Substrate Modification by Pulmonary Vein Isolation and Left Atrial Linear Ablation in Patients with Persistent Atrial Fibrillation: Its Impact on Complex-Fractionated Atrial Electrograms

Maintenance mechanism of paroxysmal atrial fibrillation from the activation occurring within the pulmonary vein: analysis using non-contact mapping

It is unclear how pulmonary veins (PVs) maintain paroxysmal atrial fibrillation (AF). To clarify the PV's arrhythmogenic role, we examined PV activation sequences during paroxysmal AF. Left superior PV (LSPV) endocardial non-contact mapping was performed after a right PV isolation in 13 paroxysmal AF patients. Activation sequences within the LSPV before and during left-sided PVs ablation were analyzed, and those in complex fractionated atrial electrogram (CFAE) areas were compared with those in non-CFAE areas. CFAEs were observed in the LSPV's proximal half (area; 8.8 ± 3.2cm2) occupying 19.9 ± 6.0% of LSPV. The number of pivoting activations, wave breaks, and fusions over CFAE areas were significantly higher than those over non-CFE areas (25.5 ± 9.3 vs. 4.5 ± 4.8 times/s, p < 0.0001; 9.1 ± 5.3 vs. 1.4 ± 1.8 times/s, p < 0.0001; 13.0 ± 4.6 vs. 5.4 ± 4.4 times/s, p < 0.0001). The conduction velocities in CFAE areas were significantly slower than in non-CFAE areas (0.6 ± 0.2 vs. 1.7 ± 0.8 m/s, p < 0.001). After delivery of ablation lesions around the left-sided PVs (13.2 ± 7.4 applications), the PV activation became organized with a loss of CFAE areas, and the frequency of the LSPV's pivoting activation, wave break, and fusion significantly decreased compared to that pre-ablation (7.3 ± 10.9 vs. 30.0 ± 11.6 times/s, p < 0.001; 2.1 ± 5.3 vs. 10.5 ± 6.2 times/s, p < 0.002; 6.0 ± 6.6 vs. 18.4 ± 8.2 times/s, p < 0.001). Subsequently, AF terminated before the left-sided PV isolation in all patients. In conclusion, high-frequency random reentry associated with pivoting activation, wave break, and fusion within the LSPV, observed mostly over CFAE areas, maintained AF. Linear ablation lesions around the PV suppressed random reentry, resulting in the loss of CFAEs and AF termination.

A novel stepwise approach incorporating ethanol infusion in the vein of Marshall for the ablation of persistent atrial fibrillation

Introduction

Apart from pulmonary vein isolation (PVI), several step-by-step procedures that aim to modify left atrial substrate have been proposed for the ablation of persistent atrial fibrillation (AF), yet the optimal strategy remains elusive. There are cumulative data suggesting an incremental benefit of adding vein of Marshall (VOM) ethanol infusion to PVI in patients with persistent AF. We sought to evaluate the feasibility and efficacy of a novel stepwise ablation approach, incorporating a VOM alcoholization step, for persistent AF.

Methods

In this single-center study, we prospectively enrolled 66 consecutive patients with symptomatic persistent AF and failure of at least one antiarrhythmic drug (ADD). The ablation procedure consisted of (i) PVI, (ii) left atrial segmentation with VOM ethanol infusion and the deployment of linear radiofrequency lesions across the roof and the mitral isthmus and (iii) electrogram-based ablation of dispersion zones. The first two steps were performed in all patients, whereas the third step was carried out only in those still in AF at the end of the second step. Atrial tachycardias during the procedure were mapped and ablated. At the end of the procedure, cavotricuspid isthmus ablation was additionally performed in all patients. The primary endpoint was 12-month freedom from AF and atrial tachycardia after a single procedure and an initial three-month blanking period.

Results

Total procedure time was 153 ± 38.5 min. Fluoroscopy time was 16 ± 6.5 min and the radiofrequency ablation time was 26.14 ± 0.26 min. The primary endpoint occurred in 54 patients (82%). At 12 months, 65% of patients were off any AAD. In the univariate Cox regression analysis, left ventricular ejection fraction < 40% was the only predictor of arrhythmia recurrence (HR 3.56; 95% CI, 1.04-12.19; p = 0.04). One patient developed a pericardial tamponade and another a minor groin hematoma.

Conclusion

A novel stepwise approach, including a step of ethanol infusion in the VOM, is feasible, safe and provides a high rate of sinus rhythm maintenance at 12 months in patients with persistent AF.

Very long term outcome after linear versus electrogram guided ablation for persistent atrial fibrillation

The optimal ablation strategy for persistent atrial fibrillation (PsAF) remains to be defined. We sought to compare very long-term outcomes between linear ablation and electrogram (EGM)-guided ablation for PsAF. In a retrospective analysis, long-term arrhythmia-free survival compared between two propensity-score matched cohorts, one with pulmonary vein isolation (PVI) and linear ablation including roof/mitral isthmus line (LINE-group, n = 52) and one with PVI and EGM-guided ablation (EGM-group; n = 52). Overall, 99% of patients underwent successful PVI. Complete block following linear ablation was achieved for 94% of roof lines and 81% of mitral lines (both lines blocked in 75%). AF termination by EGM-guided ablation was accomplished in 40% of patients. Non-PV foci were targeted in 7 (13%) in the LINE-group and 5 (10%) patients in the EGM-group (p = 0.76). During 100 ± 28 months of follow-up, linear ablation was associated with superior arrhythmia-free survival after the initial and last procedure (1.8 ± 0.9 procedures) compared with EGM-group (Logrank test: p = 0.0001 and p = 0.045, respectively). In multivariable analysis, longer AF duration and EGM-guided ablation remained as independent predictors of atrial arrhythmia recurrence. Linear ablation might be a more effective complementary technique to PVI than EGM-guided ablation for PsAF ablation.

Anatomical hotspots of fractionated electrograms in the left and right atrium: do they exist?

Aims

Targeting of complex fractionated electrograms (CFEs) in the atria is not yet beneficial in treating drug-refractory atrial fibrillation (AF). In order to gain insight into potential anatomical hotspots of fractionated electrograms, a structured literature search was performed.

Methods and results

PubMed was searched for studies describing fractionation during human atrial electrophysiological measurements (n = 565), of which 36 articles described the pre-ablation distribution of fractionated electrograms for the left atrium and/or right atrium in at least four regions. Fractionation was commonly found in high proportions within all regions of both atria, without clear preference for specific regions. Furthermore, no differences in the fractionation distribution between paroxysmal AF and persistent AF patients were observed.

Conclusion

Whereas atrial inhomogeneous conduction is widely believed to play a key role in AF initiation and perpetuation, different electrophysiological causes for fractionation and the influence of measurement properties complicate identification of the arrhythmogenic substrate. Thereby, simply targeting all CFEs would be short-sighted. Further research is warranted on how to distinguish 'physiologic CFEs' from 'pathologic CFEs', with only the latter reflecting potential targets for ablative therapy of AF.

Characterising the difference in electrophysiological substrate and outcomes between heart failure and non-heart failure patients with persistent atrial fibrillation

Aims

Characterizing the differences in substrate and clinical outcome between heart failure (HF) and non-heart failure (non-HF) patients undergoing persistent atrial fibrillation (AF) ablation.

Methods and results

Using complex fractionated electrograms (CFE) as a surrogate marker of substrate complexity, we compared the bi-atrial substrate in patients with persistent AF with and without HF, at baseline and after ablation, to determine its impact on clinical outcome. In this retrospective analysis of two prospective studies, 60 patients underwent de-novo step-wise left atrial (LA) ablation, 30 with normal left ventricular ejection fraction (LVEF) ≥ 50% (non-HF group) and 30 with LVEF ≤ 35% (HF group). Multiple high-density bi-atrial CFE maps were acquired along with AF cycle length (AFCL) at each procedural stage. Change in bi-atrial CFE areas, AFCL and outcome data were then compared. In the non-HF group, higher CFE-areas were found at baseline and at each step of the procedure in the LA. In both LA and the right atrium (RA), baseline and final CFE area were also higher in the non-HF group. Single procedure, arrhythmia-free survival at 1 year was higher in the HF group compared with the non-HF group (72% vs. 43%, log rank P = 0.04). Final total bi-atrial CFE area was an independent predictor of arrhythmia recurrence.

Conclusions

CFE represents an important surrogate marker of atrial substrate complexity. The atrial substrate in persistent AF differs between HF and non-HF with the latter representing a more complex 'primary' bi-atrial myopathy. LA focussed ablation results in more extensive substrate modification in HF and better clinical outcomes as compared with non-HF.

Combined Cryoballoon and Radiofrequency Ablation Versus Radiofrequency Ablation Alone for Long-Standing Persistent Atrial Fibrillation

BACKGROUND

To achieve sinus rhythm, ablation of long-standing persistent atrial fibrillation (LSPAF) usually requires substrate modification in addition to pulmonary vein isolation (PVI). In the present article, we aimed to compare clinical and substrate modification effects of 2 distinct PVI strategies during stepwise ablation in patients with LSPAF: (1) Combined approach: cryoballoon (CB) for PVI and radiofrequency (RF) ablation for substrate modification and (2) RF-only approach: RF ablation for both PVI and substrate modification.

MATERIALS AND METHODS

A total of 34 patients were divided into 2 groups: 19 in the combined group and 15 in the RF group. Left atrial (LA) complex fractionated atrial electrogram (CFAE) maps were acquired before and after PVI and compared between groups. The groups were compared for acute atrial fibrillation termination (AFT) rates and long-term arrhythmia-free survival.

RESULTS

A significant reduction on total LA CFAE area was observed with PVI in both groups. In the CB group, when pulmonary veins were excluded, the reduction of LA CFAE area was the most significant on the posterior wall of left atrium and which was greater than in the RF group. Although the ratio of AFT was higher in the CB group (44% versus 33%, respectively), single-procedure arrhythmia-free survival at 1 year was comparable between groups (68% in the CB group versus 66% in the RF group). Times of total procedure, fluoroscopy and post-PVI RF were all shorter in the CB group.

CONCLUSIONS

CB may cause greater substrate modification on the posterior wall and increase AFT rate during LSPAF ablation.

Does Additional Electrogram-Guided Ablation After Linear Ablation Reduce Recurrence After Catheter Ablation for Longstanding Persistent Atrial Fibrillation? A Prospective Randomized Study

Background

Although circumferential pulmonary vein isolation (CPVI) catheter ablation may not be sufficient for long‐standing persistent atrial fibrillation (L‐PeAF), it is not clear which ablation strategy is beneficial in addition to CPVI. We sought to investigate whether additional complex fractionated atrial electrogram (CFAE)‐guided ablation improves clinical outcomes in L‐PeAF patients who exhibit continuous atrial fibrillation (AF) after CPVI and linear ablation (Line).

Methods and Results

This study enrolled 137 L‐PeAF patients (71.4% male, 61.6±10.9 years old) who underwent radiofrequency catheter ablation. We conducted CPVI+Line based on the Dallas lesion set (posterior box+anterior line) after baseline CFAE mapping in all patients. If AF was defragmented (terminated or changed to atrial tachycardia), the procedure was stopped (AF‐Defrag group, n=29). If AF was maintained after CPVI+Line, we mapped the CFAE again and randomly assigned the patient to the CPVI+Line group (n=54) or the additional CFAE ablation group (CPVI+Line+CFAE group, n=54). L‐PeAF was defragmented during CPVI+Line in 21.2% of patients (29/137, AF‐Defrag group). The mean CFAE cycle length was prolonged (P<0.001), and CFAE area (CFAE cycle length <120 milliseconds) was reduced (P<0.001) after CPVI+Line in the remaining patients. Procedure time was longer in the CPVI+Line+CFAE group than the CPVI+Line group (P=0.023), but procedure‐related complication rates did not vary. During 22.3±13.2 months of follow‐up, the clinical recurrence rates were 17.2% in the AF‐Defrag group, 18.5% in the CPVI+Line group, and 32.1% in the CPVI+Line+CFAE group (log rank, P=0.166).

Conclusions

Although CPVI+Line reduces and localizes CFAE area, additional CFAE ablation after CPVI+Line does not improve the clinical outcomes of catheter ablation in patients with L‐PeAF.

Filling defects of the left atrial appendage on multidetector computed tomography: their disappearance following catheter ablation of atrial fibrillation and the detection of LAA thrombi by MDCT

Filling defects of the left atrial appendage (LAA) on multidetector computed tomography (MDCT) are known to occur, not only due to LAA thrombi formation, but also due to the disturbance of blood flow in the LAA of patients with atrial fibrillation (AF). The purpose of this study was to evaluate the impact of the maintenance of sinus rhythm via ablation on the incidence of LAA filling defects on MDCT in patients with AF. A total of 459 consecutive patients were included in the present study. Prior to ablation, MDCT and transesophageal echocardiography (TEE) were performed. AF ablation was performed in patients without LAA thrombi confirmed on TEE. The LAA filling defects were evaluated on MDCT at 3 months after ablation. LAA filling defects were detected on MDCT in 51 patients (11.1 %), among whom the absence of LAA thrombi was confirmed in 42 patients using TEE. The LAA Doppler velocity in patients with LAA filling defects was lower than that of patients without filling defects (0.61 ± 0.19 vs. 0.47 ± 0.21 m/s; P < 0.0001). The sensitivity, specificity and negative predictive value of MDCT in the detection of thrombi were 100, 91 and 100 %, respectively. No LAA filling defects were observed on MDCT at 3 months after ablation in any of the patients, including the patients in whom filling defects were noted prior to the procedure. MDCT is useful for evaluating the presence of LAA thrombi and the blood flow of the LAA. The catheter ablation of AF not only suppresses AF, but also eliminates LAA filling defect on MDCT suggesting the improvement of LAA blood flow.

Left atrial electrophysiologic feature specific for the genesis of complex fractionated atrial electrogram during atrial fibrillation

Complex fractionated atrial electrogram (CFAE) has been suggested to contribute to the maintenance of atrial fibrillation (AF). However, electrophysiologic characteristics of the left atrial myocardium responsible for genesis of CFAE have not been clarified. Non-contact mapping of the left atrium was performed at 37 AF onset episodes in 24 AF patients. Electrogram amplitude, width, and conduction velocity were measured during sinus rhythm, premature atrial contraction (PAC) with long- (L-PAC), short- (S-PAC) and very short-coupling intervals (VS-PAC). These parameters were compared between CFAE and non-CFAE regions. Unipolar electrogram amplitude was higher in CFAE than non-CFAE during sinus rhythm, L-, S- and VS-PAC (1.82 ± 0.73 vs. 1.13 ± 0.38, p < 0.001; 1.44 ± 0.54 vs. 0.92 ± 0.35, p < 0.001; 1.09 ± 0.40 vs. 0.70 ± 0.27, p < 0.001; 0.76 ± 0.30 vs. 0.53 ± 0.25 mV, p < 0.001). Laplacian bipolar electrogram amplitude was also higher in CFAE than non-CFAE during sinus rhythm, L-, S- and VS-PAC. Unipolar electrogram width was similar in CFAE and non-CFAE. Laplacian bipolar electrogram width was wider in CFAE than non-CFAE during L-, S- and VS-PAC (85.5 ± 6.8 vs. 79.6 ± 4.5, p < 0.001; 96.1 ± 9.7 vs. 84.5 ± 5.9, p < 0.001; 122.4 ± 16.0 vs. 99.6 ± 9.6 ms, p < 0.001), but not during sinus rhythm. The conduction velocity was slower in CFAE during sinus rhythm, L-, S- and VS-PAC than non-CFAE (1.7 ± 0.3 vs. 2.4 ± 0.4, p < 0.001; 1.4 ± 0.3 vs. 2.0 ± 0.5, p < 0.001; 1.2 ± 0.3 vs. 1.7 ± 0.5, p < 0.001; and 0.9 ± 0.3 vs. 1.4 ± 0.4 m/s, p < 0.001). CFAE was generated in the high amplitude atrial myocardium with slow and non-uniform conduction properties which were pronounced associated with premature activation, suggesting that heterogeneous conduction produced in high amplitude region contributes to the genesis of CFAE.

Incidence of pulmonary vein conduction recovery in patients without clinical recurrence after ablation of paroxysmal atrial fibrillation: mechanistic implications

BACKGROUND

Pulmonary vein (PV) isolation has become the mainstay acute procedural end point for paroxysmal atrial fibrillation (AF) ablation.

OBJECTIVE

To examine the incidence of conduction recovery in the PVs in patients without clinical recurrence of AF after paroxysmal AF ablation.

METHODS

From August 2008 to March 2011, 392 patients with drug-refractory PAF underwent catheter ablation in our center, a wide area circumferential ablation approach guided with a circular mapping catheter was performed with the intended endpoint of entrance block in all PVs. 276 (70.4%) of them were free from recurrence at one year follow-up, and 32 of them were enrolled to assess the incidence of PV reconnection. Forty-three patients with clinical recurrence after ablation were analyzed for comparison. The regions of gap were mapped and characterized in all of the reconnected PVs.

RESULTS

Among patients without recurrence, recovery of PV conduction was observed in 29 of 32 (90.6%) patients: 10/32 (31.2%) reconnection in 4 veins, 7/32 (21.9%) in 3 veins, 10/32 (31.2%) in 2 veins, and 2/32 (6.2%) in 1 vein. No anatomic propensity was seen because reconnection was evenly distributed throughout all veins (left superior pulmonary vein 21, left inferior pulmonary vein 20, right superior pulmonary vein 19, and right inferior pulmonary vein 23). When compared to patients with recurrence, no significant differences were seen in the proportion of patients with reconnection (P = 1.0) or in left atrium-PV intervals (73.4 ± 43.3 ms vs 61.9 ± 31.8 ms; P > .05).

CONCLUSION

A high incidence of PV reconnection was similarly observed in patients with and without recurrence of AF, suggesting that sustained PV isolation may not be required for freedom from clinical recurrence of AF.

Evaluation of linear lesions in the left and right atrium in ablation of long-standing atrial fibrillation

BACKGROUND

This randomized prospective study compared three ablation strategies in patients with long-standing persistent atrial fibrillation (LPeAF). It also explored the best procedural endpoint from among the following: circumferential pulmonary vein isolation (PVI) + left atrial (LA) linear lesions (roofline, mitral isthmus) + complex fractionated atrial electrogram (CFAE) ablation, PVI + LA linear lesions + cavotricuspid isthmus (CTI) ablation + CFAE ablation, and PVI + CFAE ablation.

METHODS AND RESULTS

A total of 210 patients with LPeAF referred for catheter ablation were enrolled and randomized into three ablation groups. The patients in group A (n = 70) underwent PVI followed by LA linear and CFAE ablation; in 93% of patients the primary endpoint was achieved (five patients with incomplete linear lesions). Of the 70 patients in group B who were subjected to PVI followed by LA linear, CFAE, and CTI ablations, in 94% of patients the primary endpoint was achieved (four patients with incomplete linear lesions). All patients in group C (n = 70) successfully underwent PVI and CFAE ablation. Direct current cardioversion was performed upon PVI, CFAE elimination, and completion of linear lesions. Patients were followed-up for atrial tachyarrhythmia recurrence for at least 24 months. After a single ablation procedure, group C (36%) exhibited the lowest success compared with group A (54%) and group B (51%) (P = 0.06). At the mean follow-up of 32 ± 9 months after the final ablation procedure, 53 patients (76%) in group A, 53 (76%) in group B, and 41 (59%) in group C were in sinus rhythm without antiarrhythmic drugs (P = 0.03).

CONCLUSIONS

In LPeAF, linear lesions in the LA help improve outcome of ablation, additional CTI ablation does not.

Ablation of complex fractionated atrial electrograms in catheter ablation for AF; where have we been and where are we going?

Catheter ablation for persistent AF remains a challenge to the ablator as the disease is now outside the veins and cannot be tackled by pulmonary vein isolation alone. In this article we describe targeting complex fractionated atrial electrograms (CFAE) as a method to guide atrial substrate modification.