Less than 1% of cardiac pacing devices are implanted in pediatric patients. The most common indication for pacemaker implantation in children is postoperative AVB. This issue has coexisted with cardiac surgery since its early days. In 1954, Walton Lillehei was the first to use a homemade epicardial wire following postoperative AVB during the closure of a ventricular septal defect in a patient undergoing surgery with cross-circulation. Seventy years later, the problem persists, occurring in up to 6% of patients undergoing congenital heart surgery. Half of these patients require permanent pacemaker (PPM) implantation by day 7 if the issue persists, with associated morbidity and mortality implications.

The article we analyze today is a retrospective single-center descriptive study that aims to assess the incidence of postoperative AVB in patients undergoing congenital heart surgery, describe the timing of PPM implantation, identify procedures with a high risk of postoperative AVB, and determine other risk factors for AVB or PPM implantation.

To achieve this, the authors consecutively reviewed all patients undergoing congenital heart surgery at their center from 2021 to 2024. A logistic regression model was used to identify risk factors.

The study found that among 9765 patients operated on, 333 (3.4%) developed this complication, and 193 (1.9%) required a PPM. The incidence of postoperative AVB was highest in patients with corrections for congenitally corrected transposition of the great arteries (27.3%), the Konno procedure (20%), mitral valve replacement (16%), and arterial switch surgery with ventricular septal defect repair and aortic arch reconstruction (15%). A total of 134 patients had transient postoperative AVB, with a mean time to resolution of 4 days. By day 7, 75% of transient postoperative AVBs had resolved. By day 12, 90% had recovered, and by day 14, 95% had resolved. Identified risk factors for postoperative AVB included older age at the time of surgery (OR = 1.012), a diagnosis of infective endocarditis (OR = 2.4), prolonged myocardial ischemia times (OR = 1.018), and high-risk procedures (OR = 1.4).

The authors conclude that postoperative AVB is not a rare complication, with half of the affected patients requiring a PPM. They identify older age at the time of surgery, infective endocarditis, and complex procedures as risk factors for developing this condition. Based on their findings, they recommend deferring PPM indication until postoperative day 12, when 90% of transient postoperative AVBs have resolved.

COMMENTARY:

Guidelines issued by the European Society of Cardiology (ESC) recommend considering PPM implantation in patients with postoperative AVB if conduction has not recovered by day 7. Some treatments have been shown to shorten recovery time, as proved in a randomized study using dexamethasone (0.4 mg/kg, with a maximum dose of 30 mg/day). Premature indication for PPM implantation in pediatric patients has significant lifelong implications. These patients will require multiple generator replacements, face a higher risk of lead fractures due to growth and material fatigue, experience increased incidence of vascular thrombosis, and carry a greater risk of system infections throughout their lives.

Determining the degree of involvement of the conduction system in certain cases is not straightforward, as it depends not only on the type of procedure but also on the underlying congenital heart disease. In the case of perimembranous ventricular septal defects (VSDs) with inlet portion or posterior extension, it is known that the conduction system lies in the lower portion of the crest. If the VSD is infundibular or outlet, the conduction system is more distant. In muscular VSDs, conduction is usually far from the defect area. However, tricuspid valve straddling implies septal malalignment, which in turn displaces the node to an abnormal position, usually inferior and to the right. In atrioventricular canal defects, the node and its bundles are displaced posteroinferiorly, originating near the coronary sinus. In contrast, in congenitally corrected transposition of the great arteries, the node and its bundles are located in an anterosuperior plane. However, if this is associated with situs inversus, the conduction system returns to a posteroinferior location. In heterotaxy syndromes, mapping the conduction system is an enigma, as dual atrioventricular nodes may be present. If we add an absent coronary sinus, predicting the conduction system’s course becomes almost impossible. Some defects, like the congenitally corrected transposition of the great arteries, have a natural history of presenting conduction disturbances. Consequently, some groups, such as Boston Children’s Hospital, perform conduction system mapping during these procedures. Thus, the type of procedure, the underlying diagnosis, surgical precautions, and the course of postoperative AVB all play a role in determining PPM implantation.

One of the major limitations of this study, aside from the inherent ones of a single-center retrospective study, is the lack of data on late-onset postoperative AVB. How safe is it to discharge a patient who regains sinus rhythm on postoperative day 10? There is evidence of conduction system compromise, and even if sinus rhythm recovers, it remains uncertain whether this will be transient. In my opinion, and in line with published guidelines, such a patient warrants PPM implantation.

In conclusion, postoperative AVB is one of the most common indications for pacemaker implantation in congenital heart disease patients, especially pediatric cases. Efforts should be made to prevent this complication, but when it occurs, we must ensure that the patient is discharged without uncertainties regarding conduction system integrity.

REFERENCE:

Kruse K, Matsubara M, Schaeffer T, Palm J, Klawonn F, Osawa T, et al. Postoperative atrioventricular block after surgery for congenital heart disease: incidence, recovery, and risks. Eur J Cardiothorac Surg. 2025 Feb 24:ezaf059. doi: 10.1093/ejcts/ezaf059.