Bachmann's Bundle Research Articles

The connection site of the Bachmann bundle to the left atrium affects atrial electrical and anatomical remodeling

Abstract Background A common route for the propagation of the conduction system from the right atrium to the left atrium (LA) is via the Bachmann bundle (BB) which is a parallel-aligned muscular structure. It is empirically known that the site of conduction from BB to LA differs depending on the patient. Purposes To clear the clinical significance of differences in the BB conduction sites in patients with atrial fibrillation (AF). Methods We studied 182 patients (90 non-paroxysmal AF, 121 males, and 68.2 ± 10.0 years) who received catheter ablation for AF. Clinical data, echocardiographic data, and blood samples were evaluated. High-density LA mapping during high right atrial pacing was constructed. The site of conduction from BB to LA, the global activation time, LA mean voltage, the abnormal conduction zone (ACZ), and the conduction block (CBZ) were evaluated. The conduction from BB was connected to the region surrounded by the left atrial roof line, the carina of the right pulmonary vein, and the base of the left atrial appendage in all patients (Figure 1). This area was divided into four regions (right-roof, mid-roof, right-anterior, and mid-anterior area), and BB conduction sites were classified into each area by three independent observers who did not know clinical data. Global activation time for the LA was calculated by subtracting the earliest from the latest activation within the LA. Isochronal activation maps were created at a 5-ms interval setting, and ACZ (Figure 2) and CBZ were identified on the activation map by locating a site with isochronal crowding of ≥3 isochrones and ≥8 isochrones, which were calculated as ≤27 cm/s and ≤10 cm/s. Results The conduction from BB was observed in 45 patients in the right-roof area, 24 in the mid-roof, 76 in the right-anterior, 23 cases in the mid-anterior, and 14 in multiple sites. Global activation time (right-roof 108±20, mid-roof 107±16, right-anterior 105±19, and mid-anterior 117±20ms, P=0.0781) was more prolonged and left atrium diameter was larger (42.1±6.6, 42.6±8.5, 42.5±6.6, and 46.4±6.6mm, P=0.0718) in patients with mid-anterior BB connections. LA mean voltage (4.90±1.94, 5.72±2.62, 4.13±1.58, and 4.88±1.96mV, P=0.0032) was higher and plasma brain natriuretic peptide level (139±138, 67±59, 128±139, and 164±197pg/mL, P=0.0861) was lower in patients with mid-roof BB connections. ACZ (41/45 91%, 20/24 83%, 73/76 96%, and 23/23 100%, P=0.0904) and CBZ (1/45 2%, 0/24 0%, 8/76 11%, and 2/23 9%, P=0.0850) appearance rates were lower in patients with mid-roof BB connections. Conclusion The connection site of the Bachmann bundle to the left atrium may affect atrial electrical and anatomical remodeling in patients with atrial fibrillation.

Verification of intra- and inter-atrial conduction during Bachmann's bundle pacing using longitudinal bi-atrial strain

Abstract Introduction Although atrial septal pacing has been reported to reduce atrial fibrillation (AF) burden, there is less evidence regarding its effect on the prevention of permanent AF and the improvement of long-term clinical outcomes. However, Bachmann's bundle pacing (BBp), which features P-wave morphology similar to sinus rhythm and shortened P-wave duration (PWD), was reported to significantly reduce permanent AF recurrences and occurrences compared with right atrial appendage pacing (RAAp) and non-specific right septal pacing. Purpose Possible mechanisms for AF suppression with BBp are that fast inter-atrial conduction through BB decreases global atrial activation time and the dispersion of the overall atrial refractoriness, and it prevents the decrease in left ventricular filling and increase in left atrial pressure associated with delayed left atrial contraction. Intra-and inter-atrial conduction during BBp was evaluated using longitudinal bi-atrial strain. Methods In patients with successful BBp implantation defined by electrocardiographic criteria using SelectSecure pacing lead and C315 delivery catheter (Medtronic, Inc), both left atrium (LA) and right atrium (RA) global longitudinal strain (GLS) in simultaneous phases were measured using Philips Ultrasound Workspace 2D Strain in apical 4-chamber view during atrial pacing to assess intra- and inter-atrial conduction delay. The atrial GLS were measured semi-automatically, and the strain rate was analyzed in the three segments of septal wall, lateral wall, and roof and their average. The negative peak of strain rate during atrial systole was the starting point of atrial contraction, and time to peak (TTP) was measured. The difference in TTP between septal and lateral walls in each atrium was measured as intra-atrial conduction delay and the difference in average TTP between LA and RA as inter-atrial conduction delay. Results Ten patients who underwent successful BBp were enrolled (Sick sinus syndrome: 3, advanced atrioventricular block: 2, complete atrioventricular block: 5). At implantation, bipolar atrial electrogram amplitude was 2.03±0.93 mV, atrial lead impedance was 632.7±157.6 Ω, and atrial pacing threshold was 0.7±0.2 V at 0.4 ms. The PWD during sinus rhythm on the 12-lead ECG was 132.8±10.6 ms, while during BBp it was 108.0±11.9 ms, which was significantly shorter in the BBp group (p<0.001). The intra-atrial conduction delay in RA and LA was 10.9 ± 12.1 ms and 12.1 ± 17.3 ms, respectively, and the inter-atrial conduction delay was 6.6 ± 8.6 ms. On the other hand, for the 10 RAAp and 10 sinus rhythm patients as control groups, the inter-atrial conduction delay was 29.7±13.8 ms and 8.5±9.5 ms, respectively. BBp had significantly less inter-atrial conduction delay than RAAp (p=0.005) and was comparable to sinus rhythm (p=0.719). Conclusion Longitudinal bi-atrial strain suggested that BBp significantly reduced inter-atrial delay and it might be effective in AF suppression.Longitudinal bi-atrial strain

Impact of conduction velocity in left atrium assessing with omnipolar technology in patients with atrial fibrillation

Abstract Background There is increased interest in exploring substrate of atrial fibrillation (AF) and recent studies have shown that atrial conduction velocity (CV) reflects the electrophysiological phenomena and plays key role in perpetuating AF. The novel omnipolar technology (OT) use three unipolar and two orthogonal bipolar signals allow us to analyze the voltage, activation direction, and CV independent of catheter position. Objective The purpose of the present study was to evaluate if the left atrium (LA) CV which assessed by OT predict the any atrial tachy-arrhythmia (AT) recurrence after initial AF ablation. Methods We enrolled 58 consecutive patients who underwent initial pulmonary vein isolation (PVI) for drug refractory AF. (mean age: 68.2±10.2 years old, 32 male(55.1%), 32 persistent AF(55.1%), CHADS2 score:1.6±0.6). After electrical PVI was achieved and remained in sinus rhythm, the LA was mapped with high density mapping catheter (Advisor HD Grid, Abott USA) utilizing with the novel OT combined with Ensite X system (Abott, USA). The conduction distance and conduction times were measured from the earliest activation site to the latest activation site in LA (Figure 1). Each conduction velocity in anterior, posterior, and septal area were also calculated as conduction distance divided by conduction time. The LA voltage was also measured. Results During a mean follow up period of 316±143 days, the recurrence of AT after initial PVI was observed in 9 (15.5%) patients. There were no significant differences in baseline demographics between AT recurrence and non-recurrence group (mean age:66±13.3 vs 68.5±10.5 years old P=0.66, CHADS2 score: 1.5±0.57 vs 1.68±0.62 P=0.59, proportion of persistent AF: 15.4% vs 15.5% P=0.82, LA volume: 102±35.9 vs 93.6±37.3ml P=0.63). The earliest activation site in LA were identified in 3 areas including anterior site of right pulmonary vein (51.7%), Bachmann bundle area (41.4%), and antero-septal area (6.89%) (Figure 2). In patients with AT recurrence, the CV in LA was significantly slower than those without AF recurrence(0.61±0.21 vs 0.81±0.16 m/s, P=0.036) whereas the whole LA voltage was not (1.52±0.75 vs 2.22±1.06 mv, P=0.28). The CV in each LA portion are similar between recurrence and non-recurrence AT group. (anterior:0.57±0.24 vs 0.81±0.23 m/s, P=0.18, posterior: 0.87±0.18 vs 1.2±0.49 m/s P=0.36, septal: 0.89±0.76 vs 1.15±0.39 m/s, P=0.41). Conclusion The earliest activation site in LA was varied in each case. The whole CV in LA is a predictor of AF recurrence after PVI whereas the CV of each LA portion and LA voltage was not.

Standardized Temporary Atrial Epicardial Wire Locations Lead to Enhanced Atrial Signal Identification.

Background: Arrhythmias, common after pediatric cardiac surgery, are associated with increased morbidity and mortality. Atrial epicardial wires (AEW) improve diagnostic accuracy but have variable pacing and sensing properties based on their location. Even so, there are no longitudinal prospective pediatric studies examining ideal placement of AEW. Methods: This multicenter study compared atrial amplitudes, pacing sensitivities and thresholds via AEW placed at Bachmann's Bundle (BB) and the interatrial groove near the right pulmonary veins (IGRPV) versus the surgeons' standard locations. An AtriAmp system was used to obtain an atrial ECG to calculate atrial and ventricular amplitude from atrial electrograms on the bedside monitor. Sensitivities and thresholds via a temporary pacemaker were documented. ANOVA tests with repeated measures and post-hoc pairwise comparisons were performed to compare variables within the first 24-h postoperative hours. Mixed effects linear regression models were employed to examine daily trends. Results: In the first 24-h following cardiac surgery, AEW at BB and IGRPV showed significantly larger atrial amplitudes than the surgeons' standard locations. In addition, there was a negative trend in atrial ECG amplitude in all AEW from postoperative days 0 to 1; however, subsequent days showed a positive mean change in atrial amplitude with largest increase seen at BB. Atrial sensing as measured by the temporary pacemaker had statistically greater atrial signal amplitude from the BB-IGRPV set in both polarities (ie, with the BB as the - or + electrode pair) as compared to the surgeons' standard locations. No difference in atrial thresholds (mA) were noted in the immediate postoperative period or over time, with a relatively low atrial threshold at all sites. Conclusion: Standardization of AEW at Bachmann's Bundle can yield largest atrial amplitudes by atrial ECG and highest atrial sensing parameters without compromising atrial thresholds.

Electrogram-guided Bachmann bundle area pacing to correct interatrial block: Initial experience, safety, and feasibility

BackgroundA lack of standard Bachman Bundle(BB) capture criteria has affected the clinical impact of Bachmann Bundle Area Pacing(BBAP) in patients with inter-atrial block(IAB). ObjectiveWe evaluated the feasibility and safety of electrogram guided BBP using sheath assisted, stylet-driven atrial lead implantation. MethodsPatients with a baseline IAB undergoing dual chamber PPI or ICD implantation were enrolled in a single center,prospective study. BBAP was attempted in all patients with the aid of a Selectra 3D S-40 delivery sheath and Solia S-60 pacing lead. BB capture was confirmed using a combination of fluoroscopy,P wave morphology,and electrophysiological criteria. These included the recording of a high frequency BB potential and a transition between non-selective(NS) to selective(S) BB capture during threshold testing. Procedure-related complications,lead parameters,and P wave morphology were assessed at implantation and follow up. ResultsPermanent BBAP was successful in 32 of the 36(88.9%) enrolled patients. Baseline P wave duration was 148.5+16.1ms. Among patients who underwent successful BBP, the final paced P wave duration was 117.8+19.6ms. There was a correction of the partial or complete interatrial block in 22(91.7%) and 6(75.0%) patients, respectively. BB potentials were recorded in 83.3% of all study patients.A transition from NS to S-BB capture could be demonstrated during threshold testing in 22(87.5%) patients. The only major complications were 2 BBAP lead dislodgements within 24 hours and a rise in pacing impedance at 3 weeks in 1 patient. ConclusionBBAP is feasible in a high percentage of patients and is associated with stable capture thresholds during follow up.

Pacemaker-induced atrial fibrillation reconsidered-associations with different pacing sites and prevention approaches.

The incidence of atrial fibrillation (AF) is significantly higher in patients with pacemakers than in the general population, which could be due to patient characteristics and the diagnostic tool of the pacemaker in detecting atrial high-rate episodes and subclinical AF, but also to the pacemaker itself providing AF-promoting conditions. It is well known that high ventricular pacemaker burden increases the likelihood of AF occurrence. However, the sites of atrial and ventricular pacing may also influence the risk for AF. The conventional sites for atrial and ventricular pacing are in the right atrial appendage and in the right ventricular apex. However, growing evidence suggests that alternative pacing sites may be superior for the prevention of AF. Bachmann bundle pacing, for example, promotes interatrial excitation conduction, resulting in atrial synchronicity and a shorter total atrial activation time, which may be preventive for the occurrence of AF. Moreover, in recent years, new ventricular pacing sites have come into focus with His bundle and left bundle branch pacing. In addition to the hemodynamic and electrophysiological cardiac benefits, these new options may also offer benefits in the prevention of AF. This review provides an overview of pacing-induced AF mechanisms and the association with different pacing sites, as well as approaches for prevention of pacing-induced AF, highlighting different sites and modes of atrial pacing and the newer sites of ventricular pacing.

Atrial anatomical variations on computed tomography angiography associated with atrial fibrillation and those predicting recurrence following pulmonary vein isolation

Abstract Background We aim to investigate the atrial anatomical variations in patients with and without atrial fibrillation (AF) using cardiac-computed tomography angiography (CCTA) and identify features associated with AF recurrence following pulmonary vein isolation. Materials and Methods We retrospectively reviewed 502 CCTAs of patients with AF performed prior to a pulmonary vein isolation procedure with 1058 CCTAs of patients without AF performed to rule out coronary artery disease between 2014 and 2017. Anatomical variations of both atria including left atrial diverticula (LAD), right atrial diverticula (RAD), Bachmann bundle shunt (BBS), and pulmonary vein anatomy were assessed. Results We found that patients with AF were older (67 ± 14 vs 63 ± 13 years, P = .039), had a higher prevalence of diabetes (24.4%) versus (14.7%), P = .006, and cerebrovascular accidents (3.8%) versus (0.9%), P = .044 when compared with patients without AF. Furthermore, on CCTAs patients with AF demonstrated a significantly higher prevalence of BBS (11% vs 4.1%, P < .001), LAD (19% vs 7.7%, P < .001), and RAD (9.8% vs 2.1%, P < .001) when compared to patients without AF. Logistic multivariable regression analyses of CCTA findings demonstrated increased odd ratios (OR) in those with AF of BBS (OR = 3.51, 95% CI, 2.32-5.35, P < .001), LAD (OR = 2.94, 95% CI, 2.12-4.07, P < .001), RAD (OR = 1.54, 95% CI, 1.19-2.11, P = .03), LA diameter (OR = 2.42, 95% CI, 1.65-3.39, P < .001). Importantly, multivariate Cox regression showed that the LA dimension is a predictor of AF recurrence (HR = 1.019, 95% CI, 1.001-1.051, P = .02). Conclusion AF patients have a higher prevalence of BBS, LAD, and RAD in comparison to patients without AF. Mean LA diameter predicts AF recurrence after the pulmonary vein isolation procedure.

Effect of atrial extrasystoles in electrophysiological properties in heart failure patients

Abstract Background Patients with heart failure (HF) most likely have an extensive arrhythmogenic substrate which increases vulnerability to atrial fibrillation (AF). Conduction disorders underlying this increased AF vulnerability -hidden during sinus rhythm- may be unmasked by spontaneous atrial extrasystole (AES). Objective The aim of this study is to investigate the impact of AES on potential arrhythmogenic electrophysiological properties in patients with HF and AES. Methods Intraoperative epicardial mapping of the right and left atrium (RA, LA), Bachmann’s bundle (BB) and pulmonary vein area (PVA) was performed in 132 patients (10 with HF and 122 without HF). Differences in unipolar potential morphologies and conduction disorders during SR and spontaneous AES were determined. Results A median of 1 (1–3) AES per patient were included. In patients with HF, AES were associated with lower median potential voltages (1.94mV versus 4.02mV, P<0.001), more low voltage areas (10.98% versus 4.97%, P=0.004) and a higher number of short double potentials (28.5% versus 13.0% of short double potentials, P<0.001) compared to patients without HF. Comparing differences (AES - SR) in parameters between patients with and without HF, there was a larger increase in long double potentials (+5.32% versus +0.31%, P<0.001), fractionated potential (+4.18% versus +0.49%, P=0.001), conduction block (+3.39% versus +0.63%, P=0.002) and continuous conduction delay and block (+6.72% versus +1.74%, P=0.001) in HF patients. Conclusions In HF patients, AES cause lower unipolar potentials voltages and more conduction disorders than in patients without HF. Differences in arrhythmogenic properties between sinus rhythm and atrial extrasystoles are more pronounced in HF patients. These results suggest that HF patients have hidden arrhythmogenic substrates that can be uncovered by AES and may explain the increased AF vulnerability.

The effect of bachmann bundle pacing on diastolic function in patients with non-obstructive HCM

Abstract Background and Objective Patients with non-obstructive HCM (nHCM) have advanced diastolic dysfunction and atrial remodeling, leading to increased heart failure hospitalisations. The objective of this study was to evaluate the role of Bachmann bundle pacing (BBP) in diastolic filling compared to right atrial appendage pacing (RAAP). Methods Forty patients with symptomatic nHCM and normal LV function were prospectively enrolled from January 2021 to June 2023. Inclusion criteria included electrocardiographic evidence of inter-atrial delay, E/e’ > 15, and an indication for ICD implantation. BBP was attempted in twenty patients, others underwent RAAP. A Biotronik Selectra 3D 40-S sheath was used for BBP in patients in whom initial lead implantation was unsuccessful. BBP was defined based on P-wave morphology and fluoroscopic lead position. The RV lead was implanted in the RV apex in all patients and the AV delay was optimized based on diastolic filling period and E/e’. Devices were programmed in DDD mode. During follow up, diastolic function, functional capacity, atrial fibrillation, and heart failure hospitalisations were assessed in both groups. Results Among the forty patients (age 48.2+7.8 yrs, males 75%, ESC-SCD Risk 4.3+0.6%), the baseline P wave duration, E/A, E/e’ were 138.4+16.4 ms, 2.5+0.5, and 17.5+2.4, respectively. Six patients (15%) had a history of paroxysmal AF (3 each in BBP and RAAP groups). Of the 16 patients (80%) who underwent successful BBP, the Selectra 3D 40-S sheath was used in 8 patients (Figure 1, Panel A). During BBP, a bachmann bundle potential was recorded in 7 of 16 patients (43.8%) (Figure 1, Panel C). The pacing threshold (1.5+0.5@0.4ms vs. 0.9+0.3@0.4ms, p=0.026) was higher and the atrial sensing (1.8+0.4 vs. 3.3+0.6, p=0.002) was lower in the BBP group compared to the RAAP group at 4 weeks and 6 months of follow up. There was an acute rise in threshold (2.1@0.4 ms) in 1 BBP patient at 4 weeks of follow up. Patients in the BBP group had a reduction in P wave duration compared to the patients in the RAAP group (-22.5 + 5.4 vs. +5.6 + 3.2 ms, p<0.001). During follow up (11.4 + 3.4 months), there was a significant improvement in diastolic function (E/e’), functional capacity (NYHA Class) and reduction in NT-proBNP in the BBB group compared to the RAAP group (Figure 1). The percentage of atrial pacing was similar in both groups (BBP 73.2 + 7.8 vs. RAAP 78.5 + 9.1 %, p=0.219). The risk of atrial fibrillation/tachycardia (12.5% vs. 35.0%, p=0.022) and heart failure hospitalisations (6.3% vs. 20%, p=0.042) was lower in the BBP group compared with RAAP during follow up. Conclusions BBP is safe and effective in improving diastolic function, functional capacity and heart failure hospitalizations in patients with nHCM.BBP Pacing using Selectra 3D 40-S SheathChange in E/e', NYHA, and NT-pro BNP

Short-term safety and feasibility of a practical approach to combined atrial and ventricular physiological pacing: An initial single-center experience

Traditional right atrial appendage (RAA) pacing accentuates conduction disturbances as opposed to Bachmann bundle pacing (BBP). The purpose of this study was to evaluate the feasibility, efficacy, and safety of routine anatomically guided high right atrial septal (HRAS) pacing with activation of Bachmann bundle combined with routine left bundle branch area pacing (LBBAP). This retrospective single-center study included 96 consecutive patients who underwent 1 of 2 strategies: physiological pacing (PP) (n = 32) with HRAS and LBBAP leads and conventional pacing (CP) (n = 64) with traditional RAA and right ventricular apical leads. Baseline characteristics, sensing, pacing thresholds, and impedances were recorded at implantation and follow-up. The PP and CP cohorts were of similar age (74.2 ± 13.8 years vs 73.9 ± 9.9 years) and sex (28.1% vs 40.6% female). There were no differences in procedural time (95.0 ± 31.4 minutes vs 86.5 ± 33.3 minutes; P = .19) or fluoroscopy time (12.1 ± 4.5 minutes vs 12.3 ± 13.5 minutes; P = .89) between cohorts. After excluding patients who received >2 leads, these parameters became significantly shorter in the CP cohort. The PP cohort exhibited higher atrial pacing thresholds (1.5 ± 1.1 mV vs 0.8 ± 0.3 mV; P <.001) and lower p waves (1.8 ± 0.8 mV vs 3.8 ± 2.3 mV; P <.001) at implantation and at follow-up. In the PP cohort, 72% of implants met criteria for BBP; of the ventricular leads, 94% demonstrated evidence of LBBAP. One lead-related complication occurred in each cohort. Routine placement of leads in the HRAS is a feasible and safe alternative to standard RAA pacing, allowing for BBP in 72% of patients. HRAS pacing can be combined with LBBAP as a routine strategy.

Bachmann bundle pacing

Bachmann bundle pacing

ECG at the Bedside: Atrial Bigeminy with Alternating long and Short PR Interval

The admission electrocardiogram of an 88-year-old woman, showed sinus rhythm, biphasic P waves in leads II, III, with the terminal vector directed upward, P duration 130 msec, PR interval 200 msec, consistent with advanced inter-atrial block. Next, atrial bigeminy occurred originating in the left atrium and delaying the sinus P waves. With the ectopic P’ measuring 60 msec, the likely path of left atrial stimuli to delaying the sinus node was through Bachmann’s bundle, by retrograde conduction. This means that inter-atrial conduction via Bachmann bundle.

Slow conduction velocity predicts atrial fibrillation recurrence after radiofrequency ablation.

To evaluate the progression of electrophysiological phenomena in atrial fibrillation (AF) and elucidate the association between the left atrial conduction velocity (LACV) and AF recurrence after pulmonary vein isolation. A total of 188 AF patients (121 paroxysmal AF and 67 persistent AF) who underwent PVI for the first time were enrolled in this prospective study. The left atrium was mapped using a 20-pole electrode catheter combined with the CARTO3 system. The conduction distances and conduction times of the left atrium from the Bachmann bundle area to the mitral isthmus were calculated. Anterior, posterior, and septal LACV were calculated as conduction distance divided by conduction time. The anterior, posterior, and septal LACVs in the AF recurrence group were slower than those in the nonrecurrence group (anterior: 0.807 [0.766, 0.848] and 1.048 [1.000, 1.093] m/s, p < .05; posterior: 1.037 [0.991, 1.084] vs. 1.315 [1.249, 1.380] m/s, p < .05; septal: 0.904 [0.862, 0.946] vs. 1.163 [1.107, 1.219] m/s, p < .05). The best cut-off value of anterior LACV for predicting AF recurrence was 0.887 m/s (sensitivity 73.9% and specificity 76.5%). Multivariate analysis showed slow anterior LACV<0.887 m/s was an independent predictor of AF recurrence with an adjusted odds ratio of 1.42 (1.04, 1.94). Slowing conduction velocity is a predictor of AF recurrence after pulmonary vein isolation.

Analysis of drug-induced and spontaneous cardioversions reveals similar patterns leading to termination of atrial fibrillation.

The mechanisms leading to the conversion of atrial fibrillation (AF) to sinus rhythm are poorly understood. This study describes the dynamic behavior of electrophysiological parameters and conduction patterns leading to spontaneous and pharmacological AF termination. Five independent groups of goats were investigated: (1) spontaneous termination of AF, and drug-induced terminations of AF by various potassium channel inhibitors: (2) AP14145, (3) PA-6, (4) XAF-1407, and (5) vernakalant. Bi-atrial contact mapping was performed during an open chest surgery and intervals with continuous and discrete atrial activity were determined. AF cycle length (AFCL), conduction velocity and path length were calculated for each interval, and the final conduction pattern preceding AF termination was evaluated. AF termination was preceded by a sudden episode of discrete activity both in the presence and absence of an antiarrhythmic drug. This episode was accompanied by substantial increases in AFCL and conduction velocity, resulting in prolongation of path length. In 77% ± 4% of all terminations the conduction pattern preceding AF termination involved medial to lateral conduction along Bachmann's bundle into both atria, followed by anterior to posterior conduction. This finding suggests conduction block in the interatrial septum and/or pulmonary vein area as final step of AF termination. AF termination is preceded by an increased organization of fibrillatory conduction. The termination itself is a sudden process with a critical role for the interplay between spatiotemporal organization and anatomical structure.

How sex affects the sinus rhythm heartbeat

BackgroundThere is increasing awareness of sex-specific differences in epidemiology and pathophysiology of atrial fibrillation (AF). It is, however, unknown whether males and females differ in atrial electrophysiological properties during sinus rhythm (SR). The aim of this study was therefore to investigate sex-based (regional) differences in electrophysiological properties during SR of the right (RA) and left (LA) atrium including Bachmanns Bundle (BB) and pulmonary vein region (PVA). MethodsIntra-operative, high resolution mapping during SR was performed in 53 matched females with males (without a history of AF), to measure lines of conduction block (CB), continuous conduction delay and block (cCDCB), conduction velocities (CV), total atrial activation times (TAT), unipolar potential voltages and percentage of low voltage areas (LVA). ResultsCompared to males, females have significantly 1) lower unipolar potential voltages and slower CV at both RA and BB, 2) more LVAs, CB and cCDCB lines and longer CB and cCDCB lines at the RA only (all P < 0.05). ConclusionsElectrophysiological properties of the atria during SR differ between males and females. These sex-based differences are particularly present at the RA and to a lesser degree at BB. In females, both the RA and BB contained more areas of conduction disorders and low voltage potentials. Future studies are required to investigate whether these areas play a role in sex-based differences in vulnerability to arrhythmias such as atrial fibrillation.

Biatrial flutters: unique circuits requiring a customized ablation approach

Abstract Introduction Atrial futters are macroreentrant tachycardias that typically involve several walls of a certain atrium, being the other atrium passively activated. Biatrial flutters (BAF) are peculiar macro-reentries associated with anterior/septal scars, involving both atria and using the interatrial connections. Purpose To characterize the mechanism of BAF a cohort of patients (pts) submitted to mapping and ablation. Methods Retrospective single-center study of pts with atypical atrial flutter submitted to ablation from 2015 to 2022. High resolution electroanatomical voltage and activation mapping were collected using Carto, Ensite or Rhythmia. Whenever the arrhythmia circuit was not fully displayed in a certain atrium, of the other atrium was mapped to fully characterize the reentrant circuit and establish the critical isthmus. Biatrial circuits were classified into 4 types: type 1, involving the mitral annulus and the tricuspid annulus, escaping the septal wall in both atria; type 2 using most of the mitral annulus and the right atrium (RA) septum; type 3, using both the left atrium (LA) and RA septum; and type 4, using most of the tricuspid annulus and the LA septum. Acute and long-term success was evaluated. Results From a total of 107 pts submitted to atypical flutter ablation, 5 pts presented BAF (3 male, median age: 55-yo), 4 of them previously submitted to cardiac surgery (CABG in 1, mitral valvuloplasty in 1, mitral+tricuspid valvuloplasty in 1 and surgical correction of aortic coarctation and ostium primum atrium septal defect in 1) and 1 had been previously submitted to pulmonary vein isolation (PVI), empirical roof line and cavotricuspid isthmus (CTI) ablation. A proximal-to-distal coronary sinus activation and extensive low-voltage areas at the septum were recognized in all these pts. The BAF mechanism was single loop in all of them, with a type 2 circuit in 2 pts, and types 1, 3 and 4 in one patient each. BAF types 1 and 4 were terminated with CTI ablation. BAF types 2 and 3 were terminated with linear ablations from the mitral annulus to the right superior PV, complemented with focal applications at Bachmann bundle insertion sites in the pts with type 2 BAF. Acute success was achieved in all pts. During a mean time of follow-up of 344±91 days, 1 pt had AFl recurrence. Conclusion BAF is a rare and complex arrhythmia, which is possible to ablate successfully by applying high-density mapping tools, a comprehensive analysis of the substrate/activation maps and a mechanism-tailored ablation strategy.

Abstract 17174: New Criteria for Block Across Anterior Mitral Line That Includes Bachmann’s Bundle in Patients With Scar Perimitral Flutter

Background: The recurrence rate of scar perimitral flutter (SMF) after anterior mitral line (AML) ablation remains high. Epicardial connections from high right atrium (HRA) to high lateral left atrium (HLA) including the Bachmann bundle (BB) plays a significant role in perimitral flutter recurrence. Hypothesis: We hypothesize that block across BB (BBB) during endocardial anterior line ablation reduces recurrence of atrial tachycardia (AT) and SMF. Methods: Patients undergoing left atrial ablation with SMF that were treated with AML were retrospectively enrolled. Pulmonary veins isolation and bidirectional AML block achieved in all patients. Baseline HRA-HLA, final HRA-HLA, and delta HRA-HLA intervals measured. Changes in HLA activation sequence determined. BBB identified when HRA-HLA interval increased with change in HLA activation sequence and confirmed with differential pacing. (Figure 1). The primary endpoint was recurrence of AT/SMF Results: We identified 101 patients, 51% comprised of women, with a mean age of 69. Patients who had AML without evidence of BBB were 48 compared to 53 patients who had AML with evidence of BBB. The mean baseline, final and delta HRA-LAA were 123 ± 42ms, 219 ± 45 ms and 96± 21 ms respectively in patients with BBB. After median follow up of 48 months, AT/SMF recurred in 43 % of patient without BBB vs 15 % in patient with BBB (p&lt;0.008) (Figure 2). In patients with BBB, delta HRA-HLA &gt;107ms discriminated between recurrence and no recurrence (p&lt;0.023ms and 93% negative predictive value) Conclusion: During endocardial AML ablation for SMF, bidirectional block with evidence of BBB is associated with significant reduction in AT/SMF recurrence.

Abstract 13542: Electrical Delay, LA Electromechanical Delay, and LA Volume Contribute to Increased LA Stiffness in Relatively Elderly Patients With Pulmonary Vein Isolation for Atrial Fibrillation

Background: Atrial dysfunction occurs after pulmonary vein isolation (PVI) for atrial fibrillation (AF), and some reports suggest that electrical conduction delay (ECD) via the Bachmann bundle could be a contributing factor. However, the relationship between ECD in the atria and LA function after PVI remains unclear. The LA reservoir strain (LARS) by speckle-tracking echocardiography (STE) is used to assess LA booster function, with a decrease indicating increased LA stiffness. Purpose: We aim to investigate ECD, LA electromechanical delay (LAEMD), and LA function in patients after PVI for AF. Methods: This single-center retrospective study included 74 patients (Mean age at 70.4 ± 9.1 years, 44 males, left ventricular ejection fraction (LVEF): 62.9 ± 6.8 %, LA volume index: LAVI 39.0 ± 10.8 ml/m 2 ) who were in sinus rhythm at the echocardiographic examination. ECD on the ECG was defined as the presence of biphasic P waves, which were classified into those not observed (group A; n=42), those observed only in III lead (group B; n=23), and those observed in all lower wall leads (II, III, aVF) (group C; n=9). LAEMD was defined as the time interval between the top of the R wave on the ECG and the start of the late diastolic wave (a') on the tissue doppler imaging, and the lateral (a' lateral) and septum (a' septum) time differences (a’ sep-lat time) were calculated. To evaluate the LA function, two-dimensional STE was analyzed. Results: Mean observation period was 19.2 months after PVI. Groups B and C showed significant differences in a' sep-lat time compared to group A. LARS was markedly reduced in all groups (average: 19.0 ± 6.3). LARS and LAVI showed a significant difference between groups A and C. Multivariate analysis of factors leading to LARS showed correlations with a', E/e'. Conclusion: These results suggest that in relatively elderly post-PVI AF patients with preserved LVEF, the ECD and LAEMD as well as LAVI may affect LA function long after PVI and contribute to increased LA stiffness.

Characterization of unipolar electrogram morphology: a novel tool for quantifying conduction inhomogeneity.

Areas of conduction inhomogeneity (CI) during sinus rhythm may facilitate the initiation and perpetuation of atrial fibrillation (AF). Currently, no tool is available to quantify the severity of CI. Our aim is to develop and validate a novel tool using unipolar electrograms (EGMs) only to quantify the severity of CI in the atria. Epicardial mapping of the right atrium (RA) and left atrium, including Bachmann's bundle, was performed in 235 patients undergoing coronary artery bypass grafting surgery. Conduction inhomogeneity was defined as the amount of conduction block. Electrograms were classified as single, short, long double (LDP), and fractionated potentials (FPs), and the fractionation duration of non-single potentials was measured. The proportion of low-voltage areas (LVAs, <1 mV) was calculated. Increased CI was associated with decreased potential voltages and increased LVAs, LDPs, and FPs. The Electrical Fingerprint Score consisting of RA EGM features, including LVAs and LDPs, was most accurate in predicting CI severity. The RA Electrical Fingerprint Score demonstrated the highest correlation with the amount of CI in both atria (r = 0.70, P < 0.001). The Electrical Fingerprint Score is a novel tool to quantify the severity of CI using only unipolar EGM characteristics recorded. This tool can be used to stage the degree of conduction abnormalities without constructing spatial activation patterns, potentially enabling early identification of patients at high risk of post-operative AF or selection of the appropriate ablation approach in addition to pulmonary vein isolation at the electrophysiology laboratory.

Bachmann's Bundle Modification in Addition to Circumferential Pulmonary Vein Isolation for Atrial Fibrillation: A Novel Ablation Strategy.

Bachmann's bundle (BB) is the main pathway of interatrial connection that could be involved in the development of atrial fibrillation (AF). Based on this hypothesis, we raised a novel ablation strategy, BB modification in addition to circumferential pulmonary vein isolation (CPVI-BB) in patients with AF. A retrospective cohort of patients with AF who underwent CPVI-BB or CPVI alone from March 2018 to July 2021 was enrolled in our study. Propensity score matching was performed in patients with paroxysmal AF and persistent AF, respectively, to reduce the risk of selection bias between the treatment strategies (CPVI-BB or CPVI alone). The primary endpoint was overall freedom from atrial arrhythmia recurrence through 12 months of follow-up. Our propensity score-matched cohort included 82 patients with paroxysmal AF (CPVI group: n = 41; CPVI-BB group: n = 41) and 168 patients with persistent AF (CPVI group: n = 84; CPVI-BB group: n = 84). Among patients with persistent AF, one-year freedom from atrial arrhythmia recurrence rate was 83.3% in the CPVI-BB group and 70.2% in the CPVI group (log-rank P = 0.047). Among patients with paroxysmal AF, no significant difference was found in the primary endpoint between two groups (85.4% in the CPVI-BB group vs. 80.5% in the CPVI group; log-rank P = 0.581). In addition, procedure-related complications and recurrence of atrial tachycardia or atrial flutter were similar between the two treatment groups, regardless of the type of AF. BB modification in addition to CPVI is an effective approach in increasing the maintenance of sinus rhythm in patients with persistent AF, while it does not improve the clinical outcomes of radiofrequency catheter ablation in patients with paroxysmal AF.