What physicians do in case of a failure of the pace-sense part of a defibrillation lead : Survey in Germany, Austria and Switzerland.

BACKGROUND: The possible treatment strategies for defects of the pace-sense (P/S) part of a defibrillation lead are either implantation of a new high-voltage (HV)-P/S lead, with or without extraction of the malfunctioning lead, or implantation of a P/S lead. METHODS: We conducted a Web-based survey across cardiac implantable electronic device (CIED) centers to investigate their procedural practice and decision-making process in cases of failure of the P/S portion of defibrillation leads. In particular, we focused on the question of whether the integrity of the HV circuit is confirmed by a test shock before decision-making. The questionnaire included 14 questions and was sent to 951 German, 341 Austrian, and 120 Swiss centers. RESULTS: The survey was completed by 183 of the 1412 centers surveyed (12.7% response rate). Most centers (90.2%) do not conduct a test shock to confirm the integrity of the HV circuit before decision-making. Procedural practice in lead management varies depending on the presentation of lead failure and whether the center applies a test shock. In centers that do not conduct a test shock, the majority (69.9%) implant a new HV-P/S lead. Most centers (61.7%) that test the integrity of the HV system implant a P/S lead. The majority of centers favor DF-4 connectors (74.1%) over DF-1 connectors (25.9%) at first CIED implantation. CONCLUSION: Either implanting a new HV-P/S lead or placing an additional P/S lead are selected strategies if the implantable cardioverter-defibrillator lead failure is localized to the P/S portion. However, conducting a test shock to confirm the integrity of the HV component is rarely performed.

Pathophysiological and therapeutic implications in patients with atrial fibrillation and heart failure.

Heart failure and atrial fibrillation are common and responsible for significant mortality of patients. Both share the same risk factors like hypertension, ischemic heart disease, diabetes, obesity, arteriosclerosis, and age. A variety of microscopic and macroscopic changes favor the genesis of atrial fibrillation in patients with preexisting heart failure, altered subcellular Ca2+ homeostasis leading to increased cellular automaticity as well as concomitant fibrosis that are induced by pressure/volume overload and altered neurohumoral states. Atrial fibrillation itself promotes clinical deterioration of patients with preexisting heart failure as atrial contraction significantly contributes to ventricular filling. In addition, atrial fibrillation induced tachycardia can even further compromise ventricular function by inducing tachycardiomyopathy. Even though evidence has been provided that atrial functions significantly and independently of confounding ventricular pathologies, correlate with mortality of heart failure patients, rate and rhythm controls have been shown to be of equal effectiveness in improving mortality. Yet, it also has been shown that cohorts of patients with heart failure benefit from a rhythm control concept regarding symptom control and hospitalization. To date, amiodarone is the most feasible approach to restore sinus rhythm, yet its use is limited by its extensive side-effect profile. In addition, other therapies like catheter-based pulmonary vein isolation are of increasing importance. A wide range of heart failure-specific therapies are available with mixed impact on new onset or perpetuation of atrial fibrillation. This review highlights pathophysiological concepts and possible therapeutic approaches to treat patients with heart failure at risk for or with atrial fibrillation.

New implantable cardiac monitor with three-lead ECG and active noise detection.

BACKGROUND: A new implantable cardiac monitor (BioMonitor, Biotronik) with a continuous remote monitoring option was prospectively implanted in patients with suspected arrhythmias or for therapy control after atrial fibrillation (AF) ablation. A three-lead ECG detection was intended to make the implantation more independent of the implantation site and the electrical heart axis. Because noise is a frequent problem in implantable cardiac monitors, an active noise detection algorithm was implemented. The aim of the trial was to evaluate the clinical performance of the device. METHODS: The device performance was evaluated in a prospective nonrandomized multicenter study with a follow-up of 12 months. Study endpoints were device-related serious adverse events at 3 months, appropriate QRS detection in direct comparison with synchronized Holter ECG recordings, sensitivity and positive predictive value of arrhythmia detection in comparison with Holter ECG and independent of it, and noise burden during the entire follow-up period. RESULTS: The implantation was successful in all 152 patients. Two device-related serious adverse events (pocket infections) occurred by 3 months. The mean QRS amplitude of 0.3 ± 0.2 mV at implantation remained stable over 12 months. QRS sensing performance indicated little over- and undersensing in most patients. More than 80 % of the patients had more than 22 h of noise-free monitoring per day. CONCLUSION: BioMonitor effectively detects patients with bradycardia, tachycardia, AF, or asystole. Active noise detection seems to reduce the transmission of meaningless data without diminishing the positive predictive value of the device.

Lacosamide cardiac safety: clinical trials in patients with partial-onset seizures.

OBJECTIVE: To evaluate the cardiac safety of adjunctive lacosamide in a large pool of adults with partial-onset seizures (POS). METHODS: Post-randomization changes from baseline for electrocardiographic (ECG) measurements, diagnostic findings, and relevant adverse events (AEs) were compared for pooled data from three randomized, placebo-controlled trials of adjunctive lacosamide for the treatment of POS. RESULTS: Lacosamide did not prolong the QTc interval or affect heart rate as determined by an analysis of data from patients randomized to lacosamide 200, 400, or 600 mg/day (n = 944) compared with placebo (n = 364). After 12-week maintenance treatment, mean changes from baseline for QRS duration were similar between the placebo and lacosamide 200 and 400 mg/day groups (0.0, -0.2, and 0.4 ms), but slightly increased for lacosamide 600 mg/day (2.3 ms). A small, dose-related mean increase in PR interval was observed (-0.3, 1.4, 4.4, and 6.6 ms for the placebo and lacosamide 200, 400, and 600 mg/day groups, respectively). First-degree atrioventricular (AV) block was reported as a non-serious AE in 0.0%, 0.7%, 0.2%, and 0.5% of patients in the same respective groups. Second- or higher degree AV block was not observed. There was no evidence of a PR-interval-related pharmacodynamic interaction of lacosamide with either carbamazepine or lamotrigine. CONCLUSIONS: Evaluation of the pooled cardiac safety data from patients with POS showed that adjunctive lacosamide at the maximum recommended dose (400 mg/day) was not clearly associated with any cardiac effect other than a small, dose-related increase in PR interval that had no evident symptomatic consequence.

[Radiation therapy in patients with cardiac pacemakers or implantable cardioverter defibrillators. Interdisciplinary safety recommendations]. / Strahlentherapie bei Patienten mit Herzschrittmachern oder implantierbaren Kardioverter-Defibrillatoren. Interdisziplinäre Sicherheitsempfehlungen.

BACKGROUND: With increasing numbers of implanted pacemakers and implantable cardioverter defibrillators (ICD) and a rising incidence of malignant tumors, there is a growing probability of radiation-mediated device dysfunction. The only guidelines for the management of patients with cardiac pacemakers in the case of radiation therapy were published in 1994 and have not been updated since then. Based on the current evidence and modern device technology, the present paper aims to develop contemporary and interdisciplinary safety recommendations for the minimization of patient risk. METHODS AND RESULTS: A systematic literature research was carried out including the most relevant medical electronic databases. The search yielded 147 articles published between 1994 and 2012 of which 45 met the selection criteria and of these studies 34 presented primary data (9 in vitro and 25 in vivo studies). The impact of ionizing radiation varied significantly between implanted devices and ranged from no functional changes to complete loss of function. Important device dysfunctions included changes in sensing capability, altered pacing pulses or rate, changed or disabled tachyarrhythmia ICD therapies, early battery depletion and loss of telemetry. Modern pacemakers and ICDs are more sensitive to radiation than older models. Potentially life-threatening complications were observed after exposure of the pulse generator to comparatively low radiation doses (0.11 Gy). CONCLUSIONS: Practical recommendations for patient management and safety are presented that can be readily adopted by any institution carrying out radiation therapy.

[Big hype about ChapGPT in medicine : Is it something for rhythmologists? What must be taken into consideration?] / Großer Hype um ChatGPT in der Medizin : Ist es etwas für den Rhythmologen? Was muss man bedenken?

ChatGPT, a chatbot based on a large language model, is currently attracting much attention. Modern machine learning (ML) architectures enable the program to answer almost any question, to summarize, translate, and even generate its own texts, all in a text-based dialogue with the user. Underlying technologies, summarized under the acronym NLP (natural language processing), go back to the 1960s. In almost all areas including medicine, ChatGPT is raising enormous hopes. It can easily pass medical exams and may be useful in patient care, diagnostic and therapeutic assistance, and medical research. The enthusiasm for this new technology shown even by medical professionals is surprising. Although the system knows much, it does not know everything; not everything it outputs is accurate either. Every output has to be carefully checked by the user for correctness, which is often not easily done since references to sources are lacking. Issues regarding data protection and ethics also arise. Today's language models are not free of bias and systematic distortion. These shortcomings have led to calls for stronger regulation of the use of ChatGPT and an increasing number of similar language models. However, this new technology represents an enormous progress in knowledge processing and dissemination. Numerous scenarios in which ChatGPT can provide assistance are conceivable, including in rhythmology. In the future, it will be crucial to render the models error-free and transparent and to clearly define the rules for their use. Responsible use requires systematic training to improve the digital competence of users, including physicians who use such programs.

[Magnetic resonance imaging and implantable cardiac devices. Current status and future perspectives of MR-compatible systems]. / Magnetresonanztomographie und implantierbare kardiale Devices. Stellenwert und Ausblick von MR-kompatiblen Systemen.

Conventional pacemakers and implantable cardioverter-defibrillators (ICD) have always been regarded as a contraindication to magnetic resonance imaging (MRI). MR-compatible systems represent a recent and particularly important innovation, since they will provide device patients with significantly improved access to MR examinations. However, the safe application of MR-compatible technology requires a detailed understanding of the strictly defined cardiologic and radiologic requirements and conditions that are to be adhered to before and during an MR examination. The present article gives an overview of problematic MR interactions with implanted devices, illustrates the most important aspects of MR-compatible pacemaker and ICD systems, analyzes their current clinical status, and offers a critical perspective.

Long-term growth hormone (GH) replacement of adult GH deficiency (GHD) benefits the heart.

OBJECTIVE: Growth hormone (GH) deficiency is related to increased cardiovascular mortality. We studied clinical status, concentration of amino-terminal-pro B-type natriuretic-peptide (NT-proBNP) and echocardiographic parameters during long-term GH replacement (GH-R). METHODS: Fifty-one patients (29 females), 45.9 ± 11.3 years (mean ± s.d.), median follow-up 36.2 months, echocardiography and laboratory determinations initially and at 12-months intervals. RESULTS: At the last follow-up (last observation carried forward) (LFU (LOCF)) insulin-like growth-factor-1 standard deviation score (IGF-1 SDS) was ±1 in 92% of the patients. The median NT-proBNP declined significantly and stabilized (-40.5%) at LFU (LOCF) due to patients with a basal NT-proBNP >125 ng/L (indicative of heart failure). The basal NT-proBNP and the final IGF-1 SDS were significant predictors of the NT-proBNP at LFU (LOCF). Initially left ventricular enddiastolic diameter (LVEDD), left ventricular posterior wall diameter (LVPWD) and ejection fraction (EF) were normal, while interventricular septum diameter (IVSD) and left ventricular mass index (LVMi) were slightly increased. LVPWD and IVSD had significantly declined by year three. The LVMi was moderately to severely abnormal in 37.3 and 52.0% of patients initially and at LFU (LOCF). At LFU (LOCF) LVMi and IGF-1 were significantly correlated in the 14 male patients of this subgroup. CONCLUSION: Long-term GH-R of GHD positively affected ISVD and LVPWD. In a subgroup of patients with severe GHD, LVMi increased concomitantly to the decline in NT-proBNP and this was positively correlated to the final IGF-1 concentration. Whether this observation indicates a positive development in a structurally altered heart muscle (reversal of adverse remodelling) or poses a future risk for heart failure needs further follow-up.

International Life Sciences Institute (Health and Environmental Sciences Institute, HESI) initiative on moving towards better predictors of drug-induced torsades de pointes.

Knowledge of the cardiac safety of emerging new drugs is an important aspect of assuring the expeditious advancement of the best candidates targeted at unmet medical needs while also assuring the safety of clinical trial subjects or patients. Present methodologies for assessing drug-induced torsades de pointes (TdP) are woefully inadequate in terms of their specificity to select pharmaceutical agents, which are human arrhythmia toxicants. Thus, the critical challenge in the pharmaceutical industry today is to identify experimental models, composite strategies, or biomarkers of cardiac risk that can distinguish a drug, which prolongs cardiac ventricular repolarization, but is not proarrhythmic, from one that prolongs the QT interval and leads to TdP. To that end, the HESI Proarrhythmia Models Project Committee recognized that there was little practical understanding of the relationship between drug effects on cardiac ventricular repolarization and the rare clinical event of TdP. It was on that basis that a workshop was convened in Virginia, USA at which four topics were introduced by invited subject matter experts in the following fields: Molecular and Cellular Biology Underlying TdP, Dynamics of Periodicity, Models of TdP Proarrhythmia, and Key Considerations for Demonstrating Utility of Pre-Clinical Models. Contained in this special issue of the British Journal of Pharmacology are reports from each of the presenters that set out the background and key areas of discussion in each of these topic areas. Based on this information, the scientific community is encouraged to consider the ideas advanced in this workshop and to contribute to these important areas of investigations over the next several years.

Improvement of lay rescuer chest compressions with a novel audiovisual feedback device : A randomized trial.

BACKGROUND: Bystander actions and skills determine among others the outcome of out-of-hospital cardiac arrest. However, the depth and rate of chest compressions (CC) are difficult to estimate for laypeople and poor CC quality may result. Our study aimed to evaluate the impact of a new feedback device on CC performance by laypeople. The percentage of CC with both correct rate and correct depth of all CC served as primary endpoint. METHODS: Forty-eight subjects with no medical background performed 2 min of CC on a manikin with and without a novel feedback device (TrueCPR™, Physio-Control, Redmond, Wash.). The device uses a novel, non-accelerometer-based technology. Participants were randomized into two groups. Group 1 performed a 2-min CC trial first with audiovisual feedback followed by a trial with no feedback information, while group 2 performed the task in reverse order. RESULTS: The absolute percentage of CC with correct rate and depth was significantly higher with the use of the device (59 ± 34% vs. 15 ± 21%, p < 0.0001). The longest interval without correct CC was significantly decreased (76.5 s vs. 27.5 s, p < 0.0001). CONCLUSION: The quality of CC carried out by laypeople is significantly improved with the use of a new feedback device. The device may be useful for cardiopulmonary resuscitation (CPR) by laypeople and for educational purposes.

[Clinical aspects of treatment with amiodarone]. / Klinische Besonderheiten der Therapie mit Amiodaron.

Amiodarone has multiple and complex electrophysiological effects that render it a very effective antiarrhythmic drug for the treatment of both, supraventricular and ventricular arrhythmias. Proarrhythmic effects of amiodarone in patients with structural heart disease are rare. However, extracardiac adverse effects occurring in association with amiodarone treatment are frequent and feared. These adverse effects have usually been related to total amiodarone exposure (i. e., dose and duration of treatment). Parallel to a more frequent use of lower amiodarone maintenance doses (100-200 mg/day), the incidence of severe unwanted extracardiac side effects has decreased. High-dose maintenance regiments (daily dose ≥300 mg) are usually obsolete. This paper discusses recommendations regarding the monitoring of cardiac and extracardiac side effects of amiodarone. They need to be regarded by physicians using amiodarone to ensure long-term safety of amiodarone therapy.

De novo mutation in the SCN5A gene associated with early onset of sudden infant death.

BACKGROUND: Congenital long QT syndrome (LQTS), a cardiac ion channel disease, is an important cause of sudden cardiac death. Prolongation of the QT interval has recently been associated with sudden infant death syndrome, which is the leading cause of death among infants between 1 week and 1 year of age. Available data suggest that early onset of congenital LQTS may contribute to premature sudden cardiac death in otherwise healthy infants. METHODS AND RESULTS: In an infant who died suddenly at the age of 9 weeks, we performed mutation screening in all known LQTS genes. In the surface ECG soon after birth, a prolonged QTc interval (600 ms(1/2)) and polymorphic ventricular tachyarrhythmias were documented. Mutational analysis identified a missense mutation (Ala1330Pro) in the cardiac sodium channel gene SCN5A, which was absent in both parents. Subsequent genetic testing confirmed paternity, thus suggesting a de novo origin. Voltage-clamp recordings of recombinant A1330P mutant channel expressed in HEK-293 cells showed a positive shift in voltage dependence of inactivation, a slowing of the time course of inactivation, and a faster recovery from inactivation. CONCLUSIONS: In this study, we report a de novo mutation in the sodium channel gene SCN5A, which is associated with sudden infant death. The altered functional characteristics of the mutant channel was different from previously reported LQTS3 mutants and caused a delay in final repolarization. Even in families without a history of LQTS, de novo mutations in cardiac ion channel genes may lead to sudden cardiac death in very young infants.

Fetoscopic transesophageal electrocardiography and stimulation in fetal sheep: a minimally invasive approach aimed at diagnosis and termination of therapy-refractory supraventricular tachycardias in human fetuses.

BACKGROUND: Therapy-refractory supraventricular tachycardia commonly results in hydrops and death in human fetuses. The purpose of this study in fetal sheep was to assess the feasibility of a minimally invasive fetoscopic approach for fetal transesophageal electrocardiography and stimulation aimed at diagnosis and termination of these tachycardias. METHODS AND RESULTS: We studied a total of 10 fetal sheep (87 to 103 days of gestation; term=145 days). We entered the amniotic cavity using a percutaneous fetoscopic approach and placed various electrophysiology catheters into the fetal esophagus. We recorded the number of animals in which fetoscopic transesophageal electrocardiography and stimulation were successful and assessed pacing success and thresholds for different catheters. In addition, we monitored for potential adverse effects from stimulation and for other complications of the operation. Recording of transesophageal electrocardiograms was successful in all fetal sheep. Capture during stimulation was successfully documented by additional fetal bipolar surface electrocardiograms in 7 fetuses. In fetuses in which fetal surface electrocardiograms were not recorded, pacing stimulus artifacts interfered with documentation of capture. Although stimulation thresholds were high, the maternal rhythm was not affected by fetal stimulation. CONCLUSIONS: Fetoscopic fetal transesophageal electrocardiography and stimulation are feasible in fetal sheep. This minimally invasive approach might have the potential to improve diagnosis and management of therapy-refractory supraventricular tachycardias in human fetuses.

Genotype-phenotype correlation in the long-QT syndrome: gene-specific triggers for life-threatening arrhythmias.

BACKGROUND: The congenital long-QT syndrome (LQTS) is caused by mutations on several genes, all of which encode cardiac ion channels. The progressive understanding of the electrophysiological consequences of these mutations opens unforeseen possibilities for genotype-phenotype correlation studies. Preliminary observations suggested that the conditions ("triggers") associated with cardiac events may in large part be gene specific. METHODS AND RESULTS: We identified 670 LQTS patients of known genotype (LQT1, n=371; LQT2, n=234; LQT3, n=65) who had symptoms (syncope, cardiac arrest, sudden death) and examined whether 3 specific triggers (exercise, emotion, and sleep/rest without arousal) differed according to genotype. LQT1 patients experienced the majority of their events (62%) during exercise, and only 3% occurred during rest/sleep. These percentages were almost reversed among LQT2 and LQT3 patients, who were less likely to have events during exercise (13%) and more likely to have events during rest/sleep (29% and 39%). Lethal and nonlethal events followed the same pattern. Corrected QT interval did not differ among LQT1, LQT2, and LQT3 patients (498, 497, and 506 ms, respectively). The percent of patients who were free of recurrence with ss-blocker therapy was higher and the death rate was lower among LQT1 patients (81% and 4%, respectively) than among LQT2 (59% and 4%, respectively) and LQT3 (50% and 17%, respectively) patients. CONCLUSIONS: Life-threatening arrhythmias in LQTS patients tend to occur under specific circumstances in a gene-specific manner. These data allow new insights into the mechanisms that relate the electrophysiological consequences of mutations on specific genes to clinical manifestations and offer the possibility of complementing traditional therapy with gene-specific approaches.

Characteristics of local electrogram predicting successful transcatheter radiofrequency ablation of left-sided accessory pathways.

OBJECTIVES: The purpose of this study was to analyze and compare the local electrograms recorded at successful and unsuccessful sites of ablation to identify the criteria that may predict successful sites and minimize unnecessary radiofrequency delivery. BACKGROUND: Transcatheter ablation of accessory pathways using radiofrequency energy requires extremely precise localization of an accessory pathway. METHODS: Local electrograms from 50 consecutive patients with left-sided accessory pathways who underwent transcatheter radiofrequency ablation were analyzed. During catheter ablation, localization of accessory pathways was performed in 39 pathways during pre-excited sinus rhythm and in 14 pathways during orthodromic tachycardia. A total of 429 local electrograms at target sites obtained before delivery of radiofrequency current was analyzed. A prospective study was performed in another 20 patients using the criteria derived from the retrospective study. RESULTS: Accessory pathway conduction block was achieved in 36 (92%) of 39 pathways in which mapping was performed during pre-excited sinus rhythm and in 9 (64%) of 14 pathways in which mapping was performed during orthodromic tachycardia (p less than 0.05). When mapping was performed during pre-excited sinus rhythm, a combination of four variables (that is, an accessory pathway potential, stability of local electrograms, atrial activation greater than 1 mV and ventricular activation preceding the onset of the delta wave) showed a 62% probability of success. In contrast, excluding these variables resulted in a 95% probability of failure (noneffective or transiently effective). The prospective study shows that the use of these criteria can significantly reduce the number of current applications. When mapping was performed during orthodromic tachycardia, recording the earliest atrial activation was the most powerful predictor of success. A stable local electrogram with a small notch on the ventricular potential, presumed to be an accessory pathway potential, may add predictive value. CONCLUSIONS: Transcatheter radiofrequency ablation is highly effective in the treatment of patients with left-sided accessory pathways. Specific characteristics of local electrograms can be important predictors of success or failure. Mapping during pre-excited rhythm renders ablation more effective than does mapping during orthodromic tachycardia.

Efficacy and safety of d,l-sotalol in patients with ventricular tachycardia and in survivors of cardiac arrest.

OBJECTIVE: The aim of this study was to assess the antiarrhythmic efficacy and safety of d,l-sotalol in patients with ventricular tachycardia (VT) or ventricular fibrillation (VF) and in survivors of cardiac arrest and to identify the factors that are associated with arrhythmia suppression and therefore might be helpful in predicting drug efficacy. BACKGROUND: Despite increasing use of the class III antiarrhythmic agent d,l-sotalol, data on its short- and long-term efficacy in a large patient cohort are lacking. Information on its long-term tolerability and safety is limited. METHODS: A total of 396 patients with inducible sustained VT or VF (VT/VF) underwent programmed stimulation before and after receiving oral d,l-sotalol (240 to 640 mg/day). Patients in whom VT/VF was rendered either noninducible or more difficult to induce (more extrastimuli or faster drive cycle length needed for VT/VF induction) were discharged on a regimen of oral d,l-sotalol. RESULTS: d,l-Sotalol suppressed VT/VF in 151 patients (38.1%) and rendered the arrhythmia more difficult to induce in 76 patients (19.2%). The extent of drug-induced prolongation of right ventricular refractoriness and a shorter VT cycle length at baseline were independent predictors of immediate drug efficacy. Torsade de pointes developed in seven patients (1.8%). Two hundred ten patients (53%) continued to receive d,l-sotalol and were followed up for 34 +/- 18 months (mean +/- SD). The actuarial rates for the absence of arrhythmic recurrence (either VT/VF or sudden death) at 1 and 3 years were 89% and 77%, respectively. Actuarial rates for overall survival at 1 and 3 years were 94% and 86%, respectively. VT/VF suppression by d,l-sotalol was an independent discriminant variable that separated patients with and without arrhythmia recurrence. However, noninducibility of VT/VF did not predict freedom from sudden death. CONCLUSION: Oral d,l-sotalol is effective and safe in patients with VT/VF. However, sudden cardiac death develops in a significant proportion of patients, and programmed stimulation seems to be of limited value for its prediction.

An anatomically and electrogram-guided stepwise approach for effective and safe catheter ablation of the fast pathway for elimination of atrioventricular node reentrant tachycardia.

OBJECTIVES: We describe a new stepwise anatomically and electrogram-guided strategy for radiofrequency catheter ablation of the fast pathway. BACKGROUND: Anatomically and electrogram-guided approaches have been developed for slow pathway ablation in patients with atrioventricular (AV) node reentrant tachycardia; however, no stepwise systematic approaches exist for fast pathway ablation. METHODS: Fifty-three patients (mean [+/- SD] age 43 +/- 11 years) with AV node reentrant tachycardia underwent attempted ablation of the fast pathway. The ablation catheter was initially positioned posterior and slightly superior to the site of the maximal His bundle recording region. At these sites, the amplitude of the local atrial potential was usually at least twice as high as the local ventricular potential, and a small proximal His bundle potential was recorded. When the first pulse was ineffective, the ablation catheter was repositioned stepwise slightly inferior to more midseptal sites. RESULTS: After a mean of 3.4 +/- 3.1 radiofrequency pulses (median 2, range 1 to 12), AV node reentrant tachycardia was noninducible in 51 patients (96%). No inadvertent complete AV block occurred. The AH interval was prolonged from 79 +/- 19 to 145 +/- 37 ms (p < 0.001). Thirty-eight patients (72%) developed complete ventriculoatrial block. Recording of a His bundle potential at the target site, stability of the local electrograms and occurrence of fast junctional rhythms during energy applications were more often observed at successful sites than transiently effective or noneffective sites. During a follow-up period of 12 +/- 7 months, 3 (6%) of 51 patients had a clinical recurrence of AV node reentrant tachycardia. CONCLUSIONS: Radiofrequency catheter ablation of the fast pathway using a combined anatomically and electrogram-guided stepwise approach is highly effective and safe. The safety of this approach seems to be due to the stable position of the ablation catheter at the interatrial septum, rather than across the tricuspid annulus, and the larger distance to the central body of the AV node and bundle of His.