Approach Considerations
Pharmacologic therapy
Little evidence suggests that the administration of steroids or immunoglobulins or the performance of plasmapheresis in the mother can reverse third-degree atrioventricular (AV) block in the fetus. However, these therapies may be helpful in early first- and second-degree heart block and in reducing associated myocardial dysfunction.
Regular and close monitoring for heart block and transplacental therapy with fluorinated steroids (dexamethasone) and beta sympathomimetics have been used by some centers with satisfactory results at the first evidence of heart block and bradycardia with hydrops, respectively. However, current evidence doesn’t support the use of fluorinated steroids in the treatment of complete AV block. [17] Prophylactic therapy is not currently indicated, because these medications can have maternal and fetal side effects. [18]
Children with complete congenital atrioventricular block (CAVB) due to heart disease, if associated with pulmonary atresia or severe stenosis, may need to be on prostaglandin therapy to keep the ductus patent.
In patients with CAVB, prophylactic antibiotic therapy during and following surgery appears to reduce the incidence of pacemaker system infections, although current studies do not reach statistical significance because of the relative rarity of this complication (approximately 1%).
Hydrops fetalis
Therapy for hydrops fetalis can be challenging in utero and after birth. A staged approach with stabilization of the patient, drainage of the effusions, the use of intravenous inotropes (dopamine) and chronotropes (isoproterenol), and placement of a pacemaker has shown some success. Some centers recommend cesarean and preterm delivery for fetuses with CAVB and hydrops fetalis.
Bradycardia
In the perinatal period, fetal bradycardia may be an incidental finding. However, when persistent bradycardia is identified in the third trimester, emergency delivery is sometimes inappropriately carried out without differentiating acute causes of bradycardia related to fetal distress from the more chronic condition of isolated CAVB.
Pacemaker Therapy
The medical care of congenital atrioventricular block (CAVB) is currently focused on identifying the optimal timing of pacemaker therapy to ensure a positive outcome. Additional care is aimed at identifying and treating the associated conditions that arise. Patients who present with symptoms as fetuses or newborns may require earlier pacing than do those who present with symptoms later in childhood. Fetuses with hydrops fetalis secondary to maternal autoimmune disease have successfully received pacing in utero; however, this has not prevented fetal demise.
Symptoms referable to bradycardia are an indication for pacing in complete CAVB. Because severe symptoms (eg, syncope) occasionally arise suddenly or sudden cardiac death can occur, additional risk factors identified from monitoring have been recommended as indications for pacing. [19]
Temporary pacing can be achieved transcutaneously, transesophageally, or transvenously. However, permanent pacemaker placement is eventually needed in most children with CAVB. Major criteria for pacing based on ECG or Holter monitoring in children include an average heart rate of less than 50 bpm, a nighttime or sleeping average heart rate of less than 45 bpm, or pauses secondary to AV block that are longer than 3 seconds.
In the setting of borderline major criteria, other criteria that may influence the decision for timing of pacemaker implantation include cardiomegaly, a high atrial rate, junctional instability (eg, junctional exit block), a broad complex escape rhythm, diminished ventricular response to exercise, QT prolongation, and complex ventricular ectopy.
When criteria are met, surgical implantation of an epicardial pacemaker should be performed, with knowledge of the implications of pacing in children and recognition of the lifelong need for pacing and pacemaker lead access. Multiple backup pacing systems at the time of surgery (eg, temporary transvenous pacing, transthoracic pacing units) are helpful to avoid the extremes of bradycardia that may be associated with anesthesia and pacemaker surgery.
Venous obstruction, small patient size, and actual or potential right-left shunting are relative contraindications for transvenous pacing. Fortunately, epicardial pacing leads have greatly improved and allow for successful pacing system insertion under these conditions. Some centers are using neonatal endocardial pacing systems.
In children beyond the neonatal period, an endocardial pacing with transvenous approach or robot-assisted thoracoscopic implantation of left ventricular leads is possible. The risk of venous occlusion appears to correlate with the ratio of available transvenous lead body sizes and the patient's body surface area. [20] Exceeding this ratio may lead to a high incidence of venous obstruction. Robot-assisted minimally invasive surgery has the advantage of avoiding intravascular endocarditis and thrombosis.
In addition, imaging of the subclavian-innominate venous channels before pacemaker lead placement is helpful for transvenous lead placement. The course of the lead should be evaluated in 2 planes to avoid inadvertent lead placement into the foramen ovale, an unroofed left superior vena cava to coronary sinus, or left-sided circulation via the subclavian artery. Either a subcutaneous or subpectoral pocket may be formed inferior to the clavicle.
Major lawsuits related to pacing in congenital atrioventricular block (CAVB) have arisen primarily because of inadvertent placements of pacing leads into the left-sided circulation. This complication can be recognized at or immediately following system placement using complementary radiographic views, usually lateral and posteroanterior (PA) or anteroposterior (AP).
Numerous pacing strategies are used in the management of congenital complete heart block in children; the interested reader is referred to the 2017 review by Chandler et al. [21]
Follow-up
Routine pacemaker follow-up visits should be maintained according to national or international guidelines. Transtelephonic pacemaker monitoring may allow for improved follow-up care and longer intervals between outpatient visits.
Activity
Patients with permanent pacing systems should be restricted from activities that result in repeated intentional direct trauma to the pacemaker area (eg, martial arts). Patients with permanent pacing systems should be restricted from exposure to high magnetic fields, such as direct magnetic resonance imaging (MRI) exposure.
