHA/HRS 2008 guidelines for device-based therapy of cardiac rhythm abnormalities: a report of the American College of Cardiology Foundation/American Heart Association Task Force on Practice Guidelines and the Heart Rhythm Society. Circulation 127:e283–e352, 2013.

  • 5.

    Janousek J, Vojtovic P, Hucin B, et al: Resynchronization pacing is a useful adjunct to the management of acute heart failure after surgery for congenital heart defects. Am J Cardiol 88:145–152, 2001.

  • 6.

    Dubin AM, Feinstein JA, Reddy VM, et al: Electrical resynchronization: a novel therapy for the failing right ventricle. Circulation 107:2287–2289, 2003.

  • 7.

    Stephenson EA, Cecchin F, Alexander ME, et al: Relation of right ventricular pacing in tetralogy of Fallot to electrical resynchronization. Am J Cardiol 93:1449–1452, 2004.

  • 8.

    Motonaga KS, Dubin AM: Cardiac resynchronization therapy for pediatric patients with heart failure and congenital heart disease: a reappraisal of results. Circulation 129:1879–1891, 2014.

The multicenter Pediatric Cardiomyopathy Registry reported on 1803 children with dilated cardiomyopathy (DCM) and demonstrated an ~3% rate of sudden death over 5 years which is lower than that seen in adult heart failure patients. Risk factors for SCD were age less than 13 to 14 years old at diagnosis, use of antiarrhythmic therapy within one month of diagnosis, left ventricular (LV) thinning with dilation, and ratio of LV posterior wall thickness to end diastolic dimension. Unfortunately, the data were limited and did not allow for analysis of arrhythmias as a risk factor for SCD, although other small studies have demonstrated a history of arrhythmias as a major cause of morbidity and mortality in children with end-stage heart failure, suggesting potential benefit from ICD implantation as a bridge to orthotopic heart transplantation, particularly given the longer times to donor procurement in younger patients.

Secondary Prevention

Indications for secondary prevention ICD implantation in pediatric patients are similar to those for adults. Data from nonrandomized studies provide support for the Class I recommendation that any pediatric patient or patient with CHD who has been resuscitated from SCA should undergo ICD implantation after a careful evaluation to exclude any potentially reversible causes ( Case Study 19-2 ). Reversible causes of SCA include Wolff-Parkinson-White syndrome, myocarditis, and some cases of drug-induced QT prolongation. Spontaneous sustained VT and unexplained syncope with inducible sustained hypotensive VT in patients with CHD are also considered class I indications for ICD implantation when other reversible hemodynamically significant lesions or arrhythmia issues have been excluded.

Case Study 19-2
Cardiac Arrest in a Pediatric Patient

History

A previously healthy 4-year-old boy presented with sudden cardiac arrest. He was at a park with his family when he ran up a jungle gym to the top of a slide. When he reached the top of the jungle gym, he suddenly stopped and went limp. His mother was able to catch him as he collapsed to the ground. He was unresponsive with irregular breathing, and she could not feel a pulse. She immediately called 911 and began bystander cardiopulmonary resuscitation. Emergency medicine personnel arrived within 10 minutes and an automatic external defibrillator (AED) was placed which detected ventricular fibrillation (VF) ( Fig. E19-5 ). He received a 70 J shock from the AED with return to sinus rhythm and spontaneous circulation. He was then brought to the hospital for further evaluation and management.

Figure E19-5, Rhythm strip recovered from the automatic external defibrillator demonstrating ventricular fibrillation.

Medications

The patient was not taking any medications.

Current Symptoms

The patient had a sudden cardiac arrest due to ventricular fibrillation with successful defibrillation in the field. When he arrived to the hospital, he was awake and alert at his baseline neurological status.

Family History

Maternal and paternal ancestry are from Thailand and China. Consanguinity between the parents is denied. There is no family history of sudden death, arrhythmias, syncope, seizures, or hearing loss.

Physical Examination

  • HR 92 bpm, BP 116/64 mm Hg, RR 18, oxygen saturation 100% on room air

  • Weight 18.7 kg, height 112 cm

  • Neck veins: not distended

  • Lungs/chest: clear

  • Heart: normal S1 and physiologically split S2. No murmurs, rubs, or gallops.

  • Abdomen: soft, nontender, nondistended. No hepatosplenomegaly

  • Extremities: normal

Laboratory Data

  • White blood cell count: 5.9 × 10 3 /µL

  • Hemoglobin: 9.4 g/dL

  • Hematocrit: 27%

  • Platelet count: 205 × 10 3 /µL

  • Sodium: 135 mmol/L

  • Potassium: 3.3 mmol/L

  • Magnesium: 1.8 mg/dL

  • Calcium: 8 mg/dL

  • Creatinine: 0.33 mg/dL

  • Blood urea nitrogen: 6 mg/dL

  • Respiratory viral panel PCR: negative

Electrocardiogram

Sinus rhythm normal intervals and axis ( Fig. E19-6 ). QTc 430 msec. Normal juvenile T wave pattern in V1-V3. Nonspecific T wave change in lead III, otherwise no T wave or ST segment abnormalities.

Figure E19-6, Baseline 12-lead electrocardiogram obtained after resuscitation showing sinus rhythm with normal intervals and axis. QTc 430 msec. Normal juvenile T wave pattern in V1-V3. Nonspecific T wave change in lead III, otherwise no T wave or ST segment abnormalities.

Echocardiogram

Normal intracardiac anatomy and normal biventricular function. No evidence of hypertrophy and no wall motion abnormalities. Normal coronary artery origins.

Cardiac MRI

Normal cardiac anatomy with normal biventricular size and function. (right ventricular end diastolic volume [RVEDV] 86 mL/m 2 , right ventricular ejection fraction [RVEF] 57%, left ventricular end diastolic volume [LVEDV] 68 mL/m 2 , left ventricular ejection fraction [LVEF] 66%). No delayed enhancement. No focal wall motion abnormalities. Normal coronary arteries.

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