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Introduction: Idiopathic ventricular fibrillation (IVF) is mainly associated with and triggered by short-coupled (R-on-T) ventricular ectopics. However, little is known about the risk of VF associated with long-coupled premature ventricular complexes (LCPVCs)., Objective: To examine the prevalence and characteristics of IVF patients presenting with LCPVCs., Methods: Consecutive patients with IVF and PVCs from five arrhythmia referral centers were reviewed. We included patients presenting LCPVCs, defined as PVCs falling after the end of the T wave, with a normal QTc interval. We evaluated demographics, medical history, and clinical circumstances associated with PVCs and VF episodes. The origin of PVCs was determined by invasive mapping., Results: Seventy-nine patients with IVF were reviewed. Among them, 12 (15.2%) met the inclusion criteria (8 women, age 36 ± 14 years). Eleven patients had documented LCPVCs initiating repetitive PVCs or sustained VF, whereas 1 had only documented isolated PVCs. In 10 of 12 patients, PVCs were recorded showing both long and short coupling intervals of 418 ± 46 and 304 ± 33 ms, respectively. Mapping showed that PVCs originated from the left Purkinje in 10 patients, from the right Purkinje in 1 patient, and both in 1 patient. Compared to other patients from the initial cohort, IVF with LCPVCs was associated with a left-sided origin of PVCs (92% in long-coupled IVF vs. 46% of left Purkinje PVCs in short-coupled IVF, p = .004)., Conclusion: Long-coupled fascicular PVCs, traditionally recognized as benign, can be associated with IVF in a subset of patients. They can induce IVF by themselves or in association with short-coupled PVCs., (© 2023 The Authors. Journal of Cardiovascular Electrophysiology published by Wiley Periodicals LLC.)

Background: Sodium channel blocker (SCB) infusion is used to unmask the electrocardiographic pattern of Brugada syndrome. The test may also induce premature ventricular complexes (PVCs) in individuals without Brugada pattern, the clinical relevance of which is little known., Objective: The purpose of this study was to describe the prevalence of short-coupled (Sc) PVCs induced by ajmaline or flecainide in patients with suspected or documented severe ventricular arrhythmias., Methods: We reviewed the SCB tests performed in 335 patients with suspected ventricular arrhythmias and structurally normal hearts in 9 centers. ScPVCs were defined as frequent and repetitive PVCs with an R-on-T pattern on SCB tests. Repeated SCB tests were performed in 7 patients and electrophysiological mapping of ScPVCs in 9., Results: Sixteen patients (8 men; mean age 36 ± 11 years) showed ScPVCs and were included. ScPVCs appeared 229 ± 118 seconds after the initiation of infusion and displayed coupling intervals of 288 ± 28 ms. ScPVC patterns were monomorphic in 12 patients, originating from the Purkinje system in mapped patients. Repetitive PVCs were induced in 15 patients (94%) including polymorphic ventricular tachycardias in 9 (56%). SCB infusion was repeated 45 (interquartile range 0.6-46) months later and induced identical ScPVC in all. SCB test was the only mean to reveal the malignant arrhythmia in 6 patients. Catheter ablation was performed in 9 patients, resulting in arrhythmia elimination in 8 with a follow-up of 6 (interquartile range 2-9) years., Conclusion: SCB can induce ScPVC, mostly from Purkinje tissue, in a small subset of patients with idiopathic ventricular arrhythmias. Its high reproducibility suggests a distinct individual mechanism., (Copyright © 2022 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.)

Background: With the growing adult congenital heart disease (ACHD) population, the number of catheter ablation procedures is expected to dramatically increase. Data reporting experience and evolution of catheter ablation in patients with ACHD, over a significant period of time, remain scarce., Aim: We aimed to describe temporal trends in volume and outcomes of catheter ablation in patients with ACHD., Methods: This was a retrospective observational study including all consecutive patients with ACHD undergoing attempted catheter ablation in a large tertiary referral centre over a 15-year period. Acute procedural success rate and freedom from recurrence at 12 and 24 months were analysed., Results: From November 2004 to November 2019, 302 catheter ablations were performed in 221 patients with ACHD (mean age 43.6±15.0 years; 58.9% male sex). The annual number of catheter ablations increased progressively from four to 60 cases per year (P<0.001). Intra-atrial reentrant tachycardia/focal atrial tachycardia was the most common arrhythmia (n=217, 71.9%). Over the study period, acute procedural success rate increased from 45.0% to 93.4% (P<0.001). Use of irrigated catheters (odds ratio [OR] 4.03, 95% confidence interval [CI] 1.86-8.55), a three-dimensional mapping system (OR 3.70, 95% CI 1.72-7.74), contact force catheters (OR 3.60, 95% CI 1.81-7.38) and high-density mapping (OR 3.69, 95% CI 1.82-8.14) were associated with acute procedural success. The rate of freedom from any recurrence at 12 months increased from 29.4% to 66.2% (P=0.001). Seven (2.3%) non-fatal complications occurred., Conclusions: The number of catheter ablation procedures in patients with ACHD has increased considerably over the past 15 years. Growing experience and advances in ablative technologies appear to be associated with a significant improvement in acute and mid-term outcomes., (Copyright © 2021 Elsevier Masson SAS. All rights reserved.)

Background: While outcomes of intra-atrial reentrant/focal atrial tachycardia (IART/FAT) catheter ablation have considerably improved in adult congenital heart disease (ACHD), recurrences remain common with different circuits frequently encountered., Objective: We aimed to assess the value of programmed atrial stimulation after successful clinical IART/FAT catheter ablation in patients with ACHD., Methods: This is a retrospective study including all patients with ACHD undergoing IART/FAT catheter ablation in a tertiary center. After successful catheter ablation of clinical arrhythmia, survival free from arrhythmia recurrence was analyzed according to whether all inducible IARTs/FATs were targeted., Results: From 2004 to 2020, 238 IART/FAT catheter ablation procedures were performed (mean age 44.1 ± 15.0 years; 61.3% men). Acute procedural success of clinical arrhythmia was achieved in 208 procedures (87.4%). Among 122 procedures with programmed atrial stimulation (58.7%), at least 1 other IART/FAT was induced in 61 patients (50%). All inducible IARTs/FATs were ablated in 54 patients (88.5%), whereas 7 patients (11.5%) presented with at least 1 nontargeted inducible IART/FAT. Patients with nontargeted inducible IART/FAT had a higher risk of atrial arrhythmia episodes than did inducible patients treated with ablation of all IARTs/FATs (hazard ratio 5.7; 95% confidence interval 1.7-18.4; P = .004), with 12-month atrial arrhythmias recurrence rates of 22.9% and 77.7%, respectively. Inducible patients with successful ablation of all IARTs/FATs had a risk of recurrence similar to that of noninducible patients (hazard ratio 0.6; 95% confidence interval 0.3-1.3; P = .215)., Conclusion: Beyond clinical IART/FAT catheter ablation in patients with ACHD, our findings suggest the interest of systematically targeting all remaining inducible arrhythmias, irrespective of whether previously documented., (Copyright © 2020 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.)

Objectives: This multicenter study sought to evaluate the long-term follow-up of patients ablated for idiopathic ventricular fibrillation (VF)., Background: Catheter ablation of idiopathic VF that targets ventricular premature beat (VPB) triggers has been shown to prevent VF recurrences on short-term follow-up., Methods: From January 2000, 38 consecutive patients from 6 different centers underwent ablation of primary idiopathic VF initiated by short coupled VPB. All patients had experienced at least 1 documented VF, with 87% having experienced > or =2 VF episodes in the preceding year. Catheter ablation was guided by activation mapping of VPBs or pace mapping during sinus rhythm., Results: There were 38 patients (21 men) age 42 +/- 13 years, refractory to a median of 2 antiarrhythmic drugs. Triggering VPBs originated from the right (n = 16), the left (n = 14), or both (n = 3) Purkinje systems and from the myocardium (n = 5). During a median post-procedural follow-up of 63 months, 7 (18%) of 38 patients experienced VF recurrence at a median of 4 months. Five of these 7 patients underwent repeat ablation without VF recurrence. Survival free of VF was predicted only by transient bundle-branch block in the originating ventricle during the electrophysiological study (p < 0.0001). The number of significant events (confirmed VF or aborted sudden death) was reduced from 4 (interquartile range 3 to 9) before to 0 (interquartile range 0 to 4) after ablation (p = 0.01)., Conclusions: Ablation for idiopathic VF that targets short coupled VPB triggers is associated with a long-term freedom from VF recurrence.

Radiofrequency ablation is the reference treatment of refractory nodal reentry. Cryoablation has the advantage of having more modulable effects and minimises the risk of permanent atrioventricular block (AVB). Its immediate efficacy seems comparable to that of radiofrequency ablation but the long-term results are not well known. Endocavitary cryoablation of the slow pathway was undertaken in 26 patients (18 women) with an average age of 47.7 +/- 72.8 years with re-entrant nodal tachycardia refractory to medical therapy. The primary success rate was 92% (24 out of 26). On average, 2.6 +/- 2.2 (1 to 10) cryoablations at - 70 degrees C were delivered and were preceded by 6.4 +/- 4.5 (1 to 16) cryomappings to locate the site of the slow pathway. During cryomapping, 8 episodes of AVB were observed in 6 patients (6 second or third degree), all of which were revertible on rewarming. No cases of permanent AVB were observed. An oesophageal stimulation test of inducibility was performed on the 4th day in 21 patients, 16 of which were not reinducible. During follow-up of 355 +/- 194 days, 22 of the 26 patients (85%) had no recurrence of the arrhythmia. Two of the 24 primary successes had a recurrence, in addition to the two primary failures. Two of the four recurrences occurred in a non-sustained form which was less disabilitating for the patient and the recurrences were controlled in the 4 patients by antiarrhythmic therapy. These results suggest that cryoablation may be a reliable and effective long-term treatment of re-entrant nodal tachycardias. If confirmed in larger series in terms of efficacy and safety, cryoablation could become the treatment of choice of re-entrant nodal tachycardia.

Radiofrequency current is the reference energy source for endocavitary ablation of arrhythmias. It is particularly well adapted for the ablation of focal arrhythmogenic substrates such as accessory pathways or foyers of automatism. Technological advances have made the lesions larger but the extension of the indications of percutaneous ablation to more complex substrates such as atrial fibrillation have justified the evaluation of alternative energies. The production of linear transmural lesions or deeper lesions which respect the parietal myocardial architecture and endocardial structure are a challenge for these energies. The capacity of functional mapping specific to cryogenics has provided this energy source with a clinical application for ablation of high risk structures whereas other energies, despite the chronicity of their experimental evaluation, are still at the stage of preliminary clinical trials with the sophisticated catheters in special indications.

Introduction: Mechanisms for thromboembolic complications during complex ablation procedures in left atrium (LA) have not been defined. The aim of this study was to determine the effect of the perfusion rate of the transseptal sheath on the incidence of thromboembolic complications during catheter ablation for atrial fibrillation (AF) or LA macroreentrant tachycardia., Methods and Results: We analyzed clinical and procedural data from 86 consecutive patients (153 procedures) referred for catheter ablation of AF (74 patients) or LA macroreentrant tachycardia (12 patients). The transseptal sheath was continuously perfused at a low flow rate (3 mL/hour) for the first 32 patients and at a high flow rate (180 mL/hour) for the subsequent 54 patients. Ablation was mainly performed using map-guided isolation of pulmonary veins for AF and three-dimensional electroanatomic mapping for LA macroreentrant tachycardia. Five patients (6% of patients and 3.5% of procedures) developed a cerebral thromboembolic complication, all during procedures using low-flow perfusion. Sheath perfusion rate and total procedure duration were the two variables significantly associated with the occurrence of stroke (P = 0.013 and 0.001, respectively). After adjustment in a multivariable analysis, sheath perfusion rate remained the only risk factor for stroke. The risk was 17 times higher using low-flow than high-flow perfusion (odds ratio 17.26, 95% confidence interval 1.14-260.81, P = 0.04). No other clinical or procedural parameters had any significant effect., Conclusion: Sheath perfusion rate is an important determinant of the risk factor for stroke during complex LA ablation procedures. Continuous high-flow perfusion appears to be effective in preventing this complication.

Catheter ablation is a radical treatment for various severe and drug-refractory arrhythmias. Radiofrequency is the reference energy for ablation, but has some limitations. Cryoenergy gradually freezes myocardial tissue, allowing the consequences to be predicted before inducing the lesion. Furthermore, the lesions are better-circumscribed and less thrombogenic than those induced by radiofrequency. Twenty-two patients (12 women) aged from 20 to 79 years with drug-refractory supraventricular arrhythmias underwent cryoablation. The ablation catheter was cooled by nitrous oxide expansion. The electrophysiological properties of the tissue are reversibly lost at a temperature of -30 degrees C, allowing cryomapping. When the appropriate target has been located, the temperature is reduced to -70 degrees C. The cryoablation is painless. The procedure was initially successful in all 12 patients with atrionodal reentrant tachycardias, usually after one or two applications. However, during the 8-month follow-up period, slower, transient tachycardia recurred in 3 patients. We observed no cases of atrioventricular (AV) block, a possible complication of radiofrequency. Cryoablation was successful and safe in two patients with an accessory pathway (Kent). In eight patients with atrial fibrillation and uncontrolled ventricular tachycardia, cryoablation was used with the aim of slowing nodal conduction. Initial success was obtained in 7 cases (3 modulations and 4 complete AV blocks) but only persisted in four cases, suggesting that more applications should be used or different sites targeted. The efficacy and safety of cryoablation make it an attractive option for the ablation of small substrates close to the nodo-Hisian tissue (atrionodal reentries and accessory pathways). New criteria must be developed to define long-term success of cryoablation of the AV node, which is successful in the acute setting.

RF ablation for paroxysmal atrial fibrillation (PAF) is a curative treatment, which when successful, eliminates the need to take antiarrhythmic drugs, be anticoagulated, and have recurrent physician visits or hospital admissions. The authors performed a retrospective cost comparison of RF ablation versus drug therapy for PAF. The study population consisted of 118 consecutive patients with symptomatic, drug refractory PAF who underwent 1.52 +/- 0.71 RF ablation procedures (range 1-4) for PAF. During a follow-up of 32 +/- 15 weeks, 85 (72%) patients remained free of clinical recurrence in absence of antiarrhythmic drugs. The cost of RF ablation was calculated in the year 2001 euros on the basis of resource use. The mean cost of pharmacologic treatment prior to ablation was 1,590 euros/patient per year. The initial cost of RF ablation for PAF was 4,715 euros, then 445 euros/year. After 5 years, the cost of RF ablation was below that of ongoing medical management, and continued to diverge thereafter. RF catheter ablation may be a cost-effective alternative to long-term drug therapy in patients with symptomatic, drug refractory PAF.

Radiofrequency remains the reference energy type for catheter ablation of rhythm disorders. In the classic indications, which are atrial flutter or tachycardia, nodal re-entry and Wolff-Parkinson-White syndrome, this energy source has the best cost-efficiency-safety ratio, subject to strict conditions of use. Some new modalities of application have further improved performance, especially active irrigation of the electrode which allows induction of deeper lesions which is very useful for the ablation of difficult atrial flutters, epicardial fascicles of Kent and ischaemic ventricular tachycardias. The only emerging alternative energy type, in the framework of classical ablation, is cold, for which the principal advantages are the homogenous and slightly thrombogenic character for the lesion involved, and the possibility of reversible applications tests which are especially useful in the ablation of structures at risk. The situation is more open-ended concerning research on ablation for atrial fibrillation or the so-called new energy types, such as ultrasound and laser, whilst recognising a renewal in interest, especially for circumferential ablation of the pulmonary veins to isolate the ectopic venous foci. Mechanical energy such as luminous energy is emitted across a catheter balloon deployed at the orifice of the vein, perpendicular to its axis, aiming to reach a continuous circumferential lesion with a minimum of applications. Equally radiofrequency has been undergoing significant evolution for this application, such as by the development of porous catheter balloons with a liquid electrode, as well as by the development of deployable circumferential catheters. Ablation is use for atrial fibrillation, by endocavity atrial segmentation remains a field of research in which radiofrequency retains an important place. It is delivered via multi-electrode catheters according to the new application modalities, either pulsed or by phase interval, which secure better efficacy by better continuity of the line of block. Research is equally underway on the use of microwaves and cold in this application.

Background: The end point for catheter ablation of pulmonary vein (PV) foci initiating atrial fibrillation (AF) has not been determined., Methods and Results: Ninety patients underwent mapping during spontaneous or induced ectopy and/or AF initiation. Ostial PV ablation was performed by use of angiograms to precisely define targeted sites. Success defined by elimination of AF without drugs was correlated with the procedural end point of the abolition of distal PV potentials. A total of 197 arrhythmogenic PV foci (97%)-single in 31% and multiple in 69%-and 6 atrial foci were identified. A discrete radiofrequency (RF) application eliminated the PV potentials in 9 PV foci, whereas 2 foci from the same PV required RF applications at separate sites in 19 cases. In others, a wider region was targeted with progressive elimination of ectopy. In 49 patients, multiple sessions were necessary owing to recurrent or new ectopy. The clinical success rates were 93%, 73%, and 55% in patients with 1, 2, and > or =3 arrhythmogenic PV foci. Recovery of local PV potential and the inability to abolish it were significantly associated with AF recurrences (90% success rate with versus 55% without PV potential abolition). PV stenosis was noted acutely in 5 of 6 cases, remained unchanged at restudy, and was associated with RF power >45 W., Conclusions: Multiple PV foci are involved in initiation of AF, and elimination of PV muscle conduction is associated with clinical success.

Atrial fibrillation (AF), the most common of all sustained cardiac arrhythmias, is frequently resistant to antiarrhythmic drugs, and physicians have seen limited success with catheter ablation limited to the right atrium. As a result, the safety and efficacy of systematic biatrial linear ablation for drug resistant AF was investigated. Forty-four patients (54 +/- 7 years) underwent catheter ablation of daily drug-resistant AF. Two right-atrial lines (1 septal and 1 cavotricuspid) and 3-4 left-atrial lines were transseptally performed: 2 joining each superior pulmonary vein to the posterior mitral annulus and 1 interconnecting them. An additional left-atrial septal line from the right superior pulmonary vein (RSPV) to the foramen ovalis was performed in 23 patients. Radiofrequency was delivered with a conventional thermocouple-equipped ablation catheter or with an irrigated tip ablation catheter for resistant cases and for sparing the endocardium. Of the 44 patients, 25 (57%) were successfully treated without antiarrhythmic drugs. Twelve patients (27%) improved (<6 hours of AF per trimester under a previously ineffective drug) and 7 (16%) were considered treatment failures. Multiple sessions were required to ablate new left-atrial macro-reentry and initiating foci (2.7 +/- 1.3 procedures per patient). Five patients had a pericardial effusion and 1 each a pulmonary embolism, an inferior myocardial infarction, and a reversible cerebral ischemic event. One patient had thrombosis of the 2 left pulmonary veins. Despite a relatively high success rate, this procedure is too long, and the safely and efficacy need to be improved and applied to a broader range of patients.

Transcatheter radiofrequency (RF) ablation of atrial fibrillation or flutter requires the creation of linear lesions. However, conventional catheters are not predictably effective because of poor endocardial contact, and limited lesion size and penetration. The purpose of the study was to assess in the right atrium, the efficacy and safety of a new catheter designed to create long myocardial tissue lesions using RF energy. The main characteristics of this 8 Fr deflectable RF ablation catheter were: (1) a perpendicularly contacting articulated bilimb electrodes ensuring stable and firm endocardial firm contact; and (2) an irrigated planar interface. Three different electrode prototypes were tested. Fourteen anesthetized sheep weighing 61 +/- 7 kg underwent RF ablation in the right atrium using three incremental power levels (25 to 45, 50, 55 to 75 W) with the aim of creating fully transmural (FT) lesions, defined as continuous and complete epicardial and endocardial lesion imprints. The animals were euthanized 1 hour later for macroscopic and histologic examinations. Forty-three of the 80 right atrial lesions created, in smooth as well as in trabeculated areas, were FT. The percentage of FT lesions increased with the applied power from 37% with 25-45 W, to 49% with 50 W, and up to 86% for 55-75 W. In all but two cases, histologic examination showed no discontinuity between FT lesions produced by both limbs resulting in 19 coalescent linear lesions with an average size of 25 x 6 x 4 mm (length x width x depth). In situ bipolar electrograms after ablation in the FT group showed split potentials and/or a marked decrease in amplitude from 2.85 +/- 1.79 to 0.33 +/- 0.14 mV (P = 0.001) accompanied by near complete disappearance of unipolar electrograms. There was no perforation due to RF ablation. In conclusion, continuous and FT lesions can be achieved in various areas of sheep atria, including the trabecular right atrium, with a perpendicularly contacting bilimb electrode catheter. It represents a promising tool for catheter ablation of atrial fibrillation and flutter.

Background: Catheter ablation of typical right atrial flutter is now widely performed. The best end point has been demonstrated to be bidirectional isthmus block. We investigated the use of irrigated-tip catheters in a small subset of patients who failed isthmus ablation with conventional radiofrequency (RF) ablation., Methods and Results: Of 170 patients referred for ablation of common atrial flutter, conventional ablation of the cavotricuspid isthmus with >21 applications failed to create a bidirectional block in 13 (7.6%). An irrigated-tip catheter ablation was performed on identified gaps in the ablation line according to a protocol found to be safe in animals: a moderate flow rate of 17 mL/min and temperature-controlled (target, 50 degrees C) RF delivery with a power limit of 50 W. Bidirectional isthmus block was achieved in 12 patients by use of a mean delivered power of 40+/-6 W with a single application in 6 patients and 2 to 6 applications in the other 6. No side effects occurred during or after the procedure., Conclusions: Irrigated-tip catheter ablation is safe and effective for achieving cavotricuspid isthmus block when conventional RF energy has failed.

Since its introduction at the beginning of the 1980s, radiofrequency ablation of accessory atrioventricular pathways has become method because of its excellent results and the indications have increased to cases in which only symptomatic improvement is the objective. These advances have been made possible by technical innovations to the generators of the radiofrequency current and, above all, to the ablation catheters which enable mapping nearly all the perimeter of the atrioventricular rings and reach all the accessory pathways irrespective of their site. The approach depends on the localisation of the accessory pathway but the criteria of mapping are the same: detection of a specific accessory pathway potential, precession or concordance (depending on the topography) of the initial peak of the endocavitary ventriculogramme and the onset of the delta wave on the surface ECG, QS morphology of the ventriculogramme on monopolar recording, shortest VA' interval in orthodromic reciprocating tachycardia for latent kent bundles. In specialised centres, the global success rate is 90 to 98% but certain sites, especially the right lateral pathways, are more difficult to attain. The complication rate is about 4% but it tends to decrease with the experience of the operating teams and close monitoring of the patients. However, there persists an uncertainty concerning potentially arrhythmogenic effects of the lesions induced which justifies restricting the indications in young children.

Between 1986 and 1994, 50 patients (mean age 63 +/- 13 years), 25 of whom had organic heart disease and presenting with atrial arrhythmias refractory to 5.6 +/- 1.6 antiarrhythmic drugs, underwent radiofrequency ablation (5 +/- 3 pulses by procedure; duration of pulses 50.5 +/- 32 s) of the proximal AV junction to create complete and permanent AV block. The escape rhythm was studied immediately after the procedure and during long-term follow-up. Immediately after the procedure, an escape rhythm was observed in 80% of the patients (junctional in 92%). Over a mean follow-up of 36 +/- 16 months in 47 patients (2 patients died before assessment of escape rhythm and 1 was lost to follow-up), an escape rhythm was present in 39 patients (83%) and absent in the remaining 8 (17%). The only significant difference between the two groups was the initial presence of an escape rhythm (P = 0.008). However, three patients with an initial escape rhythm had none during long-term follow-up. The initial presence of an escape rhythm as a predictive factor of its presence during follow-up had a sensitivity of 87%, specificity of 63%, positive predictive value of 92%, and negative predictive value of 50%. Thus, the absence of an escape rhythm during long-term follow-up causing pacemaker dependency was noted in 1 of 6 patients. This represents a limitation to this palliative treatment, which should be reserved for patients suffering from supraventricular tachycardias refractory to other treatments.

Radiofrequency currents are the reference physical agent for endocavitary ablation, especially of supraventricular tachycardias. They are delivered in a continuous mode or sinusoidal waves. Because of the high frequency between 200 and 3,000 kHz there is no stimulation of the neuromuscular cells. The mechanism of the resulting lesion is essentially related to heating of the biological surroundings of the active electrode. The temperature increase remains localised around the active electrode and its kinetics are progressive, which implies close and stable contact between the active electrode and the tissues. The lesional effect is obtained 60 to 90 degrees C in order to avoid the deleterious effects induced by temperatures of over 100 degrees C: boiling, coagulation, vaporization and carbonization of the tissues leading to an increase in impedence. The volume of lesions depends on many factors which are sometimes difficult to control in vivo. It is more closely correlated to the temperature of the active electrode than to the parameters of delivery (power, duration ...). The histological lesions correspond to scar tissue which respects the surrounding architecture. The major technological innovations of this method have resulted in an increase in the volume of the lesions produced, a reduction in the frequency of undesirable effects such as the formation of coagulum and in an immediate evaluation of the anatomic lesional effect. They have consisted in the introduction of specific electrodes and of systems of monitoring the electrical and thermal effects with the use of imaging techniques such as endovascular and transoesophageal echocardiography and angioscopy. New indications will require development of specific catheter-generator equipment to create lesions of size and shape adapted to the arrhythmogenic substrate.

Radiofrequency currents produce circumscribed tissue necrosis by progressive and localised heating. Endocardial application via the percutaneous approach with a specific electrophysiological catheter enables destruction of the anatomical substrate of many cardiac arrhythmias. The technique is well tolerated due to the absence of barometric phenomena and general anaesthesia, and the possibility of modulating the energy delivered, which explains why it has supplanted fulguration in most indications. The technological evolution aims to increase the lesional power and decrease the number of complications. This implies the development of catheters capable of delivering greater currents without the risk of thrombus formation and of generators dependent on electrical or thermal parameters. The low incidence of complications reported by centres using the technique is based on an excellent understanding of the technique, the use of appropriate material, the surveillance of parameters which allow detection of unwanted effects and the respect of a strict operation protocol. In the absence of these precautions, the wide diffusion of this technique, favored by its low cost and relative simplicity, may be associated with an increase in the number of side effects which could be lethal. This cannot be accepted in a technique with such wide indications, including arrhythmias with a usually benign long-term prognosis.