Bi-atrial high-density mapping reveals inhibition of wavefront turning and reduction of complex propagation patterns as main antiarrhythmic mechanisms of vernakalant

Aims

Complex propagation patterns are observed in patients and models with stable atrial fibrillation (AF). The degree of this complexity is associated with AF stability. Experimental work suggests reduced wavefront turning as an important mechanism for widening of the excitable gap. The aim of this study was to investigate how sodium channel inhibition by vernakalant affects turning behaviour and propagation patterns during AF.

Methods and results

Two groups of 8 goats were instrumented with electrodes on the left atrium, and AF was maintained by burst pacing for 3 or 22 weeks. Measurements were performed at baseline and two dosages of vernakalant. Unipolar electrograms were mapped (249 electrodes/array) on the left and right atrium in an open-chest experiment. Local activation times and conduction vectors, flow lines, the number of fibrillation waves, and local re-entries were determined. At baseline, fibrillation patterns contained numerous individual fibrillation waves conducting in random directions. Vernakalant induced conduction slowing and cycle length prolongation and terminated AF in 13/15 goats. Local re-entries were strongly reduced. Local conduction vectors showed increased preferential directions and less beat-to-beat variability. Breakthroughs and waves were significantly reduced in number. Flow line curvature reduced and waves conducted more homogenously in one direction. Overall, complex propagation patterns were strongly reduced. No substantial differences in drug effects between right and left atria or between goats with different AF durations were observed.

Conclusions

Destabilization of AF by vernakalant is associated with a lowering of fibrillation frequency and inhibition of complex propagation patterns, wave turning, local re-entries, and breakthroughs.

Both beat-to-beat changes in RR-interval and left ventricular filling time determine ventricular function during atrial fibrillation

Aims

The irregular atrial electrical activity during atrial fibrillation (AF) is associated with a variable left ventricular (LV) systolic function. The mechanisms determining LV function during AF remain incompletely understood. We aimed at elucidating how changes in RR-interval and LV preload affect LV function during AF.

Methods and results

Beat-to-beat speckle-tracking echocardiography was performed in 10 persistent AF patients. We evaluated the relation between longitudinal LV peak strain and preceding RR-interval during AF. We used the CircAdapt computational model to evaluate beat-to-beat preload and peak strain during AF for each patient by imposing the patient-specific RR-interval sequences and a non-contractile atrial myocardium. Generic simulations with artificial RR-interval sequences quantified the haemodynamic changes induced by sudden irregular beats. Clinical data and simulations both showed a larger sensitivity of peak strain to changes in preceding RR-interval at slow heart rate (HR) (cycle length, CL <750 ms) than at faster HR. Simulations explained this by a difference in preload of the current beat. Generic simulations confirmed a larger sensitivity of peak strain to preceding RR-interval at fast HR (CL = 600 ms: Δ peak strain = 3.7% vs. 900 ms: Δ peak strain = 0.3%) as in the patients. They suggested that longer LV activation with respect to preceding RR-interval is determinant for this sensitivity.

Conclusions

During AF, longitudinal LV peak strain is highly variable, particularly at fast HR. Beat-to-beat changes in preload explain the differences in LV systolic function. Simulations revealed that a reduced diastolic LV filling time can explain the increased variability at fast HR.

Synergistic antiarrhythmic effect of inward rectifier current inhibition and pulmonary vein isolation in a 3D computer model for atrial fibrillation

AIMS

Recent clinical studies showed that antiarrhythmic drug (AAD) treatment and pulmonary vein isolation (PVI) synergistically reduce atrial fibrillation (AF) recurrences after initially successful ablation. Among newly developed atrial-selective AADs, inhibitors of the G-protein-gated acetylcholine-activated inward rectifier current (IKACh) were shown to effectively suppress AF in an experimental model but have not yet been evaluated clinically. We tested in silico whether inhibition of inward rectifier current or its combination with PVI reduces AF inducibility.

METHODS AND RESULTS

We simulated the effect of inward rectifier current blockade (IK blockade), PVI, and their combination on AF inducibility in a detailed three-dimensional model of the human atria with different degrees of fibrosis. IK blockade was simulated with a 30% reduction of its conductivity. Atrial fibrillation was initiated using incremental pacing applied at 20 different locations, in both atria. IK blockade effectively prevented AF induction in simulations without fibrosis as did PVI in simulations without fibrosis and with moderate fibrosis. Both interventions lost their efficacy in severe fibrosis. The combination of IK blockade and PVI prevented AF in simulations without fibrosis, with moderate fibrosis, and even with severe fibrosis. The combined therapy strongly decreased the number of fibrillation waves, due to a synergistic reduction of wavefront generation rate while the wavefront lifespan remained unchanged.

CONCLUSION

Newly developed blockers of atrial-specific inward rectifier currents, such as IKAch, might prevent AF occurrences and when combined with PVI effectively supress AF recurrences in human.

Paradigm shifts in electrophysiological mechanisms of atrial fibrillation

Determining the sequence of activation is a major source of information for understanding the electrophysiological mechanism(s) of atrial fibrillation (AF). However, the complex morphology of the electrograms hampers their analysis, and has stimulated generations of electrophysiologists to develop a large variety of technologies for recording, pre-processing, and analysis of fibrillation electrograms. This variability of approaches is mirrored by a large variability in the interpretation of fibrillation electrograms and, thereby, opinions regarding the basic electrophysiological mechanism(s) of AF vary widely. Multiple wavelets, different types of re-entry including rotors, double layers, multiple focal activation patterns all have been advocated, and a comprehensive and commonly accepted paradigm for the fundamental mechanisms of AF is still lacking. Here, we summarize the Maastricht perspective and Cleveland perspective regarding AF mechanism(s). We also describe some of the key observations in mapping of AF reported over the past decades, and how they changed over the years, often as results of new techniques introduced in the experimental field of AF research.

Automatic reconstruction of the left atrium activation from sparse intracardiac contact recordings by inverse estimate of fibre structure and anisotropic conduction in a patient-specific model

AIMS

Electric conduction in the atria is direction-dependent, being faster in fibre direction, and possibly heterogeneous due to structural remodelling. Intracardiac recordings of atrial activation may convey such information, but only with high-quality data. The aim of this study was to apply a patient-specific approach to enable such assessment even when data are scarce, noisy, and incomplete.

METHODS AND RESULTS

Contact intracardiac recordings in the left atrium from nine patients who underwent ablation therapy were collected before pulmonary veins isolation and retrospectively included in the study. The Personalized Inverse Eikonal Model from cardiac Electro-Anatomical Maps (PIEMAP), previously developed, has been used to reconstruct the conductivity tensor from sparse recordings of the activation. Regional fibre direction and conduction velocity were estimated from the fitted conductivity tensor and extensively cross-validated by clustered and sparse data removal. Electrical conductivity was successfully reconstructed in all patients. Cross-validation with respect to the measurements was excellent in seven patients (Pearson correlation r > 0.93) and modest in two patients (r = 0.62 and r = 0.74). Bland-Altman analysis showed a neglectable bias with respect to the measurements and the limit-of-agreement at -22.2 and 23.0 ms. Conduction velocity in the fibre direction was 82 ± 25 cm/s, whereas cross-fibre velocity was 46 ± 7 cm/s. Anisotropic ratio was 1.91±0.16. No significant inter-patient variability was observed. Personalized Inverse Eikonal model from cardiac Electro-Anatomical Maps correctly predicted activation times in late regions in all patients (r = 0.88) and was robust to a sparser dataset (r = 0.95).

CONCLUSION

Personalized Inverse Eikonal model from cardiac Electro-Anatomical Maps offers a novel approach to extrapolate the activation in unmapped regions and to assess conduction properties of the atria. It could be seamlessly integrated into existing electro-anatomic mapping systems. Personalized Inverse Eikonal model from cardiac Electro-Anatomical Maps also enables personalization of cardiac electrophysiology models.

Pulmonary vein isolation in a real-world population does not influence QTc interval

AIMS

We aimed to examine whether routine pulmonary vein isolation (PVI) induces significant ventricular repolarization changes as suggested earlier.

METHODS AND RESULTS

Five-minute electrocardiograms were recorded at hospital's admission (T-1d), 1 day after the PVI-procedure (T+1d) and at 3 months post-procedure (T+3m) from a registry of consecutive atrial fibrillation (AF) patients scheduled for routine PVI with different PVI modalities (radiofrequency, cryo-ablation, and hybrid). Only patients who were in sinus rhythm at all three recordings (n = 117) were included. QT-intervals and QT-dispersion were evaluated with custom-made software and QTc was calculated using Bazett's, Fridericia's, Framingham's, and Hodges' formulas. Both QT- and RR-intervals were significantly shorter at T+1d (399 ± 37 and 870 ± 141 ms) and T+3m (407 ± 36 and 950 ± 140 ms) compared with baseline (417 ± 36 and 1025 ± 164 ms). There was no statistically significant within-subject difference in QTc Fridericia (T-1d 416 ± 28 ms, T+1d 419 ± 33 ms, and T+3m 414 ± 25 ms) and QT-dispersion (T-1d 18 ± 12 ms, T+1d 21 ± 19 ms, and T+3m 17 ± 12 ms) between the recordings. A multiple linear regression model with age, sex, AF type, ablation technique, first/re-do ablation, and AF recurrence to predict the change in QTc at T+3m with respect to QTc at T-1d did not reach significance which indicates that the change in QTc does not differ between all subgroups (age, sex, AF type, ablation technique, first/re-do ablation, and AF recurrence).

CONCLUSION

Based on our data a routine PVI does not result in a prolongation of QTc in a real-world population. These findings, therefore, suggest that there is no need to intensify post-PVI QT-interval monitoring.

Incidence, prevalence, and trajectories of repetitive conduction patterns in human atrial fibrillation

AIMS

Repetitive conduction patterns in atrial fibrillation (AF) may reflect anatomical structures harbouring preferential conduction paths and indicate the presence of stationary sources for AF. Recently, we demonstrated a novel technique to detect repetitive patterns in high-density contact mapping of AF. As a first step towards repetitive pattern mapping to guide AF ablation, we determined the incidence, prevalence, and trajectories of repetitive conduction patterns in epicardial contact mapping of paroxysmal and persistent AF patients.

METHODS AND RESULTS

A 256-channel mapping array was used to record epicardial left and right AF electrograms in persistent AF (persAF, n = 9) and paroxysmal AF (pAF, n = 11) patients. Intervals containing repetitive conduction patterns were detected using recurrence plots. Activation movies, preferential conduction direction, and average activation sequence were used to characterize and classify conduction patterns. Repetitive patterns were identified in 33/40 recordings. Repetitive patterns were more prevalent in pAF compared with persAF [pAF: median 59%, inter-quartile range (41-72) vs. persAF: 39% (0-51), P < 0.01], larger [pAF: = 1.54 (1.15-1.96) vs. persAF: 1.16 (0.74-1.56) cm2, P < 0.001), and more stable [normalized preferentiality (0-1) pAF: 0.38 (0.25-0.50) vs. persAF: 0.23 (0-0.33), P < 0.01]. Most repetitive patterns were peripheral waves (87%), often with conduction block (69%), while breakthroughs (9%) and re-entries (2%) occurred less frequently.

CONCLUSION

High-density epicardial contact mapping in AF patients reveals frequent repetitive conduction patterns. In persistent AF patients, repetitive patterns were less frequent, smaller, and more variable than in paroxysmal AF patients. Future research should elucidate whether these patterns can help in finding AF ablation targets.

Dynamic risk assessment to improve quality of care in patients with atrial fibrillation: the 7th AFNET/EHRA Consensus Conference

AIMS

The risk of developing atrial fibrillation (AF) and its complications continues to increase, despite good progress in preventing AF-related strokes.

METHODS AND RESULTS

This article summarizes the outcomes of the 7th Consensus Conference of the Atrial Fibrillation NETwork (AFNET) and the European Heart Rhythm Association (EHRA) held in Lisbon in March 2019. Sixty-five international AF specialists met to present new data and find consensus on pressing issues in AF prevention, management and future research to improve care for patients with AF and prevent AF-related complications. This article is the main outcome of an interactive, iterative discussion between breakout specialist groups and the meeting plenary. AF patients have dynamic risk profiles requiring repeated assessment and risk-based therapy stratification to optimize quality of care. Interrogation of deeply phenotyped datasets with outcomes will lead to a better understanding of the cardiac and systemic effects of AF, interacting with comorbidities and predisposing factors, enabling stratified therapy. New proposals include an algorithm for the acute management of patients with AF and heart failure, a call for a refined, data-driven assessment of stroke risk, suggestions for anticoagulation use in special populations, and a call for rhythm control therapy selection based on risk of AF recurrence.

CONCLUSION

The remaining morbidity and mortality in patients with AF needs better characterization. Likely drivers of the remaining AF-related problems are AF burden, potentially treatable by rhythm control therapy, and concomitant conditions, potentially treatable by treating these conditions. Identifying the drivers of AF-related complications holds promise for stratified therapy.

Different circulating biomarkers in women and men with paroxysmal atrial fibrillation: results from the AF-RISK and RACE V studies

Aims

The clinical risk profile of atrial fibrillation (AF) patients is different in men and women. Our aim was to identify sex differences in blood biomarkers in patients with paroxysmal AF.

Methods and results

Sex differences in 92 blood biomarkers were measured in 364 patients included in our discovery cohort, the identification of a risk profile to guide atrial fibrillation therapy (AF-RISK) study, assessed by multivariable logistic regression and enrichment pathway analysis. Findings were subsequently confirmed in 213 patients included in our validation cohort, the Reappraisal of Atrial Fibrillation: Interaction between HyperCoagulability, Electrical remodelling, and Vascular Destabilisation in the Progression of AF (RACE V) study. In the discovery cohort, mean age was 59 ± 12 years, 41% were women. CHA₂DS₂-VASc-score was 1.6 ± 1.4. A total of 46% had hypertension, 10% diabetes, and 50% had heart failure, predominantly with preserved ejection fraction (47%). In women, activated leucocyte cell adhesion molecule (ALCAM) and fatty acid binding protein-4 (FABP-4) were higher. In men, matrix metalloproteinase-3 (MMP-3), C-C motif chemokine-16 (CCL-16), and myoglobin were higher. In the validation cohort, four out of five biomarkers could be confirmed: levels of ALCAM (P = 1.73 × 10^–4) and FABP-4 (P = 2.46 × 10^–7) and adhesion biological pathways [false discovery rate (FDR) = 1.23 × 10^–8] were higher in women. In men, levels of MMP-3 (P = 4.31 × 10^–8) and myoglobin (P = 2.10 × 10^–4) and markers for extracellular matrix degradation biological pathways (FDR = 3.59 × 10^–9) were higher.

Conclusion

In women with paroxysmal AF, inflammatory biomarkers were more often higher, while in men with paroxysmal AF, biomarkers for vascular remodelling were higher. Our data support the clinical notion that pathophysiological mechanisms in women and men with AF may differ.

Trial registration

Clinicaltrials.gov identifier NCT01510210 for AF-RISK; Clinicaltrials.gov NCT02726698 for RACE V.

Increased fibroblast accumulation in the equine heart following persistent atrial fibrillation

•

Persistent atrial fibrillation is associated with increased fibroblast accumulation.

•

Six weeks of persistent AF is not associated with structural remodeling.

•

Fibroblasts are potentially contributing to alteration in atrial electrophysiology.

Background

Fibroblasts maintain the extracellular matrix homeostasis and may couple to cardiomyocytes through gap junctions and thereby increase the susceptibility to slow conduction and cardiac arrhythmias, such as atrial fibrillation (AF). In this study, we used an equine model of persistent AF to characterize structural changes and the role of fibroblasts in the development of an arrhythmogenic substrate for AF.

Material and methods

Eleven horses were subjected to atrial tachypacing until self-sustained AF developed and were kept in AF for six weeks. Horses in sinus rhythm (SR) served as control. In terminal open-chest experiments conduction velocity (CV) was measured. Tissue was harvested and stained from selected sites. Automated image analysis was performed to assess fibrosis, fibroblasts, capillaries and various cardiomyocyte characteristics.

Results

Horses in SR showed a rate-dependent slowing of CV, while in horses with persistent AF this rate-dependency was completely abolished (CV•basic cycle length relation p = 0.0295). Overall and interstitial amounts of fibrosis were unchanged, but an increased fibroblast count was found in left atrial appendage, Bachmann's bundle, intraatrial septum and pulmonary veins (p < 0.05 for all) in horses with persistent AF. The percentage of α-SMA expressing fibroblasts remained the same between the groups.

Conclusion

Persistent AF resulted in fibroblast accumulation in several regions, particularly in the left atrial appendage. The increased number of fibroblasts could be a mediator of altered electrophysiology during AF. Targeting the fibroblast proliferation and differentiation could potentially serve as a novel therapeutic target slowing down the structural remodeling associated with AF.

Feasibility of digital atrial fibrillation screening in an elderly population : The Ulm heart rhythm weeks

AIMS

Atrial fibrillation (AF) screening in risk populations has the potential to prevent strokes. The authors tested the feasibility of a digital program with initial photoplethysmographic (PPG) self-screening and cardiologist-attended electrocardiographic (ECG) confirmation of screen-positive cases.

METHODS

Inhabitants of the city of Ulm aged ≥ 65 years were invited to participate. After digital consent, participants were given access to a smartphone application for 14 days of self-screening (two recordings per day recommended). Screen-positive participants without known AF were invited to present to a cardiologist for AF confirmation with a 14-day ECG event recorder. PPG recordings were first analyzed by algorithm using a combination of linear and non-linear methods. The quality of pathological (classified by algorithm) PPG and all ECG recordings were checked by a telecare service. Primary outcomes included adherence to the screening protocol defined as the proportion of participants performing at least 14 PPG recordings (or until documentation of absolute arrhythmia) and the proportion of pathological PPG and all ECG recordings rejected by the telecare center.

RESULTS

A total of 215 participants registered. Of these, 204 (95%) performed at least one recording and 169 (79%) reached the performance target of two sufficient measurements per day; 75 PPG recordings were automatically classified as pathological by algorithm; 14 (19%) were rejected by the telecare service due to poor quality. Of the 12 participants with a suspected first diagnosis of AF, five visited a cardiologist as part of the study. Of 1090 ECG recordings obtained, 390 (36%) were qualified as non-diagnostic. AF was confirmed in three cases.

CONCLUSIONS

A digital AF screening program with initial self-screening and referral of screen-positive cases to a cardiologist-attended ECG-confirmation service is feasible with meaningful results in an elderly risk population. However, the availability of the target population of persons > 65 years of age for such a digital screening program appears to be limited despite extensive public relations activities.

Clinical and electrophysiological predictors of device-detected new-onset atrial fibrillation during 3 years after cardiac surgery

Aims

Postoperative atrial fibrillation (POAF) after cardiac surgery is an independent predictor of stroke and mortality late after discharge. We aimed to determine the burden and predictors of early (up to 5th postoperative day) and late (after 5th postoperative day) new-onset atrial fibrillation (AF) using implantable loop recorders (ILRs) in patients undergoing open chest cardiac surgery.

Methods and results

Seventy-nine patients without a history of AF undergoing cardiac surgery underwent peri-operative high-resolution mapping of electrically induced AF and were followed 36 months after surgery using an ILR (Reveal XT™). Clinical and electrophysiological predictors of late POAF were assessed. POAF occurred in 46 patients (58%), with early POAF detected in 27 (34%) and late POAF in 37 patients (47%). Late POAF episodes were short-lasting (mostly between 2 min and 6 h) and showed a circadian rhythm pattern with a peak of episode initiation during daytime. In POAF patients, electrically induced AF showed more complex propagation patterns than in patients without POAF. Early POAF, right atrial (RA) volume, prolonged PR time, and advanced age were independent predictors of late POAF.

Conclusions

Late POAF occurred in 47% of patients without a history of AF. Patients who develop early POAF, with higher age, larger RA, or prolonged PR time have a higher risk of developing late POAF and may benefit from intensified rhythm follow-up after cardiac surgery.

Clinicaltrials.gov number

NCT01530750.

Predictors of recurrence of atrial fibrillation within the first 3 months after ablation

Aims

Freedom from atrial fibrillation (AF) at 1 year can be achieved in 50–70% of patients undergoing catheter ablation. Recurrent AF early after ablation most commonly terminates spontaneously without further interventional treatment but is associated with later recurrent AF. The aim of this investigation is to identify clinical and procedural factors associated with recurrence of AF early after ablation.

Methods and results

We retrospectively analysed data for recurrence of AF within the first 3 months after catheter ablation from the randomized controlled AXAFA–AFNET 5 trial, which demonstrated that continuous anticoagulation with apixaban is as safe and as effective compared to vitamin K antagonists in 678 patients undergoing first AF ablation. The primary outcome of first recurrent AF within 90 days was observed in 163 (28%) patients, in which 78 (48%) patients experienced an event within the first 14 days post-ablation. After multivariable adjustment, a history of stroke/transient ischaemic attack [hazard ratio (HR) 1.54, 95% confidence interval (CI) 0.93–2.6; P = 0.11], coronary artery disease (HR 1.85, 95% CI 1.20–2.86; P = 0.005), cardioversion during ablation (HR 1.78, 95% CI 1.26–2.49; P = 0.001), and an age:sex interaction for older women (HR 1.01, 95% CI 1.00–1.01; P = 0.04) were associated with recurrent AF. The P-wave duration at follow-up was significantly longer for patients with AF recurrence (129 ± 31 ms vs. 122 ± 22 ms in patients without AF, P = 0.03).

Conclusion

Half of all early AF recurrences within the first 3 months post-ablation occurred within the first 14 days post-ablation. Vascular disease and cardioversion during the procedure are strong predictors of recurrent AF. P-wave duration at follow-up was longer in patients with recurrent AF.

Trial registration

Clinicaltrials.gov identifier NCT02227550

Temporal patterns and short-term progression of paroxysmal atrial fibrillation: data from RACE V

Aims

Atrial fibrillation (AF) often starts as a paroxysmal self-terminating arrhythmia. Limited information is available on AF patterns and episode duration of paroxysmal AF. In paroxysmal AF patients, we longitudinally studied the temporal AF patterns, the association with clinical characteristics, and prevalence of AF progression.

Methods and results

In this interim analysis of the Reappraisal of AF: Interaction Between HyperCoagulability, Electrical Remodelling, and Vascular Destabilisation in the Progression of AF (RACE V) registry, 202 patients with paroxysmal AF were followed with continuous rhythm monitoring (implantable loop recorder or pacemaker) for 6 months. Mean age was 64 ± 9 years, 42% were women. Atrial fibrillation history was 2.1 (0.5–4.4) years, CHA₂DS₂-VASc 1.9 ± 1.3, 101 (50%) had hypertension, 69 (34%) heart failure. One-third had no AF during follow-up. Patients with long episodes (>12 hours) were often men with more comorbidities (heart failure, coronary artery disease, higher left ventricular mass). Patients with higher AF burden (>2.5%) were older with more comorbidities (worse renal function, higher calcium score, thicker intima media thickness). In 179 (89%) patients, 1-year rhythm follow-up was available. On a quarterly basis, average daily AF burden increased from 3.2% to 3.8%, 5.2%, and 6.1%. Compared to the first 6 months, 111 (62%) patients remained stable during the second 6 months, 39 (22%) showed progression to longer AF episodes, 8 (3%) developed persistent AF, and 29 (16%) patients showed AF regression.

Conclusions

In paroxysmal AF, temporal patterns differ suggesting that paroxysmal AF is not one entity. Atrial fibrillation burden is low and determined by number of comorbidities. Atrial fibrillation progression occurred in a substantial number.

Trial registration number

Clinicaltrials.gov identifier NCT02726698.

Effective termination of atrial fibrillation by SK channel inhibition is associated with a sudden organization of fibrillatory conduction

AIMS

Pharmacological termination of atrial fibrillation (AF) remains a challenge due to limited efficacy and potential ventricular proarrhythmic effects of antiarrhythmic drugs. SK channels are proposed as atrial-specific targets in the treatment of AF. Here, we investigated the effects of the new SK channel inhibitor AP14145.

METHODS AND RESULTS

Eight goats were implanted with pericardial electrodes for induction of AF (30 days). In an open-chest study, the atrial conduction velocity (CV) and effective refractory period (ERP) were measured during pacing. High-density mapping of both atrial free-walls was performed during AF and conduction properties were assessed. All measurements were performed at baseline and during AP14145 infusion [10 mg/kg/h (n = 1) or 20 mg/kg/h (n = 6)]. At an infusion rate of 20 mg/kg/h, AF terminated in five of six goats. AP14145 profoundly increased ERP and reduced CV during pacing. AP14145 increased spatiotemporal instability of conduction at short pacing cycle lengths. Atrial fibrillation cycle length and pathlength (AF cycle length × CV) underwent a strong dose-dependent prolongation. Conduction velocity during AF remained unchanged and conduction patterns remained complex until the last seconds before AF termination, during which a sudden and profound organization of fibrillatory conduction occurred.

CONCLUSION

AP14145 provided a successful therapy for termination of persistent AF in goats. During AF, AP14145 caused an ERP and AF cycle length prolongation. AP14145 slowed CV during fast pacing but did not lead to a further decrease during AF. Termination of AF was preceded by an abrupt organization of AF with a decline in the number of fibrillation waves.

Chronic obstructive pulmonary disease and atrial fibrillation: an interdisciplinary perspective

Chronic obstructive pulmonary disease (COPD) is highly prevalent among patients with atrial fibrillation (AF), shares common risk factors, and adds to the overall morbidity and mortality in this population. Additionally, it may promote AF and impair treatment efficacy. The prevalence of COPD in AF patients is high and is estimated to be ∼25%. Diagnosis and treatment of COPD in AF patients requires a close interdisciplinary collaboration between the electrophysiologist/cardiologist and pulmonologist. Differential diagnosis may be challenging, especially in elderly and smoking patients complaining of unspecific symptoms such as dyspnoea and fatigue. Routine evaluation of lung function and determination of natriuretic peptides and echocardiography may be reasonable to detect COPD and heart failure as contributing causes of dyspnoea. Acute exacerbation of COPD transiently increases AF risk due to hypoxia-mediated mechanisms, inflammation, increased use of beta-2 agonists, and autonomic changes. Observational data suggest that COPD promotes AF progression, increases AF recurrence after cardioversion, and reduces the efficacy of catheter-based antiarrhythmic therapy. However, it remains unclear whether treatment of COPD improves AF outcomes and which metric should be used to determine COPD severity and guide treatment in AF patients. Data from non-randomized studies suggest that COPD is associated with increased AF recurrence after electrical cardioversion and catheter ablation. Future prospective cohort studies in AF patients are needed to confirm the relationship between COPD and AF, the benefits of treatment of either COPD or AF in this population, and to clarify the need and cost-effectiveness of routine COPD screening.

Termination of atrial fibrillation during pharmacological cardioversion in the goat requires inter-atrial synchronisation of conduction

Funding Acknowledgements

Type of funding sources: Public grant(s) – EU funding. Main funding source(s): ITN Networks PersonalizeAF: Personalized Therapies for Atrial Fibrillation. A Translational Approach, No. 860974; CATCH ME: Characterizing Atrial fibrillation by Translating its Causes into Health Modifiers in the Elderly, No. 633196; MAESTRIA: Machine Learning and Artificial Intelligence for Early Detection of Stroke and Atrial Fibrillation, No. 965286; AFib-TrainNet: EU Training Network on Novel Targets and Methods in Atrial Fibrillation, No. 675351 Netherlands Heart Foundation: CVON2014-09, RACE V Reappraisal of Atrial Fibrillation: Interaction between hyperCoagulability, Electrical remodeling, and Vascular Destabilization in the Progression of Atrial Fibrillation

Background Few studies report on mechanisms leading to termination of atrial fibrillation (AF).

Purpose To characterise electrophysiological parameters and conduction patterns during the transition from AF to sinus rhythm under various conditions of AF termination.

Methods A retrospective evaluation of 6 goat studies was performed. AF was maintained for 3-4 weeks in 29 animals. Four animals were in SR. Unipolar electrograms were acquired with one 249-electrode array/atrium. Pharmacological termination of AF was evoked by various drugs; AP14145 (n = 5), PA6 (n = 7), XAF-1407 (n = 9) vernakalant (n = 8). In animals with sinus rhythm, AF was acutely induced and terminated spontaneously. Baseline AF and ≤3 recordings of the last 10 seconds preceding AF termination were analysed. Intervals with temporal continuous and periodic activity were distinguished in the recordings. AF cycle length (AFCL), conduction velocity and path length were determined for each interval.

Results In total, 85 AF terminations were recorded. Switches between temporal continuous and periodic activity were seen frequently during AF. However, termination of AF was always preceded by a phase of periodic activity (PA). The final phase of PA persisted for a median number of 21 [IQR 10-28] cycles in the left atrium and somewhat shorter in the right atrium, Table 1. This final phase of PA was accompanied by a profound bi-atrial increase of AFCL, conduction velocity and path length and a disappearance of inter-atrial cycle length differences. Equipotent changes were not observed in the preceding PAs. During the final AF beats, the number of wave fronts were low, 1 or 2. Interestingly, 92% of the patterns during the last beats of AF involved the Bachmann’s bundle as main source of atrial conduction.

Conclusion AF termination is preceded by an increased organisation of fibrillatory conduction, associated with abrupt prolongation of the path length. Propagation in atrial free walls regularly originated from the Bachmann’s bundle. These findings suggest that AF termination was not a random process but follows common spatiotemporal patterns. Final period of temporal organisation Left atrium Right atrium Final PA start Final PA end Final PA start Final PA end Af cycle length (ms) 163 ± 37 204 ± 50* 146 ± 44 207 ± 49* Conduction velocity (cm/s) 77 ± 15 96 ± 25* 83 ± 20 103 ± 24* Path Length (cm) 12.2 ± 2.7 19.3 ± 6.3* 12.0 ± 4.1 21.2 ± 6.4* Length of final periodic activity (beats) NA 21 [IQR 10-28] NA 15 [IQR 10- 25] Electrophysiological changes during the final period periodic activity (PA). Wilcoxon signed rank test. *p &lt;0.05NA= not available

RNA-seq profiling of the atrial transcriptome reveals gender-specific patterns and interactions with atrial fibrillation and heart failure

Funding Acknowledgements

Type of funding sources: Public grant(s) – EU funding. Main funding source(s): TRAIN-HEART Innovative Training Network, funded by the European Union’s Horizon 2020 research and innovation program (under the Marie Sklodowska-Curie grant agreement no. 813716) Characterizing Atrial fibrillation by Translating its Causes into Health Modifiers in the Elderly (CATCH ME), funded by the European Union’s Horizon 2020 research and innovation program (under the grant agreement no. 633196)

Background

Atrial fibrillation (AF) is the most common cardiac arrhythmia and is associated with heart failure (HF) and stroke. Clinical and experimental data from previous studies suggest gender differences in mechanisms and phenotypes of AF: women may have more atrial fibrosis, worse outcomes after catheter ablation, and some women carry a higher risk for thromboembolic complications than men. The molecular mechanisms underlying these differences are still poorly understood.

Methods

Gender-based transcriptional patterns were assessed using paired-end, directional RNA sequencing data generated from atrial tissue biopsies in 199 patients either in sinus rhythm or with paroxysmal or persistent AF as part of the CATCH-ME project. Transcript counts were compared between genders separately in the left and right atria using the DESeq2 package in R. The models were adjusted for potential sources of confounding (age, atrial fibrillation status, heart failure status and sequencing batch). Interaction models were implemented using DESeq2 to compare gender*morbidity interactions for persistent AF and HF. Significance was assessed using likelihood ratio tests comparing models with and without the interaction terms. Results with an adjusted P-value  0.05 were considered significant and utilized for subsequent downstream assessments. Differentially expressed (DE) genes were tested for enrichment of gene ontology (GO) terms and KEGG pathways using the WebGestalt toolkit.

Results

Transcriptome-wide profiling across the cohort identified 33 sex-differentiated genes in the left atria and 51 in the right atrial samples, with 21 of these showing bilateral differences. Interestingly, 36 (44%) of the results from these analyses were comprised of non-coding transcripts, including long non-coding RNAs (lncRNAs), antisense RNAs and pseudogenes. GO and pathway enrichment analyses for these genes revealed their involvement in critical pathways such as the complement and coagulation cascades and RNA transport.  Interaction analyses between gender and AF identified two genes (MPP2 & GNAS-AS1) that were differentially transcribed in the right atria and one gene (MYL2) that was DE in the left atria by gender in persistent AF samples. A similar analysis comparing gender*HF morbidity also revealed evidence of DE. Four transcripts (HLA-DQB1-AS1, EIF1AY, UTY and ZFY-AS1) showed gender-specific differences in expression by HF status in left atria, while HLA-DQB1-AS1 was differentially regulated by gender and HF status in right atrial samples.

Conclusions

These RNA-seq analyses provide novel insights into gender-related differences in the transcriptional landscape of right and left adult human atrial appendages. Moreover, interaction analyses identified three genes DE in female atria in persistent AF and four DE genes in female atria in heart failure, providing a molecular anchor for the observed differences in atrial diseases phenotypes between men and women.

Atrial function discriminates paroxysmal AF patients with HFpEF from those without HFpEF: subanalysis from AF-RISK study

Funding Acknowledgements

Type of funding sources: Public grant(s) – EU funding. Main funding source(s): European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie. Grant support from the Dutch Heart Foundation [NHS2010B233]

Background. Atrial fibrillation (AF) and heart failure with preserved ejection fraction (HFpEF) are two cardiovascular conditions that often coexist. Overlapping symptoms, biomarker profile, and echocardiographic changes hinder the diagnosis of underlying HFpEF in patients with AF and suggest that both conditions might reflect similar remodelling processes in the heart.

Purpose. To assess cardiac remodelling in AF patients with versus without concomitant HFpEF by transthoracic echocardiography, focusing on atrial dimension and strain.

Methods. We selected 120 patients included in AF-RISK, a prospective, observational, multicentre study aiming to identify a risk profile to guide atrial fibrillation therapy study. Patients had paroxysmal AF diagnosed within three years before inclusion, had a left ventricular ejection fraction (LVEF) ≥50% and were in sinus rhythm at the moment of performing echocardiography and blood sampling. Patients were matched by nearest neighbour by age and sex with a 1:1 ratio and were classified into two groups: 1) AF with HFpEF (n = 60) and 2) AF without HFpEF (n = 60). The diagnosis of HFpEF was based on the 2016 ESC heart failure guidelines, including symptoms and signs of heart failure, N-terminal pro-B-type natriuretic peptide (NT-proBNP) ≥125pg/ml, and one of the following echocardiographic measures: left atrium volume index (LAVI) &gt;34ml/m2, left ventricular mass index ≥115g/m2 for men and ≥95g/m2 for women, average E/e’ ≥13cm/s and average e’ &lt;9cm/s. Measurements of reservoir, conduit and contraction strain of both atria were performed in apical four-chamber by echocardiography (GE, EchoPac BT12). Associations of clinical and echocardiographic characteristics were tested for collinearity by multivariable logistic regression analyses. LAVI, LV mass index and NT-proBNP were excluded from multivariable analysis since these markers were part of the HFpEF diagnostic criteria.

Results. Patients with paroxysmal AF and concomitant HFpEF had more often hypertension (72% vs. 45%, P = 0.005), had more impaired strain phases of both the left and right atria (figure 1), had comparable LVEF and global longitudinal strain (GLS) (P = 0.168 and P = 0.212, respectively). In a model adjusted for the number of comorbidities and sex, LA contraction decrease was associated with presence of HFpEF (odds ratio per 1% LA contraction-percent was 0.94, 95% confidence interval 0.87–0.99, P = 0.042). LA contraction was not explained by LAVI in patients with concomitant HFpEF (Spearman’s rho= -0.07, P = 0.08). Conclusion. Our results show that atrial function may differentiate paroxysmal AF patients with HFpEF from those without HFpEF. In patients with paroxysmal AF, more impaired strain phases of the left and right atria were associated with concomitant HFpEF, whereas ventricular function, reflected by LVEF and GLS, did not differ. Abstract Figure. Strain distribution of both atria

The relation between the atrial blood supply and the complexity of acute atrial fibrillation

Background

Patients with a history of myocardial infarction and coronary artery disease (CAD) have a higher risk of developing AF. Conversely, patients with atrial fibrillation (AF) have a higher risk of developing myocardial infarction, suggesting a link in underlying pathophysiology. The aim of this study was to assess whether coronary angiographic parameters are associated with a substrate for AF in patients without a history of AF.

Methods

During cardiac surgery in 62 patients (coronary artery bypass grafting (CABG;n = 47), aortic valve replacement (AVR;n = 9) or CABG + AVR (n = 6)) without a history of clinical AF (age 65.4 ± 8.5 years, 26.2% female), AF was induced by burst pacing. The preoperative coronary angiogram (CAG) was assessed for the severity of CAD, and the adequacy of atrial coronary blood supply as quantified by a novel scoring system including the location and severity of right coronary artery disease in relation to the right atrial branches. Epicardial mapping of the right atrium (256 unipolar electrodes) was used to assess the complexity of induced AF.

Results

There was no association between the adequacy of right atrial coronary blood supply on preoperative CAG and AF complexity parameters. Multivariable analysis revealed that only increasing age (B0.232 (0.030;0.433),p = 0.03) and the presence of 3VD (B3.602 (0.187;7.018),p = 0.04) were independently associated with an increased maximal activation time difference.

Conclusions

The adequacy of epicardial right atrial blood supply is not associated with increased complexity of induced atrial fibrillation in patients without a history of clinical AF, while age and the extent of ventricular coronary artery disease are.

Role of pre-operative transthoracic echocardiography in predicting post-operative atrial fibrillation after cardiac surgery: a systematic review of the literature and meta-analysis

AIMS

This systematic review and meta-analysis aims to evaluate the role of pre-operative transthoracic echocardiography in predicting post-operative atrial fibrillation (POAF) after cardiac surgery.

METHODS AND RESULTS

Electronic databases were searched for studies reporting on pre-operative echocardiographic predictors of POAF in PubMed, Cochrane library, and Embase. A meta-analysis of echocardiographic predictors of POAF that were identified by at least five different publications was performed. Forty-three publications were included in this systematic review. Echocardiographic predictors for POAF included surrogate parameters for total atrial conduction time (TACT), structural cardiac changes, and functional disturbances. Meta-analysis showed that prolonged pre-operative PA-TDI interval [5 studies, Cohen's d = 1.4, 95% confidence interval (CI) 0.9-1.9], increased left atrial volume indexed for body surface area (LAVI) (23 studies, Cohen's d = 0.8, 95% CI 0.6-1.0), and reduced peak atrial longitudinal strain (PALS) (5 studies, Cohen's d = 1.4, 95% CI 1.0-1.8), were associated with POAF incidence. Left atrial volume indexed for body surface was the most important predicting factor in patients without a history of AF. These parameters remained important predictors of POAF in heterogeneous populations with variable age and comorbidities such as coronary artery disease and valvular disease.

CONCLUSION

This meta-analysis shows that increased TACT, increased LAVI, and reduced PALS are valuable parameters for predicting POAF in the early post-operative phase in a large variety of patients.