Transcatheter ablation of the atrioventricular junction in refractory atrial fibrillation: A clinicopathological study.

BACKGROUND: Catheter ablation of the specialized atrioventricular junction (AVJ) with a right-side approach is an effective therapy for refractory atrial fibrillation with fast ventricular rate. Our aim is to assess the efficacy of the procedure in a single center experience and investigate the histologic findings of AVJ after catheter ablation. METHODS: A) Analysis of AVJ ablation efficacy in a consecutive series of patients with refractory atrial fibrillation; B) Histopathologic study of the conduction system by serial section technique and clinical-electrophysiologic correlation in four patients who underwent AVJ ablation. RESULTS: A) Right-sided AVJ ablation was successful in all 87 consecutive patients (mean procedural time 19.2±17.9 min). Energy applications ranged from 1 to 27 (mean 5.8±5.1) with eight patients (9%) requiring > 15 applications. B) Fibrotic disruption of atrioventricular (AV) node and/or His bundle interruption was found in three cases with previous AVJ ablation. In the case requiring a left side approach, the compact AV node and common His bundle appeared undamaged whereas extensive fibrosis of the summit of the ventricular septum, branching His bundle and proximal bundle branches was found. Noteworthy, a continuity between the septal and anterior tricuspid valve leaflets was present. CONCLUSION: Our data confirm that the ideal site for ablation of the specialized AVJ is the AV node. In selected cases with unsuccessful AV node ablation, a shift towards the His bundle is needed. A continuity between the septal and anterior leaflets of the tricuspid valve may protect the His bundle as to require multiple shocks and prolong the procedure.

Transient Type 1 Brugada Pattern without Ongoing Fever during COVID-19 Pneumonia.

Patients with COVID-19 pneumonia can develop heart problems and may also may be susceptible to proarrhythmia, virus-related issues such as fever, stress, electrolyte disturbance and adverse effects from the use of antiviral drugs. We report a transient Brugada-like ECG pattern without ongoing fever in a 57-year-old man, admitted with a diagnosis of COVID-19 pneumonia, who did not have syncope or a family history of sudden cardiac death. LEARNING POINTS: Patients with COVID-19 pneumonia can develop heart problems.A transient Brugada-like ECG pattern was observed in a non-febrile COVID-19 patient.SARS-CoV-2 may have a direct effect on myocardial ion channels.

Anticoagulation after catheter ablation of atrial fibrillation: An unnecessary evil? A systematic review and meta-analysis.

BACKGROUND: Anticoagulation in patients with atrial fibrillation (AF) is currently based on clinical parameters (CHA2 DS 2 -VASc score) that have been shown to predict cerebrovascular events (CVE). Controversy exists as to whether CVE risk persists unmodified after successful catheter ablation, as observational studies suggest a lower risk of CVE. Current guidelines recommend continued oral anticoagulation (OAC) based on the CHA 2 DS 2 -VASc score risk profile. METHODS: We conducted a systematic literature review of all studies published up to July 31, 2018, that reported CVE after catheter ablation of AF and compared patients on or off OAC. Random-effects models were used to demonstrate the risk of CVE and major bleeding in on-OAC vs off-OAC patients. This analysis was further stratified by CHADS2 and CHA 2 DS 2 -VASc score. RESULTS: We retained 16 studies, 10 prospective cohort and 6 retrospective cohort, that met inclusion criteria, and which enrolled 25 177 patients: 13 166 off-OAC and 12 011 on-OAC. No significant difference in the incidence of CVE emerged between on-OAC and off-OAC patients after AF ablation (risk ratio, 0.66; confidence interval [CI], 0.38, 1.15). Similar results were found after stratification by CHADS2 and CHA 2 DS 2 -VASc score. Off-OAC patients suffered significantly less bleeding than those on OAC (RR, 0.17; CI, 0.09, 0.34). Of note, the percentage of patients with AF recurrence impacts the treatment effect in the two groups ( P = 0.001). CONCLUSIONS: In this metanalysis, the risk-benefit ratio favored the suspension of OAT after successful AF ablation even in patients at moderate-high risk. Whether the reported results can be extended also to non-vitamin K antagonist oral anticoagulants warrants further investigations.

Morphology of right atrial appendage for permanent atrial pacing and risk of iatrogenic perforation of the aorta by active fixation lead.

BACKGROUND: Permanent atrial pacing usually involves lead placement in the right atrial appendage (RAA). Anatomical studies addressing features predisposing to complications are scanty. OBJECTIVE: To assess the morphology of RAA in the perspective of pacing, including the morphology of tenia sagittalis (TS) and the spatial relationship with the aorta. METHODS: The gross anatomy of the RAA has been analyzed in a consecutive series of 100 hearts following a case of iatrogenic perforation of the aorta by active fixation lead located in the RAA. Transmural RAA sections were taken from 40 hearts to assess the wall thickness at the level of pectinate muscles (PMs) and of inter-PMs spaces and the distance between adjacent PMs. RESULTS: The TS was present in 90% of cases (single trunk, 76%; double trunk, 13%; and triple trunk, 1%), demarcating the proximal antral RAA region (facing the adjacent aorta) from the distal saccular RAA region (facing the pulmonary infundibulum). The RAA free wall in the inter-PMs spaces is usually paper-thin and translucent. Histomorphometric analysis reveals that the RAA wall mean thickness was 1.38 ± 0.05 mm (range 0.64-4.25 mm) at the level of PMs and 0.39 ± 0.23 mm (range 0.09-1.05 mm) at the level of inter-PMs spaces. The mean distance between adjacent PMs was 0.88 ± 0.99 mm (range 0.04-4.12 mm). CONCLUSION: In 90% of hearts, a well-defined TS separates the distal saccular from the proximal antral RAA, the latter being closely adjacent to the ascending aorta. The paper-thin wall between PMs is potentially at risk of perforation, and aortic injury could occur when active fixation leads are anchored in the antral RAA, as demonstrated in an iatrogenic fatal case.

Results from a single-blind, randomized study comparing the impact of different ablation approaches on long-term procedure outcome in coexistent atrial fibrillation and flutter (APPROVAL).

BACKGROUND: This study examined the impact of different ablation strategies on atrial fibrillation (AF) recurrence and quality of life in coexistent AF and atrial flutter (AFL). METHODS AND RESULTS: Three-hundred sixty enrolled patients with documented AF and AFL were blinded and randomized to group 1, AF±AFL ablation (n=182), or group 2, AFL ablation only (n=178). AF recurrence was evaluated with event recording and 7-day Holter at 3, 6, 9, and 12-month follow-ups. Quality of life was assessed at baseline and at the 12-month follow-up with 4 questionnaires: the Medical Outcome Study Short Form, the Hospital Anxiety and Depression Score, the Beck Depression Inventory, and the State-Trait Anxiety Inventory. Of the 182 patients in group 1, 58 (age, 63±8 years; 78% male; left ventricular ejection fraction, 59±8%) had AF+AFL ablation and 124 (age, 61±11 years; 72% male; left ventricular ejection fraction, 59±7%) had AF ablation only. In group 2 (age, 62±9 years; 76% male; left ventricular ejection fraction, 58±10%), only AFL was ablated by achieving bidirectional isthmus conduction block. Baseline characteristics were not different across groups. At 21±9 months of follow-up, 117 in group 1 (64%) and 34 in group 2 (19%) were arrhythmia free (P<0.001). In group 1, scores on most quality-of-life subscales showed significant improvement at follow-up, whereas group 2 patients derived relatively minor benefit. CONCLUSIONS: In coexistent AF and AFL, lower recurrence rate and better quality of life are associated with AF ablation only or AF+AFL ablation than with lone AFL ablation. Furthermore, quality of life directly correlates with freedom from arrhythmia, as shown in this study for the first time in patients blinded to the procedure. CLINICAL TRIAL REGISTRATION: URL: http://www.clinicaltrial.gov/. Unique identifier: NCT01439386.

Anticoagulation Issues in Patients with AF.

The evaluation of the risk of stroke for individual patients with atrial fibrillation (AF) is a crucial factor in the decision to provide anticoagulation therapy. Novel oral anticoagulants, as compared with warfarin, are associated with a lower or similar rate of stroke and systemic embolism and a lower rate of hemorrhagic stroke. These drugs are administered at a fixed dose, have a shorter peak action and half-life, and do not require international normalized ratio monitoring. After a successful AF ablation, oral anticoagulation therapy discontinuation seems to be feasible in patients with a CHADS2 score greater than or equal to 2 and normal left atrial (LA) function. However, larger prospective randomized trials are needed to confirm the safety of this strategy.

Left atrial appendage: an underrecognized trigger site of atrial fibrillation.

BACKGROUND: Together with pulmonary veins, many extrapulmonary vein areas may be the source of initiation and maintenance of atrial fibrillation. The left atrial appendage (LAA) is an underestimated site of initiation of atrial fibrillation. Here, we report the prevalence of triggers from the LAA and the best strategy for successful ablation. METHODS AND RESULTS: Nine hundred eighty-seven consecutive patients (29% paroxysmal, 71% nonparoxysmal) undergoing redo catheter ablation for atrial fibrillation were enrolled. Two hundred sixty-six patients (27%) showed firing from the LAA and became the study population. In 86 of 987 patients (8.7%; 5 paroxysmal, 81 nonparoxysmal), the LAA was found to be the only source of arrhythmia with no pulmonary veins or other extrapulmonary vein site reconnection. Ablation was performed either with focal lesion (n=56; group 2) or to achieve LAA isolation by placement of the circular catheter at the ostium of the LAA guided by intracardiac echocardiography (167 patients; group 3). In the remaining patients, LAA firing was not ablated (n=43; group 1). At the 12+/-3-month follow-up, 32 patients (74%) in group 1 had recurrence compared with 38 (68%) in group 2 and 25 (15%) in group 3 (P<0.001). CONCLUSIONS: The LAA appears to be responsible for arrhythmias in 27% of patients presenting for repeat procedures. Isolation of the LAA could achieve freedom from atrial fibrillation in patients presenting for a repeat procedure when arrhythmias initiating from this structure are demonstrated.

Periprocedural stroke and management of major bleeding complications in patients undergoing catheter ablation of atrial fibrillation: the impact of periprocedural therapeutic international normalized ratio.

BACKGROUND: Catheter ablation of atrial fibrillation is associated with the potential risk of periprocedural stroke, which can range between 1% and 5%. We developed a prospective database to evaluate the prevalence of stroke over time and to assess whether the periprocedural anticoagulation strategy and use of open irrigation ablation catheter have resulted in a reduction of this complication. METHODS AND RESULTS: We collected data from 9 centers performing the same ablation procedure with the same anticoagulation protocol. We divided the patients into 3 groups: ablation with an 8-mm catheter off warfarin (group 1), ablation with an open irrigated catheter off warfarin (group 2), and ablation with an open irrigated catheter on warfarin (group 3). Outcome data on stroke/transient ischemic attack and bleeding complications during and early after the procedures were collected. Of 6454 consecutive patients in the study, 2488 were in group 1, 1348 were in group 2, and 2618 were in group 3. Periprocedural stroke/transient ischemic attack occurred in 27 patients (1.1%) in group 1 and 12 patients (0.9%) in group 2. Despite a higher prevalence of nonparoxysmal atrial fibrillation and more patients with CHADS2 (congestive heart failure, hypertension, age >75 years, diabetes mellitus, and prior stroke or transient ischemic attack) score >2, no stroke/transient ischemic attack was reported in group 3. Complications among groups 1, 2, and 3, including major bleeding (10 [0.4%], 11 [0.8%], and 10 [0.4%], respectively; P>0.05) and pericardial effusion (11 [0.4%], 11 [0.8%], and 12 [0.5%]; P>0.05), were equally distributed. CONCLUSIONS: The combination of an open irrigation ablation catheter and periprocedural therapeutic anticoagulation with warfarin may reduce the risk of periprocedural stroke without increasing the risk of pericardial effusion or other bleeding complications.

The risk of thromboembolism and need for oral anticoagulation after successful atrial fibrillation ablation.

OBJECTIVES: The aim of this multicenter study was to evaluate the safety of discontinuing oral anticoagulation therapy (OAT) after apparently successful pulmonary vein isolation. BACKGROUND: Atrial fibrillation (AF) is associated with an increased risk of thromboembolic events (TE) and often requires OAT. Pulmonary vein isolation is considered an effective treatment for AF. METHODS: We studied 3,355 patients, of whom 2,692 (79% male, mean age 57 +/- 11 years) discontinued OAT 3 to 6 months after ablation (Off-OAT group) and 663 (70% male, mean age 59 +/- 11 years) remained on OAT after this period (On-OAT group). CHADS(2) (congestive heart failure, hypertension, age [75 years and older], diabetes mellitus, and a history of stroke or transient ischemic attack) risk scores of 1 and > or =2 were recorded in 723 (27%) and 347 (13%) Off-OAT group patients and in 261 (39%) and 247 (37%) On-OAT group patients, respectively. RESULTS: During follow-up (mean 28 +/- 13 months vs. 24 +/- 15 months), 2 (0.07%) Off-OAT group patients and 3 (0.45%) On-OAT group patients had an ischemic stroke (p = 0.06). No other thromboembolic events occurred. No Off-OAT group patient with a CHADS(2) risk score of > or =2 had an ischemic stroke. A major hemorrhage was observed in 1 (0.04%) Off-OAT group patient and 13 (2%) On-OAT group patients (p < 0.0001). CONCLUSIONS: In this nonrandomized study, the risk-benefit ratio favored the suspension of OAT after successful AF ablation even in patients at moderate-high risk of TE. This conclusion needs to be confirmed by future large randomized trials.

Impact of systematic isolation of superior vena cava in addition to pulmonary vein antrum isolation on the outcome of paroxysmal, persistent, and permanent atrial fibrillation ablation: results from a randomized study.

BACKGROUND: Pulmonary veins (PVs) have been shown to represent the most frequent sites of ectopic beats initiating paroxysmal atrial fibrillation (AF). However, additional non-PV triggers, arising from different areas, have been reported as well. One of the most common non-PV sites described is the superior vena cava. AIMS: The purpose of the study was to investigate the impact resulting from the systematic isolation of the superior vena cava (SVCI) in addition to pulmonary vein antrum isolation (PVAI) on the outcome of paroxysmal, persistent, and permanent AF ablation. METHODS: A total of 320 consecutive patients who had been referred to our center in order to undergo a first attempt of AF ablation were randomized into 2 groups. Group I (160 patients) underwent PVAI only; Group II (160 patients) underwent PVAI and SVCI. RESULTS: AF was paroxysmal in 134 (46%), persistent in 75 (23%), and permanent in 111 (31%) of said patients. SVCI was performed on 134 of the 160 patients (84%) in Group II. SVC isolation was not performed on the remaining 26 patients either because of phrenic nerve capture or the lack of SVC potentials. Comparison of the outcome data between the 2 groups, after a follow-up of 12 months, revealed a significant difference in total procedural success solely with patients manifesting paroxysmal atrial fibrillation (56/73 [77%] Group I vs. 55/61 [90%] Group II; P = 0.04; OR 2.78). CONCLUSIONS: In our study, the strategy of the empiric SVCI in addition to PVAI has improved the outcome of AF ablation solely in patients manifesting paroxysmal AF.

Novel ICE-guided registration strategy for integration of electroanatomical mapping with three-dimensional CT/MR images to guide catheter ablation of atrial fibrillation.

INTRODUCTION: Image integration is used in AF ablation procedures. To maximize the efficacy of image integration, it is essential to obtain good alignment between the electroanatomical map and the 3D image of the heart. In the present study, we compared an ICE-guided landmark registration with an ICE-guided focused endocardial surface registration. METHODS AND RESULTS: In 20 patients, registration was based on posterior landmarks acquired under ICE guidance (group A); in another 20 matched patients, a new ICE-guided focused endocardial surface registration technique was used (group B). In these latter patients, a single landmark was acquired in the inferior part of the LIPV, and several surface points were recorded in the posterior area of the left PV antrum and around the antra of the right PVs. The mean ablation point-to-CT image distance was calculated in both groups. In group A, the mean landmark point-to-CT image distance was also calculated after adding the surface registration. The mean landmark point-to-CT image distance was 4.62 +/- 1.65 mm and increased to 7.66 +/- 2.44 mm when surface registration was added. The ablation point-to-CT image distance was significantly shorter in group B (1.73 +/- 0.29 mm vs 3 +/- 0.99 mm; P < 0.001). CONCLUSIONS: This ICE-guided focused endocardial surface registration seems to be superior to landmark registration in achieving a better alignment between the CT/MR image and the electroanatomical map. The concurrent use of standard surface registration may result in rotation of the atrial chamber.

Integration of positron emission tomography/computed tomography with electroanatomical mapping: a novel approach for ablation of scar-related ventricular tachycardia.

BACKGROUND: Despite the recent advances in cardiac mapping, ablation of scar-related ventricular tachycardia (VT) still remains a clinical challenge. A detailed electroanatomical map is a prerequisite for accurate localization and ablation of the VT substrate. OBJECTIVE: The purpose of this study was to evaluate the feasibility and accuracy of integrating the positron emission tomography (PET)/computed tomography (CT) with the electroanatomical map and compare the accuracy of the voltage-based scar with the biological scar. METHODS: Patients undergoing radiofrequency ablation (n = 19) for scar-related VT were enrolled. CT angiography and PET scans were performed for all patients. Tomographic and volumetric data from both images were processed and coregistered using internally designed software. That image was segmented in an electrophysiology mapping system and registered to the electroanatomical map. Eight different thresholds were applied on the voltage map to define the scar. The surface areas of the biological and electrical dense scars at different thresholds were measured and compared. RESULTS: The PET/CT image was well integrated with the electroanatomical map with a mean surface registration error of 5.1 +/- 2.1 mm. Of the eight different thresholds defining the scar, the surface area of the scar at a threshold of 0.9 mV (68.6 +/- 49.2 cm(2)) correlated best with the surface area of the PET-based scar (70.4 +/- 49.3 cm(2)) and had the least total area error (4.8 +/- 1.8 cm(2)) compared with the 0.5 threshold (29.7 +/- 23.9 cm(2)). CONCLUSION: Integrating PET/CT with the electroanatomical map is feasible and accurate. Based on the biological scar, readjustment of the voltage scar threshold to 0.9 mV is suggested. In view of the better accuracy of PET/CT in defining scar, the need for acquiring detailed voltage maps may be obviated.

Role of transoesophageal echocardiography in evaluating the effect of catheter ablation of atrial fibrillation on anatomy and function of the pulmonary veins.

AIMS: Radiofrequency ablation (ABL) of pulmonary veins (PVs) is an effective treatment of atrial fibrillation (AF). The aim of this study was to evaluate the possible morphological and functional consequences of this procedure on PV during a 12-month follow-up. METHODS AND RESULTS: Ninety-six patients underwent transoesophageal echocardiography (TEE) before ABL, and 48 h, 3, and 12 months later. The peak velocity, mean velocity, mean/peak flow velocity, and diameter of each vein were measured at every follow-up examination. All patients also underwent multidimensional computer tomography (MCT) 3 months after ABL. At the first control, a 5% reduction in PV diameters and an increase in the peak velocity, mean velocity, and mean/peak velocity (34.3, 42.2, and 6.9, respectively: P < 0.000) of their Doppler flow were observed. Later follow-up examinations revealed no further significant increase in PV narrowing or flow velocities. MCT showed PV stenoses (>50%) in four PVs, while TEE showed a >100% increase over basal values in flow velocities and a plateau configuration of the pulsed-wave Doppler spectrum. CONCLUSION: ABL of AF reduces the diameter and increases the flow velocities of PV. However, critical stenosis is rare and can be diagnosed by TEE through a marked change in the velocities and in the configuration of the Doppler flow.

Efficacy, safety, and outcome of atrial fibrillation ablation in septuagenarians.

AIMS: Catheter ablation is an effective treatment for atrial fibrillation (AF). The outcome of AF ablation in septuagenarians is not clear. Our aim was to evaluate success rate, outcome, and complication rate of AF ablation in septuagenarians. METHODS AND RESULTS: We collected data from 174 consecutive patients over 75 years of age who underwent AF ablation from 2001 to 2006. AF was paroxysmal in 55%. High-risk CHADS score (>or=2) was present in 65% of the population. Over a mean follow-up of 20 +/- 14 months, 127 (73%) maintained sinus rhythm (SR) with a single procedure, whereas 47 patients had recurrence of AF. Twenty of them had a second ablation, successful in 16 (80%). Major acute complications included one CVA and one hemothorax (2/194 [1.0%]). During the follow-up, three patients had a CVA within the first 6 weeks after ablation. Warfarin was discontinued in 138 out 143 patients (96%) who maintained SR without AADs with no embolic event occurring over a mean follow-up of 16 +/- 12 months. CONCLUSION: AF ablation is a safe and effective treatment for AF in septuagenarians.

Role of anticoagulation therapy after pulmonary vein antrum isolation for atrial fibrillation treatment.

BACKGROUND: Atrial fibrillation (AF) increases the risk of atrioembolic stroke. However, the role of anticoagulation therapy (OAT) in preventing cerebrovascular accidents (CVA) after intracardiac echocardiography-guided pulmonary vein antrum isolation (ICE-PVAI) is still unclear. In the present study, we evaluated the incidence of CVA following the interruption of OAT 3 months after ICE-PVAI. METHODS: Between September 2002 and March 2004, 85 consecutive patients (72 men, mean age 62 +/- 7 years) underwent ICE-PVAI for symptomatic drug-refractory AF. Heart disease was present in 61 patients (72%) (left ventricular ejection fraction = 58 +/- 6%, LA diameter 44 +/- 6 mm). Eighty-five consecutive patients who underwent electrical cardioversion (EC) for AF, matched for age, sex and heart disease, served as a control group. After 3 months, OAT was stopped unless one of the following conditions was observed: (i) AF-recurrence; (ii) severe pulmonary vein stenosis; (iii) non-good atrial contractility on transesophageal echocardiography; or (iv) other indications for OAT. RESULTS: In the study group, OAT was stopped after 3 months in 77 patients (90%) and no CVA occurred during the remaining follow-up (15 +/- 7 months). In the control group, 1 month after EC, OAT was stopped by the referring physician in 29 patients (34%). A stroke occurred in five patients (6%) (P = 0.09; mean P = 0.059) during follow-up. In two of these (2%), the stroke was fatal. CONCLUSIONS: Stopping OAT 3 months after ICE-PVAI seems to be safe in patients without AF recurrences after the first 3 months following ablation. Further randomized-controlled studies are needed to confirm these preliminary data.

[Sports physicians and prescription of sports therapy]. / Il medico dello sport e la prescrizione della sport-terapia.

The older age of the population, together with some bad habits, first of all the lack of regular physical activity, is giving rise to a huge increase in the epidemiologic burden of cardiovascular diseases in our country. Epidemiological, clinical and laboratory studies have provided definitive evidence that physical activity is able to improve fitness and to reduce cardiovascular morbidity and mortality. Moreover, physical exercise also seems to significantly reduce the risk of developing other chronic diseases with a high economic impact, such as obesity, osteoporosis, diabetes, tumors, and depression. For this reason, physical exercise has been proposed as a preventive and therapeutic strategy that is physiological, economic and efficacious in different clinical conditions. However, despite the fact that the benefits of an active lifestyle have been demonstrated by numerous scientific data, only a minority of Italians engage in regular physical exercise. Promoting physical activity in the general population and in patients affected by cardiovascular disease is therefore one of the primary objectives of our healthcare institutions in the next decades.

Antiarrhythmic Effect of Statin Therapy and Atrial Fibrillation A Meta-Analysis of Randomized Controlled Trials.

The aim of this meta-analysis was to improve the evaluation of the possible antiarrhythmic effect of statins on atrial fibrillation (AF) incidence orrecurrence.

Atrial fibrillation in patients with a dual defibrillator: characteristics of spontaneous and induced episodes and effect of ventricular tachyarrhythmia induction.

BACKGROUND: The pattern of FF intervals during atrial fibrillation (AF) has been analyzed in induced and spontaneous AF episodes, after the induction of ventricular fibrillation (VF) and after atrial shock, in order to suggest practical considerations for AF management in patients implanted with antitachycardia devices. METHODS: In 13 patients implanted with a dual-chamber defibrillator, FF intervals were analyzed during two separate induced AF episodes, before and after VF induction over AF, as well as during spontaneous AF episodes and after unsuccessful atrial shocks. The following parameters were considered: mean atrial cycle length (CL), atrial CL stability, and standard deviation of the atrial cycle. RESULTS: The AF pattern had comparable characteristics considering two separate inductions of AF, as well as spontaneous AF episodes. Ventricular tachyarrhythmia induction resulted in a shortening of atrial CL (P < 0.02) and in a less organized AF pattern (P < 0.005). Changes in the FF interval after ineffective shock therapy showed a shortening of AF cycles after shocks with energies far below the defibrillation threshold. CONCLUSIONS: (a) The AF pattern is reproducible in separate inductions of sustained AF and in spontaneous episodes, (b) dynamic changes involving a shortening of the AF cycle and an evolution to a less homogeneous pattern occur after VF induction, revealing a complex interplay between AF and VF, and (c) FF interval analysis after ineffective shock delivery may allow the relationship between delivered shock energy and effective defibrillation energy to be estimated, thereby providing practical suggestions for step-up protocols in atrial cardioversion.