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.

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.

Background and Aims Pulsed field ablation (PFA) is a new, non-thermal ablation modality for pulmonary vein isolation (PVI) in patients with atrial fibrillation (AF). The multi-center EU-PORIA (EUropean Real World Outcomes with Pulsed Field AblatiOn in Patients with Symptomatic AtRIAl Fibrillation) registry sought to determine the safety, efficacy, and learning curve characteristics for the pentaspline, multielectrode PFA catheter. Methods All-comer AF patients from seven high-volume centers were consecutively enrolled. Procedural and follow-up data were collected. Learning curve effects were analyzed by operator ablation experience and primary ablation modality. Results In total, 1,233 patients (61% male, mean age 66±11years, 60% paroxysmal AF) were treated by 42 operators. In 169 patients (14%), additional lesions outside the PVs were performed, most commonly at the posterior wall (n=127). Median procedure and fluoroscopy times were 58 [IQR: 40-87] and 14 [9-21] min, respectively, with no differences due to operator experience. Major complications occurred in 21/1233 procedures (1.7%) including pericardial tamponade (14; 1.1%) and transient ischemic attack or stroke (n=7; 0.6%), of which one was fatal. Prior cryo-balloon users had less complications. At a median follow-up of 365 [323-386] days, the Kaplan-Meier estimate of arrhythmia-free survival was 74% (80% for paroxysmal and 66% for persistent AF). Freedom from arrhythmia was not influenced by operator experience. In 149 (12%) patients a repeat procedure was performed due to AF recurrence and 418/584 (72%) PVs were durably isolated. Conclusion The EU-PORIA registry demonstrates a high single-procedure success rate with an excellent safety profile and short procedure times in a real-world, all-comer AF patient population.

FibroScan failure and poorly reliable LSM are uncommon. The most important determinants of poorly reliable results are older age, obesity, higher liver stiffness and the operator, the latter emphasizing the need for adequate training.

We have developed a simple analytical model of absorbed dose from external beam radiotherapy treatments in the 6 to 25 MV beam energy range. The model has been tested on measured data from multiple treatment machines and techniques, and is broadly applicable to contemporary external beam radiation therapy.

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 5 37) or RFA (n 5 43) were enrolled. PV ostial diameters decreased significantly less with PFA than with RFA (% change; long axis: 0.9% 6 8.5% vs 211.9% 6 16.3%; P , .001 and short axis: 3.4% 6 12.7% vs 212.9% 6 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.

External-beam radiation therapy is safe, effective and widely used to treat cancer. With 5-year cancer survival for adults above 70%, increasingly research is focusing on quantifying and reducing treatment-related morbidity. Reducing exposures to healthy tissues is one strategy, which can be accomplished with advanced-technology radiotherapies, such as intensity-modulated photon therapy and proton therapy. Both of these modalities provide good conformation of the therapeutic dose to the tumor volume, but they also deliver stray radiation to the whole body that increases the risk of radiogenic second cancers. To minimize these risks, one needs to create and compare candidate treatment plans that explicitly take into account these risks. Currently, clinical practice does not include routine calculation of stray radiation exposure and, consequently, the assessment of corresponding risks is difficult. In this article, we review recent progress toward stray dose algorithms that are suitable for large-scale clinical use. In particular, we emphasize the current state of physics-based dose algorithms for intensity-modulated photon radiotherapy and proton therapy.

A burgeoning population of cancer survivors is at risk of late health effects following radiation therapy including second cancers, with the majority of these cancers occurring outside of the treatment volume of the primary cancer. Commercial radiotherapy treatment planning systems underestimate the out-of-field dose. Previous analytical models of out-of-field dose have assumed radial symmetry and/or approximated the dimensions of collimators as semi-infinite planes. The purpose of this work was to develop a physics-based analytical model of total absorbed dose from primary, scattered, and leakage radiation for square fields from a 6 MV beam at any arbitrary point in a phantom, including in-plane, cross-plane, and out-of-plane locations. The model includes the essential physics of radiation transport through beam-limiting-devices including rounded edges of MLC leaves. The model agreed well with measurements and Monte Carlo simulations of absorbed dose in a water-box phantom and was validated for field-sizes ranging from 2 × 2 to 20 × 20 cm 2 . The signed and unsigned average percent differences were −3.0% and 15.9%, respectively, for all points and field-sizes considered. An extended gamma index analysis reveals a 92% pass rate with criteria of 3 mm distance-to-agreement, 3% relative dose difference in-field, and 3 mGy Gy −1 absolute dose difference out-of-field. The average wall-clock time to calculate dose to one million points was 3.3 min. These results suggest that it is feasible to calculate absorbed dose from both therapeutic and stray radiation using physics-based analytical models with good accuracy, thus overcoming a major obstacle to routinely assessing exposures. Additionally, this work demonstrates the importance of relaxing certain simplifications such as assuming a radially symmetric stray-dose distribution. Because the model is physics-based and may be reconfigured according to the dimensions of beamlimiting-devices, adapting it to other treatment units should be straight forward. Uses for such a model include clinical and research applications, such as clinical trials and epidemiological studies.