Congenital and childhood atrioventricular blocks: pathophysiology and contemporary management

Abstract

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.

Keywords: Congenital heart disease; Heart block; Outcomes; Pacemaker; Pathophysiology.

Fig. 1

Complete atrioventricular block: unpaced electrocardiogram. Postoperative 12-lead electrocardiogram demonstrating complete heart block with slow ventricular escape rate, after tricuspid valve replacement

Fig. 2

Complete atrioventricular block: paced electrocardiogram. Twelve-lead electrocardiogram from patient demonstrating atrial sensed ventricular paced rhythm

Fig. 3

Permanent pacemaker with epicardial leads (VVI pacing)

Fig. 4

Permanent pacemaker with transvenous leads. Growth and change in a loop of an endocardial lead. A 4-year-old boy with childhood isolated nonimmune atrioventricular block underwent pacemaker implantation using a transvenous lead. Radiographs at 4 years of age (a, VVI pacing), 6 years later (b, DDD pacing), and 9 years later (c, DDD pacing). Note the change in the loop of the lead as the child grows

Fig. 5

Cardiac resynchronization therapy with epicardial leads. A 5-year-old boy who underwent a neonatal Ross procedure had postoperative complete heart block and left ventricular dysfunction. He was implanted with epicardial multisite pacing with right atrial, right ventricular (a and b, black star), and left ventricular (a and b, black arrow) leads. Biventricular pacing allow shortening of the paced QRS (c, 224 ms) compared with right ventricular pacing alone (d, 128 ms)

Fig. 6

Cardiac resynchronization therapy with transvenous leads. A 14-year-old boy with dilated cardiomyopathy and left ventricular dysfunction, second-degree AV block, and an episode of ventricular fibrillation had implantation of a biventricular implantable cardioverter-defibrillator with a transvenous right ventricular lead (a and b, black star) and a transvenous left ventricular lead into the coronary sinus (a and b, black arrow)