Transvenous pacing in infants and children with congenital heart disease

Congenital and childhood atrioventricular blocks: pathophysiology and contemporary management

Atrioventricular block is classified as congenital if diagnosed in utero, at birth, or within the first month of life. The pathophysiological process is believed to be due to immune-mediated injury of the conduction system, which occurs as a result of transplacental passage of maternal anti-SSA/Ro-SSB/La antibodies. Childhood atrioventricular block is therefore diagnosed between the first month and the 18th year of life. Genetic variants in multiple genes have been described to date in the pathogenesis of inherited progressive cardiac conduction disorders. Indications and techniques of cardiac pacing have also evolved to allow safe permanent cardiac pacing in almost all patients, including those with structural heart abnormalities.

CONCLUSION

Early diagnosis and appropriate management are critical in many cases in order to prevent sudden death, and this review critically assesses our current understanding of the pathogenetic mechanisms, clinical course, and optimal management of congenital and childhood AV block.

WHAT IS KNOWN

• Prevalence of congenital heart block of 1 per 15,000 to 20,000 live births. AV block is defined as congenital if diagnosed in utero, at birth, or within the first month of life, whereas childhood AV block is diagnosed between the first month and the 18th year of life. As a result of several different etiologies, congenital and childhood atrioventricular block may occur in an entirely structurally normal heart or in association with concomitant congenital heart disease. Cardiac pacing is indicated in symptomatic patients and has several prophylactic indications in asymptomatic patients to prevent sudden death. • Autoimmune, congenital AV block is associated with a high neonatal mortality rate and development of dilated cardiomyopathy in 5 to 30 % cases. What is New: • Several genes including SCN5A have been implicated in autosomal dominant forms of familial progressive cardiac conduction disorders. • Leadless pacemaker technology and gene therapy for biological pacing are promising research fields. In utero percutaneous pacing appears to be at high risk and needs further development before it can be adopted into routine clinical practice. Cardiac resynchronization therapy is of proven value in case of pacing-induced cardiomyopathy.

An alternate technique to pacing in complex congenital heart disease: assessment of the left thoracotomy approach

BACKGROUND

Pacing in children with congenital heart disease often requires alternate approaches to standard transvenous pacing. The surgical approach used to implant the pacemaker leads has been shown to impact lead survival. There is a paucity of pediatric literature describing the experience using a left thoracotomy approach.

OBJECTIVES

To report on short- and mid-term experiences with pacemaker implant via the left thoracotomy approach in children with complex congenital heart disease.

METHODS AND RESULTS

Data were abstracted retrospectively from patients' hospital charts. To date, the left thoracotomy technique has been used in 11 patients with complex heart disease, with a median of three prior cardiac operations. The median patient age was five years (range of two months to 23 years of age). The pacing indications were acquired postoperative atrioventricular block (n=5), sinus node dysfunction (n=5) and long QT syndrome (n=1). There were no intraoperative complications or long-term complications from this approach. The pacing thresholds at implant and follow-up were acceptable in all patients. One patient died in follow-up for reasons unrelated to the pacemaker or arrhythmia.

CONCLUSIONS

The placement of epicardial pacemaker leads via the left thoracotomy approach is a safe and effective alternative to transvenous pacing in pediatric patients with complex congenital heart disease.

Endocardial Pacemaker Implantation in Infants Weighing <= 10 Kilograms

Epicardial pacemaker implantation is the most common approach for small children requiring pacemaker implantation, though it is not free from complications. This article reviews the experience with endocardial pacemaker implantation, as an alternative approach, in children < or =10 kg at two centers. Thirty-nine children, median age 3.8 months (2 days-35 months), weight 4.6 kg (2.3-10 kg) underwent endocardial permanent pacing (VVI/R in 38, DDDR in 1). Indications for pacing were complete heart block (CHB) in 34 (congenital in 21, postsurgical in 12, congenitally corrected transposition of the great arteries 1), long QT syndrome in 3, and sinus bradycardia in 2 children. Two children with postsurgical CHB died 7 days and 3 weeks after implantation, respectively, due to heart failure and septicemia, despite appropriate pacemaker therapy. Over a median follow-up of 4.3 years (9 months-15.3 years), 12 patients underwent 18 generator replacements. Five patients were upgraded to physiological pacing. Ten patients underwent 12 ventricular lead advancements. Ventricular lead extraction was attempted 11 times in nine patients and succeeded 10 times. Two patients were converted to epicardial dual chamber systems. Two prepectorally placed generators required resiting due to threatened skin necrosis. Infective endocarditis on the lead, 9 months postimplant required removal of the system in one patient. The subclavian vein was found to be asymptomatically thrombosed in four patients. Endocardial permanent pacing is feasible and effective in children < or = 10 kg and an acceptable alternative to epicardial pacing.

Inferior vena cava loop of the implantable cardioverter defibrillator endocardial lead: a possible solution of the growth problem in pediatric implantation

The ICD is an important treatment option in adults and children with life-threatening tachyarrhythmias. The possibility of lead displacement caused by growth and the lack of dedicated leads and devices poses special problems in pediatric ICD implantation. We describe our experience in three children in whom we left a redundant lead loop within the inferior vena cava (IVC) is allow for further growth. Since February 1998, three children underwent ICD implantation at our institution. A lead (screw-in) was advanced into the right ventricular apex, and a loop was created in the IVC by progressively withdrawing the stylet and pushing in the lead. Satisfactory sensing and pacing threshold values were obtained and a successful single 16-J defibrillation test was performed. No complications were encountered. After a mean follow-up of 16 months, with a mean increase in body weight and height of 4.1 +/- 0.5 Kg and 6.3 +/- 0.4 cm, respectively, chest X ray showed some release of additional lead length, in the absence of dislodgments, while significant changes in pacing/sensing parameters were not found. In conclusion, the creation of a loop within the IVC allows the lead to adjust for growth in children receiving an ICD. This approach is feasible and safe.

A cosmetic approach for pectoral pacemaker implantation in young girls

Pectoral placement of pacemaker generators, combined with use of a redundant intravascular lead portion, reduces the need for endocardial lead advancement during growth in children. While the use of small generators and submuscular pockets has contributed to cosmetic acceptability, the conventional subclavicular incision may occasionally form a keloid scar that is unacceptable in young girls. A modified implantation technique was used in five girls (age 2.6-13.3 years) during implantation of VDD (n = 2), VVIR (n = 2), and DDDR (n = 1) pacemakers. A 5-cm incision was made in the axilla along the line of the pectoralis major and dissection was continued below the muscle to create a pocket for the generator. Subclavian vein puncture was performed from the axillary incision and beneath the pectoralis major muscle using standard or extra long needles with a needle guard. Peel away sheaths were used for lead positioning. The generator was placed in the submuscular pocket and the wound closed with absorbable sutures. At follow-up, pacemaker function was excellent and neither the scars nor pacemakers were visible from the front. In conclusion, the axillary incision with direct subclavian vein puncture from below the pectoralis major muscle offers the advantages of pectoral pacemaker implantation through a single cosmetic incision.

Transmural atrial pacing in patients with postoperative congenital heart disease

INTRODUCTION

Some patients with postoperative congenital heart disease require permanent cardiac pacing, but the use of transvenous or epicardial pacing leads may be limited by type of cardiac malformation, venous connections, body size, or fibrosis. Transmural atrial pacing may provide an alternative in difficult patients, but to date has been described in only a few articles with small patient numbers, and data from lead performance are lacking.

METHODS AND RESULTS

Records were reviewed in 18 consecutive patients (4 months to 21 years old) with postoperative congenital heart disease receiving transmural atrial pacing leads from July 1994 to December 1996. Implantation materials and techniques were described. Lead sensing and capture thresholds obtained acutely and during short-term follow-up (mean: 11.0 months) were evaluated, and comparisons were made between patients with postoperative Fontan anatomy and non-Fontan patients, and between patients receiving steroid-eluting and nonsteroid leads. Overall, the median acute sensing and capture thresholds of transmural leads were 4.1 m V and 0.7 V at 0.5 msec, respectively. Median follow-up thresholds were 2.8 m V and 0.8 V, respectively. Performance of leads in Fontan patients was similar to those in non-Fontan patients. Steroid-eluting leads had a chronic capture threshold of 0.6 V versus 0.9 V for nonsteroid leads (P = 0.038).

CONCLUSION

Transmural atrial pacing leads were successfully implanted in patients with diverse ages and types of postoperative congenital heart disease. Lead performance was acceptable both acutely and during the first year of follow-up.

Use of an atrial loop to extend the duration of endocardial pacing in a neonate

Use of an atrial loop has been proposed as a means of extending the longevity of endocardial pacing systems in small children who require ventricular pacing. A few reports have demonstrated the effectiveness of this method at reducing the number of interventions in infants and small children, but there is little reported experience in neonates. Permanent endocardial ventricular demand pacing was performed in a 3.4-kg neonate. The generator was placed in a prepectoral pocket and a redundant loop of lead was left in the atrium to cater for further growth. At 32 months he weighs 13.6 kg and the loop has uncoiled leaving additional lead slack for further growth.

Single pass VDD pacing in children and adolescents

Use of a single pass lead for VDD pacing in complete heart block is well described in adults, but there are only brief reports of its use in children. We have used standard adult size single pass leads in 13 children and adolescents aged 3.7-17.2 years (mean 10.1 years) and weighing 13.5-76 kg (mean 34.8 kg). Congenital complete heart block was present in 7 patients, surgical complete heart block in 5 patients and 2:1 AV block of unknown cause in 1 patient. In four patients, the VDD system was their first pacing system. In nine of the patients, 1-6 previous systems had been used and simultaneous extraction of ventricular leads and/or atrial leads was performed. Leads of four different types were used: Brilliant IMP15Q, Brilliant + IMR15Q, CapSure 5032, and Unipass 425-13 with 4 different generators: Saphir 600, Saphir II 620, Thera VDD 8948, and Unity 292-07. At implantation, via a subclavian vein puncture, excess lead was advanced into the right atrium to allow both atrial sensing and slack for further growth. Ventricular thresholds ranged from 0.2-0.7 V. The minimal atrial amplitude was 0.7-4 mV and the maximum amplitude was 2.5-8 mV. There were no complications. All patients have maintained adequate atrial signals for reliable pacing with follow up of 3-36 months (mean 17.6 months) during which time some have undergone considerable growth. Reliable atrial synchronous ventricular pacing is possible in growing children with complete heart block using a standard adult single pass lead.

Single pass lead VDD pacing in children and adolescents

Implantation of permanent pacemakers in children and adolescents is possible but usually is limited to single chamber generators. The natural growth of these patients may require physiological pacing, but until recently two leads were required for this type of pacing. The single pass lead VDD pacing mode makes possible physiological pacing by using only one lead, for both atrial sensing and ventricular sensing and pacing. The feasibility of VDD pacing using endocardial lead was evaluated in 16 children and adolescents with congenital or postsurgical atrioventricular block. Their mean age was 7.9 +/- 4.9 years (range 1-16 years) and the smallest patient's weight was 8.2 kg. In all the patients, a single pass pacing lead with atrial sensing rings and bipolar ventricular pacing and sensing capability was implanted through the left or right subclavian vein. The pacemaker generator was implanted in a rectopectoral position. The mean atrial electrogram during the implantation was 4.2 +/- 2.1 mV and 2.6 +/- 1.9 mV after a mean of 1 week. The ventricular pacing threshold was 0.5 +/- 0.2 V; the ventricular pacing impedance was 560 +/- 95 omega; and the ventricular electrogram amplitude was 9.9 +/- 2.1 mV. This is a first report to demonstrate the feasibility of atrial synchronous ventricular endocardial pacing using a single pass lead in a relatively large group of children and adolescents.

Transatrial lead placement for endocardial pacing in children

Transvenous placement of endocardial leads in children may be difficult due to restrictions and complications of vascular access. We have placed endocardial leads from a transatrial approach in 5 children with various cardiac malformations. The usual surgical approach involved an anterolateral thoracotomy and, under fluoroscopic guidance, passage of the lead tip directly through the right atrial wall and across the tricuspid valve to the apex of the right ventricle. At a mean follow-up time of 23.2 months (range, 12.0 to 27.9 months), all patients have low thresholds for myocardial capture, and there have been no complications. We conclude that placement of endocardial leads by a transatrial approach provides an excellent alternative to an epicardial system in children destined for lifelong pacing.

Endocardial pacemakers in children: lead length and allowance for growth

Permanent endocardial pacing in small children is feasible but is limited by two problems: sufficient extra lead has to be left within the heart to allow for growth and the excess has to be coiled behind the pacemaker, limiting the benefit from smaller generators. The required intravascular lead length in 120 children and adults was measured on posteroanterior chest X ray and was correlated with standing height. Measurements were made from the mid-point of the left clavicle to the apex of the right ventricle in a curve simulating the usual endocardial lead position. In 60 children, aged 2.0-15.9 years, intravascular lead length (range 15.5-29.0 cm) correlated well with height (0.83-1.70 m), r = 0.91. In 60 adults, mean age 54.9 years, intravascular lead length (25.5-35.6 cm) also correlated well with height (1.45-1.85 m), r = 0.71. In 20 adults the excess extravascular lead length, measured during pacemaker implantation via the subclavian route, was 15.1-33.7 cm and was inversely correlated with height. A child's eventual adult height can be predicted and, using our data, the extra length of lead necessary to allow for growth can be computed. Available endocardial pacing leads are usually 58- to 64-cm long. The excess extravascular lead is a major practical difficulty in children. Shorter leads would avoid the problem of excess lead and facilitate long-term pacing in small children.

Steroid-eluting epicardial pacing leads in pediatric patients: encouraging early results

OBJECTIVES

This study evaluated the pacing and sensing characteristics of a new porous-tipped steroid-eluting epicardial lead in a group of pediatric patients.

BACKGROUND

Pacing in children may be complicated by small patient size, patient growth and the prevalence of structural congenital heart disease in children requiring pacing. Epicardial pacing has been associated with a high incidence of problems with sensing and capture, prompting the use of transvenous endocardial pacing when possible. In some children, epicardial pacing may still be desirable because of small patient size, potential for caval obstruction, previous cardiac surgery limiting transvenous access to the heart, or the need to repair congenital heart disease at the time of pacemaker insertion.

METHODS

Twelve patients aged 3 weeks to 18 years underwent placement of 23 epicardial pacing leads (8 atrial, 15 ventricular). Pulse width thresholds, sensing thresholds and lead impedance were measured weekly for 6 weeks, then at 3, 6, 12 and 18 months after pacemaker implantation. The median duration of follow-up was 12 months.

RESULTS

Ventricular pulse width thresholds did not change over time, whereas atrial pulse width thresholds improved significantly. At 6 months, the mean pulse width threshold at 2.5 V for the atrial and ventricular leads was 0.10 +/- 0.03 and 0.19 +/- 0.09 ms, respectively. The thresholds were slightly lower at 12 and 18 months. At the most recent follow-up, all atrial leads sensed appropriately at 2.5 mV and all ventricular leads at 5 mV.

CONCLUSIONS

These encouraging early results suggest that steroid-eluting epicardial pacing leads may be an attractive option for children needing epicardial pacing. Their excellent pacing and sensing characteristics may allow reliable dual-chamber pacing in infants who are too small for transvenous pacing.

Transvenous pacemakers in children: relation of lead length to anticipated growth

Although transvenous pacing is feasible in infants and children, uncertainty remains as to how to allow for future growth at the time of lead insertion. Accordingly, we retrospectively reviewed the relation between age and transvenous lead length. Standard posteroanterior chest roentgenograms were reviewed for 26 patients with transvenous pacemakers inserted at Babies Hospital and Presbyterian Hospital between 1985 and 1989. Sixteen of these were children (age range, 0.75 to 15 years) and 10 were adults (age range, 27 to 90 years). The intravascular length of right ventricular pacing leads was measured as projected on the roentgenogram. In 10 children, the presence of lead loops in the right atrium required the lead length that would have resulted from conventional placement to be estimated. Results for right ventricular pacing lead lengths were correlated with age using linear regression analysis. Average uncorrected lead length measured on the roentgenogram was 345 +/- 35 mm (standard deviation) in adults and 222 +/- 51 mm in children. The use of right atrial loops increased implanted lead length by an estimated 79 mm, from 188 +/- 26 to 267 +/- 43 mm. The difference between lead length in children and adults was analyzed. Approximately 190 mm of additional right ventricular pacing lead in infants and 100 mm in 10-year-old children was needed for growth to adult size. We conclude that an 80-mm right atrial lead loop will allow 6 to 12 years (mean, 8 years) of growth in infants and children without the need for reoperation to adjust lead length.