Pulsed field ablation prevents chronic atrial fibrotic changes and restrictive mechanics after catheter ablation for atrial fibrillation.

AIMS: Pulsed field ablation (PFA), a non-thermal ablative modality, may show different effects on the myocardial tissue compared to thermal ablation. Thus, this study aimed to compare the left atrial (LA) structural and mechanical characteristics after PFA vs. thermal ablation. METHODS AND RESULTS: Cardiac magnetic resonance was performed pre-ablation, acutely (<3 h), and 3 months post-ablation in 41 patients with paroxysmal atrial fibrillation (AF) undergoing pulmonary vein (PV) isolation with PFA (n = 18) or thermal ablation (n = 23, 16 radiofrequency ablations, 7 cryoablations). Late gadolinium enhancement (LGE), T2-weighted, and cine images were analysed. In the acute stage, LGE volume was 60% larger after PFA vs. thermal ablation (P < 0.001), and oedema on T2 imaging was 20% smaller (P = 0.002). Tissue changes were more homogeneous after PFA than after thermal ablation, with no sign of microvascular damage or intramural haemorrhage. In the chronic stage, the majority of acute LGE had disappeared after PFA, whereas most LGE persisted after thermal ablation. The maximum strain on PV antra, the LA expansion index, and LA active emptying fraction declined acutely after both PFA and thermal ablation but recovered at the chronic stage only with PFA. CONCLUSION: Pulsed field ablation induces large acute LGE without microvascular damage or intramural haemorrhage. Most LGE lesions disappear in the chronic stage, suggesting a specific reparative process involving less chronic fibrosis. This process may contribute to a preserved tissue compliance and LA reservoir and booster pump functions.

Pulsed field ablation selectively spares the oesophagus during pulmonary vein isolation for atrial fibrillation.

AIMS: Extra-atrial injury can cause complications after catheter ablation for atrial fibrillation (AF). Pulsed field ablation (PFA) has generated preclinical data suggesting that it selectively targets the myocardium. We sought to characterize extra-atrial injuries after pulmonary vein isolation (PVI) between PFA and thermal ablation methods. METHODS AND RESULTS: Cardiac magnetic resonance (CMR) imaging was performed before, acutely (<3 h) and 3 months post-ablation in 41 paroxysmal AF patients undergoing PVI with PFA (N = 18, Farapulse) or thermal methods (N = 23, 16 radiofrequency, 7 cryoballoon). Oesophageal and aortic injuries were assessed by using late gadolinium-enhanced (LGE) imaging. Phrenic nerve injuries were assessed from diaphragmatic motion on intra-procedural fluoroscopy. Baseline CMR showed no abnormality on the oesophagus or aorta. During ablation procedures, no patient showed phrenic palsy. Acutely, thermal methods induced high rates of oesophageal lesions (43%), all observed in patients showing direct contact between the oesophagus and the ablation sites. In contrast, oesophageal lesions were observed in no patient ablated with PFA (0%, P < 0.001 vs. thermal methods), despite similar rates of direct contact between the oesophagus and the ablation sites (P = 0.41). Acute lesions were detected on CMR on the descending aorta in 10/23 (43%) after thermal ablation, and in 6/18 (33%) after PFA (P = 0.52). CMR at 3 months showed a complete resolution of oesophageal and aortic LGE in all patients. No patient showed clinical complications. CONCLUSION: PFA does not induce any signs of oesophageal injury on CMR after PVI. Due to its tissue selectivity, PFA may improve safety for catheter ablation of AF.

Ostial dimensional changes after pulmonary vein isolation: Pulsed field ablation vs radiofrequency ablation.

BACKGROUND: Pulmonary vein (PV) stenosis is an important potential complication of PV isolation using thermal modalities such as radiofrequency ablation (RFA). Pulsed field ablation (PFA) is an alternative energy that causes nonthermal myocardial cell death. OBJECTIVE: The purpose of this study was to compare the effect of PFA vs RFA on the incidence and severity of PV narrowing or stenosis. METHODS: Data were analyzed from 4 paroxysmal atrial fibrillation ablation trials using either PFA or RFA; because of absent CT scans or poor computed tomography scan quality, 73 of 153 patients (47.7%) were excluded. Baseline and 3-month cardiac computed tomography scans were reconstructed into 3-dimensional images, and the long and short axes of the PV ostia were quantitatively and qualitatively assessed in a randomized blinded manner by 2 physicians. RESULTS: A total of 299 PVs from 80 patients after either PFA (n = 37) or RFA (n = 43) were enrolled. PV ostial diameters decreased significantly less with PFA than with RFA (% change; long axis: 0.9% ± 8.5% vs -11.9% ± 16.3%; P < .001 and short axis: 3.4% ± 12.7% vs -12.9% ± 18.5%; P < .001). After a combined quantitative/qualitative analysis, mild (30%-49%), moderate (50%-69%), or severe (70%-100%) PV narrowing was observed, respectively, in 9.0% (15 of 166), 1.8% (3 of 166), and 1.2% (2 of 166) of PVs in the RFA cohort but in none of the PVs after PFA (P < .001). Overall, PV narrowing/stenosis was present in 0% and 0% vs 12.0% and 32.5% of PVs and patients who underwent PFA and RFA, respectively. CONCLUSION: This study indicates that unlike after RFA, the incidence and severity of PV narrowing/stenosis after PV isolation is virtually eliminated with PFA.

Catheter ablation of scar-related atypical atrial flutter.

AIMS: The aim of the study was to assess the impact of isthmus location of atypical atrial flutters/atrial tachycardias (ATs) on outcomes of catheter ablation. Atrial tachycardias are clinically challenging arrhythmias that can occur in the presence of atrial scar--often due to either cardiac surgery or prior ablation for atrial fibrillation. We previously demonstrated a catheter ablation approach employing rapid multielectrode activation mapping with targeted entrainment manoeuvrs. However, the role that AT isthmus location plays in acute and long-term success of ablation remains uncertain. METHODS AND RESULTS: Retrospective multicenter analysis of 91 consecutive AT patients undergoing ablation using a systematic four-step approach: (i) high-density activation mapping; (ii) analysis of atrial activation to identify wavefronts of electrical propagation; (iii) targeted entrainment of putative channels; and (iv) irrigated radiofrequency ablation of constrained regions of the circuit. Clinical outcomes, procedural details, and clinical profiles were determined. A total of 171 ATs (1.9 ± 1.0 per patient, 26% septal ATs) were targeted for ablation. The acute success rates were 97 and 77% for patients with either non-septal ATs or septal ATs, respectively (P = 0.0023). Similarly, the long-term success rates were 82 and 67% for patients with either no septal ATs or at least one septal AT, respectively (P = 0.1057). The long-term success rates were 75, 88, and 57% for patients with ATs associated with prior catheter ablation, cardiac surgery or MAZE, and idiopathic atrial scar, respectively. CONCLUSION: Catheter ablation of AT can be successfully performed employing a strategy of combined high-density activation and entrainment mapping. Septal ATs are associated with higher rates of acute and long-term recurrences.

Areas with complex fractionated atrial electrograms recorded after pulmonary vein isolation represent normal voltage and conduction velocity in sinus rhythm.

AIMS: Although complex fractionated atrial electrograms (CFAEs) are purported to represent critical sites for atrial fibrillation (AF) perpetuation, the mechanism and the significance of CFAE in the genesis of AF remain poorly understood. This study evaluated the relationship between CFAE and areas of abnormal atrial tissue defined by low-voltage electrograms (LVE) and signal average of the P-wave (SAPW). METHODS AND RESULTS: Complex fractionated atrial electrogram maps were obtained after pulmonary vein isolation in 15 patients with persistent AF. Patients were then cardioverted and voltage/activation maps were acquired in normal sinus rhythm (NSR). Total left atrium (LA), CFAE and LVE areas were measured as % of total LA area (mean ± SD). Conduction velocities of normal, LVE and CFAE areas were also measured during NSR. Patients underwent signal averaged ECG of the P-wave in NSR within 24 h of the procedure. Complex fractionated atrial electrograms areas accounted for 33 ± 24% of total LA. In NSR, only 12 ± 10% of LA area had LVE. There was no anatomic correlation between CFAE sites and LVE; the area of overlap between CFAE and LVE was only 1.6 ± 1.5%. Conduction velocity was faster in CFAE areas (2.3 ± 1.4 m/s) than in normal voltage areas (1.3 ± 0.3 m/s), and LVE areas (1.1 ± 0.7 m/s, P = 0.06). A positive correlation was only found between LVE areas and SAPW duration (r = 0.7, P = 0.04). CONCLUSION: Areas of CFAEs correspond to areas of normal atrial voltage and normal conduction velocity during NSR. Complex fractionated atrial electrogram probably represents the response of normal healthy atrial tissue to rapid pulmonary vein activation.

Acute electrical isolation is a necessary but insufficient endpoint for achieving durable PV isolation: the importance of closing the visual gap.

AIMS: Temporary, ablation-mediated effects such as oedema may cause reversible pulmonary vein (PV) isolation. To investigate this, point-by-point circumferential ablation was performed to achieve acute electrical PV isolation with an incomplete circumferential ablation line. Then, the impact of this intentional 'visual gap' (ViG) on the conduction properties of the ablation lesion set was assessed with adenosine and pacing manoeuvres. METHODS AND RESULTS: Twenty-eight patients undergoing ablation for paroxysmal (n= 20) or persistent atrial fibrillation (n= 8) were included. Pulmonary vein (PV) ablation was performed around ipsilateral vein pairs. Once acute isolation was achieved, ablation was halted and the presence and size of the ViG were calculated. The ViG electrophysiological properties were tested with pace capture along the ViG at 10 mA/2 ms, and assessment for dormant PV conduction with adenosine. Despite electrical isolation, a ViG was present in 75% (n= 42/56) of vein pairs (21 of 28 left PVs and 21 of 28 right PVs). There was no difference in the ViG size between the left and right PVs (22.1 ± 14.2 and 17.3 ± 11.3 mm, P > 0.05). Dormant PV connections were revealed by adenosine in more than a quarter (n= 12/42) of acutely isolated PV pairs, of which the majority were dependent on conduction through the ViG. CONCLUSIONS: Electrical PV isolation can usually be achieved without complete circumferential ablation. However, more than a quarter of these 'isolated' PVs exhibit dormant conduction-predominantly via the un-ablated 'ViGs' in the ablation lesion set. These findings support the hypothesis that reversible tissue injury contributes to PV isolation that may be acute but not necessarily durable.