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BACKGROUND Atrioventricular nodal reentrant tachycardia (AVNRT) is a frequent supraventricular tachycardia in children and young adults. Despite favourable success rates of catheter ablation, conventional fluoroscopic catheter guidance is associated with risks of low-dose ionizing radiation for the patient and the personnel. Here we describe a technique for zero-fluoroscopy catheter ablation using contact force technology. PATIENTS AND METHODS Zero-fluoroscopy catheter ablation was attempted in 12 patients with AVNRT (median age 20 years; range 11-75 years). An ablation catheter with integrated contact force sensor and a nonfluoroscopic electroanatomical mapping system was used for visualization of cardiovascular structures. Mean contact forces during mapping and ablation were restricted to an upper limit of 50 g to avoid cardiovascular injuries. RESULTS Zero-fluoroscopy catheter ablation was performed successfully and uneventfully in all patients. There were no arrhythmia recurrences during a median follow-up of 6.2 months (range 2.7-12.8). CONCLUSION Zero-fluoroscopy catheter ablation of AVNRT is possible and appears simple yet safe, when a nonfluoroscopic electroanatomical mapping system is used in combination with an ablation catheter with integrated contact force sensor. The presented technique could thus be easily employed in most electrophysiological laboratories.

Catheter ablation has become the first line of therapy in patients with symptomatic, recurrent, drug-refractory atrial fibrillation. However, catheter ablation of persistent atrial fibrillation is still a challenge. Various rather complex ablation strategies exist and their results are not very favorable. Therefore, the aim of our study was to evaluate a well-defined reasonable approach to catheter ablation of persistent atrial fibrillation. The strategy consisted of a circumferential pulmonary vein ablation in combination with a potential-guided segmental approach to achieve complete pulmonary vein isolation and a linear lesion at the roof of the left atrium. A total of 43 patients (30 men, 13 women; mean age 55 years (SD ± 9 years)) with symptomatic persistent atrial fibrillation were enrolled in this study. All patients underwent catheter ablation of persistent atrial fibrillation using the above-mentioned approach (with the CARTO or the NAVX system). Additionally, catheter ablation of the mitral isthmus and the right atrial isthmus was performed in selected cases. In all patients, cardiac MRI or multi-detector spiral computed tomography was performed prior to the ablation procedure and a surface rendered model of the left atrium was created. After discharge, patients were scheduled for repeated visits at the arrhythmia clinic at 1, 3, 6, 9, and 12 months after the ablation procedure. The ablation procedure could be performed as planned in all 43 patients. Nine patients had to undergo a repeat ablation procedure, so that a total of 52 procedures were evaluated. An additional linear lesion was created at the mitral isthmus in three patients (7%) during the initial procedure and in one patient (2.3%) during the second procedure. Catheter ablation of the right atrial isthmus was performed in 11 patients (25.6%) during the first procedure and in four additional patients during the redo procedure (9.3%). Twenty-four out of 43 patients (55.8%) experienced an arrhythmia recurrence within the first 3 months after ablation requiring an electrical cardioversion. At 1-year follow-up, analysis of a 7-day Holter monitoring revealed no evidence for an arrhythmia recurrence in 26 of 43 patients (60.5%). In nine of 43 patients (20.9%), only short episodes of paroxysmal atrial fibrillation were documented. In eight patients (18.6%), a recurrence of persistent atrial fibrillation (>48 h) was revealed by the long-term recordings. A duration of persistent atrial fibrillation >3 months was the most powerful predictor for arrhythmia recurrences at 1-year follow-up. A subgroup analysis revealed a markedly higher rate of stable sinus rhythm at 1-year follow-up in patients with a short duration of atrial fibrillation (≤3 months) compared to patients with a longer duration of AF (>3 months) prior to the procedure (72.0% versus 44.4%). There were no major complications. Catheter ablation of persistent atrial fibrillation can be performed safely and effectively using this ablation strategy (especially in patients with short-lasting persistent atrial fibrillation (≤3 months)).

Background In some patients, above-average alcohol consumption before occurrence of atrial fibrillation (AF) in terms of a "holiday heart syndrome" (HHS) can be determined. There is evidence that long before development of apparent alcohol-induced cardiomyopathy, above-average alcohol consumption generates an arrhythmogenic substrate which abets the onset of AF. Changes of atrial current densities in terms of an electrical remodeling after sustained short-term ethanol infusion in rabbits as a potential part of HHS pathophysiology were examined in this study. Methods Rabbits of the ethanol group (EG) received sustained short-term intravenous alcohol infusion for 120 hours (during infusion period, blood alcohol level did not fall below 158 mg/dl), whereas NaCl 0.9% was infused in the placebo group (PG). Using patch clamp technique in whole-cell mode, atrial current densities were measured and compared between both groups. Results Ethanol infusion did not alter current densities of I(to) [58.7 +/- 5.0 pA/pF (PG, n = 20 cells) vs. 53.9 +/- 5.0 pA/pF (EG, n = 24)], I(sus) [11.3 +/- 1.4 pA/pF (PG, n = 20) vs. 10.2 +/- 1.0 pA/pF (EG, n = 24)], and I(K1) [-1.6 +/- 0.3 pA/pF (PG, n = 17) vs. -2.0 +/- 0.3 pA/pF (EG, n = 22)]. However, alcohol infusion resulted in a remarkable reduction of I(Ca,L) current densities [-28.4 +/- 1.8 pA/pF (PG, n = 20) vs. -15.2 +/- 1.4 pA/pF (EG, n = 22)] and I(Na) [-75.4 +/- 3.6 pA/pF (PG, n = 17) vs. -35.4 +/- 4.4 pA/pF (EG, n = 21)], respectively. Conclusion Sustained short-term ethanol infusion in rabbits alters atrial current densities. HHS might be favored by alcohol-induced atrial electrical remodeling.

Wir berichten von einem Patienten mit ventrikularen Tachyarrhythmien, die wahrend einer manifesten Sepsis nach schwerer Brandverletzung in einen elektrischen Sturm mundeten. Das Oberflachen EKG in der Akutphase zeigte Zeichen von zwei moglichen Ursachen fur diesen lebensbedrohlichen Zustand: 1.) Brugada-Syndrom 2.) kardiale Ischamie. In Angesicht der komplexen klinischen Situation (manifeste Sepsis, Brandverletzungen) differierte unser Behandlungsansatz vom ublichen Management des elektrischen Sturms: unter der primaren Annahme eines fieber-induzierten Brugada-Syndroms initiieren wir eine aggressive Normalisierung der Korpertemperatur anstelle von einer antiadrenergen und antiarrhythmischen Behandlung beziehungsweise einer Koronarangiographie zum Ausschluss einer kardialen Ischamie als Trigger des elektrischen Sturms.

SENGES, J.C., et al.: Variability of Holter Electrocardiographic Findings in Patients Fulfilling the Noninvasive MADIT Criteria. In the MADIT study, a selected group of postinfarction patients with asymptomatic nonsustained ventricular tachycardia (NSVT) has been shown to benefit from prophylactic ICD treatment. The present study analyzed the variability of NSVT in a patient population fulfilling the noninvasive MADIT criteria. Three consecutive Holter ECGs were performed in weekly intervals in 68 postinfarction patients with an LVEF ≤ 0.35. Patients with NSVT underwent programmed ventricular stimulation (PVS); patients were implanted with an ICD if sustained VT or VF was inducible. If NSVT was found in at least two recordings, the arrhythmia was defined as reproducible. In 28 (41%) of the 68 patients, NSVT was found in at least one recording. Seventeen patients revealed NSVT in the first, the remaining 11 in the second registration; no patient had NSVT only in the third Holter. Of the patients with NSVT, 50% had only one, 39% had two, and 11% had three positive recordings. Thus, reproducible NSVT was found in only 50% of the patients with NSVT. Predictors for reproducibility were LVEF > 0.27, NYHA Class I, absence of digitalis therapy, and > 2 NSVT per 24-hour period. Reproducible NSVT was not associated with risk factors such as elevated mean heart rate, reduced heart rate variability, late potentials, or inducibility of sustained VT during PVS. During 17 ± 9 months of follow-up, seven (10%) patients experienced arrhythmic events: two without and five with previously documented NSVT. In the latter patients, first occurrence of NSVT was consistently in the first Holter; only two of them had reproducible NSVT. In postinfarction patients, the risk factor NSVT exhibits marked spontaneous variability, especially in those with a low number of NSVT per 24-hour period, LVEF < 0.27 or NYHA III, which limits its clinical value as a selection criterion for PVS. Reproducibility of NSVT itself does not seem to be an independent risk factor.

Background Conventional catheter ablation of cardiac arrhythmias is associated with radiation risks for patients and laboratory personnel. However, nonfluoroscopic catheter guidance may increase the risk for inadvertent cardiac injury. A novel radiofrequency ablation catheter capable of real-time tissue-tip contact force measurements may compensate for nonfluoroscopic safety issues. Objective To investigate the feasibility of contact force–controlled zero-fluoroscopy catheter ablation. Methods In 30 patients (including 12 pediatric patients), zero-fluoroscopy catheter ablation of right-sided (right atrium, n=20; right ventricle, n=2) and left atrial (n = 8) arrhythmias was attempted. Inclusion criteria were symptomatic suspected atrioventricular nodal reentrant tachycardia, atrioventricular reentrant tachycardia, focal right atrial and ventricular arrhythmias, and lone atrial fibrillation. A novel irrigated-tip catheter with an integrated contact force sensor was used for nonfluoroscopic 3-dimensional electroanatomical mapping and radiofrequency ablation. Transseptal access was gained under transesophageal guidance for ablation of left-sided arrhythmias. Results Procedural success without fluoroscopy was achieved in 29 of the 30 patients (97%). In 1 patient, endocardial nonfluoroscopic ablation failed because of an epicardial accessory pathway within a coronary sinus aneurysm. Mean total contact force and amplitude of force undulations were kept below 50 g during mapping and below 40 g during ablation to prevent contact force peaks (>100 g). Apart from a transient second-degree type I atrioventricular block, no complications occurred. The mean procedure time was 2.8 ± 0.9 hours. There were no arrhythmia recurrences during a mean follow-up of 6.2 ± 4.2 months. Conclusion Contact force–controlled zero-fluoroscopy catheter ablation is generally feasible in right-sided and left atrial cardiac arrhythmias.

Introduction. Tachycardia-induced atrial remodelling (as an equivalent to atrial fibrillation) can be influenced by the renin-angiotensin system. Effects of a seven-day enalapril pre-treatment (EPT, 0.16 mg/kg body weight subcutaneously every 24 h) on ionic currents underlying tachycardia-induced early electrical remodelling after 24 h rapid atrial pacing (RAP, 600 beats/min) in rabbit atrium were studied. Materials and methods. Animals were divided into four groups (n=4 each): control; paced only; enalapril only; and enalapril and paced, respectively. Using patch-clamp technique in whole-cell mode, current densities were measured in isolated atrial myocytes. Results. EPT nearly doubled L-type calcium current (ICa,L, −7.7±0.6 pA/pF [control] vs. f −12.3±1.2 pA/pF [enalapril only]). RAP reduced ICa,L to −3.6±0.7 pA/pF (paced only). Also after EPT, RAP led to a significant downregulation of ICa,L by 39% (−7.5±1.3 pA/pF [paced and enalapril]). RAP decreased transient outward potassium current (Ito, −45%, 51.5±3.9 pA/pF [control] vs. 28.5±4.5 pA/pF [paced only]). EPT did not alter Ito (44.2±8.1 pA/pF [enalapril only]). However, RAP did not affect Ito in enalapril-treated animals and averaged 50.4±9.8 pA/pF (paced and enalapril). Conclusions. In summary, EPT has several effects on ion channels in rabbit atrium: 1) EPT increases ICa,L current density, but cannot prevent its downregulation due to RAP; 2) EPT has no influence on Ito current density, but can prevent its downregulation due to RAP. Although changes of single ion channels must be interpreted in context of the complex atrial electrophysiology as a whole, our results provide a possible explanation of the in vivo observation that angiotensin-converting enzyme inhibition is mainly beneficial on the early electrical remodelling due to the atrial fibrillation-equivalent RAP.

Telemedical ICD monitoring has the potential to enhance patient safety. The "home-monitoring" (HM) feature transmits selected device-related data to a service-center via mobile phone network. In case of a potential emergency situation, event reports are generated automatically. This prospective observational study was designed to test whether HM is effective and reliable in early detection of device failure.Consecutive patients receiving ICD, CRT-D or CRT pacemaker systems with HM feature were included. Regular follow-up visits were performed 1, 3, 6, 9 and 12 months after implantation in the first year, and every 6 months thereafter. All event reports transmitted by HM were analyzed and severe device-related events (serious lead or device dysfunction, hospitalization, death) were documented including timing, type and mode of detection.Sixty-nine patients were included and followed for 18 +/- 9 months. A total of 206 event reports were transmitted, prompted by VF/VT-episodes (n = 193), ineffective ICD shocks (n = 7), abnormal pacing impedance (n = 4) or battery depletion (n = 2). 8 SAEs were observed (RV lead fracture; n = 5, connector defect; n = 1, sensing defect, n = 1, RV lead dislodgement, n = 1). There was no device-related death. 6 out of 8 SAEs were discovered by HM (sensitivity, 75%). Without HM, these events would have been detected with a theoretical delay of 1.9 +/- 0.5 months in the first year (3 monthly FU) and 4.9 +/- 0.5 months in the following years (6 monthly FU).This pilot study demonstrates that HM enables early detection of ICD failure and appears to enhance patient safety.

At present, patients with documented sustained VT or resuscitated cardiac arrest (CA) are treated with ICDs. The aim of this study was to retrospectively evaluate if a routine electrophysiological study should be recommended prior to ICD implantation. In 462 patients referred for ICD implantation because of supposedly documented VT (n = 223) or CA (n = 239), electrophysiological study was routinely performed. In 48% of the patients with CA, sustained VT or VF was inducible. Electrophysiological study suggested conduction abnormalities (n = 11) or supraventricular tachyarrhythmias (n = 3) in conjunction with severely impaired left ventricular function to have been the most likely cause of CA in 14 (5.9%) of 239 patients. Likewise, sustained VT was only inducible in 48% of patients with supposedly documented VT. Of these inducible VTs, nine were diagnosed as right ventricular outflow tract tachycardia or as bundle branch reentry tachycardia. Supraventricular tachyarrhythmias judged to represent the clinical event were the only inducible arrhythmia in 35 (16%) patients (AV nodal reentrant tachycardia [n = 7], AV reentry tachycardia [n = 4], atrial flutter [n = 19], and atrial tachycardia [n = 5]). Based on findings from the electrophysiological study, ICD implantation was withheld in 14 (5.9%) of 239 patients with CA and in 44 (19.7%) of 223 patients with supposedly documented VT. During electrophysiological study, VT or VF was only reproducible in about 50% of patients with supposedly documented VT or CA. Electrophysiological study revealed other, potentially curable causes for CA or supposedly documented VT in 12.6% (58/462) of all patients, indicating that ICD implantation can potentially be avoided or at least postponed in some of these patients. Based on these retrospective data, routine electrophysiological study prior to ICD implantation seems to be advisable.

Budipine is a non-dopaminergic antiparkinsonian drug causing acquired forms of Long QT syndrome (aLQTS). As a consequence, the manufacturer has restricted the use of budipine in patients who exhibit additional risk factors for the development of "Torsades-de-Pointes" tachycardias (TdP). The molecular basis of this serious side effect has not been elucidated yet. Human ether-a-go-go related gene (HERG) channel block being the main cause of drug induced QT prolongation, we investigated the effect of budipine on the rapid component of the delayed-rectifier potassium current (I(K(r))) in guinea pig cardiomyocytes and on HERG potassium channels heterologously expressed in Xenopus oocytes. In guinea pig cardiomyocytes, budipine (10 microM) inhibited I(K(r)) by 86% but was without any effect on calcium currents. In Xenopus oocytes, HERG potassium channels were blocked by budipine with an IC(50) of 10.2 microM. Onset of block was fast and block was only slowly and incompletely reversible upon washout. Budipine blocked HERG channels in the open and inactivated state, but not in the closed states. The half-maximal activation voltage was slightly shifted towards more negative potentials. Steady-state inactivation of HERG was also influenced by budipine. Budipine block was neither voltage- nor frequency-dependent. In HERG channel mutants Y652A and F656A, drug affinity was reduced dramatically. Therefore, these two aromatic residues in the channel pore are likely to form a main part of the binding site for budipine. In summary, this is the first study that provides a molecular basis for the budipine-associated aLQTS observed in clinical practice. Furthermore, these findings underline the importance of the aromatic residues Y652 and F656 in the binding of lipophilic drugs to HERG channels.

WERETKA, S., et al.: Far-Field R Wave Oversensing in a Dual Chamber Arrhythmia Management Device: Predisposing Factors and Practical Implications. Initial experience with the Medtronic Jewel 7250, the ICD designed to detect and treat ventricular and supraventricular tachyarrhythmias, is very promising. Its effectiveness, however, depends on sensing performance, which has not yet been systematically examined. The aim of the study was to determine the incidence of, predisposing factors for, and practical implications of far-field R wave oversensing (FFRWOS) in this dual chamber ICD. During a total follow-up of 797 months in 48 patients who had the Jewel 7250, follow-up strip charts, 12-channel Holter recordings and, in particular cases, Holter recordings with intracardiac markers were analyzed for the presence of FFRWOS. FFRWOS was documented in ten (21.3%) patients. Compared to other lead locations, the right atrial appendage lead position was most frequently associated with FFRWOS (7/27 vs 3/21, P < 0.05). Patients with FFRWOS had significantly more treated and nontreated atrial episodes, many of which were judged to have been detected inappropriately. In one case, inappropriate atrial antitachycardia pacing due to R wave oversensing triggered sustained ventricular tachycardia, terminated eventually with a high energy shock. In dual chamber ICDs, FFRWOS may represent a frequent phenomenon possibly leading to serious consequences. For atrial leads, a lateral atrial wall position seems to be preferable. In most cases, FFRWOS can be eliminated by optimization of atrial sensing parameters. Given the possibility of ventricular proarrhythmia with atrial pacing therapy, the capability of ventricular backup defibrillation in respective devices is at least reassuring.