Pediatric Pacemaker Implantation

Pacemaker therapy in children involves unique issues regarding patient size, growth, development, and the possible presence of congenital heart disease; accordingly, this topic reviews aspects of pediatric pacemaker implantation and follow-up, with particular attention to the difficulties encountered with smaller children and patients with coexistent congenital heart defects.[1, 2, 3, 4, 5]

Transvenous pacemaker implantation in young patients was previously limited by generator size and lead diameter in comparison to vascular dimensions and capacitance. Historically, epicardial pacing was more common in children. As technology has improved, generators and leads have become smaller and more advanced, allowing transvenous pacing systems in children; pacemaker therapy is now possible in neonates.

Pediatric pacemaker implantation is performed primarily to treat abnormalities of sinoatrial (SA) node (ie, sinus node) or atrioventricular (AV) node function that lead to an insufficient heart rate. In addition, pacemakers are used (although less commonly) for other disorders, such as congenital long QT syndrome and cardiomyopathy. A specialized type of pacemaker therapy known as cardiac resynchronization therapy (CRT) is used adjunctively in pediatric patients with heart failure.[6, 7]  In addition, although relatively rare and decreasing in incidence, acute permanent pacemaker implantation after heart transplanation in children can occur and is associated with biatrial anastomosis, antiarrhythmic use, and older donor age; there is also an increased risk for posttransplant infection and dialysis but survival does not appear to be adversely affected by permanent pacemaker implantation.[8]

Chronotropic incompetence is the term used to describe the inability of the SA node to increase heart rate adequately as needed for the degree of activity. Sinus node dysfunction is a related term that describes an inappropriately low heart rate (either sinus or nonsinus) due to abnormal activity of the normal SA node.

AV blocks occur in three degrees of severity, as follows:

• First degree: The impulse is conducted through the AV node, albeit delayed.
• Second degree: Not all impulses are conducted through the AV node.
• Third degree: AV block is complete, and none of the impulses are conducted across the AV node.

Causes of SA or AV node dysfunction can be divided into two distinct categories: congenital and acquired. Congenital causes include congenital AV block and congenital SA node dysfunction, which is notably less common. Congenital heart block is often due to autoantibody production from maternal systemic lupus erythematosus (SLE).[9] Also, congenital heart block may be associated with congenital heart disease, such as L-transposition of the great arteries.

Acquired forms of heart block or SA node dysfunction are caused by infection or injury, whereas other forms are idiopathic. Infections include viral myocarditis and Lyme disease. Surgical repair of congenital heart disease is the predominant cause of nodal or conduction tissue injury.

Permanent pacing in children is a successful procedure that results in physiologic heart rates. Pacing also allows the pediatric patient to return to normal activity and lifestyle. The prognosis is excellent, because modern generation pacing systems allow physiologic atrial-synchronous, rate-responsive pacing in the vast majority of patients, even small infants and children with congenital heart disease.

Indications

Although indications for pacing in children differ from those in adults, both include abnormalities in sinoatrial (SA) node and atrioventricular (AV) node function. The American Heart Association (AHA) and the American College of Cardiology (ACC) publishes guidelines and updates for implanting pacing systems in children.[10, 11, 12, 13]  The AHA’s scientific statements on pacing in children and adolescents divide the recommendations for pacemaker implantation in children into several classes reflecting the strength (or the absence) of the indication.[13]  These indications continue to evolve as the definition of the natural history of the disease improves and pacemaker technology and diagnostic methods advance.

Class I signifies that pacing is indicated and includes the following[13] :

• Advanced second- or third-degree AV block with symptomatic bradycardia, ventricular dysfunction, or low cardiac output
• SA node dysfunction with symptoms during age-inappropriate bradycardia (The definition varies with the patient’s age and expected heart rate.)
• Postoperative advanced second- or third-degree AV block that is not expected to resolve or that persists for at least 7 days
• Congenital third-degree AV block with a wide QRS escape rhythm, complex ventricular ectopy, or ventricular dysfunction
• Congenital third-degree AV block in an infant with a heart rate lower than 55 beats/min or with congenital heart disease and a heart rate below 70 beats/min

Class IIa signifies that there is general agreement that pacing is indicated and includes the following[13] :

• Prevention of recurrent episodes of intra-atrial reentrant tachycardia in patients with congenital heart disease and sinus bradycardia (Sinus node dysfunction may intrinsic or due to antiarrhythmic therapy.)
• Congenital third-degree AV block beyond the first year of life, with an average heart rate lower than 50 beats/min, abrupt pauses in ventricular rate that are 2-3 times the basic cycle length, or symptoms due to chronotropic incompetence
• Sinus bradycardia in a child with complex heart disease, with a resting heart rate lower than 40 beats/min or pauses in ventricular rate exceeding 3 seconds
• Patients with congenital heart disease and impaired hemodynamics due to sinus bradycardia or loss of AV synchrony
• Unexplained syncope in a patient with a prior congenital heart surgery complicated by transient complete heart block with residual fascicular block

Class IIb signifies that although there is no consensus, implantation may reasonably be considered for the following[13] :

• Transient postoperative third-degree AV block that reverts to sinus rhythm with residual bifascicular block
• Congenital third-degree AV block in an asymptomatic infant, child, or young adult with an acceptable rate and function and narrow QRS
• Asymptomatic sinus bradycardia following biventricular repair of congenital heart disease, with a heart rate lower than 40 beats/min or pauses in ventricular rate exceeding 3 seconds

Contraindications

Class III signifies that pacing is not indicated and includes the following[13] :

• Transient postoperative AV block with return of normal AV conduction in an otherwise asymptomatic patient
• Asymptomatic postoperative bifascicular block with or without first-degree AV block
• Asymptomatic type I second-degree AV block
• Asymptomatic sinus bradycardia with the longest relative risk interval shorter than 3 seconds and a minimum heart rate higher than 40 beats/min

In addition, expected survival of less than 6 months is a relative contraindication to permanent pacing therapy for patients who are terminally ill. Patients who fully regain normal conduction after transient postoperative heart block typically do not need to receive a permanent pacemaker.

Best practices

Congenital (or acquired) structural heart disease presents additional issues for pacemaker implantation in children. These patients may have a more critical reliance on adequate hemodynamic status. Optimal hemodynamic performance is achieved with atrial synchronous pacing.

Maintaining atrioventricular (AV) synchrony in this population may be more important than in children who have structurally normal hearts. For example, in a newborn with congenital complete heart block but a structurally normal heart, an epicardial ventricular pacing system initially suffices to meet hemodynamic needs. In contrast, a newborn with significant structural heart disease, heart block, and congestive heart failure may benefit more from a dual-chamber system to obtain AV synchrony and meet hemodynamic needs.

In general, the transvenous route is a reasonable approach for children weighing at least 10-15 kg, although successful transvenous pacing is reported in neonates without complications. Physical considerations that may preclude transvenous pacing include intracardiac shunting, low-flow states, and anatomic barriers (eg, mechanical tricuspid valves).

Transvenous lead placement in congenital heart patients often requires nonstandard positioning because of variations in venous and intracardiac anatomy. The atrial appendage is sometimes amputated with cannulation for cardiac bypass, and atrial anatomy is often different. The use of active-fixation leads allows easier sampling of nonstandard pacing sites and easier removal.

In specific operations for congenital heart disease, such as the Fontan procedure, the right medial wall is often viable; in postoperative Mustard and Senning procedures, superior aspects of the systemic venous atrium are optimal. High-output pacing is imperative testing for diaphragmatic or phrenic nerve stimulation, particularly in lateral pacing sites. The active pacing lead tip may be used for mapping of optimal tissue implant sites.

Although anticoagulation is not universally recommended, it may help patients who have leads implanted in low-flow chambers. It is also important to consider the possibility of future rhythm complications in children who have undergone palliative repairs. For example, a child who develops heart block after a Fontan procedure needs ventricular pacing. These children are also at risk for sinoatrial (SA) node dysfunction; thus, placing an epicardial atrial pacing lead concurrent with placing a ventricular lead may prove beneficial in the future.

Certain populations are at greater risk for the development of atrial tachycardia; therefore, pacemaker type is important. A patient with SA node dysfunction who is at risk for atrial tachycardia should probably have a generator placed that also allows antitachycardia pacing, either manual or automatic. There are automatic atrial antitachycardia pacemakers that have been shown to be effective in pediatric congenital heart disease patients.

For those patients with heart failure, cardiac resynchronization therapy (CRT) may be used in conjunction with medical therapy to improve cardiac function and quality of life. Although indications for CRT in pediatrics remain controversial, important anatomic considerations are noted. CRT requires two strategically placed leads in the ventricles (typically one in the right ventricle and one in the left ventricle) that pace two ventricular areas to synchronize ventricular contraction. A transvenous approach requires a patent coronary venous system that is accessed via the coronary sinus. Typically, the left ventricular lead is placed through the coronary sinus and then carefully maneuvered into one of the tributary cardiac veins of the left ventricle. Patients with congenital heart disease often have distorted coronary venous anatomy; in these patients, CRT may require an epicardial approach. A hybrid approach may be considered in select patients, such as dextro-transposition of the great arteries (d-TGA) following Mustard or Senning repair where transvenous leads are placed in the systemic venous atrium and pulmonary ventricle with an epicardial lead placed on the systemic ventricle.

Procedural planning

Single-chamber versus dual-chamber pacing

Whether dual-chamber synchronous pacing (see the image below) is superior to single-chamber ventricular pacing remains a subject of debate.[14, 15, 16, 17] Atrial-based pacing, which includes AAI(R), DDD, and VDD(R) pacing modes, has been shown to be superior to ventricular-based (VVIR) pacing in studies of adults, although controversy regarding DDD versus VVI pacing continues. Several large-scale prospective studies are attempting to illuminate these issues.

In adult studies, dual-chamber pacing may have lower morbidity and mortality compared with ventricular pacing in patients with congestive heart failure, valvular heart diseases, and hypertensive heart disease. Studies indicate higher incidences of death, stroke, atrial fibrillation, pacemaker syndrome, and heart failure during VVI pacing than during DDD pacing.

An apparently convincing argument advocates atrial-based pacing (either single-chamber AAI[R]) or dual-chamber modes) over ventricular-based pacing modalities, although whether DDD is better than AAI(R) for patients with intact AV conduction is less clear.

Experimental data that address pacing in children are more limited, and some conclusions are extrapolated from adult patient series. Common pacing indications in children are similar to those in adults (eg, SA or AV node dysfunction), although concomitant cardiac, medical, psychological, and size-related issues often differ markedly. Rate-responsive ventricular pacing often has been used in children with complete AV block. Rate-responsive ventricular pacing also responds adequately to the physiologic requirements of healthy active children.

Many pediatric patients, however, have underlying structural heart disease, tachyarrhythmia, and hemodynamic derangements that compromise ventricular performance. In addition, pediatric patients frequently have structural anatomic barriers to implantation and limited access to cardiac chambers.

Many patients who have previously undergone atrial surgical procedures (eg, Fontan, Mustard, or Senning procedures) have both bradyarrhythmia and tachyarrhythmia. Some studies have demonstrated higher atrial-pacing failure rates in these patients, presumably as a consequence of higher atrial pressures, scarring, and ischemia.

A large retrospective series revealed no significant differences between many patients who had undergone Fontan or atrial switch procedures.[18] Investigators compared these patients with others who underwent Fontan surgery and received no permanent pacemaker, an atrial single-chamber pacemaker, a ventricular-based pacing system, or a dual-chamber pacing system. No clear choice of pacing modality emerged for pediatric single-ventricle patients.[18] The use of multisite pacing for cardiac resynchronization therapy in single-ventricle patients has been used in multiple centers with improved hemodynamics compared to the traditional single-site pacing.[19, 20]

Epicardial versus endocardial pacing sites

The main difference in lead implantation is the route of placement. Although the vast majority of adult pacemaker patients have transvenous lead placement, children have an almost even distribution of transvenous and epicardial lead implantation.

For some time, epimyocardial pacing was the most common pediatric pacing application.[21] At present, epicardial pacing is primarily used when transvenous pacing is contraindicated or for patients undergoing concomitant heart surgery. Contraindications to transvenous pacing include prosthetic tricuspid valves, right-to-left intracardiac shunts, congenital heart disease, surgery precluding transvenous access to cardiac chambers, recurrent transvenous lead dislodgment, and, probably, minimum patient size.

Advantages of epicardial implantation include the absence of a need to provide vascular continuity with the cardiac chambers and the avoidance of concerns about venous thrombosis. Disadvantages include more frequent reports of sensing and capture failure, higher rates of insulation and conductor fractures, and the need for an open chest approach (eg, via a thoracotomy, a sternotomy, or a subxiphoid or subcostal incision). However, less-invasive surgical options are available in the pediatric population, including utilization of a mini-thoracotomy or subxiphoid approach and pericardial window for pericardial lead placement.

Transvenous pacing is feasible in infants and small children. Smaller pacemaker generators and thinner lead diameters simplify the placement of permanent transvenous pacing systems. However, the easier placement of transvenous leads in small patients does not imply that this approach is necessarily superior to others.

Current practice suggests that transvenous pacing leads routinely can be placed in children who weigh more than 10 kg, although there are reports of centers performing transvenous implants in children weighing less than 10 kg with good outcomes.[22]  There is even a case report of a successful pacemaker implant for complete heart block in a low birth weight infant (803 g).[23] As pacing technology continues to reduce lead body diameter, it is likely that children with even smaller body weights can be considered for transvenous placement. However, because of continued growth and vigorous activity, pediatric patients have distinctly higher lead fracture and failure rates than adults do.

Actual survival comparisons have been performed for transvenous pacing leads in children. These comparisons show progressive lead failure over time from fracture, insulation discontinuities, adapter or header failures, or pacing exit block.

Advantages of the transvenous route include avoidance of thoracotomy, lower pacing thresholds (and thus longer battery life), and lower incidences of exit block and lead fractures. Disadvantages include a slightly higher dislodgment rate (eg, with passive fixation devices), potential venous occlusion,[24] possible embolic events (eg, from an intracardiac shunt), a slight risk of endocarditis, and subclavian crush syndrome.

Minimally invasive pericardial lead placement, both with pacemaker and defibrillator functionality, have been attempted in an animal model with acute and chronic success, with the potential for future use in the human pediatric population.[25, 26]

Twiddler syndrome, in which permanent malfunction of a pacemaker from manipulation of the pulse generator, can also occur in children with potential lead dislodgment, generator migration, or pacing failure due to twisting of the leads or generator in the pocket. Significant vascular access challenges can also relate to congenital heart diseases and surgical corrections.

For patients with congenital or idiopathic atrioventricular (AV) block, test for maternal lupus antibodies (anti-Ro, anti-La), and measure Lyme titers. AV block due to Lyme carditis is typically reversible with appropriate antibiotic treatment.

Echocardiography is used to determine the underlying anatomy, particularly the presence of L-looping of the ventricles (ie, physiologically corrected transposition of the great arteries), which has a high association with the development of AV block. Echocardiographic data are also useful to assess ventricular function and to determine the presence of congenital heart disease or intracardiac shunts.

Phlebography may be helpful before transvenous pacemaker implantation, particularly for patients who have undergone prior surgery or central venous line placement. Arm phlebography can outline the course of the venous system and confirm continuity with the heart. Variants (eg, left superior vena cava to coronary sinus connections and other vascular anomalies) can be easily identified.

Performing chest radiography before pacemaker implantation to identify heart chamber sizes and potential vascular abnormalities (eg, right aortic arch) is reasonable. In addition, imaging should be performed in patients with existing pacing systems to visualize the lead positions.

Electrocardiography (ECG) is essential for documenting the rhythm before the pacemaker is implanted (see the images below).

A pacemaker is an electronic device, approximately the size of a pocket watch, that senses intrinsic heart rhythms and provides electrical stimulation when indicated. Cardiac pacing can be either temporary or permanent.

Permanent pacing is most commonly accomplished through transvenous placement of leads to the endocardium (ie, right atrium or ventricle) or epicardium (ie, to the left ventricular surface via the coronary sinus), which are subsequently connected to a pacing generator placed subcutaneously in the infraclavicular region.

Implantable pacemakers

Permanent pacemakers are implantable devices that sense intrinsic cardiac electric potentials and, if these are too infrequent or absent, transmit electrical impulses to the heart to stimulate myocardial contraction. A specialized type of pacemaker therapy, cardiac resynchronization therapy (CRT) with biventricular pacing, with or without an implantable cardioverter-defibrillator (ICD), has been used as adjunctive therapy for patients with heart failure.

Implantable defibrillators

The implantable cardioverter-defibrillator (ICD) is first-line treatment and prophylaxis for patients at risk for ventricular tachycardia (VT) or ventricular fibrillation (VF). Current devices offer tiered therapy with programmable antitachycardia pacing schemes, as well as low-energy and high-energy shocks in multiple tachycardia zones.

Dual-chamber, rate-responsive bradycardia pacing is available in all ICDs, and sophisticated discrimination algorithms minimize shocks for atrial fibrillation, sinus tachycardia, and other non–life-threatening supraventricular tachyarrhythmias. Diagnostic functions, including stored electrograms, allow for verification of shock appropriateness.

Pacemaker size and type

Size is an important factor in pacemaker selection, particularly for infants and smaller children. Modern generators have markedly reduced mass, width, and circumference, and single-chamber and dual-chamber devices are similarly sized.

No pacemaker is specifically designed for pediatric use. Each generator has special features and options, which vary among different manufacturers and specific models. Some features may be particularly appropriate or inappropriate for children. For example, because pacemakers are designed primarily for adults, the resting heart rate is expected to be lower than 100 beats/min. Most pacemakers released before 1996 had a maximum rate limit of 120-130 beats/min, which may be inadequate for a neonate or critically ill postoperative infant.

A programmable lower and upper rate limit may require a higher setting in children to compensate for increased demands on myocardial oxygen consumption, cardiac output response to exercise, and increased predicted maximum heart rates with exertion. Unfortunately, battery longevity is sacrificed in favor of optimizing hemodynamic performance. Because cardiac output is more critically dependent on heart rate in children, the requirement for faster pacing rates increases battery expenditure.

Pacemaker leads

Fixation mechanisms in transvenous leads are divided into active-fixation tips and passive-fixation leads. In general, active-fixation leads are more commonly used in children because they can be more easily removed if necessary.

Active-fixation leads have a screw on the end that penetrates the endocardium. These mechanisms either are covered in a dissolvable material (eg, gelatin, sugar cap) to protect the delicate veins during insertion or have an intricate screw extension-retraction mechanism that allows the operator to enter the vein and cardiac chambers without an exposed screw.

Active-fixation leads can be fixated almost anywhere in the endocardium; they may be especially valuable for patients with left ventricular lead placements (eg, corrected transposition of great arteries) or those without a right atrial appendage (eg, most postoperative patients with congenital heart disease). Active-fixation leads are more easily removed, even after being implanted for many years. This feature is a distinct advantage for young patients, who may need multiple pacemaker system replacements over a lifetime.

Passive-fixation mechanisms use small tines or fins near the distal tip, which become entrapped in the right ventricular trabeculations and lodge within scars over time. These leads do not require a screw-in device but are facilitated by placement in a trabeculated region, which may not be routinely available in patients with congenital heart disease. Passive-fixation leads are more difficult to extract when implanted for long periods and, therefore, may be less appropriate for pediatric patients because multiple revisions are anticipated.

The tips of the leads may have special coatings to improve pacing characteristics or to decrease surrounding tissue inflammation. The most common is a steroid-eluting tip, which continually disperses a tiny amount of dexamethasone (or another corticosteroid) into the local tip-tissue interface.[27]

These steroid-eluting leads, available in both passive-fixation and active-fixation tips, prevent subacute threshold rise, which is seen several weeks after lead implantation. This benefit can be critically important in children, who typically have a greater inflammatory response to tissue injury and a larger threshold rise.

Titanium nitride and other metallic compounds have also been used to increase the surface area at the tip-tissue interface; this increased surface area should improve pacing and sensing performance.

Relatively recent advances in leadless pacemaker technology allow for a pacemaker to be inserted using a transcatheter approach; the Nanostim leadless pacemaker (approved for use in select international markets only)[28] and the Micra transcatheter pacing device[29, 30] are only approved for use in patients older than 18 years. These devices can provide VVIR pacing only and have not been studied in the pediatric population, but they may prove to be a viable option in the future.

Postoperative follow-up is routine and simplified. During the initial few months after surgery, evaluate the patient to assess for a possible rise in the capture thresholds secondary to inflammation and exit block. Program a safety margin to avoid possible loss of capture because of a subacute threshold rise, which may be seen in the first several weeks, particularly with epimyocardial implants or non–steroid-eluting leads.

Remote monitoring of pacing systems is simple and convenient, and it is done wirelessly over a cellular network in the majority of cases. Remote monitoring technology has become more sophisticated, allowing for seamless transmission of events or symptoms, adequate detection of clinically relevant events, and decreased frequency of outpatient clinic visits.[31, 32]

For patients who are pacemaker-dependent, dizziness, presyncope, or syncope warrants a full device interrogation of both the leads and pulse generator to ensure proper function of the device.

Children with implanted devices are generally more active than adults; the child’s continuing bodily growth and development create additional concerns and further increase demands on pacing systems. Contact sports add stress and strain on pacemaker generators and leads. Children with pacing devices have higher incidences of lead-related complications than adults, presumably secondary to growth and vigorous exertion. Younger patients are more apt to participate in contact sports and to continue to engage in vigorous activities. In a multivariate analysis of 1905 pediatric patients implanted with a cardiac device from a single device company and monitored remotely, the overall daily average activity was 5.4 hours, and increased level of activity was associated with being male and younger, as well as having experienced a shock and having a pacemaker versus an implantable cardioverter-defibrillator, an epicardial device site, and the rate response turned off.[33]

Resumption of normal activities, as feasible, and promotion of healthy development without incurring significant additional risks are important goals of pediatric health care. Physicians must identify potential concerns and obstacles that patients and families may encounter and must offer strategies to guide them through their adjustment.

In 2015, the American Heart Association (AHA) and American College of Cardiology (ACC) published their recommendations regarding competitive athletics and cardiovascular abnormalities.[34] There are specific recommendations for athletes with permanent pacemakers, all of which are class 1:

• Generally, athletes with permanent pacemakers should be cleared for athletic participation if there are no limiting structural heart conditions or symptoms.
• Athletes who are completely pacemaker dependent should not engage in sports in which there is a risk of collision that could result in damage to the pacemaker system.
• Athletes treated with a pacemaker who are not pacemaker dependent may participate in sports with a risk of collision or trauma if they understand and accept the risk of damage to the pacemaker system and they have no structural heart disease that precludes participation.
• For athletes with permanent pacemakers, protective equipment should be considered for participation in contact sports that have the potential to damage the implanted device.

Provide a thorough and adequate explanation of pacemaker implantation procedures to the patient and family members. Document the indications for permanent pacing and outline the plan for route of access. Make relevant surgical decisions after comprehensive consideration of the following factors:

• Transvenous versus epicardial approach
• Single-chamber pacing versus dual-chamber pacing versus cardiac resynchronization therapy
• Vascular access and continuity
• Prepectoral versus submuscular pocket
• Handedness of the patient and left-side versus right-side implantation
• Presence of structural heart disease, intracardiac shunts, and obstruction to the right heart chambers
• Relevant medical, surgical, and anesthesia history
• Allergies
• Risks of the procedure, including pacemaker-specific risks
• Finite battery longevity, lead failure, and the likely potential for reoperation

A sterile environment is absolutely essential for implantation. Proper facilities include an operating room, a cardiac catheterization laboratory, or an electrophysiology laboratory. The implantation procedure may be performed with either general or local anesthesia, depending on the patient’s age and the planned route of implantation.

For the transvenous approach, one can perform either a cephalic vein cutdown or percutaneous subclavian (or axillary) vein puncture to access the venous system. Position a wire in the right heart with pacing leads placed in the right atrium or ventricle. Testing is performed using cables connected to a pacing system analyzer, which can ascertain adequate sensing of intrinsic waves, capture thresholds, and lead impedances.

The generator is then connected to the leads, and a pacemaker pocket is fashioned either prepectorally or subpectorally, usually with blunt dissection, cauterization, or both. The generator is placed in the pocket, and the incision is closed in multiple layers. The choice between a subcutaneous and submuscular pectoral pocket is operator-dependent. The submuscular pocket may create a better cosmetic result and be less prone to trauma, but there are risks related to difficult reoperation and increased bleeding with subsequent procedures.

Leaving a generous amount of slack in the lead to allow uncurling may reduce the risk of lead fracture or dislodgment with linear growth (see the image below). Studies have been performed to estimate the amount of intracardiac lead redundancy necessary to allow for anticipated growth.[35]

The epicardial approach is typically performed via a subcostal or subxiphoid incision, a thoracotomy, or a sternotomy. The pacing leads are attached to epicardial surfaces and then tested for capture, sensing, and lead impedances. As with the transvenous approach, a pocket is created, typically in the subrectus region of the abdomen (or in the pectoral region), with subcutaneous tunneling of the leads from the epicardial sites to the pocket.

As a rule, most patients remain hospitalized for 12-48 hours after the operation, depending on their age, complexity of the procedure, and the route of access.

Aside from several weeks of restriction from heavy lifting, extreme stretching of the accessed shoulder (for transvenous implants), and vigorous activities, patients may resume normal activities of daily living after the procedure. These restrictions are particularly important after passive lead implantation to avoid dislodgment. The incision must be kept clean and dry and typically heals within 7-10 days.

Antibiotic prophylaxis after the first 24 hours has not been demonstrated to reduce the risk of pacemaker system or pocket infection. Patients are instructed to immediately report any symptoms/signs of possible infection.

For patients with newly implanted cardiac resynchronization therapy (CRT) devices, clinicians may choose to optimize the system (specifically the pacemaker timings) with the help of echocardiography (tissue Doppler imaging and speckle-tracking). A study has shown no difference in clinical outcomes between electrocardiography and echocardiography optimization of CRT in pediatric patients, although further study is ongoing.[36]

Complications of pacemaker implantation involve the immune response to artificial materials and the body's response to the pacemaker system.

Pacemaker generators are typically very reliable and have a low failure rate. The lithium iodide battery has a limited longevity of 5-15 years. Battery depletion is not a complication but a normal occurrence.

Risk factors for complications related to epicardial pacemakers in neonates and infants include young age (37</ref> In addition, the development of pacing induced ventricular dysfunction (PIVD) in children receiving dual-chamber pacemakers for complete heart block following congenital heart surgery appears to be influenced by the underlying structural heart defect. One study comprising 47 children younger than 2 years who developed postsurgical complete heart block noted an association in nine children between PIVD with double outlet right ventricle, transposition of the great arteries (TGA) with ventricular septal defect, atrioventricular canal defect, mitral valve replacement, and congenitally corrected TGA, but not with tetralogy of Fallot alone, ventricular septal defect alone, atriventricular canal defect with tetralogy of Fallot, or subaortic membrane.[38]

A rare complication following epicardial pacemaker implantation is cardiac strangulation, which may be associated with a lack of consistent imaging for the diagnosis.[39]  Close monitoring of lead placement and close follow-up in patients aged 6 months or younger at the the time of implantation is advised.[39]  

Pacing leads are more prone to failure, particularly in children.[40] Leads may fail at the conductor wires or in the insulation material (polyurethane or silicone). Lead failure typically results in inappropriate sensing or capture (ie, underpacing or overpacing).

Infection of the pacemaker system is a serious complication and almost always necessitates complete system removal, administration of intravenous antibiotics, and system replacement at a remote site. However, in selected cases, pacemaker system infection can occasionally be effectively treated with a prolonged course of antibiotics, without system removal.

Twiddler syndrome is an interesting finding caused by repetitive and often unintentional twisting of the generator in the pacemaker pocket, causing lead dislodgment or fracture and pacemaker failure.[41] It is most commonly observed in patients with behavioral issues.

Significant vascular access challenges can also relate to congenital heart diseases and surgical corrections.

Finally, chronic right ventricular pacing over long periods (eg, decades) has been shown in a small group of patients to lead to decreased cardiac function.[42]

The goals of pharmacotherapy are to reduce morbidity and prevent complications.

Class Summary

Routinely, cefazolin 1 g (or 25 mg/kg) is administered intravenously (IV) 1 hour before the procedure. If the patient is allergic to penicillins or cephalosporins, vancomycin 1 g IV, clindamycin 600 mg IV, or another appropriate antibiotic may be administered preoperatively.

Cefazolin

Cefazolin is a first-generation semisynthetic cephalosporin that arrests bacterial cell wall synthesis, inhibiting bacterial growth.

Vancomycin

Vancomycin is a potent antibiotic that is directed against gram-positive organisms and that is active against Enterococcus species. Vancomycin is indicated for patients who cannot receive or have not responded to penicillins and cephalosporins and for patients who have infections with resistant staphylococci.

Clindamycin (Cleocin, Cleocin Pediatric, ClindaMax Vaginal)

Clindamycin is an antibiotic that interrupts protein synthesis and is active against gram-positive organisms, including most methicillin-resistant Staphylococcus aureus (MRSA) strains.  Clindamycin can be used as an alternative to vancomycin in penicillin-allergic patients.

Class Summary

Local anesthetics block the initiation and conduction of nerve impulses.Anesthetics used for the permanent pacemaker insertion include bupivacaine and lidocaine.

Bupivacaine (Marcaine)

Bupivacaine decreases permeability to sodium ions in neuronal membranes. This results in the inhibition of depolarization, blocking the transmission of nerve impulses.

Lidocaine (Xylocaine)

Lidocaine is an amide local anesthetic used in 1-2% concentration. The 1% preparation contains 10 mg of lidocaine for each 1 mL of solution; the 2% preparation contains 20 mg of lidocaine for each 1 mL of solution. Lidocaine inhibits depolarization of type C sensory neurons by blocking sodium channels.

To improve local anesthetic injection, cool the skin with ethyl chloride before injection. Use smaller-gauge needles (eg, 27 gauge or 30 gauge). Make sure the solution is at body temperature. Infiltrate very slowly to minimize the pain. The time from administration to onset of action is 2-5 minutes, and the effect lasts for 1.5-2 hours.