Intra-atrial Conduction Research Articles

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

Increased inter-atrial and intra-atrial conduction times in pediatric patients with non-alcoholic fatty liver disease.

The global incidence of pediatric non-alcoholic fatty liver disease (NAFLD) is rising, and it is linked to various potentially dangerous complications such as cardiovascular complications, particularly atrial fibrillation (AF). Atrial electromechanical conduction delay (EMD) has been reported as an early predictor for AF development. This study aimed to explore the link between NAFLD and the increased risk of AF development. This cross-sectional study was performed on 100 newly diagnosed NAFLD children (aged 14-18 years) as the patient group and 100 healthy individuals as a control group. Transthoracic echocardiography and simultaneous electrocardiography (ECG) recording were employed to estimate atrial electromechanical properties. EMD values were calculated for the inter-atrial, left intra-atrial, and right intra-atrial. Our results showed that pediatric patients with NAFLD exhibited significantly prolonged EMD values in the left and right intra-atrial as well as in inter-atrial regions compared to the control group (P = 0.03, P < 0.001, P < 0.01, respectively). Conclusion: Children with NAFLD show atrial electromechanical alterations that may presage AF in adulthood.

Bradycardia-dependent conduction block of the atrial tissue in a patient after double-chamber implantable cardioverter defibrillator implantation

Seldom are reports of phase 4 block or bradycardia-dependent conduction block in atrial tissue found in the literature. Here, we describe the case of a patient with sick sinus syndrome with Torsade de Pointes who, following the implantation of a double-chamber implantable cardioverter defibrillator, developed intra-atrial bradycardia-dependent conduction block. The patient's optimal pacing parameters were achieved by raising the rate.

Study of P wave dispersion in patients with paroxysmal atrial fibrillation and its role in prediction of atrial fibrillation recurrence

BackgroundIt has been known that increased P wave duration and P wave dispersion reflect prolongation of intra-atrial and interatrial conduction time and the inhomogeneous propagation of sinus impulses, which are well-known electrophysiologic characteristics in patients with atrial arrhythmias and especially paroxysmal atrial fibrillation. The objective of this study was assessment of P wave dispersion value in cases with paroxysmal atrial fibrillation and its role in predicting recurrence.ResultsForty-eight patients with documented paroxysmal AF were subjected to clinical evaluation, electrocardiogram and routine Doppler echocardiogram. We found that a statistically significant association was detected between P wave dispersion and older age, diabetic and hypertensive cases with positive correlation also detected with left atrial dimension (LAD), left ventricle size and diastolic dysfunction grade. Mean corrected P wave dispersion and corrected QT interval were higher among cases using sotalol, ca channel blockers, among cases using nitrates and among cases with Morris index > 0.04. Higher mean value of corrected QT was associated with biphasic P v1 shape. Old age, female sex, P wave dispersion and QT wave dispersion are statistically significant predictors of PAF recurrence.ConclusionP wave dispersion in patients with paroxysmal atrial fibrillation was strongly correlated to older age, diabetic and hypertensive patients and also with left atrial dimension (LAD), left ventricle size and diastolic dysfunction grade. Also, mean corrected P wave dispersion can predict atrial fibrillation recurrence in patients with Morris index > 0.04, old age, female sex, and QT wave dispersion.

Exercise-Induced Electrocardiographic Changes in Healthy Young Males with Early Repolarization Pattern.

Background: Exercise-induced modifications in ECG parameters among individuals with an early repolarization pattern (ERP) have not been evaluated in detail. We aimed to assess this phenomenon, with potential associations with arrhythmogenesis. Methods: Twenty-three young, healthy males with ERP (ERP+) participated in this study, alongside a control group, which consisted of nineteen healthy males without ERP (ERP-). ECGs at baseline, at peak exercise (Bruce protocol), and during the recovery phase were analyzed and compared between the two groups. Results: The treadmill test demonstrated strong cardiovascular fitness, with similar chronotropic and pressor responses in both groups. In the baseline ECGs, the QRS complex and the QT interval were shorter in the ERP+ group. During exercise, the P-wave duration was significantly longer and the QRS was narrower in the ERP+ group. In the recovery phase, there was a longer P wave and a narrower QRS in the ERP+ group. During the treadmill test, the J wave disappeared or did not meet the criteria required for ERP diagnosis. Conclusions: The slowed intra-atrial conduction found during exercise could be predictive of atrial arrhythmogenesis in the setting of ERP. The disappearing of J waves during exercise, due to increased sympathetic activity, has potential clinical significance.

Long-term outcomes after catheter ablation for idiopathic atypical atrial flutter

BackgroundIdiopathic atypical (non–cavotricuspid isthmus–dependent) atrial flutter (IAAFL) may be seen in patients without structural heart disease and without previous cardiac surgery or ablation. ObjectiveThis study sought to determine the patient characteristics, electrophysiologic and electroanatomic properties, and clinical outcomes after ablation in patients with IAAFL. MethodsWe retrospectively compared IAAFL patients with cavotricuspid isthmus–dependent AFL (C-AFL) patients undergoing catheter ablation. The primary outcome was a composite of death from cardiovascular causes, ischemic stroke, and hospitalization for worsening of heart failure. ResultsOf 180 patients who underwent catheter ablation for AFL, 89 were included in this study (22 IAAFL and 67 C-AFL). Electrophysiologic study showed significantly longer intra-atrial conduction time and lower atrial voltage during sinus rhythm in the IAAFL group compared with the C-AFL group. The atrial scar was observed in all 22 IAAFL patients, with the most common sites being the posterior or lateral wall of the right atrium in 10 (45.5%) and the anterior wall of the left atrium in 8 (36.4%). During 3.5 ± 2.8 years of follow-up, the composite primary end point occurred significantly more frequently in the IAAFL group (hazard ratio [HR], 3.45; 95% confidence interval [CI], 1.20–9.89; P = .015). In multivariable analysis, brain natriuretic peptide levels (HR, 1.01; 95% CI, 1.00–1.01, per 1 pg/mL; P = .01) and IAAFL (HR, 4.14; 95% CI, 1.21–14.07; P = .02) were independently associated with the primary outcome. ConclusionIAAFL in patients had distinct electrophysiologic features suggestive of atrial cardiomyopathy. These patients are at risk for development of cardiovascular adverse events after ablation.

Simultaneous assessment of mechanical and electrical function in Langendorff-perfused ex-vivo mouse hearts.

The Langendorff-perfused ex-vivo isolated heart model has been extensively used to study cardiac function for many years. However, electrical and mechanical function are often studied separately-despite growing proof of a complex electro-mechanical interaction in cardiac physiology and pathology. Therefore, we developed an isolated mouse heart perfusion system that allows simultaneous recording of electrical and mechanical function. Isolated mouse hearts were mounted on a Langendorff setup and electrical function was assessed via a pseudo-ECG and an octapolar catheter inserted in the right atrium and ventricle. Mechanical function was simultaneously assessed via a balloon inserted into the left ventricle coupled with pressure determination. Hearts were then submitted to an ischemia-reperfusion protocol. At baseline, heart rate, PR and QT intervals, intra-atrial and intra-ventricular conduction times, as well as ventricular effective refractory period, could be measured as parameters of cardiac electrical function. Left ventricular developed pressure (DP), left ventricular work (DP-heart rate product) and maximal velocities of contraction and relaxation were used to assess cardiac mechanical function. Cardiac arrhythmias were observed with episodes of bigeminy during which DP was significantly increased compared to that of sinus rhythm episodes. In addition, the extrasystole-triggered contraction was only 50% of that of sinus rhythm, recapitulating the "pulse deficit" phenomenon observed in bigeminy patients. After ischemia, the mechanical function significantly decreased and slowly recovered during reperfusion while most of the electrical parameters remained unchanged. Finally, the same electro-mechanical interaction during episodes of bigeminy at baseline was observed during reperfusion. Our modified Langendorff setup allows simultaneous recording of electrical and mechanical function on a beat-to-beat scale and can be used to study electro-mechanical interaction in isolated mouse hearts.

Effects of childhood obesity on myocardial performance, autonomic and conduction properties of the heart.

Childhood obesity tends to persist into adulthood and associated with increase in developing ischemic and non-ischemic cardiovascular diseases. We aimed to evaluate the effect of obesity on cardiac functions, atrial electromechanical coupling, and heart rate response, which are considered to be predictors of atrial fibrillation and sudden cardiac arrest. Study population included 52 obese children and 52 healthy controls. We performed 12-lead electrocardiography, echocardiographic examination, and treadmill exercise testing. Mitral, septal, and tricuspid segments were analysed by tissue Doppler imaging. Myocardial performance index (p = 0.011, p < 0.001, and p = 0.001, respectively) was higher and E'/A' ratio (p = 0.011, p < 0.001, and p < 0.001, respectively) was lower in obese group than controls. Atrial electromechanical coupling was longer in the obese group at all three segments (p < 0.001, p = 0.009, and p = 0.04, respectively). They had significantly longer interatrial (p < 0.001) and intra-atrial (p = 0.003) electromechanical conduction delay. While chronotropic index was similar between two groups, heart rate reserve was lower in obese children than controls (p = 0.043). The 1st- and 2nd-minute heart rate recovery indices of the obese group were lower compared to controls (p < 0.001 and p = 0.03, respectively). Body mass index was positively correlated with intra- and inter-atrial conduction times, whereas it was negatively correlated with heart rate recovery indices. We showed a deterioration in the diastolic function, atrial conduction, and heart rate response properties in children with obesity. Given the prognostic importance of these parameters, obese patients are might be at risk for atrial fibrillation and severe dysrhythmias from a young age.

Abstract 12072: EKG Appearance and Evolution of Baseline EKG-Characteristics in the Worldwide First Genetically Modified Porcine-to-Human Xenotransplant (“Pig Heart-in-Human Body”)

Introduction: The worldwide first genetically modified porcine-to-human cardiac xenotransplantation was performed in January 2022 at the University of Maryland with the recipient surviving for 61 days. Methods: Daily 12- lead ECGs were obtained during the post-operative period. Results: Accepted “pig heart-in-pig body” ECG parameters demonstrate a short PR interval (50-120ms), short QRS (70-90ms) and short QT (260-380ms). However, the first-ever EKG of a genetically modified heart xenotransplant (“pig heart-in-human body”) demonstrated a relatively longer PR interval of 190ms, QRS duration of 138ms and QT of 538ms (in setting of sinus bradycardia, interventricular conduction delay and inferior/antero-lateral T wave inversions; Figure 1). Prolonged intrinsic PR intervals remained stable during the post-operative course with 210±22ms [range 142-246ms]. However, atrial pacing demonstrated evidence of decremental intra-atrial conduction delay/AV-conduction delay most pronounced on day 12 (PR: 380ms). QRS duration remained prolonged with 145±16ms [range 116-192ms] but shortened during the post-operative course (day 21-40 vs 41-60: 148±14ms vs 132±11ms; p&lt;0.001). Increased QT persisted with 509±54ms [range 384-650ms] with dynamic fluctuations (QT nadir around day 14 (428±22ms vs 533±36ms; p&lt;0.001). Conclusions: ECG parameters of the first genetically modified porcine-to-human cardiac xenotransplant (“pig heart-in-human body”) demonstrated prolongation over the usually encountered ECG measurements in the donor (“pig heart- in-pig body”) including changes in cardiac depolarization and repolarization. Prolonged ECG parameters persisted but showed dynamic changes during post-operative period. This provides a first insight into the novel and evolving field of xenotransplanation suggesting a complex interplay of inter-species physiology and porcine denervation in addition to post-surgical and medication-related changes.

Does conduction heterogeneity determine the supervulnerable period after atrial fibrillation?

Atrial fibrillation (AF) resumes within 90 s in 27% of patients after sinus rhythm (SR) restoration. The aim of this study is to compare conduction heterogeneity during the supervulnerable period immediately after electrical cardioversion (ECV) with long-term SR in patients with AF. Epicardial mapping of both atria was performed during SR and premature atrial extrasystoles in patients in the ECV (N = 17, age: 73 ± 7 years) and control group (N = 17, age: 71 ± 6 years). Inter-electrode conduction times were used to identify areas of conduction delay (CD) (conduction times 7–11 ms) and conduction block (CB) (conduction times ≥ 12 ms). For all atrial regions, prevalences and length of longest CB and continuous CDCB lines, magnitude of conduction disorders, conduction velocity, biatrial activation time, and voltages did not differ between the ECV and control group during both SR and premature atrial extrasystoles (p ≥ 0.05). Hence, our data suggest that there may be no difference in biatrial conduction characteristics between the supervulnerable period after ECV and long-term SR in AF patients.Graphical abstractThe supervulnerable period after AF termination is not determined by conduction heterogeneity during SR and PACs. It is unknown to what extent intra-atrial conduction is impaired during the supervulnerable period immediately after ECV and whether different right and left atrial regions are equally affected. This high-resolution epicardial mapping study (upper left panel) of both atria shows that during SR the prevalences and length of longest CB and cCDCB lines (upper middle panel), magnitude of conduction disorders, CV and TAT (lower left panel), and voltages did not differ between the ECV and control group. Likewise, these parameters were comparable during PACs between the ECV and control group (lower left panel). †Non-normally distributed. cm/s = centimeters per second; mm = millimeter; ms = millisecond; AF = atrial fibrillation; AT = activation time; BB = Bachmann’s bundle; cCDCB = continuous lines of conduction delay and block; CB = conduction block; CD = conduction delay; CT = conduction time; CV = conduction velocity; ECV = electrical cardioversion; LA = left atrium; LAT = local activation times; PAC = premature atrial complexes; PVA = pulmonary vein area; RA = right atrium; SR = sinus rhythm; TAT = total activation time.

Benefit of right inferior pacing on conduction across Bachmanns Bundle

Abstract Background Bachmann's Bundle (BB) is the main preferential route for interatrial conduction and plays an important role in initiation and perpetuation of atrial tachyarrhythmia such as atrial fibrillation (AF). Especially in patients with inter- and intra-atrial conduction disorders, the conventional site for placement of right atrial (RA) pacing lead in the RA appendage (RAA) has been questioned as it results in a higher incidence of AF. However, it remains unknown how pacing from various sites affects conduction at BB. Purpose To examine the impact of programmed stimulation from the left and right atrium on activation and electrophysiological features of BB. Methods Intra-operative high-resolution epicardial mapping of BB was performed during sinus rhythm (SR) and programmed stimulation in 32 patients (29 male, 65±10 years). Programmed stimulation included a fixed rate sequence of average SR cycle length minus 50 ms provided from the RAA, junction of the RA with inferior caval vein (RAinf) and left atrial appendage (LAA). Electrophysiological features included unipolar voltage, conduction velocity, potential type (single, short/long double and fractionated) and conduction delay/block (CDCB). Results The average cycle length during SR was 962 [869–1085] ms. Pacing from RAA resulted in comparable activation patterns as during SR. As expected, pacing from LAA resulted in left-to-right conduction across BB. However, during pacing from RAinf in most patients activation started in the centre of BB. Compared to SR, the least amount of differences in electrophysiological features was found during pacing from the RAA, followed by pacing from RAinf and LAA. Unipolar voltages, conduction velocity and potential type distribution were similar. However, during pacing from RAinf, total activation time decreased compared to SR (44 [38–62] ms vs 60 [51–67] ms, P=0.012), while total activation time increased by pacing from LAA (66 [60–72] ms, P=0.020). The total activation time during pacing from RAinf was lower compared to LAA (P&amp;lt;0.001) and RAA pacing (P=0.001). During pacing from LAA, the amount of CDCB increased compared to SR (6.6 [4.1–9.9] % vs 8.7 [5.6–12.8] %, P=0.009), while there were no differences in CDCB between SR and pacing from both RAA and RAinf. Reduction of CDCB was most often achieved during pacing from RAinf (12 patients), especially in patients who already had a higher amount of CDCB during SR (8.0 [7.3–11.2] % vs 4.3 [3.0–5.9] %, P&amp;lt;0.001). Reduction of both CDCB and total activation time was achieved in 10 patients by pacing from RAinf, while only 6 patients benefitted from RAA pacing. These patients had similar amount of conduction disorders. Conclusions Pacing from the inferior RA results in a remarkable decrease of total activation time and conduction disorders compared to pacing from the LAA or RAA. As specific patients may benefit more from inferior RA pacing, locations for pacing lead placement should be individualized. Funding Acknowledgement Type of funding sources: None.

Treatment of atrial tachycardia arising after superior transseptal approach mitral valve surgery: Insights from ultra‐high‐density mapping to prevent atrioventricular block

Mitral valve surgery employing a superior transseptal approach (STA) is associated with arrhythmogenicity and intra-atrial conduction delay, despite being optimal for visualization of the surgical field. It is sometimes difficult to treat atrial tachycardias (AT) that arise after STA. To investigate AT circuits that arise after STA in detail in order to identify the optimal ablation line, using ultra high-resolution mapping (UHRM). We retrospectively analyzed 12 AT from 10 patients (median age 70 years, 9 males) who had undergone STA surgery. The tachycardias were mapped using the Rhythmia mapping system (Boston Scientific, Natick, Massachusetts). The 12 STA-related AT (STA-AT) circuits were classifiable as follows according to location of the optimal ablation line: (1) peri-septal incision STA-AT (n = 3), (2) cavotricuspid isthmus dependent STA-AT (n = 7) and (3) biatrial tachycardia (n = 2). Radiofrequency (RF) application terminated 11 of the 12 STA-AT. We found that difference in STA-AT circuit type was due to characteristics of the septal incision line made for STA. UHRM was important in identifying optimal ablation sites that did not create additional conduction disturbances in the right atrium. ATs after STA involve complex arrhythmia circuits due to multiple and long incision lines in the right atrium. Accurate understanding of the arrhythmia circuit and sinus conduction in the right atrium after STA is recommended for treating post-surgical tachycardia in a minimally invasive manner. This article is protected by copyright. All rights reserved.

Surgical and Electrical Anatomy of the Inter-Nodal and Intra-Atrial Conduction System in the Heart.

An anatomical understanding of the atrial myocardium is crucial for surgeons and interventionists who treat atrial arrhythmias. We reviewed the anatomy of the inter-nodal and intra-atrial conduction systems. The anterior inter-nodal route (#1) arises from the sinus node and runs through the ventral wall of the atrial chambers. The major branch of route #1 approaches the atrioventricular node from the anterior aspect. Other branches of route #1 are Bachmann’s bundle and a vestibular branch around the tricuspid valve. The middle inter-nodal route (#2) begins with a broad span of fibers at the sinus venarum and extends to the superior limbus of the oval fossa. The major branch of route #2 joins with the branch of route #1 at the anterior part of the atrioventricular node. The posterior inter-nodal route (#3) is at the terminal crest and gives rise to many branches at the pectinate muscles of the right atrium and then approaches the posterior atrioventricular node after joining with the vestibular branch of route #1. The branches of the left part of Bachmann’s bundle and the branches of the second inter-nodal route form a thin myocardial network at the posterior wall of the left atrium. These anatomical structures could be categorized into major routes and side branches. There are 9 or more anatomical circles in the atrial chambers that could be structural sites for macro re-entry. The implications of normal and abnormal structures of the myocardium for the pathogenesis and treatment of atrial arrhythmias are discussed.

Characterization of pre-existing arrhythmogenic substrate associated with de novo early and late postoperative atrial fibrillation

BackgroundPoAF is the most common complication after cardiac surgery and may occur in patients with pre-existing arrhythmogenic substrate. Characterization of this substrate could aid in identifying patients at risk for PoAF. We therefore compared intra-atrial conduction parameters and electrogram morphology between patients without and with early- (≤5 days after surgery) and late- (up to 5 years) postoperative atrial fibrillation (PoAF). Methods and resultsEpicardial mapping of the right and left atrium and Bachmann's Bundle (BB) was performed during sinus rhythm (SR) in 263 patients (207male, 67 ± 11 years). Unipolar potentials were classified as single, short or long double and fractionated potentials. Unipolar voltage, fractionation delay (time difference between the first and last deflection), conduction velocity (CV) and conduction block (CB) prevalence were measured. Comparing patients without (N = 166) and with PoAF (N = 97), PoAF was associated with lower CV and more CB at BB. Unipolar voltages were lower and more low-voltage areas were found at the left and right atrium and BB in PoAF patients. These differences were more pronounced in patients with late-PoAF (6%), which could even occur up to 5 years after surgery. Although several electrophysiological parameters were related to PoAF, age was the only independent predictor. ConclusionsPatients with de novo PoAF have more extensive arrhythmogenic substrate prior to cardiac surgery compared to those who remained in SR, which is even more pronounced in late-PoAF patients. Future studies should evaluate whether intra-operative electrophysiological examination enables identification of patients at risk for developing PoAF and hence (preventive) therapy.

The role of alcohol consumption on echocardiographic and electrophysiologic changes in atrial fibrillation.

A wealth of evidence suggests that alcohol consumption is a risk factor for atrial fibrillation (AF); however, the mechanisms underlying this association are unclear. This makes it challenging to develop therapeutic strategies in patients with AF attributed to alcohol consumption. To investigate the echocardiographic and electrophysiologic changes caused by alcohol consumption in patients with AF. The study was registered in Chinese Clinical Trial Registry (Registration number ChiCTR2000041575). Data on 134 consecutive non-valvular AF patients who underwent radiofrequency catheter ablation in our center was collected from April 1, 2019 to June 30, 2020. Patients were divided into no-alcohol (72) and alcohol groups [categorized into light (34), moderate (11) and heavy (17) alcohol consumption]. All patients underwent echocardiographic and electrophysiologic examinations for the assessment of left atrial (LA) strain, inter-atrial conduction, intra-atrial conduction, and atrial effective refractory period (ERP). Overall, the mean age was 61 ± 11 years and 87 (65%) were males. Compared with the no-alcohol group, impaired peak LA longitudinal strain, obvious inter-atrial conduction delay and increasing ERP dispersion were observed in the alcohol group. Intra-atrial conduction delay and ERP dispersion increased with increasing amounts of alcohol consumption. Alcohol consumption was associated with substantial abnormal echocardiographic and electrophysiologic changes in AF patients. These changes may contribute to the occurrence and progression of AF attributed to alcohol consumption, which may help in the development of new strategies for the prevention and management of AF. However further investigation is required.

PC-578-03 RIGHT ATRIAL ATYPICAL FLUTTER WITH 2:1 INTRA-ATRIAL BLOCK MIMICKING LEFT ATRIAL FOCAL AND LOCALISED REENTRANT TACHYCARDIA

Atrial-level blocks are known confounders for diagnosis of SVTs and commonly occur after previous linear ablation lesions. 1. To demonstrate importance of recognition of atrial-level block in SVT diagnosis and treatment. 2. To review underlying assumptions in using entrainment to localize SVT origins. 3. To discuss the importance of thorough biatrial mapping in determination of unclear SVT mechanisms. N/A A 74y M with a history of bioprosthetic MV replacement, atypical RA flutter ablation (2018), and permanent pacemaker (2020) for sick sinus syndrome presented with fatigue and 76% AF/AT burden. For index RA ablation, both an intercaval line using bridging scar near the atriotomy site anterior to the appendage and a cavotricuspid isthmus line were made. Tachycardia was induced via burst pacing. Initial entrainment from CS suggested a L-sided tachycardia. A Pentaray map of the tachycardia showed LA anteroseptal reentry with entrainment at the site giving a PPI-TCL < 30ms. PVI and anteroseptal line were performed which changed cycle length but not CS activation. LA re-mapping demonstrated focal breakout near RIPV; ablation lengthened cycle length to 290ms without rhythm cessation. After PVI confirmation, mapping of the RA showed 2:1 intra-atrial conduction in the lateral RA with 1:1 conduction in the septal RA (fig A). Mapping 1:1 areas of RA conduction showed a gap in previous IVC line with intact CTI block with the majority of the cycle length at the posteroseptal floor (fig B), immediately opposite the site of initial LA anteroseptal reentry (fig C). During ablation of IVC line gap, progressive lengthening of the TCL was noted followed by termination of rhythm without inducibility (fig D). Response to entrainment assumes 1:1 conduction through the entire circuit, and contributed to the appearance of a left sided tachycardia upon initial CS entrainment. The finding of a LA RIPV tachycardia upon remapping the LA after PVI is consistent with a separate focal tachycardia but could represent epicardial connections from the CS to the posterior LA.

Analysis of clinically-reported, memantine-induced cardiovascular adverse responses using the halothane-anesthetized dogs: Reverse translational study

Although NMDA receptor antagonist memantine is considered to be better tolerated than cholinesterase inhibitors on treating Alzheimer's disease, several types of cardiovascular adverse events have been associated with memantine treatment, including hypertension, myocardial infarction, severe bradycardia and QT-interval prolongation. In order to clarify how memantine induces these cardiovascular adverse events, we assessed its electropharmacological effects using the halothane-anesthetized dogs (n = 4). Memantine hydrochloride was intravenously administered in doses of 0.01, 0.1 and 1 mg/kg over 10 min, providing subtherapeutic, clinically-relevant and supratherapeutic concentrations, respectively. The low to high doses increased the mean blood pressure and left ventricular contraction and enhanced the atrioventricular nodal conduction, suggesting an increase of sympathicotonic output from the central nervous system similarly to donepezil, which might induce myocardial ischemia in patients with coronary artery disease. Meanwhile, the high dose suppressed the intra-atrial conduction and the low to high doses inhibited the intra-ventricular conduction, indicating potential to induce severe bradycardic adverse event by advanced cardiac conduction block in susceptible patients. Memantine alone did not induce repolarization delay, indicating lack of risk for inducing torsade de pointes. Thus, these in vivo experimental findings may provide basic information to better understand the clinically observed adverse events of memantine.

Prediction of Recurrent Atrial Tachyarrhythmia After Receiving Atrial Flutter Ablation in Patients With Prior Cardiac Surgery for Valvular Heart Disease.

Background: Surgical scars cause an intra-atrial conduction delay and anatomical obstacles that facilitate the perpetuation of atrial flutter (AFL). This study aimed to investigate the outcome and predictor of recurrent atrial tachyarrhythmia after catheter ablation in patients with prior cardiac surgery for valvular heart disease (VHD) who presented with AFL.Methods: Seventy-two patients with prior cardiac surgery for VHD who underwent AFL ablation were included. The patients were categorized into a typical AFL group (n = 45) and an atypical AFL group (n = 27). The endpoint was the recurrence of atrial tachyarrhythmia during follow-up. A multivariate analysis was performed to determine the predictor of recurrence.Results: No significant difference was found in the recurrence rate of atrial tachyarrhythmia between the two groups. Patients with concomitant atrial fibrillation (AF) had a higher recurrence of typical AFL compared with those without AF (13 vs. 0%, P = 0.012). In subgroup analysis, typical AFL patients with concomitant AF had a higher incidence of recurrent atrial tachyarrhythmia than those without it (53 vs. 14%, P = 0.006). Regarding patients without AF, the typical AFL group had a lower recurrence rate of atrial tachyarrhythmia than the atypical AFL group (14 vs. 40%, P = 0.043). Multivariate analysis showed that chronic kidney disease (CKD) and left atrial diameter (LAD) were independent predictors of recurrence.Conclusions: In our study cohort, concomitant AF was associated with recurrence of atrial tachyarrhythmia. CKD and LAD independently predicted recurrence after AFL ablation in patients who have undergone cardiac surgery for VHD.

Reduction of Conduction Velocity in Patients with Atrial Fibrillation.

It is unknown to what extent atrial fibrillation (AF) episodes affect intra-atrial conduction velocity (CV) and whether regional differences in local CV heterogeneities exist during sinus rhythm. This case-control study aims to compare CV assessed throughout both atria between patients with and without AF. Patients (n = 34) underwent intra-operative epicardial mapping of the right atrium (RA), Bachmann’s bundle (BB), left atrium (LA) and pulmonary vein area (PVA). CV vectors were constructed to calculate median CV in addition to total activation times (TAT) and unipolar voltages. Biatrial median CV did not differ between patients with and without AF (90 ± 8 cm/s vs. 92 ± 6 cm/s, p = 0.56); only BB showed a CV reduction in the AF group (79 ± 12 cm/s vs. 88 ± 11 cm/s, p = 0.02). In patients without AF, there was no predilection site for the lowest CV (P5) (RA: 12%; BB: 29%; LA: 29%; PVA: 29%). In patients with AF, lowest CV was most often measured at BB (53%) and ranged between 15 to 22 cm/s (median: 20 cm/s). Lowest CVs were also measured at the LA (18%) and PVA (29%), but not at the RA. AF was associated with a prolonged TAT (p = 0.03) and decreased voltages (P5) at BB (p = 0.02). BB was a predilection site for slowing of conduction in patients with AF. Prolonged TAT and decreased voltages were also found at this site. The next step will be to determine the relevance of a reduced CV at BB in relation to AF development and maintenance.

Proarrhythmic atrial structural and molecular remodeling with advancing age. Implications for post-coronary artery bypass grafting atrial fibrillation occurrence

Abstract Funding Acknowledgements Type of funding sources: Public grant(s) – National budget only. Main funding source(s): This work was supported by a grant of the Romanian Ministry of Education and Research, CNCS-UEFISCDI Background Advancing age has been identified as a strong predictor of post-coronary artery bypass grafting (CABG) atrial fibrillation (AF). However, the exact substrate underlying this increased aging-related propensity to post-CABG AF remains insufficiently understood. Purpose We aimed to assess whether a preexisting electrical, structural, autonomic, and/or molecular remodeling could explain the increased risk of elderly individuals for post-CABG AF occurrence. Methods Thirty-one consecutive patients free of AF history scheduled for an elective CABG procedure were prospectively evaluated. All patients underwent continuous ECG monitoring prior to and following the CABG procedure, up to the day of discharge. The occurrence of post-CABG AF was recorded. The right atrial appendage, normally considered "surgical waste", was collected and divided into 3 samples that were used for single cell action potential recordings using the microelectrode technique, for histological, and mRNA analysis. Electrical remodeling preexistent to CABG was assessed by P-wave analysis (i.e., amplitude, duration, fragmentation) using 12-lead surface ECG and Lewis leads recordings and atrial action potential analysis (i.e., amplitude, duration). Atrial structural remodeling was evaluated using echocardiographic (i.e., left atrial [LA] area and antero-posterior diameter) and histological (i.e., fibrosis and fat tissue infiltration) parameters. Autonomic remodeling was evaluated using heart rate variability analysis based on the pre-CABG Holter ECG recordings. Molecular remodeling was assessed by mRNA analysis of several genes previously incriminated in AF occurrence (i.e., CACNA1C, GJA5, KCNE2, KCNJ2, KCNQ1, and SCN5A). Results Post-CABG AF occurred in 11 (35.4%) patients. Patients with post-CABG AF were significantly older than their non-arrhythmic counterparts (65.2 ± 5.8 years vs. 58.0 ± 10.4 years; p = 0.04). Age above 59 years predicted post-CABG AF with 81.8% sensitivity and 57.9% specificity. All analyzed electrical and autonomic parameters were similar between patients above and below the age of 59 years (all p &amp;gt;0.05). However, patients &amp;gt;59 years had significantly higher LA area and diameter (both p&amp;lt; 0.01), more important atrial fatty infiltration (p = 0.02), and significantly lower mRNA expression of SCN5A (p = 0.01). Conclusion In the present cohort, post-CABG AF occurrence was 3.4-fold more common in patients &amp;gt;59 years than in their younger peers. Although there was no evidence of aging-related cellular electrical or autonomic remodeling, elderly individuals presented significantly more important LA dilation and atrial fatty infiltration, and significantly lower expression of SCN5A, encoding for Na+ channels. These changes could contribute to the increased aging-related propensity to post-CABG AF by altering intra-atrial conduction and promoting reentry.