Catheter ablation of atrial fibrillation: current status, techniques, outcomes and challenges

Atrial fibrillation (AF) is the most common human arrhythmia. Interventional treatment with catheter ablation is an established technique that is increasingly applied and has become one of the main treatment modalities in patients with AF. Ablation results in significant improvement of symptoms and the quality of life. There is as yet no clear evidence of any impact of the procedure on hard clinical endpoints, except in patients with heart failure, who seem to benefit significantly from ablation. The cornerstone of the procedure is the achievement of pulmonary vein isolation. Radiofrequency energy is the main applied energy source, but cryoballoon ablation has emerged as a safe and effective alternative to radiofrequency ablation. Additional ablation strategies and novel technical features have been proposed but without unequivocal proof of clinical benefit. The most promising of these seems to be substrate mapping of the left atrium with substrate modification in areas with low voltage as an adjunct to pulmonary vein isolation. Complication rates remain considerable despite accumulated experience and can be partly reduced by application of preventive measures.

Individually tailored vs. standardized substrate modification during radiofrequency catheter ablation for atrial fibrillation: a randomized study.

Aims: This randomized single-centre study sought to compare the efficacy and safety of pulmonary vein isolation (PVI) plus voltage-guided ablation vs. PVI with or without linear ablation depending on the type of atrial fibrillation (AF). Methods and results: Overall, 124 ablation-naive patients with paroxysmal or persistent AF were randomized to PVI with (persistent AF) or without (paroxysmal AF) additional linear ablation (control group) vs. PVI plus ablation of low-voltage areas (LVAs) irrespective of AF type. Bipolar voltage mapping was performed during stable sinus rhythm. An LVA consisted of ≥ 3 adjacent mapping points that each had a peak-to-peak amplitude ≤0.5 mV. After a mean follow-up of 12 ± 3 months, significantly more patients in the LVA ablation group were free from atrial arrhythmia recurrence >30 s off antiarrhythmic drugs (AADs) after a single procedure (primary endpoint) compared with control group patients [40/59 (68%) vs. 25/59 (42%), log-rank P = 0.003]. Arrhythmia-free survival on or off AADs was found in 33/59 control group patients (56%) and in 41/59 LVA ablation group patients (70%) (adjusted log-rank P = 0.10). During the 7 day Holter monitoring period at 12 months, significantly more patients in the LVA ablation group were free from arrhythmia recurrence on or off AADs [45/50 (90%) vs. 33/46 (72%), P = 0.04]. No between-group differences were observed regarding procedure duration, fluoroscopy time, and major complications. Conclusion: In this single-centre study, individually tailored substrate modification guided by voltage mapping was associated with a significantly higher arrhythmia-free survival rate compared with a conventional approach applying linear ablation according to AF type.

Prospective, multicenter validation of a clinical risk score for left atrial arrhythmogenic substrate based on voltage analysis: DR-FLASH score.

BACKGROUND: Left atrial (LA) low-voltage areas (LVAs) are frequently observed in patients with atrial fibrillation (AF) and may predict AF recurrence after catheter ablation. OBJECTIVE: The aim of this study was to develop and validate a clinical tool to identify LVAs that are associated with AF recurrence after pulmonary vein isolation (PVI). METHODS: In a cohort of 238 patients, voltage maps were created during LA procedures. LVAs were defined as areas with electrogram amplitudes <0.5 mV. On the basis of regression analysis, predictors of LA substrate were identified. These parameters were used to establish a dedicated risk score (DR-FLASH score, based on diabetes mellitus, renal dysfunction, persistent form of AF, LA diameter >45 mm, age >65 years, female sex, and hypertension). This risk score was then prospectively validated in a multicenter cohort of 180 patients. The association of the score with long-term recurrence of atrial arrhythmias after circumferential PVI was tested in a retrospective cohort of 484 patients. RESULTS: The DR-FLASH score effectively identified LVA substrate (C statistic = 0.801, P < .001). In the prospective multicenter validation cohort, the predictive value of the DR-FLASH score was confirmed (C statistic = 0.767, P < .001). The probability for the presence of LA substrate increased by a factor of 2.2 (95% confidence interval [CI] 1.6-2.9, P < .001) with each point scored. Furthermore, the risk of AF recurrence after PVI increased by a factor of 1.3 (95% CI 1.1-1.5, P < .001) with every additional point and was almost 2 times higher in patients with a DR-FLASH score >3 (odds ratio 1.7, 95% CI 1.1-2.8, P = .026). CONCLUSION: The DR-FLASH score may be useful to identify patients who may require extensive substrate modification instead of PVI alone.

Tailored atrial substrate modification based on low-voltage areas in catheter ablation of atrial fibrillation.

BACKGROUND: Reduced electrogram amplitude has been shown to correlate with diseased myocardium. We describe a novel individualized approach for catheter ablation of atrial fibrillation (AF) based on low-voltage areas (LVAs) in the left atrium (LA). We sought to assess (1) the incidence of LVAs in patients undergoing AF catheter ablation, (2) the distribution of LVAs within the LA, and (3) the effect of an individualized ablation strategy on long-term rhythm outcomes. METHODS AND RESULTS: In 178 patients with paroxysmal or persistent AF, LA voltage maps were created during sinus rhythm after circumferential pulmonary vein isolation. Subsequent substrate modification was confined to the presence of LVA (<0.5 mV) and inducible regular atrial tachycardias. LVAs were identified in 35% and 10% of patients with persistent and paroxysmal AF, respectively. The LA roof and the anterior, septal, and posterior wall LA were most often affected. The 12-month atrial tachycardias/AF-free survival was 62% for patients without LVAs and 70% for patients with LVAs and tailored substrate modification (P=0.3). Success rate in a comparison group of 26 LVA patients without further substrate modification was 27%. CONCLUSIONS: LVAs can be found at preferred sites in 10% of patients with paroxysmal AF and in 35% of patients with persistent AF. This is the first clinical report describing a consistent voltage-based approach for substrate modification in addition to circumferential pulmonary vein isolation irrespective of AF type. Application of this limited individualized approach may have the potential to compensate for the impaired 12-month outcome of patients with endocardial structural defects.

Catheter ablation of atrial fibrillation supported by novel nonfluoroscopic 4D navigation technology.

BACKGROUND: The MediGuide technology (MGT) represents a novel sensor-based electromagnetic 4-dimensional (4D) navigation system allowing real-time catheter tracking in the environment of prerecorded X-ray loops. OBJECTIVE: To report on our clinical experience in atrial fibrillation (AF) ablation with recently available MGT-enabled ablation catheters. METHODS: The MGT was used in addition to a conventional 3D mapping system in 80 patients with AF (age 61 ± 10 years; 47 men; 40 with persistent AF), who underwent circumferential pulmonary vein isolation and voltage mapping with and without substrate modification. Short native right anterior oblique/left anterior oblique loops were used as background movies for the nonfluoroscopic placement of sensor-equipped diagnostic catheters into the coronary sinus and the right ventricle. After single transseptal puncture, selective angiograms of the pulmonary veins were used as background movies for near nonfluoroscopic left atrial reconstruction. Computed tomography registration as well as mapping/ablation was performed by using the new open-irrigated MGT-enabled ablation catheter. RESULTS: MGT application was not associated with a change in established workflow. Large parts of the procedure (mean entire duration 167 ± 47 minutes) could be done without additional fluoroscopy, whereas median residual fluoroscopy duration of 4.6 (interquartile range: 2.9, 7.1) minutes was mainly used for the acquisition of background loops, transseptal puncture, occasional verification of transseptal sheath position, and manipulation of the circular mapping catheter. Three (4%) minor complications occurred. CONCLUSIONS: The MGT integrates easily into the workflow of standard AF ablation and allows for high-quality nonfluoroscopic 4D catheter tracking. This results in low radiation exposure for patients and staff without complicating the workflow of the procedure.

Quantitative analysis of isolation area and rhythm outcome in patients with paroxysmal atrial fibrillation after circumferential pulmonary vein antrum isolation using the pace-and-ablate technique.

BACKGROUND: We sought to determine the relationship between the size of the left atrial isolated surface area (ISA) after pulmonary vein antrum isolation for paroxysmal atrial fibrillation (AF) and rhythm outcome during a 12-month follow-up. METHODS AND RESULTS: One hundred one consecutive patients with paroxysmal AF (mean age, 59±11 years; median [range] AF history, 36 [24-96] months; mean left atrial size, 42±6 mm) were enrolled. The ISA was defined as the ratio of the total isolated antral surface area excluding the pulmonary veins to the sum of the total isolated antral surface area and the left atrial posterior wall surface area, while considering the individual characteristics of antral anatomy. All surface areas were assessed using the NavX system. Patients were divided into 4 groups according to ISA (group I: <50%; group II: 50 to <60%; group III: 60 to <70%; group IV: ≥70%). The average ISA for all patients was 59.2±11.6%. Subgroup analysis showed that ISA was 42.8±4.2% in group I (n=23), 54.2±3.0% in group II (n=23), 64.3±3.0% in group III (n=33), and 73.9±3.6% in group IV (n=22). After a 12-month follow-up period, 70% of patients in group I, 78% in group II, 97% in group III, and 100% in group IV were free from AF and atrial macroreentrant tachycardia. There was a significant difference between groups I and III, I and IV, II and III, and II and IV but not groups I and II and groups III and IV (log-rank test P=0.024, 0.016, 0.037, 0.044, 0.584, and 0.500, respectively). Receiver operating characteristic curve analysis yielded an optimal cutoff value of 55% for ISA. CONCLUSIONS: After 12 months, a larger ISA was associated with a significantly lower AF and macroreentrant tachycardia recurrence rate. ISA≥55% may thus serve as a predictor for long-term success after pulmonary vein antrum isolation.

Circumferential pulmonary vein isolation and linear left atrial ablation as a single-catheter technique to achieve bidirectional conduction block: the pace-and-ablate approach.

BACKGROUND: Pulmonary vein (PV) isolation has become a cornerstone for ablation of atrial fibrillation (AF). Circular mapping catheter (CMC)-guided techniques for detection of lesion gaps are challenging. OBJECTIVE: The present study describes a new concept of circumferential PV ablation aiming at bidirectional conduction block based on simultaneous pacing and ablation through the tip of a single mapping/ablation catheter. METHODS: A total of 147 patients with AF received circumferential PV ablation. In persistent AF, a posterior "box" lesion and a mitral isthmus line were added. All procedures were performed in sinus rhythm. Gaps within the left atrial (LA) ablation lines were detected and closed using voltage and pace mapping through the mapping/ablation catheter. Bidirectional conduction block was the procedural end point. Subsequently, the end point was validated by an independent electrophysiologist using a CMC. RESULTS: Procedural and radiation time measured 188 +/- 55 and 37 +/- 15 min. Bidirectional PV conduction block (lack of PV potentials and lack of LA capture) was found in 140 of 147 (95%) patients with single mapping/ablation catheter and in 138 of 147 (94%) patients with CMC. Early PV reconduction was seen in 22 of 147 (15%) patients. After 12 months follow-up, 84% of the patients were free from AF and/or atrial macro-re-entrant tachycardia. The rate of reablations was 10% and 24% for patients with paroxysmal and persistent AF, respectively. CONCLUSION: Pacing and ablation from the tip of the mapping/ablation catheter is feasible to detect and close gaps within long atrial ablation lines to consistently achieve bidirectional conduction block.

Color-coded three-dimensional entrainment mapping for analysis and treatment of atrial macroreentrant tachycardia.

BACKGROUND: Mapping and ablation of atrial macroreentrant tachycardia focus on activation mapping with identification of the area of slow conduction. OBJECTIVE: The purpose of this study was to evaluate a new concept for analysis and treatment of macroreentrant tachycardia based on color-coded three-dimensional (3D) entrainment mapping and subsequent placement of strategic lesion lines. METHODS: Twenty-six patients presented with macroreentrant tachycardia (cycle length 329 +/- 70 ms). Using nonfluoroscopic systems (CARTO 12, NavX 14), sequential mapping of the target atrium was performed. On each mapping point, the 3D location was paired with color-coded entrainment information so that the reentrant circuit could be directly visualized. RESULTS: Procedural duration, fluoroscopy time, and radiofrequency time measured 181 +/- 58, 37 +/- 19, and 31 +/- 17 minutes, respectively. Thirty-nine macroreentrant tachycardias were ablated: perimitral 9, around pulmonary vein ostium 6, through left atrial roof 5, around left atrial appendage 3, right atrial cavotricuspid isthmus dependent 6, around right atrial scar 2, around superior vena cava 1, within the septum 5, and within the coronary sinus 2. Tachycardia termination and noninducibility of any macroreentrant tachycardia was the procedural end-point. In case of left atrial macroreentrant tachycardia, pulmonary vein isolation was completed. Follow-up with serial 7-day Holter covered 302 +/- 82 days. Two (8%) patients experienced recurrences of a pretreated macroreentrant tachycardia. CONCLUSION: In patients with macroreentrant tachycardia, color-coded 3D entrainment mapping is feasible to accurately determine and visualize the 3D location of the reentrant circuit and to plan a strategic ablation line concept. That approach, not targeting the area of slow conduction of the circuit, resulted in excellent procedural success (100%), with long-term freedom from any tachycardia recurrences in 88% of patients.