Repeat catheter ablation for atrial fibrillation

Catheter ablation of atrial fibrillation (AF) is an established therapy that reduces AF burden, improves quality of life, and reduces the risks of cardiovascular outcomes. Although there are clear guidelines for the application of de novo catheter ablation, there is less evidence to guide recommendations for repeat catheter ablation in patients who experience recurrent AF. In this review, we examine the rationale for repeat ablation, mechanisms of recurrence, patient selection, optimal timing, and procedural strategies. We discuss additional important considerations, including treatment of comorbidities and risk factors, risk of complications, and effectiveness. Mechanisms of recurrent AF are often due to non-pulmonary vein (non-PV) triggers; however, there is insufficient evidence supporting the routine use of empiric lesion sets during repeat ablation. The emergence of pulsed field ablation may alter the safety and effectiveness of de novo and repeat ablation. Extrapolation of data from randomized trials of de novo ablation does not optimally inform efficacy in cases of redo ablation. Additional large, randomized controlled trials are needed to address important clinical questions regarding procedural strategies and timing of repeat ablation.

Atrial Ablation Lesion Evaluation by Cardiac Magnetic Resonance: Review of Imaging Strategies and Histological Correlations

Cardiac magnetic resonance (CMR) imaging is a valuable noninvasive tool for evaluating tissue response following catheter ablation of atrial tissue. This review provides an overview of the contemporary CMR strategies to visualize atrial ablation lesions in both the acute and chronic postablation stages, focusing on their strengths and limitations. Moreover, the accuracy of CMR imaging in comparison to atrial lesion histology is discussed. T2-weighted CMR imaging is sensitive to edema and tends to overestimate lesion size in the acute stage after ablation. Noncontrast agent-enhanced T1-weighted CMR imaging has the potential to provide more accurate assessment of lesions in the acute stage but may not be as effective in the chronic stage. Late gadolinium enhancement imaging can be used to detect chronic atrial scarring, which may inform repeat ablation strategies. Moreover, novel imaging strategies are being developed, but their efficacy in characterizing atrial lesions is yet to be determined. Overall, CMR imaging has the potential to provide virtual histology that aids in evaluating the efficacy and safety of catheter ablation and monitoring of postprocedural myocardial changes. However, technical factors, scanning during arrhythmia, and transmurality assessment pose challenges. Therefore, further research is needed to develop CMR strategies to visualize the ablation lesion maturation process more effectively.

Twenty-five years of research in cardiac imaging in electrophysiology procedures for atrial and ventricular arrhythmias

Catheter ablation is nowadays considered the treatment of choice for numerous cardiac arrhythmias in different clinical scenarios. Fluoroscopy has traditionally been the primary imaging modality for catheter ablation, providing real-time visualization of catheter navigation. However, its limitations, such as inadequate soft tissue visualization and exposure to ionizing radiation, have prompted the integration of alternative imaging modalities. Over the years, advancements in imaging techniques have played a pivotal role in enhancing the safety, efficacy, and efficiency of catheter ablation procedures. This manuscript aims to explore the utility of imaging, including electroanatomical mapping, cardiac computed tomography, echocardiography, cardiac magnetic resonance, and nuclear cardiology exams, in helping electrophysiology procedures. These techniques enable accurate anatomical guidance, identification of critical structures and substrates, and real-time monitoring of complications, ultimately enhancing procedural safety and success rates. Incorporating advanced imaging technologies into routine clinical practice has the potential to further improve clinical outcomes of catheter ablation procedures and pave the way for more personalized and precise ablation therapies in the future.

Magnetic resonance detection of advanced atrial cardiomyopathy increases the risk for atypical atrial flutter occurrence following atrial fibrillation ablation

AIMS

Recurrence of arrhythmia after catheter ablation of atrial fibrillation (AF) in the form of atypical atrial flutter (AFL) is common among a significant number of patients and often requires redo ablation with limited success rates. Identifying patients at high risk of AFL after AF ablation could aid in patient selection and personalized ablation approach. The study aims to assess the relationship between pre-existing atrial cardiomyopathy and the occurrence of AFL following AF ablation.

METHODS AND RESULTS

We analysed a cohort of 1007 consecutive AF patients who underwent catheter ablation and were included in a prospective registry. Patients who did not have baseline cardiac magnetic resonance imaging and late gadolinium enhancement (LGE-CMR) or did not experience any recurrences were excluded. A total of 166 patients were included gathering 56 patients who underwent re-ablation due to AFL recurrences and 110 patients who underwent re-ablation due to AF recurrences (P = 0.11). A multiparametric assessment of atrial cardiomyopathy was based on basal LGE-CMR, including left atrial (LA) volume, LA sphericity, and global and segmental LA fibrosis using semiautomated post-processing software. Out of the initial cohort of 1007 patients, AFL and AF occurred in 56 and 110 patients, respectively. An age higher than 65 [odds ratio (OR) = 5.6, 95% confidence interval (CI): 2.2-14.4], the number of previous ablations (OR = 3.0, 95% CI: 1.2-7.8), and the management of ablation lines in the index procedure (OR = 2.5, 95% CI: 1.0-6.3) were independently associated with AFL occurrence. Furthermore, several characteristics assessed by LGE-CMR were identified as independent predictors of AFL recurrence after the index ablation for AF, such as enhanced LA sphericity (OR = 1.3, 95% CI: 1.1-1.6), LA global fibrosis (OR = 1.03, 95% CI: 1.01-1.07), and increased fibrosis in the lateral wall (OR = 1.03, 95% CI: 1.01-1.04).

CONCLUSION

Advanced atrial cardiomyopathy assessed by LGE-CMR, such as increased LA sphericity, global LA fibrosis, and fibrosis in the lateral wall, is independently associated with arrhythmia recurrence in the form of AFL following AF ablation.

Effect of fibrosis regionality on atrial fibrillation recurrence: insights from DECAAF II

AIMS

The amount of fibrosis in the left atrium (LA) predicts atrial fibrillation (AF) recurrence after catheter ablation (CA). We aim to identify whether regional variations in LA fibrosis affect AF recurrence.

METHODS AND RESULTS

This post hoc analysis of the DECAAF II trial includes 734 patients with persistent AF undergoing first-time CA who underwent late gadolinium enhancement magnetic resonance imaging (LGE-MRI) within 1 month prior to ablation and were randomized to MRI-guided fibrosis ablation in addition to standard pulmonary vein isolation (PVI) or standard PVI only. The LA wall was divided into seven regions: anterior, posterior, septal, lateral, right pulmonary vein (PV) antrum, left PV antrum, and left atrial appendage (LAA) ostium. Regional fibrosis percentage was defined as a region's fibrosis prior to ablation divided by total LA fibrosis. Regional surface area percentage was defined as an area's surface area divided by the total LA wall surface area before ablation. Patients were followed up for a year with single-lead electrocardiogram (ECG) devices. The left PV had the highest regional fibrosis percentage (29.30 ± 14.04%), followed by the lateral wall (23.23 ± 13.56%), and the posterior wall (19.80 ± 10.85%). The regional fibrosis percentage of the LAA was a significant predictor of AF recurrence post-ablation (odds ratio = 1.017, P = 0.021), and this finding was only preserved in patients receiving MRI-guided fibrosis ablation. Regional surface area percentages did not significantly affect the primary outcome.

CONCLUSION

We have confirmed that atrial cardiomyopathy and remodelling are not a homogenous process, with variations in different regions of the LA. Atrial fibrosis does not uniformly affect the LA, and the left PV antral region has more fibrosis than the rest of the wall. Furthermore, we identified regional fibrosis of the LAA as a significant predictor of AF recurrence post-ablation in patients receiving MRI-guided fibrosis ablation in addition to standard PVI.

Cryoballoon-Induced Circumferential Pulmonary Vein Fibrosis, Assessed by Late Gadolinium-Enhancement Cardiac Magnetic Resonance Imaging, and Its Correlation with Clinical Atrial Fibrillation Recurrence

BACKGROUND

Prior studies evaluating post-atrial fibrillation (AF) ablation pulmonary vein (PV) ostial gaps via magnetic resonance imaging (MRI) have shown circumferential PV fibrosis in a minority of patients, and their correlation with AF recurrence was weak. These studies were mostly based on radio-frequency AF ablations.

AIM

We aimed to assess cryoballoon ablation-induced PV fibrosis via MRI and its correlation with AF recurrence.

METHODS AND RESULTS

This was a prospective study of consecutive patients with symptomatic AF who underwent pre- and post-ablation MRI to assess baseline and ablation-induced fibrosis, respectively. Post-ablation PV gaps were assessed by new semi-quantitative visual analysis assisted by computerized ADAS analysis. AF recurrence monitored via multiple ECGs and event monitoring at 6 and 12 months post ablation. Nineteen patients with 80 PVs were included, age 56 ± 11, with paroxysmal and persistent AF in 17/19 and 2/19 patients, respectively. Baseline MRI showed minimal LA fibrosis. All patients underwent successful cryoballoon PV electrical isolation. Post-ablation MRI revealed circumferential PV fibrosis among 63/80 (78.8%) PVs and partial fibrosis with major gaps among 17/80 (21.2%) PVs. AF recurred within one year in 5/9 (55.5%) patients with partial PV fibrosis, while no AF recurred among the 10 patients in whom all PVs had circumferential fibrosis (p < 0.01). Similarly, there were significantly more PVs without circumferential fibrosis (due to major gaps) among patients with AF recurrence as compared with patients without AF recurrence (42.9% vs. 13.5%; p < 0.01).

CONCLUSION

Cryoballoon AF ablation results in circumferential PV fibrosis in the majority of PVs, as assessed by a new clinically relevant MRI-LGE analysis. Significant correlation was found between major PV gaps on post-ablation MRI and AF recurrence, suggesting that MRI might have the ability to predict AF recurrence.

Predictive value of late gadolinium enhancement cardiovascular magnetic resonance in patients with persistent atrial fibrillation: dual-centre validation of a standardized method

Aims

With recurrence rates up to 50% after pulmonary vein isolation (PVI) in persistent atrial fibrillation (AF), predictive tools to improve patient selection are needed. Patient selection based on left atrial late gadolinium enhancement (LGE) cardiovascular magnetic resonance (CMR) has been proposed previously (UTAH-classification). However, this approach has not been widely established, in part owed to the lack of standardization of the LGE quantification method. We have recently established a standardized LGE-CMR method enabling reproducible LGE-quantification. Here, the ability of this method to predict outcome after PVI was evaluated.

Methods and results

This dual-centre study (n = 219) consists of a prospective derivation cohort (n = 37, all persistent AF) and an external validation cohort (n = 182; 66 persistent, 116 paroxysmal AF). All patients received an LGE-CMR prior to first-time PVI-only ablation. LGE was quantified based on the signal-intensity-ratio relative to the blood pool, applying a uniform LGE-defining threshold of >1.2.  In patients with persistent AF in the derivation cohort, left atrial LGE-extent above a cut-off value of 12% was found to best predict relevant low-voltage substrate (≥2 cm two with <0.5 mV during sinus rhythm) and arrhythmia-free survival 12 months post-PVI. When applied to the external validation cohort, this cut-off value was also predictive of arrhythmia-free survival for both, the total cohort and the subgroup with persistent AF (LGE < 12%: 80% and 76%; LGE > 12%: 55% and 44%; P = 0.007 and P = 0.029, respectively).

Conclusion

This dual-centre study established and validated a standardized, reproducible LGE-CMR method discriminating PVI responders from non-responders, which may improve choice of therapeutic approach or ablation strategy for patients with persistent AF.

Non-invasive assessment of pulmonary vein isolation durability using late gadolinium enhancement magnetic resonance imaging

AIMS

Electrical reconnection of pulmonary veins (PVs) is considered an important determinant of recurrent atrial fibrillation (AF) after pulmonary vein isolation (PVI). To date, AF recurrences almost automatically trigger invasive repeat procedures, required to assess PVI durability. With recent technical advances, it is becoming increasingly common to find all PVs isolated in those repeat procedures. Thus, as ablation of extra-PV targets has failed to show benefit in randomized trials, more and more often these highly invasive procedures are performed only to rule out PV reconnection. Here we aim to define the ability of late gadolinium enhancement (LGE)-magnetic resonance imaging (MRI) to rule out PV reconnection non-invasively.

METHODS AND RESULTS

This study is based on a prospective registry in which all patients receive an LGE-MRI after AF ablation. Included were all patients that-after an initial PVI and post-ablation LGE-MRI-underwent an invasive repeat procedure, which served as a reference to determine the predictive value of non-invasive lesion assessment by LGE-MRI.: 152 patients and 304 PV pairs were analysed. LGE-MRI predicted electrical PV reconnection with high sensitivity (98.9%) but rather low specificity (55.6%). Of note, LGE lesions without discontinuation ruled out reconnection of the respective PV pair with a negative predictive value of 96.9%, and patients with complete LGE lesion sets encircling all PVs were highly unlikely to show any PV reconnection (negative predictive value: 94.4%).

CONCLUSION

LGE-MRI has the potential to guide selection of appropriate candidates and planning of the ablation strategy for repeat procedures and may help to identify patients that will not benefit from a redo-procedure if no ablation of extra-PV targets is intended.

Atrial cardiomyopathy: from cell to bedside

Atrial cardiomyopathy refers to structural and electrical remodelling of the atria, which can lead to impaired mechanical function. While historical studies have implicated atrial fibrillation as the leading cause of cardioembolic stroke, atrial cardiomyopathy may be an important, underestimated contributor. To date, the relationship between atrial cardiomyopathy, atrial fibrillation, and cardioembolic stroke remains obscure. This review summarizes the pathogenesis of atrial cardiomyopathy, with a special focus on neurohormonal and inflammatory mechanisms, as well as the role of adipose tissue, especially epicardial fat in atrial remodelling. It reviews the current evidence implicating atrial cardiomyopathy as a cause of embolic stroke, with atrial fibrillation as a lagging marker of an increased thrombogenic atrial substrate. Finally, it discusses the potential of antithrombotic therapy in embolic stroke with undetermined source and appraises the available diagnostic techniques for atrial cardiomyopathy, including imaging techniques such as echocardiography, computed tomography, and magnetic resonance imaging as well as electroanatomic mapping, electrocardiogram, biomarkers, and genetic testing. More prospective studies are needed to define the relationship between atrial cardiomyopathy, atrial fibrillation, and embolic stroke and to establish a prompt diagnosis and specific treatment strategies in these patients with atrial cardiomyopathy for the secondary and even primary prevention of embolic stroke.

Ablation Lesion Assessment with MRI

Late gadolinium enhancement (LGE) MRI is capable of detecting not only native cardiac fibrosis, but also ablation-induced scarring. Thus, it offers the unique opportunity to assess ablation lesions non-invasively. In the atrium, LGE-MRI has been shown to accurately detect and localise gaps in ablation lines. With a negative predictive value close to 100% it can reliably rule out pulmonary vein reconnection non-invasively and thus may avoid unnecessary invasive repeat procedures where a pulmonary vein isolation only approach is pursued. Even LGE-MRI-guided repeat pulmonary vein isolation has been demonstrated to be feasible as a standalone approach. LGE-MRI-based lesion assessment may also be of value to evaluate the efficacy of ventricular ablation. In this respect, the elimination of LGE-MRI-detected arrhythmogenic substrate may serve as a potential endpoint, but validation in clinical studies is lacking. Despite holding great promise, the widespread use of LGE-MRI is still limited by the absence of standardised protocols for image acquisition and post-processing. In particular, reproducibility across different centres is impeded by inconsistent thresholds and internal references to define fibrosis. Thus, uniform methodological and analytical standards are warranted to foster a broader implementation in clinical practice.

Applications of multimodality imaging for left atrial catheter ablation

Atrial arrhythmias, including atrial fibrillation and atrial flutter, may be treated through catheter ablation. The process of atrial arrhythmia catheter ablation, which includes patient selection, pre-procedural planning, intra-procedural guidance, and post-procedural assessment, is typically characterized by the use of several imaging modalities to sequentially inform key clinical decisions. Increasingly, advanced imaging modalities are processed via specialized image analysis techniques and combined with intra-procedural electrical measurements to inform treatment approaches. Here, we review the use of multimodality imaging for left atrial ablation procedures. The article first outlines how imaging modalities are routinely used in the peri-ablation period. We then describe how advanced imaging techniques may inform patient selection for ablation and ablation targets themselves. Ongoing research directions for improving catheter ablation outcomes by using imaging combined with advanced analyses for personalization of ablation targets are discussed, together with approaches for their integration in the standard clinical environment. Finally, we describe future research areas with the potential to improve catheter ablation outcomes.

Effect of Continuous Subcutaneous Injection of Insulin Analogues in Pregnant Women with Diabetes Mellitus Complicated with Ketoacidosis

OBJECTIVE

To investigate the clinical effect of continuous subcutaneous injection of insulin analogues in pregnant women with diabetes mellitus complicated with ketoacidosis.

METHODS

A total of 92 pregnant patients with diabetes mellitus complicated with ketoacidosis from June 2014 to January 2021 were selected. All patients were randomly divided into an observation group and control group according to the method of random number. The control group received intravenous infusion of insulin, and the observation group received continuous subcutaneous infusion of quick-acting insulin analogues. The clinical effects of the two groups were observed.

RESULTS

The time needed to control blood glucose <13.8 mmol/L, the amount of insulin needed to control blood glucose <13.8 mmol/L, the time needed to correct DKA, and the amount of insulin needed to correct DKA in the observation group were significantly less than those in the control group (P < 0.05). Compared with the control group, the average occurrence times of hypoglycemia, the length of stay, the total amount of insulin in hospital, and the total amount of insulin used during pregnancy in the observation group were significantly less than those in the control group (P < 0.05). The values of SCr, CRP, BUN, arterial blood gas pH, and adiponectin in the two groups were significantly improved as compared with those before treatment, and the improvement in the observation group was significantly better than that in the control group (P < 0.05). After treatment, the fasting blood glucose, 2-hour postprandial blood glucose, carbon dioxide binding capacity, and glycosylated hemoglobin in the experimental group were significantly better than those in the routine group, and the difference was statistically significant (P < 0.05).

CONCLUSION

Continuous subcutaneous injection of insulin analogues is effective in the treatment of diabetic patients with ketoacidosis, which can effectively improve blood glucose, carbon dioxide binding capacity, and glycosylated hemoglobin and accelerate the negative conversion of urinary ketone body. It is worth popularizing to reduce the occurrence of hypoglycemia and the dose of insulin and shorten the time of hospitalization.

Late gadolinium enhancement-MRI determines definite lesion formation most accurately at 3 months post ablation compared to later time points

AIMS

Neither the long-term development of ablation lesions nor the capability of late gadolinium enhancement (LGE)-MRI to detect ablation-induced fibrosis at late stages of scar formation have been defined. We sought to assess the development of atrial ablation lesions over time using LGE-MRI and invasive electroanatomical mapping (EAM).

METHODS AND RESULTS

Ablation lesions and total atrial fibrosis were assessed in serial LGE-MRI scans 3 months and >12 months post pulmonary vein (PV) isolation. High-density EAM performed in subsequent repeat ablation procedures served as a reference. Serial LGE-MRI of 22 patients were analyzed retrospectively. The PV encircling ablation lines displayed an average LGE, indicative of ablation-induced fibrosis, of 91.7% ± 7.0% of the circumference at 3 months, but only 62.8% ± 25.0% at a median of 28 months post ablation (p < 0.0001). EAM performed in 18 patients undergoing a subsequent repeat procedure revealed that the consistent decrease in LGE over time was owed to a reduced detectability of ablation-induced fibrosis by LGE-MRI at time-points > 12 months post ablation. Accordingly, the agreement with EAM regarding detection of ablation-induced fibrosis and functional gaps was good for the LGE-MRI at 3 months (κ .74; p < .0001), but only weak for the LGE-MRI at 28 months post-ablation (κ .29; p < .0001).

CONCLUSION

While non-invasive lesion assessment with LGE-MRI 3 months post ablation provides accurate guidance for future redo-procedures, detectability of atrial ablation lesions appears to decrease over time. Thus, it should be considered to perform LGE-MRI 3 months post-ablation rather than at later time-points > 12 months post ablation, like for example, prior to a planned redo-ablation procedure.

Left atrial wall thickness of the pulmonary vein reconnection sites during atrial fibrillation redo procedures

BACKGROUND

Left atrial wall thickness (LAWT) has been related to pulmonary vein (PV) reconnections after atrial fibrillation (AF) ablation. The aim was to integrate 3D-LAWT maps in the navigation system and analyze the relationship with local reconnection sites during AF-redo procedures.

METHODS

Consecutive patients referred for AF-redo ablation were included. Procedure was performed using a single catheter technique. LAWT maps obtained from multidetector computerized tomography (MDCT) were imported into the navigation system. LAWT of the circumferential PV line, the reconnected segment and the reconnected point, were analyzed.

RESULTS

Sixty patients [44 (73%) male, age 61 ± 10 years] were included. All reconnected veins were isolated using a single catheter technique with 55 min (IQR 47-67) procedure time and 75 s (IQR 50-120) fluoroscopy time. Mean LAWT of the circumferential PV line was 1.46 ± 0.22 mm. The reconnected segment was thicker than the rest of segments of the circumferential PV line (2.05 + 0.86 vs. 1.47 + 0.76, p < .001 for the LPVs; 1.55 + 0.57 vs. 1.27 + 0.57, p < .001 for the RPVs). Mean reconnection point wall thickness (WT) was at the 82nd percentile of the circumferential line in the LPVs and at the 82nd percentile in the RPVs.

CONCLUSION

A single catheter technique is feasible and efficient for AF-redo procedures. Integrating the 3D-LAWT map into the navigation system allows a direct periprocedural estimation of the WT at any point of the LA. Reconnection points were more frequently present in thicker segments of the PV line. The use of 3D-LAWT maps can facilitate reconnection point identification during AF-redo ablation.

Multimodality imaging for atrial fibrosis detection in the era of precision medicine

In recent years, atrial fibrillation (AF) has increasingly become a focus of attention because it represents the most encountered arrhythmia in clinical practice and a major cause of morbidity and mortality. Issues underlying AF have long been debated; nevertheless, electrical, contractile, and structural remodeling is demonstrated to be the pivotal contributor to arrhythmic substrate. Fibrosis is a hallmark of arrhythmogenic structural remodeling, resulting from an accumulation of fibrillar collagen deposits, as a reparative process to replace degenerating myocardium with concomitant reactive fibrosis, which causes interstitial expansion. Although the precise role of fibrosis in AF initiation and maintenance remains to be fully elucidated, a better definition of its extent and distribution may assist in designing individually tailored ablation approaches and improving procedure outcomes by targeting the fibrotic substrates with an organized strategy employing imaging resources. A deep comprehension of the mechanisms underlying atrial fibrosis could be crucial to setting up improved strategies for preventing AF-promoting structural remodeling. Imaging modalities such as echocardiography, cardiac computed tomography, and cardiac magnetic resonance, combined sometimes with invasive electroanatomical mapping, could provide valuable information for the optimal patients’ management if their use is not limited to cardiac anatomy study but extended to characterize abnormal left atrial substrate. Although pulmonary vein isolation is usually efficacious in treating paroxysmal AF, it is not sufficient for many patients with nonparoxysmal arrhythmias, particularly those with longstanding persistent AF. Noninvasive imaging techniques play a pivotal role in the planning of arrhythmic substrates ablation and show a strong correlation with electro-anatomic mapping, whose novel multipolar mapping catheters allow nowadays a more precise comprehension of atrial substrate. This review aims to explore the impact of the various imaging modalities for the detection of atrial fibrosis and their role in the management of AF.