Management of postoperative complete heart block in infants and children

Natural history and current therapy for complete heart block in children and patients with congenital heart disease

Complete heart block, either congenital or acquired, in children and patients with congenital heart disease is a relatively frequent occurrence requiring therapy. The natural history of this condition has been distorted by the advent of new diagnostic and therapeutic modalities. The therapy of complete heart block is evolving with new data suggesting that traditional treatment strategies utilizing right ventricular apical pacing may have inadvertent deleterious effects on cardiac function. In the following manuscript, the natural history of complete heart block is reviewed and the current therapy examined.

Natural history of postoperative heart block in congenital heart disease: Implications for pacing intervention

After half a century of major progress in congenital heart disease management, atrioventricular conduction block continues to complicate 1-3% of surgical procedures. Unless treated with an implanted pacemaker, permanent postoperative heart block is associated with 28-100% mortality. Postoperative heart block often proves to be transient, typically resolving within 10 days of onset. The duration of postoperative heart block is widely used as a key determinant for permanent pacemaker implantation. Current professional pacemaker implantation guidelines are largely based on this criterion. However, available natural history data suggest that other factors, such as residual conduction system injury, likely play a role in increasingly recognized cases of very late postoperative mortality and morbidity in patients who have experienced transient postoperative heart block. As growing numbers of congenital heart disease patients survive into adulthood, and artificial pacemaking capabilities continue to improve, it might be necessary to reconsider and refine currently accepted pacing indications for postoperative heart block.

Implantation of transvenous pacemakers in infants and small children

A series of 14 infants and small children ranging from 7 months to 7 years in age (mean, 2.5 years) underwent implantation of transvenous pacemaker systems. Three factors are of utmost importance in children: small subclavian vein size, thin subcutaneous layer in the chest, and growth. A five-point protocol is followed strictly: (1) duplex assessment of upper veins, (2) use of active fixation leads, (3) use of short (36 to 45 cm) leads, (4) anchoring of pulse generator with nonabsorbable material to prevent migration, and (5) routine use of the "lateral approach" in children more than 2 years old when the pulse generator is implanted in the chest. Because lead diameters measure 2 to 2.3 mm, a one-lead system needs a vein diameter of 5 mm (cross-sectional area of 19 mm2). A two-lead system needs a vein at least 7 mm in diameter and a cross-sectional area of 38 mm2 to prevent vein occlusion. Therefore all children less than 3 years of age had the leads implanted via the internal jugular vein. In 50% of children between 4 and 7 years of age, the internal jugular system also was used. Children more than 7 years old have leads implanted via the subclavian veins. Duplex ultrasound assessment of the upper veins is important to decide route of implantation. Use of short leads is recommended to reduce bulk at the pulse generator site. The "lateral approach" prevents problems at the generator implantation site.

Atrioventricular pacing in congenital heart disease

We have attempted to optimize cardiac performance in patients with congenital heart disease requiring artificial pacing by using pacemakers capable of both sensing and pacing both the atrium and the ventricle (DDD). We reviewed our results with 88 patients receiving DDD devices to determine the safety and dependability of these devices in children. Age ranged from 1 hour to 25 years. Endocardial leads were used in 68 patients, whereas epicardial leads were used in 20 patients. Previous cardiac procedures had been done in 30 patients. There were nine deaths but none due to pacemaker malfunction. Endocardial leads functioned better than epicardial leads. Ninety-eight percent of patients with endocardial leads and 62% of patients with epicardial leads were maintained in the DDD mode. Complications were infrequent and all were corrected without long-term sequelae. The DDD mode may offer considerable benefits to children who require artificial pacing. Our data allow us to conclude that most children can be paced safely and dependably in the DDD mode.

Pacemakers in children: an update

This report reviews recent pacemaker technological advances as they apply to infants, children, and adolescents. Indications for pacemaker implantation in children have evolved since the 1984 Joint Task Force Guidelines. Recent data show that pacemaker implantation should be strongly considered in patients who have (1) asymptomatic congenital complete AV block with a mean heart rate less than 50 beats/min or other evidence of junctional instability; (2) congenital AV block with long QT interval; or (3) congenital long QT syndrome with bradyarrhythmias, or when conventional beta-blocker therapy is unsuccessful. Permanent pacemaker implantation is not necessarily an effective prophylactic measure against sudden death in patients following their operation who are receiving drug therapy for atrial tachyarrhythmias, and so is not absolutely indicated. New developments in lead technology have made transvenous lead systems more feasible for pediatric use. Because epicardial leads are required for small infants and for cosmetic reasons in some older children, design improvements are needed to enhance epicardial lead performance. Rate-responsive pacing is an acceptable alternative to dual-chamber pacing for augmenting exercise tolerance, and for children with sinus node dysfunction it is the preferred pacing mode. Pacemakers with automatic antitachycardia capabilities and with noninvasive electrophysiology features are valuable in children with atrial tachyarrhythmias. New data suggest that chronic atrial pacing also may be effective in controlling atrial tachyarrhythmias. New developments in pacemaker systems for the young parallel those for the older population, but differences between adult and pediatric patients demand ongoing increased participation by pediatric cardiologists.

Transient atrioventricular block after open-heart surgery for congenital heart disease

The records of 22 patients with transient atrioventricular (AV) block after open-heart surgery for congenital heart disease from 1972 to 1978 were reviewed to determine the natural history of this entity. Preoperatively, no patient had AV block; 3 had right bundle branch block (BBB), 1 had left BBB and 5 had nonspecific intraventricular conduction delay. Complete AV block developed in 20 patients and Mobitz II AV block in 2. Transient AV block occurred intraoperatively in 14 patients and within 48 hours postoperatively in 8; AV block persisted for greater than or equal to 48 hours postoperatively in all patients, for a mean of 7.3 days (range 2 to 28). During a follow-up of 5.5 years (range 2.5 to 10), late AV block developed in 2 patients. None of the 18 patients whose escape QRS complex morphology during AV block was similar to the final QRS complex during normal sinus rhythm or atrial fibrillation with AV conduction had late AV block, whereas 2 of the 4 in whom it differed did (p less than 0.01). There was no difference in the escape rate between the 2 groups. Thus, late development of high-grade AV block is infrequent among patients with transient postoperative AV block. An escape QRS complex during postoperative AV block that differs from the QRS complex seen on recovery of normal sinus rhythm or atrial fibrillation with anterograde conduction may identify those at high risk of late AV block.

Cardiac pacing in children

Twenty patients aged between 12 months and 13 years underwent permanent pacemaker implantation. The main indication for pacing was post-surgical atrioventricular block. The complication rate was high and related mainly to infections and lead system problems. The use of small multiprogrammable pacemakers is expected to reduce the reoperation rate for system malfunction and elective replacement. Newer methods of electrode insertion and active fixation devices in smaller diameter leads make endocardial pacing a practical alternative to epicardial pacing in the larger child who did not require a pacing system at the time of surgery.

Pacemakers in young patients: 1977

Recent experience with implanted cardiac pacemakers in nine young patients is reported. Advance in technology include improved pacemaker generator design and placement, and improved lead design and placement. No patients died; our only complication, failure to capture, required repositioning of the lead. All pacemaker replacements were elective. This series helps to define the more favorable current prognosis for the young patient needing pacemaker therapy.

Postoperative complete heart block in 64 children treated with and without cardiac pacing

Between 1957 and 1973, a total of 64 children had complete heart block during intracardiac surgery were treated by one of three methods: (1) No pacemaker: Six of the 13 patients in this group had reversion to sinus rhythm. Seven patients continued to have complete heart block, and five of these died of Stokes-Adams episodes. Two patients continue to have complete heart block without pacemaker insertion. (2) Temporary pacemaker: Seventeen of 25 patients had reversion to sinus rhythm and the temporary pacemaker was removed; the other 8 continued to have complete heart block. Five of the eight died--three of Stokes-Adams episodes and two at the time of cardiac reoperation. Three remain asymptomatic without placement of a permanent pacemaker. Six died of postoperative complications unrelated to heart block or pacemaker implantation. None of the other 20 experienced Stokes-Adams attacks. There was one late death in this group. Although there are problems in using permanent pacemakers and electrode systems, in these patients with operatively induced complete heart block their use was associated with a low mortality rate.

Cardiac pacing in children and adolescents

Nineteen patients aged 1 month to 18 years underwent implantation of a cardiac pacemaker and were followed up for up to 9 years (average duration of pacing 54 months). Complete heart block was present in 16 patients and sinus nodal dysfunction in 3. Heart block was presumably of congenital orgin in eight, secendary to cardiac surgery in seven and subsequent to cardiac catheterization in one. Sinus nodal dysfunction was of presumed congenital origin in one and occurred after cardiac surgery in two. Pacing was required because of syncopal attacks in eight patients, three of whom had congestive heart failure or low cardiac output on physiologic studies. It was required in four because of congestive heart failure, in two because of low cardiac output (one with a wide QRS complex), and in five for postoperative rhythm control. With return of sinus rhythm after 2 and 3 months, respectively, pacing was discontinued in two patients. One child was partially corrected disease died within 3 months, one died of wound breakdown and sepsis after 10 months of pacing and one died suddenly 4 years after implantation. All others have returned to normal activity; only one requires cardiac medication. The degree of emotional stability has been striking. Asynchronous and atrial synchronous pacing are of equal therapeutic value. The very small radiofrequency implanted receiver has been useful in younger children. The major problems have been caused by the large size and short longevity of the generators and the child's growth stressing the lead system. Transvenously implanted pacemakers have presented no greater management problems than those placed during thoracotomy.