Anatomically Determined Functional Conduction Delay in the Posterior Left Atrium

Ablative Management of Persistent Atrial Fibrillation (PeAF) with Posterior Wall Isolation (PWI): Where Do We Stand?

Atrial fibrillation is a diverse clinical entity, with persistent atrial fibrillation (PeAF) being particularly challenging to manage. Through this paper, we discuss notable developments in our understanding of ablative strategies for managing PeAF, with a special focus on posterior wall isolation (PWI).

Effect of Catheter Ablation Using Pulmonary Vein Isolation With vs Without Posterior Left Atrial Wall Isolation on Atrial Arrhythmia Recurrence in Patients With Persistent Atrial Fibrillation: The CAPLA Randomized Clinical Trial

Importance

Pulmonary vein isolation (PVI) alone is less effective in patients with persistent atrial fibrillation (AF) compared with paroxysmal AF. The left atrial posterior wall may contribute to maintenance of persistent AF, and posterior wall isolation (PWI) is a common PVI adjunct. However, PWI has not been subjected to randomized comparison.

Objective

To compare PVI with PWI vs PVI alone in patients with persistent AF undergoing first-time catheter ablation.

Design, Setting, and Participants

Investigator initiated, multicenter, randomized clinical trial involving 11 centers in 3 countries (Australia, Canada, UK). Symptomatic patients with persistent AF were randomized 1:1 to either PVI with PWI or PVI alone. Patients were enrolled July 2018-March 2021, with 1-year follow-up completed March 2022.

Interventions

The PVI with PWI group (n = 170) underwent wide antral pulmonary vein isolation followed by posterior wall isolation involving linear ablation at the roof and floor to achieve electrical isolation. The PVI-alone group (n = 168) underwent wide antral pulmonary vein isolation alone.

Main Outcomes and Measures

Primary end point was freedom from any documented atrial arrhythmia of more than 30 seconds without antiarrhythmic medication at 12 months, after a single ablation procedure. The 23 secondary outcomes included freedom from atrial arrhythmia with/without antiarrhythmic medication after multiple procedures, freedom from symptomatic AF with/without antiarrhythmic medication after multiple procedures, AF burden between study groups at 12 months, procedural outcomes, and complications.

Results

Among 338 patients randomized (median age, 65.6 [IQR, 13.1] years; 76.9% men), 330 (97.6%) completed the study. After 12 months, 89 patients (52.4%) assigned to PVI with PWI were free from recurrent atrial arrhythmia without antiarrhythmic medication after a single procedure, compared with 90 (53.6%) assigned to PVI alone (between-group difference, -1.2%; hazard ratio [HR], 0.99 [95% CI, 0.73-1.36]; P = .98). Of the secondary end points, 9 showed no significant difference, including freedom from atrial arrhythmia with/without antiarrhythmic medication after multiple procedures (58.2% for PVI with PWI vs 60.1% for PVI alone; HR, 1.10 [95% CI, 0.79-1.55]; P = .57), freedom from symptomatic AF with/without antiarrhythmic medication after multiple procedures (68.2% vs 72%; HR, 1.20 [95% CI, 0.80-1.78]; P = .36) or AF burden (0% [IQR, 0%-2.3%] vs 0% [IQR, 0%-2.8%], P = .47). Mean procedural times (142 [SD, 69] vs 121 [SD, 57] minutes, P < .001) and ablation times (34 [SD, 21] vs 28 [SD, 12] minutes, P < .001) were significantly shorter for PVI alone. There were 6 complications for PVI with PWI and 4 for PVI alone.

Conclusions and Relevance

In patients undergoing first-time catheter ablation for persistent AF, the addition of PWI to PVI alone did not significantly improve freedom from atrial arrhythmia at 12 months compared with PVI alone. These findings do not support the empirical inclusion of PWI for ablation of persistent AF.

Trial Registration

anzctr.org.au Identifier: ACTRN12616001436460.

Short-term results of two strategies in thoracoscopic ablation for lone atrial fibrillation

Background: Thoracoscopic ablation is an effective treatment of patients with atrial fibrillation. Nowadays, 2 types of ablative devices are available in clinical practice allowing one to perform the thoracoscopic procedure Medtronic and AtriCure. However, the contemporary clinical literature does not have enough data that would compare these two approaches. Aims: to perform a comparative analysis of the short-term results of two minimally invasive strategies in thoracoscopic ablation for atrial fibrillation. Methods: 232 patients underwent thoracoscopic ablation for atrial fibrillation in two clinical centers for the period from 2016 to August 2021. The patients were divided into 2 groups. The first group was represented by those patients to whom a Medtronic device was applied (n=140), the second group was treated with an AtriCure device (n=92). The patients were comparable in their age, gender, initial severity of the condition. The follow-up consisted of laboratory tests, chest Х-ray, electrocardiography, 24-hour Holter monitor, echocardiography. The structure and prevalence of postoperative and intraoperative complications, specifics of the postoperative period were compared between the two groups. Results: According to the structure and prevalence of intraoperative complications the 2 groups are comparable to each other: 4.3% and 1.1% for the 1st group and 2nd group, respectively (p 0.05). The postoperative complications had developed in 6 (4.3%) and 5 (5.4%) patients in groups 1 and 2, respectively (p 0.05). At the time of discharge from hospital, a sinus rhythm was registered in 93.6% of patients (1st group), and 85.9% (2nd group) (p 0.05). Conclusions: Both strategies have demonstrated comparable short-term results in patients with lone atrial fibrillation. A further research is needed to evaluate the effectiveness of this strategy in a long-term period.

Long-term follow-up of thoracoscopic ablation in long-standing persistent atrial fibrillation

OBJECTIVES

Catheter ablation of long-standing persistent atrial fibrillation (LSPAF) remains challenging, with suboptimal success rates obtained following multiple procedures. Thoracoscopic ablation has shown effective at creating transmural lesions around the pulmonary veins and box; however, long-term rhythm follow-up data are lacking. This study aims, for the first time, to assess the long-term outcomes of thoracoscopic pulmonary vein and box ablation in LSPAF.

METHODS

Rhythm follow-up consisted of continuous rhythm monitoring using implanted loop recorders or 24-h Holter recordings. Rhythm status and touch-up interventions were assessed up to 5 years.

RESULTS

Seventy-seven patients with symptomatic LSPAF underwent thoracoscopic ablation in 2 centres. Freedom from atrial arrhythmias at 5 years was 50% following a single thoracoscopic procedure and 68% allowing endocardial touch-up procedures (performed in 21% of patients). The mean atrial fibrillation burden in patients with continuous monitoring was reduced from 100% preoperatively to 0.1% at the end of the blanking period and 8.0% during the second year. Antiarrhythmic drug use decreased from 49.4% preoperative to 12.1% and 14.3% at 2 and 5 years, respectively (P < 0.001). Continuous rhythm monitoring resulted in higher recurrence detection rates compared to 24-h Holter monitoring at 2-year follow-up (hazard ratio: 6.5, P = 0.003), with comparable recurrence rates at 5-year follow-up.

CONCLUSIONS

Thoracoscopic pulmonary vein and box isolation are effective in long-term restoration of sinus rhythm in LSPAF, especially when complemented by endocardial touch-up procedures, as demonstrated by the 68% freedom rate at 5 years. Continuous rhythm monitoring revealed earlier, but not more numerous documentation of recurrences at 5-year follow-up.

Catheter ablation for persistent atrial fibrillation: A multicenter randomized trial of pulmonary vein isolation (PVI) versus PVI with posterior left atrial wall isolation (PWI) - The CAPLA study

BACKGROUND

The success of pulmonary vein isolation (PVI) is reduced in persistent AF (PsAF) compared to paroxysmal AF. Adjunctive ablation strategies have failed to show consistent incremental benefit over PVI alone in randomized studies. The left atrial posterior wall is a potential source of non-PV triggers and atrial substrate which may promote the initiation and maintenance of PsAF. Adding posterior wall isolation (PWI) to PVI had shown conflicting outcomes, with earlier studies confounded by methodological limitations.

OBJECTIVES

To determine whether combining PWI with PVI significantly improves freedom from AF recurrence, compared to PVI alone, in patients with PsAF.

METHODS

This is a multi-center, prospective, international randomized clinical trial. 338 patients with symptomatic PsAF refractory to anti-arrhythmic therapy (AAD) will be randomized to either PVI alone or PVI with PWI in a 1:1 ratio. PVI involves wide antral circumferential pulmonary vein (PV) isolation, utilizing contact force sensing ablation catheters. PWI involves the creation of a floor line connecting the inferior aspect of the PVs, and a roof line connecting the superior aspect of the PVs. Follow up is for a minimum of 12 months with rhythm monitoring via implantable cardiac device and/or loop monitor, or frequent intermittent monitoring with an ECG device. The primary outcome is freedom from any documented atrial arrhythmia of > 30 seconds off AAD at 12 months, after a single ablation procedure.

CONCLUSIONS

This randomized study aims to determine the success and safety of adjunctive PWI to PVI in patients with persistent AF.

Repeat procedures for recurrent persistent atrial fibrillation: A propensity-matched score comparison between left atrial linear ablation with radiofrequency and posterior wall isolation with the cryoballoon

AIMS

To evaluate the clinical outcome in patients undergoing repeat procedures for recurrent persistent atrial fibrillation following an index cryoballoon (CB-A) pulmonary vein isolation ablation on a mid-term follow-up of 12 months.

METHODS

In this propensity score-matched comparison, 50 patients undergoing left atrial posterior wall isolation (LAPWI) with the CB-A were matched to 50 patients treated with additional linear ablation using radiofrequency catheter ablation (RFCA).

RESULTS

Meantime to repeat the procedure was 9.74 ± 4.36 months. At 12 months follow-up freedom from atrial tachyarrhythmias (ATas) was achieved in 82% of patients in the LAPWI group and in 62% of patients in the linear ablation group (P = .03). Regression analysis demonstrated that relapses during the blanking period and LA dimensions were independent predictors of ATas recurrences following the repeat procedure.

CONCLUSION

LAPWI using CB-A is associated with a significantly higher freedom from atrial arrhythmias when compared with the RFCA mediated left atrial linear lesions on a mid-term follow-up of 12 months in patients with persAF undergoing a redo procedure.

Spatial and temporal variability of rotational, focal, and irregular activity: Practical implications for mapping of atrial fibrillation

BACKGROUND

Charge density mapping of atrial fibrillation (AF) reveals dynamic localized rotational activation (LRA), irregular activation (LIA) and focal firing (FF). Their spatial stability, conduction characteristics and the optimal duration of mapping required to reveal these phenomena and has not been explored.

METHODS

Bi-atrial mapping of AF propagation was undertaken using AcQMap (Acutus Medical) and variability of activation patterns quantified up to a duration of 30 s. The frequency of each pattern was quantified at each unique point of the chamber over two separate 30-s recordings before ablation and R² calculated to quantify spatial stability. Regions with the highest frequency were identified at increasing time durations and compared to the result over 30 s using Cohen's kappa. Properties of regions with the most stable patterns were assessed during sinus rhythm and extrastimulus pacing.

RESULTS

In 21 patients, 62 paired LA and RA maps were obtained. LIA was highly spatially stable with R² between maps of 0.83 (0.71-0.88) compared to 0.39 (0.24-0.57), and 0.64 (0.54-0.73) for LRA and FF, respectively. LIA was most temporally stable with a kappa of >0.8 reached by 12 s. LRA showed greatest variability with kappa >0.8 only after 22 s. Regions of LIA were of normal voltage amplitude (1.09 mv) but showed increased conduction heterogeneity during extrastimulus pacing (p = .0480).

CONCLUSION

Irregular activation patterns characterized by changing wavefront direction are temporally and spatially stable in contrast with LRA that is transient with least spatial stability. Focal activation appears of intermediate stability. Regions of LIA show increased heterogeneity following extrastimulus pacing and may represent fixed anatomical substrate.

Premature atrial stimulation accentuates conduction abnormalities in cardiac surgery patients that develop postoperative atrial fibrillation

BACKGROUND

postoperative atrial fibrillation (POAF) is a common cardiac surgery complication that is associated with increased complications and negative outcomes, but the association between presurgical atrial conduction abnormalities and POAF has not been investigated clinically during premature atrial S1S2 stimulation. This clinical study sought to examine whether intraoperative premature atrial stimulation reveals increased areas of slowed and/or blocked conduction in patients that develop POAF.

METHODS

High-density intraoperative epicardial left atrial mapping was conducted in 20 cardiac surgery patients with no prior history of atrial fibrillation (AF). In 20 patients, 6 (30%) developed POAF. A flexible-array of 240-electrodes was placed on the posterior left atrial wall in between the pulmonary veins. Activation maps were generated for sinus and premature atrial S1S2 stimulated beats. The area of conduction block (CB), conduction delay (CD) and the combination of both (CDCB) for conduction velocity < 0.1, 0.1 ≤ x < 0.2 and < 0.2 m/s, respectively were quantified.

RESULTS

For a premature atrial S2 beat with shortest cycle length captured, conduction velocity maps revealed a significantly higher area for CD (13.19 ± 6.59 versus 6.06 ± 4.22 mm², p = 0.028) and CDCB (17.36 ± 8.75 versus 7.41 ± 6.39 mm², p = 0.034), and a trend toward a larger area for CB (4.17 ± 3.66 versus 1.34 ± 2.86 mm², p = 0.063) in patients who developed POAF in comparison to those that remained in the sinus. Sinus and S1 paced beats did not show substantial differences in abnormal conduction areas between patients with and without POAF.

CONCLUSION

In comparison to sinus and S1 beats, premature atrial S2 beats accentuate conduction abnormalities in the posterior left atrial wall of cardiac surgery patients that developed POAF.

Is the abnormal conduction zone of the left atrium a precursor to a low voltage area in patients with atrial fibrillation?

BACKGROUND

The abnormal conduction zone (ACZ) in the left atrium (LA) has attracted attention as an arrhythmia source in atrial fibrillation (AF). We investigated the hypothesis that the ACZ is related to the low voltage area (LVA) or the LA anatomical contact areas (CoAs) with other organs.

METHODS AND RESULTS

We studied 100 patients (49 non-paroxysmal AF, 66 males, and 67.9 ± 9.9 years) who received catheter ablation for AF. High-density LA mapping during high right atrial pacing was constructed. Isochronal activation maps were created at 5-ms interval setting, and the ACZ was identified on the activation map by locating a site with isochronal crowding of ≥3 isochrones, which are calculated as ≤27 cm/s. The LVA was defined as the following; mild ( < 1.3 mV), moderate (<1.0 mV), and severe LVA (<0.5 mV). The CoAs (ascending aorta-anterior LA, descending aorta-posterior LA, and vertebrae-posterior LA) were assessed using computed tomography. The ACZ was linearly distributed, and observed in 95 patients (95%). The ACZ was most frequently observed in the anterior wall region (77%). A longer ACZ was significantly associated with a larger LA size and a prevalence of non-PAF. The 51.2 ± 36.2% of ACZ overlapped with mild LVA, 32.9 ± 32.8% of ACZ with moderate LVA, and 14.6 ± 22.0% of ACZ with severe LVA. In contrast, only 25.6 ± 28.0% of ACZ matched with the CoAs.

CONCLUSION

The ACZ reflects LA electrical remodeling and may be a precursor finding of the low voltage zone and not the LA CoAs in patients with atrial fibrillation.

Impact of atrial programmed electrical stimulation techniques on unipolar electrogram morphology

INTRODUCTION

Intra-atrial conduction abnormalities are associated with the development of atrial fibrillation (AF) and cause morphological changes of the unipolar atrial electrogram (U-AEGM). This study examined the impact of different atrial programmed electrical stimulation (APES) protocols on U-AEGM morphology to identify the most optimal APES protocol provoking conduction abnormalities.

METHODS

APES techniques (14 protocols) were applied in 30 patients referred for an electrophysiology study, consisting of fixed rate, extra, and decremental stimuli at different frequencies. U-AEGM morphologies including width, amplitude, and fractionation for patients without (control group) and with a history of AF (AF group) were examined during APES. In addition, sinus rhythm (SR) U-AEGMs preceding different APES protocols were compared to evaluate the morphology stability over time.

RESULTS

U-AEGM morphologies during SR before the APES protocols were comparable (all P > .396). Atrial refractoriness was longer in the AF group compared to the control group (298 ± 48 vs 255 ± 33 ms; P ≤ .020), but did not differ between AF patients with and without amiodarone therapy (278 ± 48 vs 311 ± 40 ms; P ≥ .126). Compared to the initial SR morphology, U-AEGM width, amplitude, and fractionation changed significantly during the 14 different APES protocols, particularly in the AF group. In both groups, U-AEGM changes in morphology were most pronounced during fixed-rate stimulation with extra stimuli (8S1-S2 = 400-250 ms).

CONCLUSION

APES results in significant changes in U-AEGM morphology, including width, amplitude, and fractionation. The impact of APES differed between APES sequence and between patients with and without AF. These findings suggest that APES could be useful to identify AF-related conduction abnormalities in the individual patient.

European multicentre experience of staged hybrid atrial fibrillation ablation for the treatment of persistent and longstanding persistent atrial fibrillation

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The 2 stage hybrid method combines epicardial and endocardial ablation.

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Its main role is for drug refractory, long-standing persistent AF.

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56% were free of atrial arrhythmia recurrence at 18 months post the second stage catheter ablation off antiarrhythmic drugs.

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During follow-up 10.8% of patients had redo catheter ablation.

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75% of the 175 patents were in sinus rhythm at latest clinical follow-up including those on antiarrhythmic drugs.

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Clinically important complications occurred in 5% with 1 death (0.6%).

The management of non-paroxysmal atrial fibrillation (AF) remains controversial. We examined the efficacy and safety of the 2 stage Hybrid AF ablation approach by analysing the largest series of this technique reported so far.

Methods

The approach aims to electrically isolate the left atrial posterior wall incorporating the pulmonary veins (‘box-set’pattern). An initial video-assisted thoracoscopic (VATS) epicardial ablation is followed after a minimum of 8 weeks by endocardial radiofrequency catheter ablation.

Results

Of 175 patients from 4 European cardiothoracic centers, who underwent the surgical (COBRA Fusion, AtriCure Inc) 1st stage ablation, 166 went on to complete 2nd stage catheter ablation. At median follow up of 18 months post 2nd stage procedure 93/166 (56%) had remained free of AF or atrial tachycardia (AT) recurrence off antiarrhythmic drugs. 110/175 62.9% were in sinus rhythm off all antiarrhythmic drugs at last clinic follow-up (132/175 75.4% including those on antiarrhythmic drugs). 18 patients (10.8%) underwent a further re-do ablation (mean of 1.1 ablations per patient) 105/166 (63%) remained free of AF/AT recurrence off antiarrhythmic drugs following last ablation procedure.

Latterly, ILRs have been implanted in patients (n = 56); 60% have remained fully arrhythmia free and 80% have shown AF burden < 5% at a median 14 months follow-up [IQR: 13.5 (8–21.5)]. Only 10.9% have reverted to persistent AF. 5 patients (2.9%) had a perioperative stroke and 4 patients (2.3%) exhibited persistent weakness of the right hemidiaphragm following stage 1 VATS epicardial ablation. One patient died following stroke (overall mortality 0.6%).

Conclusions

In patients with non-paroxysmal AF with unfavourable characteristics for catheter ablation, the staged hybrid approach results in acceptable levels of freedom from recurrent atrial arrhythmia, however, complication rates are higher than with catheter ablation alone.

The Effects of Valvular Heart Disease on Atrial Conduction During Sinus Rhythm

Different arrhythmogenic substrates for atrial fibrillation (AF) may underlie aortic valve (AV) and mitral valve (MV) disease. We located conduction disorders during sinus rhythm by high-resolution epicardial mapping in patients undergoing AV (n = 85) or MV (n = 54) surgery. Extent and distribution of conduction delay (CD) and block (CD) across the entire right and left atrial surface was determined from circa 1880 unipolar electrogram recordings per patient. CD and CB were most pronounced at the superior intercaval area (2.5% of surface, maximal degree 6.6%/cm²). MV patients had a higher maximal degree of CD at the lateral left atrium than AV patients (4.2 vs 2.3%/cm², p = 0.001). A history of AF was most strongly correlated to CD/CB at Bachmann’s bundle and age. Although MV patients have more conduction disorders at the lateral left atrium, disturbed conduction at Bachmann’s bundle during sinus rhythm indicates the presence of atrial remodeling which is related to AF episodes.

Five-year results of a modified left atrial maze IV procedure in the treatment of atrial fibrillation: a randomized study

Background

The left atrial maze IV (LAM‐IV) alone has been used to eliminate atrial fibrillation (AF) without severe right heart diseases. However, we felt that it could be improved and developed a modified LAM‐IV (MLAM‐IV). In this prospective trial, we aimed to investigate 5‐year clinical outcomes of AF in patients treated by the novel MLAM‐IV technique.

Methods

Between September 2012 and October 2013, 120 patients who underwent valve surgery and bipolar radiofrequency ablation for AF were randomized into the LAM‐IV group (n = 60) or MLAM‐IV group (n = 60). At postoperative follow‐up examinations, data were recorded at 1, 3 and 6 months, and annually thereafter.

Results

The mean ablation time and postoperative ventilation time were shorter in the MLAM‐IV group than in the LAM‐IV group (P < 0.001 and P = 0.03, respectively). At 5 years, the rate of freedom from AF was 69.0% in the MLAM‐IV group and 60.0% in the LAM‐IV group (hazard ratio 0.71, 95% confidence interval 0.39 to 1.32, P = 0.42). There were no differences with respect to the early operative mortality and major complications, late mortality, and major adverse events.

Conclusions

The MLAM‐IV provides a technically simpler ablation process. The MLAM‐IV was associated with less ventilation support in the early postoperative period. The long‐term efficacy of the MLAM‐IV in the treatment of AF is comparable to that of the LAM‐IV.

Cryoballoon Ablation in Patients With Paroxysmal Atrial Fibrillation: An Evaluation of Cohorts With and Without Structural Heart Disease

BACKGROUND

Pulmonary vein isolation (PVI) is the most widely adopted strategy for paroxysmal atrial fibrillation (PAF) ablation. Limited evidence on acute results and late outcomes of cryoballoon (CB)-PVI in patients with structural heart disease (SHD) exist. The aim of this analysis was to compare acute procedural results and the 1-year recurrence rate of a single CB-PVI procedure in a PAF population with and without SHD.

METHOD

From April 2012 to May 2017, a total of 2,031 patients with AF underwent CB-PVI and were followed prospectively in the framework of the One Shot TO Pulmonary vein isolation (1STOP) ClinicalService project, involving 36 Italian cardiology centres. We identified patients with SHD according to criteria proposed by current ESC guidelines: left ventricular (LV) systolic or diastolic dysfunction, long-standing hypertension with LV hypertrophy, and/or other structural heart disease. Data on procedural outcomes and long-term freedom from AF recurrence were evaluated.

RESULTS

Our population consisted of 1,452 patients, of whom 282 (19.4%) were classified as having SHD. Compared to non-SHD patients, the SHD cohort was older (mean ± standard deviation, 62.9 ± 9.0 vs 58.2 ± 11.4 years; p < 0.001), was more frequently male (79.1% vs 69.8%; p < 0.002), had a higher thrombo-embolic risk (CHA₂DS₂VASc ≥2: 63.4% vs 40.2%; p < 0.001), had a higher body mass index (27.7 ± 3.9 vs 26.4 ± 3.9 kg/m²; p < 0.001), had a larger atrial diameter (43.8 ± 7.0 vs 40.2 ± 5.8 mm; p < 0.001), and had a lower LV ejection fraction (57.2 ± 7.7% vs 60.7 ± 6.0%; p < 0.001). At the time of ablation, 73% of patients were on class Ic or III anti-arrhythmic drugs. Procedure time (106.9 ± 41.5 vs 112.1 ± 46.8 min; p = 0.248), fluoroscopic time (28.7 ± 14.7 vs 28.6 ± 15.2 min; p = 0.819), and complication rate (3.9% vs 4.8%; p = 0.525) were not different between the SHD and non-SHD cohorts. However, the acute success rate (98.9% vs 97.7%; p = 0.016) was higher in patients with SHD. After a follow-up of 13.4 ± 12.8 months, freedom from symptomatic recurrence was 78.0% for SHD and 78.4% for non-SHD (p = 0.895). Recurrence rate was not related to either left atrial size or LVEF. In the SHD cohort, Class Ic or III anti-arrhythmic drugs treatment decreased from 70.7% of patients before ablation to 28.7% of patients after CB-PVI (p = 0.001).

CONCLUSIONS

CB-PVI was extensively applied to treat patients with PAF. Unlike previous PVI experiences, the acute success and recurrence rate after a single procedure was not related to the presence of SHD or to the degree of cardiac remodelling. Further studies are required to define whether CB-PVI has a useful role in patients with a significantly reduced ejection fraction as those patients were under-represented in the current population.

Clamping versus nonclamping thoracoscopic box ablation in long-standing persistent atrial fibrillation

OBJECTIVE

To compare clinical outcomes of clamping devices and linear nonclamping devices for isolation of the posterior left atrium (box) in thoracoscopic ablation of long-standing persistent atrial fibrillation.

METHODS

Eighty patients who underwent thoracoscopic pulmonary vein and box isolation using a bipolar clamping device (42 patients) or bipolar nonclamping device (38 patients) to create the roof/inferior lesions for box isolation were included from 2 centers. Follow-up consisted of 24-hour Holter at regular intervals. Freedom from AF during 1-year follow-up and catheter repeat interventions were compared between groups.

RESULTS

Acute intraoperative electrical isolation of the box compartment was significantly higher in the clamping group than in the nonclamping group (100% and 79%, respectively, P < .01). At 1-year follow-up, 91% of the clamping group and 79% of the nonclamping group were in sinus rhythm. During 1-year follow-up, recurrence rates did not significantly differ between the 2 groups (P = .08). Repeat catheter interventions were required in 10% of the clamping group and 21% of the nonclamping group (P = .15). Conduction gaps in the roof or inferior lesions were found in 1 patient (2%) in the clamping group versus 4 patients (11%) in the nonclamping group (P = .13).

CONCLUSIONS

Thoracoscopic pulmonary vein and box isolation are highly effective in restoring sinus rhythm in long-standing persistent atrial fibrillation on short-term follow-up. Comparison of clamping and nonclamping devices revealed lower rates of intraoperative exit block of the box in the nonclamping group. However, this did not translate into a significant difference in atrial fibrillation freedom at short-term (1-year) follow-up.

Atrial Dyssynchrony: A New Predictor for Atrial High-Rate Episodes in Patients with Cardiac Resynchronization Therapy

Background: Heart failure may induce atrial dyssynchrony. We aim to investigate whether preimplantation left atrial (LA) dyssynchrony could predict newly detected atrial high-rate episodes (AHRE) after receiving cardiac resynchronization therapy defibrillator (CRT-D). Methods: We conducted a retrospective analysis of consecutive patients who received CRT-D for standard indications and without a history of atrial fibrillation. The standard deviation of the time-to-peak strain in each LA segment during ventricular systole (SDs) and late diastole (SDa) were calculated to quantify LA dyssynchrony using two-dimensional speckle tracking echocardiography before device implantation. Patients were divided into the AHRE group and the AHRE-free group, depending on the presence of AHRE during device interrogation. Results: Thirty-one patients (28%) had newly detected AHRE during a mean follow-up of 21 ± 9 months. Patients in the AHRE group had higher SDs (8.2 ± 2.6% vs. 6.3 ± 2.3%, p < 0.001) and SDa (5.4 ± 1.8% vs. 4.1 ± 1.4%, p < 0.001) values before implantation than patients in the AHRE-free group. In the multivariate logistic analysis, both SDs (OR 1.325, 95% CI: 1.074–1.636, p =0.009) and SDa (OR: 1.499, 95% CI: 1.071–2.098, p= 0.018) were independent predictors of newly detected AHRE. At a cutoff value of 7.4% for SDs and 5.3% for SDa, the Kaplan-Meier survival analysis showed that patients with higher SDs and SDa had significantly increased risks of newly detected AHRE after receiving CRT-D. Conclusions: Dyssynchronous LA lengthening and contraction could assist in the prediction of newly detected AHRE in patients with CRT-D.

Effects of additional ablation of low-voltage areas after Box isolation for persistent atrial fibrillation

BACKGROUND

Previous studies reported that ablation of low-voltage areas (LVAs) after pulmonary vein isolation (PVI) improves the success rate in persistent atrial fibrillation (PerAF) patients with LVAs. However, the need for LVA ablation in addition to the posterior left atrial isolation, Box isolation (BOXI), for PerAF is unclear. We evaluated the effects of LVA ablation after BOXI for PerAF with LVAs.

METHODS

In 115 patients with PerAF (75 longstanding PerAF), LA voltage maps were created during sinus rhythm after PVI. Subsequently, BOXI was performed. In 61 patients without LVAs (<0.5 mV), BOXI alone was performed. Fifty-four patients with LVAs were randomly assigned to BOXI plus LVA ablation (33 patients) or BOXI alone (21 patients).

RESULTS

The rate of AF termination or cardioversion after BOXI was significantly higher than that after PVI (100% vs 88%, P < 0.001). The inducibility of atrial tachyarrhythmia after BOXI was significantly lower than that after PVI (27% vs 100%, P < 0.001). During 24 ± 9 months of follow-up after a single procedure, atrial tachyarrhythmia-free rate in the patients with LVAs, was significantly lower than that without LVAs (65% vs 82%, P = 0.043). However, the success rate was not significantly different between the BOXI plus LVA ablation group and the BOXI alone group of patients with LVAs (67% vs 62%, P = 0.722).

CONCLUSION

BOXI facilitates AF termination and its non-inducibility. Among patients with PerAF, BOXI alone may be adequate in cases without LVAs. Although cases with LVAs have higher risk of AF recurrence, additional LVA ablation does not improve the outcomes much.

Novel Insights in the Activation Patterns at the Pulmonary Vein Area

BACKGROUND

Extensiveness of conduction delay and block at the pulmonary vein area (PVA) was quantified in a previous study. We hypothesized that the combination of lines of conduction block with multiple concomitantly entering sinus rhythm wavefronts at the PVA may result in increased arrhythmogenicity and susceptibility to atrial fibrillation (AF).

METHODS

Intraoperative high-density epicardial mapping of PVA (N≈450 sites, interelectrode distances: 2 mm) was performed during sinus rhythm in 327 patients (241 male [74%], 67±10 [21-84] years) with and without preoperative AF. For each patient, activation patterns at the PVA were quantified, including the location of entry sites of wavefronts, direction of propagation, and their relative activation times. The association between activation patterns and the presence of AF was examined.

RESULTS

Excitation of the PVA occurred via multiple consecutive wavefronts in the vast majority of patient (N=216, 81%). In total, 561 wavefronts were observed, which mostly propagated through the septal or paraseptal regions towards the PVA (N=461, 82%). A substantial dissociation of consecutive wavefronts was observed with Δactivation times of 10.6±8.8 (0-46) ms. No difference was observed in Δactivation times of consecutive wavefronts during sinus rhythm between patients without and with AF. An excitation-based risk factor model, including conduction delay ≥6 mm, conduction block ≥6 mm, and conduction delay and block ≥16 mm, wavefronts via the posteroinferior to posterosuperior regions and multiple opposing wavefronts, demonstrated a 5-fold risk of AF when multiple risk factors were present.

CONCLUSIONS

In contrast to previous findings, quantification of activation patterns at the PVA on high-resolution scale demonstrated complex patterns with often multiple entry sites and high interindividual variability. Altered patterns of activation, consisting of multiple opposing wavefronts combined with long lines of conduction slowing, were associated with the presence of AF.

The hemodynamic and atrial electrophysiologic consequences of chronic left atrial volume overload in a controllable canine model

OBJECTIVE

The purpose of this study was to determine the effects of chronic left atrial volume overload on atrial anatomy, hemodynamics, and electrophysiology using a titratable left ventriculoatrial shunt in a canine model.

METHODS

Canines (n = 16) underwent implantation of a shunt between the left ventricle and the left atrium. Sham animals (n = 8) underwent a median sternotomy without a shunt. Atrial activation times and effective refractory periods were determined using 250-bipolar epicardial electrodes. Biatrial pressures, systemic pressures, left atrial and left ventricle diameters and volumes, atrial fibrillation inducibility, and durations were recorded at the initial and at 6-month terminal study.

RESULTS

Baseline shunt fraction was 46% ± 8%. The left atrial pressure increased from 9.7 ± 3.5 mm Hg to 13.8 ± 4 mm Hg (P < .001). At the terminal study, the left atrial diameter increased from a baseline of 2.9 ± 0.05 cm to 4.1 ± 0.6 cm (P < .001) and left ventricular ejection fraction decreased from 64% ± 1.5% to 54% ± 2.7% (P < .001). Induced atrial fibrillation duration (median, range) was 95 seconds (0-7200) compared with 0 seconds (0-40) in the sham group (P = .02). The total activation time was longer in the shunt group compared with the sham group (72 ± 11 ms vs 62 ± 3 ms, P = .003). The right atrial and not left atrial effective refractory periods were shorter in the shunt compared with the sham group (right atrial effective refractory period: 156 ± 11 ms vs 141 ± 11 ms, P = .005; left atrial effective refractory period: 142 ± 23 ms vs 133 ± 11 ms, P = .35).

CONCLUSIONS

This canine model of mitral regurgitation reproduced the mechanical and electrical remodeling seen in clinical mitral regurgitation. Left atrial size increased, with a corresponding decrease in left ventricle systolic function, and an increased atrial activation times, lower effective refractory periods, and increased atrial fibrillation inducibility. This model provides a means to understand the remodeling by which mitral regurgitation causes atrial fibrillation.

Characterization and consistency of interactions of triggers and substrate at the onset of paroxysmal atrial fibrillation

Aims

Initiating mechanisms of atrial fibrillation (AF) remain poorly understood, involving complex interaction between triggers and the atrial substrate. This study sought to classify the transitional phenomena, hypothesizing that there is consistency within and between patients in trigger-substrate interaction during transition to AF.

Methods and results

Non-contact left atrial (LA) mapping was performed in 17 patients undergoing ablation for paroxysmal AF. All had spontaneous ectopy. Left atrial activation from the first ectopic to established AF was examined offline to characterize the initiating and transitional sequence of activation. In 57 fully mapped spontaneous AF initiations in 8 patients, all involved interaction of pulmonary venous/LA triggers with a septopulmonary line of block (SP-LOB) also evident in sinus rhythm, by 4 different transitional mechanisms characterized by (i) continuous focal firing: AF resulted from fragmentation of each ectopic wavefront through gaps in the SP-LOB and persisted only while focal firing continued (n = 18/32%) (ii) transient focal firing, wavefront fragmentation at the SP-LOB produced wavelet re-entry that persisted after cessation of an initiating ectopic source (n = 12/21%), (iii) of two separate interacting ectopic foci (n = 15/26%), or from (iv) transiently stable macroreentry (n = 12/21%), around the SP-LOB extending to the LA roof, resulting in progressive wavefront fragmentation. It was found that 79 ± 22% of each of the initiations in individual patients showed the same triggering mechanism.

Conclusion

Onset of paroxysmal AF can be described by discrete mechanistic categories, all involving interaction of ectopic activity with a common SP-LOB. Within/between-patient consistency of initiations suggests constancy of the interacting triggers and substrate, and supports the concept of mechanistically tailored treatment.

The feasibility of a Box isolation strategy for non-paroxysmal atrial fibrillation in elderly patients

BACKGROUND

Catheter ablation of non-paroxysmal atrial fibrillation (non-PAF) is a therapeutic challenge especially in elderly patients. This study describes the feasibility of a posterior left atrium isolation as a substrate modification in addition to pulmonary vein isolation, the so-called Box isolation, for elderly patients with non-PAF.

METHODS

Two hundred twenty-nine consecutive patients who underwent Box isolations for drug-refractory non-PAF were divided into two groups according to their age; younger group comprising 175 patients aged <75 years and elderly group comprising 54 patients aged ≥75 years.

RESULTS

During 23.7±12.0 months of follow-up, the arrhythmia-free rates after one procedure were 53.1% in younger group versus 48.1% in elderly group (p=0.50). Following the second procedure, all patients had electrical conduction recoveries along the initial Box lesion. However, a complete Box re-isolation was highly established in both age groups (87.1% vs. 92.9%, respectively; p=1.00). Recurrence of macro-reentrant atrial tachycardia was mainly associated with the gaps through the initial Box lesion in both age groups (25.8% vs. 21.4%, p=1.00), but typical cavo-tricuspid isthmus (CTI) dependent atrial flutter was significantly observed in the elderly patients' group only (all events were observed within 6 months after the initial procedure; 3.2% vs. 28.6%, p=0.009). After two procedures, the arrhythmia-free rates increased to 73.1% in younger group versus 66.7% in elderly group (p=0.38). The occurrence rate of procedural-related complications did not differ between the two age groups, and there were no life-threatening complications even in elderly patients.

CONCLUSIONS

Box isolation of non-PAF is effective and safe even in elderly patients. A prophylactic CTI ablation combined with Box isolation might be feasible to improve the long-term outcome.

Obstructive Sleep Apnea Treatment and Atrial Fibrillation: A Need for Definitive Evidence

Prevalence rates of atrial fibrillation (AF) and obstructive sleep apnea (OSA) are rising on a global scale. Epidemiological data have consistently demonstrated an independent association between the 2 conditions. Investigators pose that pathophysiologic features of OSA enable progression of the AF substrate; these features include abnormalities of gas exchange, autonomic remodeling, atrial stretch, and inflammation. Furthermore, many of the mechanistic perturbations that impact the AF substrate in OSA can be substantially attenuated by effective treatment with continuous positive airway pressure (CPAP). Clear associations of OSA treatment and improved AF control have been observed across multiple clinical contexts. However, the precision and generalizability of these findings are unclear in view of the data's observational nature. Although risk factor management has emerged as a critical component of AF treatment, effective control of many AF risk factors can be challenging in the longer term. In view of the efficacy and sustainability of CPAP therapy, OSA raises its profile as a prime candidate for intervention. However, translation of this strategy to the broader framework for AF management requires robust data from randomized controlled trials.

The role of N-terminal pro-brain natriuretic peptide in prediction of postoperative atrial fibrillation

AIM

To analyze prognostic value of different factors in postoperative atrial fibrillation prediction.

MATERIAL AND METHODS

Study included 39 patients with coronary artery disease without previous paroxysmal atrial fibrillation. Multiple correlation, logistic regression and ROC-analysis were performed to create predictive model of postoperative atrial fibrillation prognosis. Authors have analyzed most of described in literature preoperative predictors of atrial fibrillation to define the role of different risk factors. Prognostic role of N-terminal pro-brain natriuretic peptide (NT-proBNP) is assessed.

RESULTS

We revealed high informativeness of NT-proBNP to predict postoperative atrial fibrillation after on-pump coronary artery bypass grafting.

Techniques for automated local activation time annotation and conduction velocity estimation in cardiac mapping

Measurements of cardiac conduction velocity provide valuable functional and structural insight into the initiation and perpetuation of cardiac arrhythmias, in both a clinical and laboratory context. The interpretation of activation wavefronts and their propagation can identify mechanistic properties of a broad range of electrophysiological pathologies. However, the sparsity, distribution and uncertainty of recorded data make accurate conduction velocity calculation difficult. A wide range of mathematical approaches have been proposed for addressing this challenge, often targeted towards specific data modalities, species or recording environments. Many of these algorithms require identification of activation times from electrogram recordings which themselves may have complex morphology or low signal-to-noise ratio. This paper surveys algorithms designed for identifying local activation times and computing conduction direction and speed. Their suitability for use in different recording contexts and applications is assessed.

Clinical significance of early atrial arrhythmia type and timing after single ring isolation of the pulmonary veins

AIMS

Early atrial arrhythmia following atrial fibrillation (AF) ablation is associated with higher recurrence rates. Few studies explore the impact of early AF (EAF) and atrial tachycardia (EAT) on long-term outcomes. Furthermore, EAF/EAT have not been characterized after wide pulmonary vein isolation. We aimed to characterize EAF and EAT and its impact on late AF (LAF) and AT (LAT) after single ring isolation (SRI).

METHODS AND RESULTS

We recruited 119 (females 21, age 58 ± 10 years) consecutive patients with AF (paroxysmal 76, persistent 43) undergoing SRI. Early atrial fibrillation/ early atrial tachycardia was defined as AF/AT within 3 months post-procedure (blanking period). Patients were followed for median 2.8[2.2-4] years. Early atrial fibrillation occurred in 28% (n = 33) and EAT in 25% (n = 30). At follow-up, 25% (n = 30) had LAF and 28% (n = 33) had LAT. Patients with EAF and EAT had higher rates of LAF (48 vs. 16%, P<0.0001) and LAT (60 vs. 16%, P < 0.0001), respectively. Independent predictors of LAF were EAF (3.53(1.72-7.29) P = 0.001); and of LAT were EAT (5.62(2.88-10.95) P < 0.0001) and procedure time (1.38/ h(1.07-1.78) P = 0.04). Importantly, EAF did not predict LAT and EAT did not predict LAF. Early atrial fibrillation late in the blanking period was associated with higher rates of LAF (73% for month 3 vs. 25% for Months 1-2, P = 0.004). However, EAT timing did not predict LAT.

CONCLUSION

Early atrial fibrillation and EAT are predictive of LAF and LAT, respectively. Early atrial fibrillation late in the blanking period has greater predictive significance for LAF. This timing is not relevant for LAT. Early arrhythmia type and timing have important prognostic significance following SRI.

CLINICAL TRIAL REGISTRATION

http://www.anzctr.org.au;ACTRN12606000467538.

Variability of P-wave morphology predicts the outcome of circumferential pulmonary vein isolation in patients with recurrent atrial fibrillation

INTRODUCTION

Severe atrial structural remodeling may reflect irreversible damage of the atrial tissue in patients with atrial fibrillation (AF) and is associated with changes of P-wave duration and morphology. Our aim was to study whether variability of P-wave morphology (PMV) is associated with outcome in patients with AF after circumferential PV isolation (CPVI).

METHODS AND RESULTS

70 consecutive patients (aged 60±9years, 46 men) undergoing CPVI due to symptomatic AF were studied. After cessation of antiarrhythmic therapy, standard 12-lead ECG during sinus rhythm was recorded for 10min at baseline and transformed to orthogonal leads. Beat-to-beat P-wave morphology was subsequently defined using a pre-defined classification algorithm. The most commonly observed P-wave morphology in a patient was defined as the dominant morphology. PMV was defined as the percentage of P waves with non-dominant morphology in the 10-min sample. At the end of follow-up, 53 of 70 patients had no arrhythmia recurrence. PMV was greater in patients without recurrence (19.5±17.1% vs. 8.2±6.7%, p<0.001). In the multivariate logistic regression model, PMV≥20% (upper tertile) was the only independent predictor of ablation success (OR=11.4, 95% CI 1.4-92.1, p=0.023). A PMV≥20% demonstrated a sensitivity of 41.5%, a specificity of 94.1%, a PPV of 96.7%, and an NPV of 34.0% for free of AF after CPVI.

CONCLUSIONS

We report a significant association between increased PMV and 6-month CPVI success. PMV may help to identify patients with very high likelihood of freedom of AF 6-months after CPVI.

The role of action potential alternans in the initiation of atrial fibrillation in humans: a review and future directions

This review highlights the role of atrial monophasic action potential duration (APD) in understanding atrial electrical properties in paroxysmal, persistent, and permanent atrial fibrillation (AF) states. Alternans of APD and rate maladaptation in a spatially divergent way appear mechanistically involved in AF initiation, development, and persistence. The underlying pathophysiology warrants further investigation.

Atrial conduction slows immediately before the onset of human atrial fibrillation: a bi-atrial contact mapping study of transitions to atrial fibrillation

OBJECTIVES

The aim of this study was to determine whether onset sites of human atrial fibrillation (AF) exhibit conduction slowing, reduced amplitude, and/or prolonged duration of signals (i.e., fractionation) immediately before AF onset.

BACKGROUND

Few studies have identified functional determinants of AF initiation. Because conduction slowing is required for reentry, we hypothesized that AF from pulmonary vein triggers might initiate at sites exhibiting rate-dependent slowing in conduction velocity (CV restitution) or local slowing evidenced by signal fractionation.

METHODS

In 28 patients with AF (left atrial size 43 ± 5 mm; n = 13 persistent) and 3 control subjects (no AF) at electrophysiological study, we measured bi-atrial conduction time (CT) electrogram fractionation at 64 or 128 electrodes with baskets in left (n = 17) or both (n = 14) atria during superior pulmonary vein pacing at cycle lengths (CL) accelerating from 500 ms (120 beats/min) to AF onset.

RESULTS

Atrial fibrillation initiated in 19 of 28 AF patients and no control subjects. During rate acceleration, conduction slowed in 23 of 28 AF patients (vs. no control subjects, p = 0.01) at the site of AF initiation (15 of 19) or latest activated site (20 of 28). The CT lengthened from 79 ± 23 ms to 107 ± 39 ms (p < 0.001) on acceleration, in a spectrum from persistent AF (greatest slowing) to control subjects (least slowing; p < 0.05). Three patterns of CV restitution were observed: 1) broad (gradual CT prolongation, 37% patients); 2) steep (abrupt prolongation, at CL 266 ± 62 ms, 42%); and 3) flat (no prolongation, 21% AF patients, all control subjects). The AF initiation was more prevalent in patients with CV restitution (17 of 23 vs. 2 of 8; p = 0.03) and immediately followed abrupt re-orientation of the activation vector in patients with broad but not steep CV restitution (p < 0.01). Patients with broad CV restitution had larger atria (p = 0.03) and were more likely to have persistent AF (p = 0.04). Notably, neither amplitude nor duration (fractionation) of the atrial signal at the AF initiation site were rate-dependent (both p = NS).

CONCLUSIONS

Acceleration-dependent slowing of atrial conduction (CV restitution) precedes AF initiation, whereas absence of CV restitution identifies inability to induce AF. Conduction restitution, but not fractionated electrograms, may thus track the functional milieu enabling AF initiation and has implications for guiding AF ablation and pharmacological therapy.

Direction-dependent conduction abnormalities in the chronically stretched atria

AIMS

There is increasing evidence of the role direction-dependent conduction plays in the arrhythmogenic interaction between ectopic triggers and abnormal atrial substrates. We thus sought to characterize direction-dependent conduction in chronically stretched atria.

METHODS AND RESULTS

Twenty-four patients with chronic atrial stretch due to mitral stenosis and 24 reference patients with left-sided accessory pathways were studied. Multipolar catheters placed at the lateral right atrium, crista terminalis, and coronary sinus (CS) characterized direction-dependent conduction along linear catheters and across the crista terminalis. Bi-atrial electroanatomic maps were created in both sinus rhythm and an alternative wavefront direction by pacing from the distal CS. This allowed an assessment of conduction velocities, electrogram, and voltage characteristics during wavefronts propagating in different directions.  While differing wavefront directions caused changes in both chronic atrial stretch and reference patients (P< 0.001 for all), these direction-dependent changes were greater in chronic atrial stretch compared with reference patients, who exhibited greater slowing in conduction velocities (P= 0.09), prolongation of bi-atrial activation time (P= 0.04), increase in number (P< 0.001) and length (P< 0.001) of lines of conduction block, increase in fractionated electrograms (P< 0.001), and decrease in voltage (P= 0.08) during left-to-right compared with right-to-left atrial activation. These direction-dependent changes were associated with a greater propensity for chronically stretched atria to develop atrial fibrillation (P= 0.02).

CONCLUSIONS

Atrial remodelling in chronic atrial stretch exacerbates physiological direction-dependent conduction characteristics. Our data suggest that the greater direction-dependent conduction seen in patients with chronic atrial stretch may promote arrhythmogenesis due to ectopic triggers from the left atrium.