Background: Bachmann's bundle (BB) may potentially play a role in the earlier onset and faster progression of atrial fibrillation in adult patients with congenital heart disease (CHD). It is unknown whether electrophysiological alterations already exist at BB in pediatric patients with CHD and whether they are related to aging. Objective: This study aimed to investigate BB electrophysiology in pediatric patients with CHD and assess the impact of age on BB electrophysiology. Methods: BB mapping was conducted in 55 patients (0.2–17.5 years). Activation patterns, potential voltages, low-voltage areas (LVAs), potential morphology, and conduction disorders of BB were analyzed and correlated with age. Results: Right-to-left activation across BB occurred in 96.4% of patients. Potential voltage was on average 7.2 ± 3.0 mV, and LVAs occurred in 85.4% of patients. Median local conduction velocity was 96.6 (72.9–121.0) cm/s, and conduction block occurred in 56.4% of patients. Most potentials were single and short-double potentials; long-double and fractionated potentials were recorded in 49.1% and 72.7% of patients, respectively. Age was weakly correlated with potential voltages (r = 0.312, P = .020) and moderately with local conduction velocity (r = 0.439, P < .001), but not with potential morphology or conduction block. Conclusion: In pediatric patients with CHD, BB already contains a considerable amount of conduction disorders, LVAs, and potentials with complex morphology. The prevalence of these early electrophysiological alterations is not age related and does not differ among the right, left, and middle parts of BB.

Arrhythmias significantly contribute to morbidity and mortality in patients with congenital heart disease (CHD). While postoperative factors predisposing to arrhythmias are well-established, early electrophysiological alterations in pediatric CHD remain poorly understood. This review summarizes current knowledge on postnatal cardiac maturation, conduction-system development, and electrophysiological abnormalities in pediatric patients with and without CHD. Importantly, arrhythmia prevalence, mechanisms, and clinical relevance are systematically discussed across three pediatric groups, including healthy children and patients with unrepaired and repaired CHD. Understanding developmental arrhythmogenic mechanisms may facilitate early risk stratification, guide clinical management decisions, and improve long-term outcomes for pediatric patients with CHD. This review discusses the complex interplay between cardiac maturation, congenital defects, and arrhythmogenesis. It also outlines future directions that include noninvasive monitoring, selective intraoperative mapping, animal model studies, and standardized data collection to improve early risk stratification and long-term outcomes in children with CHD.

Background: Areas of conduction disorders play an important role in both initiation and perpetuation of AF and can be recognized by specific changes in unipolar potential morphology. For example, EGM fractionation may be caused by asynchronous activation of adjacent cardiomyocytes because of structural barriers such as fibrotic strands. However, it is unknown whether there are sex differences in unipolar potential morphology. Therefore, atrial potential morphologies during sinus rhythm (SR) were compared between male and female patients. Methods: Based on propensity score matching, 62 male and female patients in whom high-resolution mapping of the right atrium (RA), left atrium (LA), and pulmonary vein area (PVA) including Bachmann's bundle (BB) was performed during coronary bypass grafting surgery and/or valvular heart surgery. Unipolar potentials were classified as single potentials (SPs), short double potentials (SDPs), long double potentials (LDP), fractionated potentials (FPs) and fraction duration (FD). The proportion of conduction block lines was also determined. Results: Female patients had a higher proportion of SDPs, LDPs and FPs at the RA, and SDPs at BB. At the PVA, there were less SPs and more SDPs and FPs. In females, FDs were longer at the RA and PVA, and potential voltages of only SPs were lower at the RA (all P < 0.05). Females also had more CB at the RA and at PVA (P < 0.05). Conclusion: In females, the proportion of single unipolar potentials indicative of smooth conduction, was lower compared to males, at the RA and PVA and to a lesser degree at BB. Females also had more CB at RA and PVA. Hence, these results may reflect sex-differences in the degree of electrical remodeling.

Background: Aging induces structural remodeling, altering atrial electrogram morphology. Over time, structural and consequently electrical remodeling creates a substrate for atrial fibrillation. In structural heart disease, age-induced remodeling comes on top of a pre-existing degree of structural remodeling due to pressure or volume overload. Objective: Investigate the severity of age-related electrical remodeling in patients undergoing surgery for structural heart disease by utilizing a high resolution epicardial mapping approach. Methods: Five seconds of sinus rhythm were recorded intraoperatively at the right atrium (RA), Bachmann's bundle (BB), the left atrium, and the pulmonary vein area. Potential voltage, low-voltage area (LVA) and conduction velocity (CV) were assessed in all regions. Results: 104 patients were included (62,5 % male, age: 26–84 years) and categorized in three age groups: young-age (age <60 years, n = 40), middle-age (age 60–71 years, n = 33), or old-age (age ≥72 years, n = 31) group. Compared to the young-age group, the old-age group had 1) lower median potential voltages at RA (4.65 [3.53–5.62]mV versus 5.94 [4.86–6.79]mV, p = 0.001) and 2) lower CV at RA (87.86 [82.53–96.67]cm/s versus 94.81 [90.14–98.59]cm/s, p = 0.016) and BB (83.38 [67.72–94.96]cm/s versus 98.84 [86.58–102.90]cm/s, p = 0.005). Conclusions: Age-related electrophysiological changes in patients with structural heart disease include reduction in atrial potential voltages and slowing of CV. These changes were less pronounced in the middle-age group. This indicates that electrical remodeling is a combination of both the underlying heart disease and the aging process. However, the less pronounced changes in the middle-age group may reflect a more gradual progression of age-related remodeling.

Background: There is increasing evidence that presentation, progression, and management of atrial arrhythmias, such as atrial fibrillation (AF), differ between women and men. Bachmann’s bundle (BB) is the main route for interatrial conduction, and sex-related differences in structural and electrical remodeling of BB may contribute to differences in AF development between women and men. Objective: Investigate whether sex differences in the electrophysiological properties of BB assessed by high-resolution and density maps exist in patients with AF. Methods: Sinus rhythm at BB was recorded for 5 s during cardiac surgery. Potential voltage, low-voltage area (LVA), conduction heterogeneity, unipolar potential morphology, and conduction velocity were assessed for both men and women. Results: The study population consisted of 108 patients (73 men, 35 women). Women had significantly lower potential voltages (5th percentile: 0.7 mV [0.6–1.0] vs 1.1 mV [0.6–1.4], p = 0.028), more LVAs (10.8% [4.6–19.7] vs 4.3% [2.2–11.7], p = 0.012) and more long double potentials (11.1% [3.6–13.5] vs 5.0% [1.0–10.3], p = 0.015) compared to men. Conclusions: We observed sex-related differences in the electrical remodeling of BB in AF patients. Women have a higher proportion of low voltage potentials, and more abnormal potential morphologies compared to men. These findings may reflect sex-specific differences in the underlying substrate of AF at BB.

The electrical arrhythmogenic substrate underlying the most common cardiac arrhythmia atrial fibrillation (AF) may consist of conduction disorders, low-voltage areas, or fractionated potentials. High-density and resolution epicardial mapping (HDREM) approaches have been introduced to quantify and visualize electrophysiological properties of the atria. These approaches are essential for obtaining innovative insights into arrhythmogenic substrates and identifying novel targets for therapy. The aim of this review is to summarize and discuss the (1) contribution of HDREM studies to the knowledge on atrial arrhythmogenesis and (2) future applications of HDREM of atria in daily clinical practice.