Search

Background: A remote magnetic navigation (MN) system is available for radiofrequency ablation of atrial fibrillation (AF), challenging the conventional manual ablation technique. The myocardial markers were measured to compare the effects of the two types of MN catheters with those of a manual-irrigated catheter in AF ablation.Methods: AF patients underwent an ablation procedure using either a conventional manual-irrigated catheter (CIR, n = 65) or an MN system utilizing either an irrigated (RMI, n = 23) or non-irrigated catheter (RMN, n = 26). Levels of troponin T (TnT) and the cardiac isoform of creatin kinase (CKMB) were measured before and after ablation.Results: Mean procedure times and total ablation times were longer employing the remote magnetic system. In all groups, there were pronounced increases in markers of myocardial injury after ablation, demonstrating a significant correlation between total ablation time and post-ablation levels of TnT and CKMB (CIR r = 0.61 and 0.53, p < 0.001; RMI r = 0.74 and 0.73, p < 0.001; and RMN r = 0.51 and 0.59, p < 0.01). Time-corrected release of TnT was significantly higher in the CIR group than in the other groups. Of the patients, 59.6% were free from AF at follow-up (12.2 ± 5.4 months) and there were no differences in success rate between the three groups.Conclusions: Remote magnetic catheters may create more discrete and predictable ablation lesions measured by myocardial enzymes and may require longer total ablation time to reach the procedural endpoints. Remote magnetic non-irrigated catheters do not appear to be inferior to magnetic irrigated catheters in terms of myocardial enzyme release and clinical outcome. [ABSTRACT FROM AUTHOR]

Objectives: We sought to investigate the incidence of atrial fibrillation after catheter ablation for typical atrial flutter and to determine the predictors for symptomatic atrial fibrillation that required a further additional dedicated ablation procedure., Design: 127 patients underwent elective cavotricuspid isthmus ablation with the indication of symptomatic, typical atrial flutter. The occurrence of atrial flutter, atrial fibrillation, cerebrovascular events and the need for additional ablation procedures for symptomatic atrial fibrillation was assessed during long-term follow-up., Results: The majority of patients (70%) manifested atrial fibrillation during a follow-up period of 68 ± 24 months, and a significant proportion (42%) underwent one or multiple atrial fibrillation ablation procedures after an average of 26 months from the index procedure. Recurrence of typical atrial flutter was rare. Ten patients (8%) suffered cerebrovascular events. Earlier documentation of atrial fibrillation (OR 3.53), previous use of flecainide (OR 3.33) and left atrial diameter (OR 2.96) independently predicted occurrence of atrial fibrillation during the follow-up. A combination of pre- and intra-procedural documentation of atrial fibrillation (OR 3.81) and previous use of flecainide (OR 2.43) independently predicted additional atrial fibrillation ablation., Discussion: Atrial fibrillation occurred in the majority of patients after ablation for typical atrial flutter and 42% of them required an additional dedicated ablation procedure. Pre- and intraprocedural documentation of atrial fibrillation together with previous use of flecainide independently predicted atrial fibrillation occurrence and a need for additional ablation. Anticoagulation treatment should be continued in high-risk patients in spite of clinical disappearance of atrial flutter.

Aims: Complex fractionated electrogram (CFE) ablation in addition to pulmonary vein isolation is an accepted strategy for the treatment of non-paroxysmal atrial fibrillation (AF). We sought to determine the effect of flecainide on the distribution and extension of CFE areas., Methods: Twenty-three non-paroxysmal AF patients were enrolled in this prospective study. A first CFE map was obtained under baseline conditions by sampling 5 s of continuous recording from the distal electrodes of the ablation catheter. Intravenous flecainide (1 mg/kg) was administered over 10 min and followed by 30-min observation time. A second CFE map was obtained with the same modalities. CFE-mean values, CFE areas, and atrial electrogram amplitude were retrieved from the electro-anatomical mapping system (Ensite NavX)., Results: After flecainide administration, CFE-mean values increased (111.5 ± 55.3 vs. 132.3 ± 65.0 ms, p < 0.001) with a decrease of CFE area (32.9%) in all patients. Atrial electrogram amplitude decreased significantly (0.30 ± 0.31 vs. 0.25 ± 0.20 mV, p < 0.001). We observed 80.9% preservation of CFE areas. A CFE mean of 78 ms was the best cutoff for predicting stable CFE areas., Conclusions: Flecainide reduces the extension of CFE areas while preserving their spatial localization. A CFE-mean value <80 ms may be crucial to define and locate stable CFE areas.

Introduction: Previous studies have validated the use of impedance fall as a measure of the effects of ablation. We investigated whether catheter-to-tissue contact force correlated with impedance fall during atrial fibrillation ablation., Methods and Results: A total of 394 ablation points from 35 patients who underwent atrial fibrillation ablation were selected and analyzed in terms of the presence of stable catheter contact in non-ablated areas in the left atrium. A fixed power output (30 W) was applied for 60 seconds. Contact force, impedance fall, and force-direction angle were retrieved and exported for off-line analysis. Qualified points were divided into 5 groups according to the level of contact force (1-5 g, 6-10 g, 11-15 g, 16-20 g, and >20 g). An acute impedance fall was observed in the first 10 seconds followed by a plateau in group I and by a further fall in the other groups. Group V showed a rise in impedance during the last 20 seconds of ablation. Levels of impedance fall at each time point were significantly different among all the groups (P<0.001) except between groups III and IV. There was a significant correlation between contact force and maximum impedance fall (rho = 0.54, P<0.01). Lesions with a force-direction angle of 0-30° had significantly lower contact force and maximum impedance fall than those with angles of 30-60° and 60-135° (P<0.01)., Conclusions: Under stable catheter conditions, contact force correlates with impedance fall during 60 seconds of ablation. Contact force exceeding 5 g produces greater impedance fall, which probably indicates adequate lesion formation. A contact force greater than 20 g may lead to late tissue overheating., (© 2013 Wiley Periodicals, Inc.)

Purpose: The adjunctive ablation of areas of complex fractionated electrogram (CFE) to pulmonary vein isolation (PVI) is an emerging strategy for patients with non-paroxysmal atrial fibrillation (AF). We studied the long-term outcomes of this approach., Methods: Sixty-six patients (mean age 58 ± 9, 86.4 % male) with non-paroxysmal AF underwent ablation procedures consisting of PVI plus extensive CFE ablation. Post-ablation atrial tachycardia (AT) was also targeted if presented. All patients were followed up regularly on an ambulatory basis by means of ECG and Holter recordings., Results: After a mean follow-up period of 40 ± 14 months and 1.7 ± 0.7 procedures, 38 patients (57.6 %) were free of arrhythmias, 15 (22.7 %) displayed clinical improvement and 13 (19.7 %) suffered recurrences of persistent AF/AT. Females displayed poorer long-term outcomes than males (arrhythmia-free 22.2 vs. 63.2 %, p < 0.05). Multivariate analysis demonstrated that long duration of uninterrupted AF prior to the procedure was an additional predictor of long-term failure (odds ratio 1.49, p < 0.01). ROC analysis (area under curve 0.80; p < 0.001) estimated 3.5 years as the optimal cut-off point for predicting long-term failure (sensitivity 85 %, specificity 74 %). The cumulative data showed a significantly higher percentage of arrhythmia-free patients when the duration of AF had been ≤ 2 years (69.7 %) and ≤ 4 years (68.9 %) than when it was > 4 years (33.3 %; p < 0.01)., Conclusions: PVI + CFE ablation in non-paroxysmal AF appears to provide a reasonable proportion of arrhythmia-free patients during long-term follow-up. Poorer long-term results can be expected among female patients and those with an uninterrupted AF duration of > 4 years.

Aims: We investigated the relationship between arrhythmia burden, left atrial volume (LAV) and N-terminal pro-B-type natriuretic peptide (NT-pro-BNP) at baseline and after long-term follow-up of atrial fibrillation (AF) ablation., Methods: We studied 38 patients (23 paroxysmal, 6 women, mean age 56 ± 11) scheduled for AF ablation. LAV was calculated on the basis of computed tomography images at baseline and long-term follow-up, and arrhythmia burden was graded from self-reported frequency and duration of AF episodes., Results: After a mean period of 22 ± 5 months, 28/38 patients (11/15 persistent) were free from AF recurrence. At baseline there were no differences in mean LAV (125 vs. 130 cm(3), p = 0.7) or median NT-pro-BNP (33.5 vs. 29.5 pmol/L, p = 0.9) between patients whose ablation had been successful or otherwise. At long-term follow-up, there was a marked decrease in LAV (105 vs. 134 cm(3), p < 0.05) and level of NT-pro-BNP (7 vs. 17.5 pmol/L, p < 0.05) in the successful ablation patients. NT-pro-BNP correlated with LAV both at baseline (r = 0.71, p < 0.001) and at follow-up (r = 0.57, p < 0.001). Arrhythmia burden correlated with both NT-pro-BNP (r = 0.47, p < 0.01) and LAV (r = 0.52, p < 0.01). A decrease in NT-pro-BNP at follow-up of >25% of baseline value had a specificity of 0.89 and a sensitivity of 0.6 (receiver operator characteristics, accuracy 0.82) for ablation success., Conclusions: NT-pro-BNP correlates with LAV and arrhythmia burden in AF patients and both NT-pro-BNP and LAV decrease significantly after successful ablation. A decrease in NT-pro-BNP of >25% from the baseline value could be useful as a marker of ablation success.

Background: The first use of magnetic navigation for radiofrequency ablation of supraventricular tachycardias, was published in 2004. Subsequently, the method has been used for treatment of most types of tachyarrhythmias. This paper provides an overview of the method, with special emphasis on usefulness of a new remote-controlled magnetic navigation system., Material and Methods: The paper is based on our own scientific experience and literature identified through a non-systematic search in PubMed., Results: The magnetic navigation system consists of two external electromagnets (to be placed on opposite sides of the patient), which guide an ablation catheter (with a small magnet at the tip of the catheter) to the target area in the heart. The accuracy of this procedure is higher than that with manual navigation. Personnel can be quickly trained to use remote magnetic navigation, but the procedure itself is time-consuming, particularly for patients with atrial fibrillation. The major advantage is a considerably lower radiation burden to both patient and operator, in some studies more than 50 %, and a corresponding reduction in physical strain on the operator. The incidence of procedure-related complications seems to be lower than that observed with use of manually operated ablation catheters. Work is ongoing to improve magnetic ablation catheters and methods that can simplify mapping procedures and improve efficacy of arrhythmia ablation. The basic cost for installing a complete magnetic navigation laboratory may be three times that of a conventional electrophysiological laboratory., Interpretation: The new magnetic navigation system has proved to be applicable during ablation for a variety of tachyarrhythmias, but is still under development.

Introduction: Substrate-based radiofrequency ablation for treatment of atrial fibrillation (AF) is still under development. The purpose of this study was to investigate the different characteristics and distribution of complex fractionated atrial electrograms (CFAE) in both atria in patients with paroxysmal and persistent AF., Methods and Results: The NavX system was used to map the left and right atria and the coronary sinus in 20 AF patients (ten persistent). An automated algorithm calculates the average time interval between consecutive deflections (complex fractionated electrogram (CFE) mean). All recordings were visually inspected off-line and interpreted either as continuous, fragmented, mixed CFAE, or non-CFAE, and their locations were determined. Electrograms with intermittent CFAE characteristics were also regarded as non-CFAEs. There were more CFAEs in persistent AF than in paroxysmal AF (52% vs. 44% of total registrations, p < 0.05), and CFAEs were more widespread in both atria in persistent AF patients. There were also more continuous CFAEs (70% vs. 59% of total CFAEs, p < 0.05), and less mixed and intermittent CFAEs (22% vs. 30% and 16% vs. 21% of total CFAEs, respectively, p < 0.05) in persistent AF. Fragmented CFAEs had more high-voltage signals than other groups. Employing the automated algorithm for CFAE mapping, a CFE mean cut-off value of < or =80 ms provides a sensitivity and specificity of 87.4% and 81.2%, respectively., Conclusions: CFAEs distribute in preferential areas and arrange in different patterns in both atria. Patients with persistent AF have more continuous CFAEs and higher temporal signal stability than patients with paroxysmal AF.

A 15-year-old boy who had been given an orthotopic heart transplant 12 years earlier underwent radiofrequency ablation after 14 months of tachycardia. At the time of the procedure, the patient presented moderate signs of heart failure and tachycardia-induced cardiomyopathy. During electroanatomical mapping we identified a focal atrial tachycardia with origin in the donor right atrium and bi-directional atrio-atrial conduction. After successful focal ablation the patient had two alternating atrial activation patterns, representing the recipient and the donor heart sinus rhythm. Two months after the ablation heart failure symptoms were in regress, and the patient was still in sinus rhythm.

Background: Pulmonary vein (PV) isolation is used for the treatment of atrial fibrillation (AF). Complex fractionated atrial electrogram (CFAE) mapping has been introduced to guide AF ablation. However, the spatial relationship between PV and CFAE is not well defined., Methods and Results: The study included 21 patients (mean age 57 +/- 11 years, 17 men, 14 paroxysmal, two persistent, and five long-standing persistent AF) referred for PV isolation. Electrograms were sampled for 8 seconds at each site during stable AF (13 induced). High-frequency was defined as <80 ms of CFAE value. The distance between CFAE and the nearest PV ostium was measured. The PV ostia and antra were demarcated by fluoroscopy guidance and endocardial reconstruction. Among 82 PV mapped (left common four, superior 17, inferior 17; right superior 21, inferior 21, middle 2), 52.4% and 25.6% of high-frequency CFAE were located on the anterior and posterior walls, respectively, inside the PV or at the ostium. No high-frequency CFAE was observed in two out of 60 and one out of 20 PV anteriorly, versus seven out of 60 and 11 out of 20 PV (P < 0.001) posteriorly, in paroxysmal and persistent AF, respectively. In the PV with high-frequency CFAE, the mean shortest distances to the PV ostia in paroxysmal versus persistent AF were 2.7 +/- 5.1 versus 7.4 +/- 5.4 mm anteriorly (P < 0.01), and 6.5 +/- 6.4 versus 9.4 +/- 8.4 mm posteriorly (ns)., Conclusions: During PV isolation, extending the ablation lesions by up to 10 mm from the PV ostia might cover most high-frequency CFAE around the PV antra. High-frequency CFAE were more often located in the PV ostia in paroxysmal than in persistent AF.

Background: During pulmonary vein isolation for treatment of atrial fibrillation (AF), a significant delay in atrio-pulmonary vein (PV) conduction is often observed. We sought to investigate this conduction delay in various PV in individual patients., Methods: We studied 385 AF patients (mean age: 54 +/- 11 years, 74 women) who underwent segmental PV isolation (PVI). A circular decapolar catheter was used to record electrograms at the PV ostia. The time delay from local atrial potential to PV potential was measured in each vein. Conduction delay (CD) was defined as the longest time interval >20 ms observed during PVI., Results: For patients treated for the first time, CD was more frequently observed in the left common and the right and left superior PVs (84.2%, 67.9%, and 66.2%, respectively) and less frequently in the left and right inferior and right middle PVs (54.3%, 40.0%, and 30.8%, respectively). Veins with CD required more ablation applications (12.4 vs 9.9) and a higher ablated segmental fraction (72.3% vs 63.7%). CD was observed in 75.2% (109/145) of the PVs in which focal activity was detected. Older patients had a higher incidence of PVs with CD than younger patients. There were no gender differences., Conclusions: The incidence of CD was highest in the left common and superior PVs, in older patients and in PVs with focal activity. PVs with CD required more ablation applications and a larger area of ablation around the ostia. These observations were not found during repeat procedures.

Background: Catheter ablation has been increasingly applied in children and adolescents with tachyarrhythmias. The aim of this article is to assess the results of ablation therapy of tachycardias in patients below 18 years of age at Haukeland University Hospital., Material and Methods: 141 patients (70 boys and 71 girls, aged 5-17 (13.5 +/- 3.5 ) years with tachyarrhythmias underwent an electrophysiologic study and catheter ablation in the period 1992-2007., Results: Ablation was successfully performed in 138/141 (98%) patients., The procedure was repeated (3 patients twice) until the arrhythmia substrate disappeared in 16 of 138 patients. 81/141 (57%) patients had accessory pathways; 52 (37%) had double atrioventricular nodal pathways, 48 had concealed and 33 patients had overt (classical Wolff-Parkinson-White-syndrome) atrioventricular pathways. 8 (6%) patients had other atrial or ventricular tachyarrhythmias and 4 (3%) had organic heart disease. Use of a 3D mapping system was decisive for success for ablation in patients with complex cardiac diseases. Procedure-related complications were observed in 2/141 (1.4%) patients of whom one had a temporary third degree and one had a permanent first-degree atrioventricular block which did not entail further treatment., Conclusion: Catheter ablation of tachycardia in children and adolescents is a safe treatment method with a high success rate and few complications and should be preferred before drug therapy.

Aims: The recurrence of atrial fibrillation (AF) after pulmonary vein (PV) isolation is still a challenge. We investigated a new approach to treating AF patients by silencing electrical activity in the posterior inter-pulmonary-vein atrium (PIA)., Methods and Results: Three ablation steps are required to obtain PIA electrical silence: electrical PV isolation, the creation of two lines of lesions between the two superior and inferior PVs and the abolition of residual electrical signals within the PIA. The endpoint was the electrical silence and the inability to pace in the PIA. The posterior inter-pulmonary-vein atrium silence was obtained in 42 AF patients (56 +/- 9 years, four women). Recurrence of AF and atrial flutter was observed in 14 (33.3%) patients after the first procedure. Freedom from atrial arrhythmias after the second procedure was displayed by 94.4, 85.7, and 60.0% of patients with paroxysmal, persistent, and permanent AF, respectively. The left atrium (LA) volume was larger, and the percentages of the silent area of the LA surface and voltages were lower in patients with AF recurrence than in recurrence-free patients., Conclusion: Posterior inter-pulmonary-vein atrium electrical silence can greatly decrease the AF recurrence. The clinical AF recurrence may be related to an enlarged LA, a low percentage of electrically silent area, and low voltage in the LA.

Objective: To perform a systematic review of randomized controlled trials (RCTs) on catheter ablation for atrial fibrillation (AF)., Background: Radiofrequency catheter (RF)-ablation around pulmonary vein ostia and in left atrium may reduce or prevent recurrence of AF, as documented in observational studies and registry reports; however, few RCTs are available., Methods: Using relevant search phrases, Cochrane Library, MEDLINE and EMBASE were searched for RCTs, last time in May 2007. Titles and abstracts were screened. When entry criteria were fulfilled, full-text papers were read and graded according to quality and relevance., Results: One thousand and ninety four abstracts were evaluated, and five RCTs included (578 randomized patients). The studies had moderate quality and relevance, but the results were consistent: ablation is better than drug treatment in preventing AF recurrence; the relative risk (95% CI)) one year after ablation ranged from 0.20 (0.08-0.51) to 0.62 (0.39-0.99)., Conclusions: Results from observational and registry studies are confirmed: RF-ablation reduces recurrence rate of AF, and can be done with few serious complications. Limitations are few patients>70 years, and only one year follow-up.

Background and Study Objective: Patients with paroxysmal or persistent atrial fibrillation (AF) can be treated by pulmonary vein (PV) isolation. Although the recurrence rate after the procedure is relatively high, the long-term outcomes after initially recurrence-free procedures remains unclear. We examined the rates of recurrence of AF after PV isolation., Methods: Our study included 278 consecutive patients with drug-refractory AF (mean age = 53 +/- 11 years, 228 men). PV isolation was based on the disappearance of PV potentials recorded from a circumferential catheter after segmental ostium ablation. Cavo-tricuspid isthmus lines and additional atrial lines were performed in 124 and 28 patients, respectively. Patients were monitored for a mean of 26 +/- 11 months (range 12-56). Recurrence was defined as >/= 1 episodes of symptomatic or asymptomatic AF > 1 month after the procedure., Results: A total of 120 (34) patients had >/= 1 recurrence of AF > 1 month after the procedure, of whom 14 (4) had a first recurrence > 6 months after the procedure. There was a significantly higher recurrence rate among patients with persistent AF., Conclusions: A relatively high AF recurrence rate was observed after PV isolation. AF may recur late after the ablation procedure, though the majority of recurrences occurred within 6 months after the first procedure. There were no differences in incidence or time of occurrence of late recurrences between patients with paroxysmal versus persistent AF.

Purpose: Ramp and burst pacing as treatment for atrial tachycardia (AT), one known trigger mechanism of atrial fibrillation (AF) are available in permanent pacemakers to reduce the burden of AF. An analysis of the success rate of three consecutive antitachycardia pacing sequences is presented., Method: The AT 500 (Medtronic) pacemaker was implanted in 36 patients (18 female, mean age 77+/-11 years) with pacemaker indication due to tachybrady arrhythmias (n=34), and other indications (n=2). A standardized AT treatment of 8 sequences of ramp followed by six and four sequences burst pacing was programmed on after 1 month of tachycardia detection only. 5 consecutive sinus beats or 3 min with atrial rhythm not classified as AF or AT defined treatment success and was registered at 3 months follow-up., Results: 2979 episodes (mean 85+/-316) in 17 patients (7 female) were treated and analyzed. The overall treatment success increased from 42+/-27% to 44+/-31% and 45+/-31% during the consecutive ATP sequences (ns). The average ATP success of the first ramp pacing sequences was 95+/-10%, the second ramp ATP sequence was successful in 3+/-6%, and the last ramp ATP sequence in 2+/-5%., Conclusion: 95% of the 45% treatment success of a standard AT treatment was achieved by the first ramp pacing sequence. Further antitachycardia pacing sequences did not increase the success rate significantly.

Background: Pacemaker treatment of known trigger mechanisms for atrial tachyarrhythmias (AT) and atrial fibrillation (AF) has shown reduction in the incidence of AF. A new arrhythmia management device, which included storage of AT/AF (for tailoring treatment) and three prevention algorithms and one for treatment, was examined in order to identify the influence on arrhythmia episodes over a 12-month follow-up (FU) period., Methods: Twenty-three consecutive patients with known tachybradyarrhythmias were examined. Seven patients had to be excluded (two outliers, four developed permanent AF, one had no detection algorithm turned on at implantation). The remaining 16 patients showed 2723 episodes (675 treated episodes) for evaluation of the effect on episodes/month/patient (e/m/p), treatment success, duration of episodes, circadian distribution and quality of life., Results: The AT/AF e/m/p were reduced from 37 +/- 102 e/m/p at 1-month FU to 16 +/- 48 e/m/p at 3-month FU, 15 +/- 48 e/m/p at 6-month FU and 10 +/- 28 e/m/p at 12-month FU (p < 0.05), according to fewer subjective symptoms. Treatment success remained stable during the observation period (29-40%). Only minor changes in the duration of episodes and the distribution of start times were observed., Conclusion: Tailoring treatment by the pacemaker examined with several prevention and treatment algorithms reduces e/m/p and might be a promising supplement in the treatment of selected patients with known AT/AF and bradycardia.

Objective: The rate response of a pacemaker (PM) was compared with the sinus rate in patients during repeated exercise tests, at different settings of the rate response parameters., Methods and Results: In patients with paroxysmal sick sinus syndrome (n=3) or atrioventricular block (n=8), a rate responsive PM was implanted. The activity-dependent pacing rate is represented by the sensor indicated rate (SIR). Each patient performed a treadmill test at 1 month, 1 year, and 2 years after implantation. Prior to the 1 and 2 year tests PM parameters were changed to produce a larger rate increase, especially at moderate levels of daily life activity. During the tests the O(2) consumption and CO(2) production were measured, breath-by-breath, to determine the workload and the anaerobic threshold. On average the workload (oxygen consumption), the patient's sinus rate, and the SIR, showed a linear increase with the workload imposed by the treadmill. In the 1 month and 1 year test the SIR was much lower than the spontaneous rhythm, especially at low or moderate workloads. On the more dynamic setting of several rate adaptive parameters at 2 years, the SIR changed significantly and was close to the spontaneous HR., Conclusions: The examined PM provides a paced heart rate that is proportional to the workload. For the first time the effect of reprogramming rate response parameters to produce an SIR that is similar to the sinus rate is shown in this study.

Patients with paroxysmal atrial fibrillation (PAF) can be treated by pulmonary vein (PV) isolation. However, the recurrence rate after this procedure is relatively high. We sought to evaluate the quality of life (QOL) of patients with PAF recurrence after PV isolation and to analyze factors related to recurrences. Seventy-two drug-refractory PAF patients (59 men, 13 women, mean age 52 +/- 10) were included. PV isolation was based on the disappearance of PV potentials recorded from a Lasso catheter after segmental ostium ablation. Automatic foci were observed in 47 patients (65.3%) during the procedure. A mean of 3.1 +/- 0.9 PVs was isolated. Patients were followed for a mean of 10.3 +/- 5.1 months, during which 27 experienced >1 episode of PAF. QOL was scored from 0 (situation before ablation) to 10 (no episode after ablation) based on a questionnaire completed by 69 patients (95.8%). QOL was judged very good in 26 patients (none with PAF recurrences), better in 30 (15 with PAF recurrences), unchanged in 11 (10 with recurrences), and worse in 2 patients with PAF recurrences. Longer histories of PAF and a lower percentage of patients with automatic foci identified during the procedure were observed in the group with, than in the group without recurrences (P < 0.05). PV isolation improved QOL in patients with PAF, including in patients with recurrences. The length of PAF history and observation of automatic foci may be of importance for recurrences of PAF during long-term follow-up.

Objective: To quantify long term effects of cardiac resynchronisation therapy (CRT) by biventricular pacing in patients with heart failure (HF)., Methods: Regional changes in left ventricular (LV) contraction patterns effected by CRT in 19 patients with HF (12 with ischaemia; mean (SD) age 66 (9) years) with bundle branch block were examined by colour Doppler tissue velocity imaging (c-TVI). Time differences during main systolic tissue velocity peak (SYS) were compared in the basal and mid LV interventricular septum and in the corresponding LV free wall segments., Results: From baseline to long term (9.8 (3.0) months) CRT, ejection fraction increased from 21.8 (5.4)% to 30.8 (7.6)%, LV end diastolic diameter decreased from 7.6 (0.9) cm to 7.1 (0.8) cm, and end systolic diameter decreased from 6.4 (1.2) cm to 6.0 (1.2) cm (p < 0.05). LV peak tissue velocities were unchanged during follow up. At baseline, SYS in LV free wall was typically delayed by an average of 29 ms in the basal LV site and by 18 ms in the mid LV site. The regional movements of the LV free wall and interventricular septum were separated by an average of only 14 ms and -4 ms (p < 0.05) at the basal site and by -21 ms and -16 ms at the mid LV site during short term and long term CRT, respectively., Conclusions: The improved haemodynamic functions observed during CRT may be explained by a significant resynchronisation of the regional LV movement pattern during long term follow up.

Unlabelled: A QRS width greater than 120 ms is assumed to be a marker of inter- and intraventricular asynchrony in severe heart failure (HF) patients. Color Doppler tissue velocity imaging (c-TVI) with a time resolution of 10 ms was used to study regional left ventricular (LV) longitudinal systolic contraction pattern in HF patients with left and right bundle branch block (LBBB and RBBB) and in patients with normal QRS width. We studied 12 women and 23 men with severe HF, with a mean age of 66 +/- 11 years in New York Heart Association functional Class 2.9 +/- 0.6. Twenty patients had LBBB and 10 of those were accepted for cardiac resynchronization therapy by biventricular pacing (CRT). Ten patients had normal QRS width, and five had RBBB. In the echocardiographic apical four chamber view, regional peak LV tissue velocities and regional LV time differences of peak tissue velocities were compared at basal and mid-LV segments. There were no significant differences in regional mean peak tissue velocities among the patient groups. In patients with LBBB accepted for CRT, the LV lateral free-wall movement at basal LV was 29 ms delayed during main systole, almost significantly different from LBBB patients not accepted for CRT (P = 0.075). Even in HF patients with normal QRS width or RBBB, significant asynchronous longitudinal LV contraction was observed., Conclusions: For the detection of regional longitudinal LV contraction asynchrony in patients with severe HF, supplementary methods to the surface ECG, such as c-TVI, are strongly recommended.

Background: Atrial fibrillation is associated with increased morbidity and twice the mortality compared to individuals without fibrillation. Treatment with antiarrhythmic drugs has limited effect in paroxysmal atrial fibrillation., Material and Method: The group of patients comprised 59 men and 13 women with an average age of 51 +/- 10, the majority of whom had failed several drug regimens; some had undergone repeated DC conversions. A new method based on radiofrequency ablation and isolation of pulmonary veins from the left atrium may offer curative treatment for paroxysmal atrial fibrillation. The basis for this method is that foci in or close to the pulmonary veins initiate or drive atrial fibrillation. These foci may be identified by transseptal access to the left atrium and isolation of the veins from the left atrium using radiofrequency energy., Results: The group of 72 patients underwent 86 procedures. Foci were observed in 65.3%. Isolation of 3.1 +/- 0.9 veins was performed in 71 patients. During a follow up period of 10.3 +/- 5.1 months, 60.9% reported absence of fibrillation and 81.2% reported cure or considerable improvement. Complications included drainage of pericardial effusion in one patient, cerebral embolus with partial visual impairment in one patient, and an asymptomatic pulmonary vein stenosis in one patient., Conclusion: Paroxysmal atrial fibrillation can be treated in selected patients using pulmonary vein isolation with low to moderate risk of complications. Longer follow up is necessary for full evaluation of effect.

OBJECTIVE--The feasibility of color Doppler tissue velocity imaging (c-TVI) with a high time resolution of 10 ms for simultaneous measurement of the temporal characteristics of regional left ventricular (LV) tissue velocities at different LV sites was examined. Methods and results--In 20 subjects with structurally normal hearts, inter- and intraobserver agreement and the beat-to-beat variation were tested in c-TVI profiles from basal and mid-LV segments of the interventricular septum (IS) and of the lateral free wall (LFW). For peak tissue velocities a mean error of less than 1 cm/s was demonstrated. For systolic regional LV velocity time difference, the mean error was +/- 5 ms, with the best agreement when sampling from basal LV sites. For diastolic regional LV velocity time differences, the mean error was +/- 12 ms. The longitudinal LV movement pattern demonstrated a pattern of incremental tissue velocity from basal to mid-LV, and from IS to LFW sites. Conclusion--The c-TVI method has acceptable inter- and intraobserver agreement and is sufficiently accurate to disclose regional time aspects of LV contraction and relaxation.

Bundle branch block in patients with severe heart failure (HF) may result in asynchronous regional left ventricular (LV) contraction. Colour Doppler tissue velocity imaging (c-TVI) allows tissue velocity profiles to be measured with a resolution of 10 ms. Normal subjects (n = 30) showed a synchronous regional longitudinal LV pattern of movement, and HF patients with bundle branch block (n = 30) showed asynchronous contraction and relaxation patterns which were quantified by c-TVI as ranging from -22 to 19 ms. This asynchronous LV contraction probably contributes to the deterioration of LV function in HF patients., (Copyright (c) 2004 S. Karger AG, Basel.)

Unlabelled: Double Posterior Lines of Block in Typical Atrial Flutter., Introduction: The crista terminalis (CT) has been shown to be a barrier to transverse conduction during typical atrial flutter (AFL). However, some studies have demonstrated the presence of functional block in the sinus venosa region but not at the CT. The aim of this study was to define these regions of block in the right atrium using a three-dimensional noncontact mapping system., Methods and Results: In 39 AFL patients (33 men and six women, mean age 56 +/- 13 years), a noncontact multielectrode array was used to reconstruct electrograms in the right atrium. Isochronal and isopotential propagation mapping was performed during AFL and during pacing from the coronary sinus ostium and the low lateral wall (cycle length from 600 to 240 msec) in sinus rhythm after creation of isthmus block. A single line of block along the CT area was found in 18 patients (46%). Two lines of block were found in 21 patients (54%), with the first line located along the CT area. The second was located in the sinus venosa region in 20 patients (51%) and in the lateral wall in 1 patient (3%). In all patients, the block in the lower part of the CT was observed during AFL (60%) and during pacing at all cycle lengths (48%-62%). The length and proportion of block were inversely proportional to pacing cycle length., Conclusion: Double lines of block were frequently observed in patients with AFL, and both lines may form the posterior boundaries of the AFL circuit. Block was fixed in the lower part of the CT and was functional in the upper part of the CT.

Objective: To quantify ventricular resynchronisation by biventricular pacing using colour tissue Doppler velocity imaging (c-TVI)., Design and Patients: c-TVI shows regional tissue velocity profiles with a very high time resolution (10 ms). Eighteen patients were studied from an apical four chamber view at baseline and after a one month follow up of biventricular pacing. Regional left ventricular peak tissue velocities and regional time differences during the cardiac cycle were compared in the basal and mid interventricular septal segments of the left ventricle, and in the corresponding segments in the left ventricular free wall., Results: From baseline to follow up, mean peak tissue velocities changed only during isovolumic contraction in the basal interventricular septum and the left ventricular free wall. At baseline the peak main systolic tissue velocities in the left ventricular free wall were typically delayed by an average of 42 ms in the basal left ventricular site and by 14 ms in the mid left ventricular site compared with the corresponding sites in the interventricular septum. After resynchronisation by biventricular pacing those regional movements were separated by an average of only 7 ms at the basal site, but there was still a 21 ms earlier movement of the left ventricular free wall in the mid left ventricular site. The diastolic movement pattern remained unchanged from baseline to follow up., Conclusions: c-TVI showed a significant asynchronous regional longitudinal movement of basal left ventricular sites at baseline. A change to a more synchronous longitudinal left ventricular movement pattern during biventricular pacing was demonstrated.

Digoxin-immune antibody fragments (Fab) for treatment of digitalis intoxication was introduced in 1976. Many reports have been published concerning this therapy for children, but few have focused on its immediate reversal of cardiac as well as extracardiac life-threatening manifestations of digoxin toxicity. We present a case of life-threatening digitalis intoxication in a child with postoperative renal insufficiency, after a Sennings procedure for transposition of the great arteries. Digoxin administration according to the nationally recommended dosage and intervals unexpectedly resulted in serum levels in the toxic range. Severe cardiac arrhythmias, haemodynamic instability and a rapid-increasing serum potassium level resulted. This report demonstrates how administration of Fab according to the manufacturer's dosage recommendation reversed the tachyarrhythmia immediately and re-established a normal level of serum potassium within minutes.

The cavotricuspid isthmus (CTI) is a slow conduction area in the circuit of typical atrial flutter. However, conventional methods are limited by the inaccuracy of measurements of distance on the surface of the heart. The aim of the study was to define the conduction properties of the atrial flutter circuit along the tricuspid annulus by using a three-dimensional noncontact mapping system. In 34 atrial flutter patients (30 men, 4 women; mean age 54 +/- 14; 27 counter-clockwise, 4 clockwise, and 3 both), a noncontact multielectrode array was used to reconstruct electrograms in the right atrium. Isochronal and isopotential propagation mapping was performed during atrial flutter. The conduction velocity was calculated by dividing conduction time by surface distance. The right atrium along the tricuspid annulus was divided into five regions: lateral wall, superior right atrium, septum, septal CTI, and lateral CTI. Conduction velocities were 0.99 +/- 0.85, 1.67 +/- 1.21, 1.58 +/- 1.05, 0.82 +/- 0.72, and 1.68 +/- 1.00 m/s in counter-clockwise and 0.81 +/- 0.71, 2.61 +/- 1.90, 1.52 +/- 0.91, 0.91 +/- 0.80 and 1.91 +/- 0.83 m/s in clockwise, respectively. Conduction velocities were significantly slower in the septal CTI and lateral wall than in the lateral CTI, the septum, and the superior right atrium (P < 0.05). No significant difference was found between the septal CTI and the lateral wall. Conduction within the septal CTI was slower in patients treated with antiarrhythmic agents than in untreated patients (P < 0.05). The septal part of the CTI (but not the lateral CTI) and the lateral wall are slow conduction zones in the atrial flutter circuit, and both may, therefore, be mechanically important for the development of atrial flutter.

Introduction: Complete isthmus block has been used as an endpoint for radiofrequency ablation for common atrial flutter (AF). We sought to systematically evaluate extremely slow conduction (ESC), which is easily misinterpreted as complete block., Methods and Results: We studied 107 consecutive patients (92 men, 15 women, 58 +/- 11 years) who had undergone a successful AF ablation procedure. A 24-pole catheter was positioned along the tricuspid annulus spanning the isthmus. Complete isthmus block was defined as the presence of a complete corridor of double potentials along the ablation line. Activation delay time (AT), activation difference (deltaA) between two adjacent dipoles, maximum activation difference (deltaA(max)), change in polarity (CP) and change in amplitude (CA) of the bipolar atrial electrogram were recorded and P-wave morphology in the surface electrocardiogram was analyzed. ESC was observed in 16 patients. Between ESC and complete block, differences were found on the two lateral dipoles adjacent to the ablation line (AT: 148 +/- 17 vs. 183 +/- 27 ms and 155 +/- 18 vs. 170 +/- 28 ms, P < 0.01; deltaA: -91 +/- 22 vs. -126 +/- 28 ms and -7 +/- 13 vs. 13 +/- 6 ms, P < 0.01). Statistically significant differences in CP were detected on the relevant dipoles (7/16 vs. 14/16 and 6/16 vs.13/16, P < 0.05). No significant difference was found either in CA or in terminal P wave positivity. Mean deltaA(max) were 13.8 +/- 5.0 and 27.8 +/- 9.5 ms (P < 0.001) respectively in ESC and complete block. Two types of ESC, regular and irregular, were demonstrated during the ablation procedure., Conclusions: (1) ESC was observed in 15% of the patients during the AF ablation procedure. (2) The parameters of AT, deltaA, and CP may help to differentiate ESC from complete block. DeltaA(max) might be the most powerful indicator. (3) To verify complete block, it is essential to position the mapping catheter across the CTI in order to demonstrate the activation sequence up to the ablation line.

Aims: Cavotricuspid isthmus conduction (CIC) is closely associated with the maintenance and recurrence of common atrial flutter (AFL). This study systematically sought to assess the prevalence and characteristics of acute CIC recovery during AFL ablation and to define its predictors and its relationship with the results of long-term follow-up., Methods and Results: A total of 124 consecutive patients (105 men, 19 women, mean age 58 +/- 11 years) who underwent successful AFL ablation were included. The procedure endpoint was defined as complete bi-directional CIC block. During an observation period of 30 min, the incidence of CIC restoration was 34.% in patients and 39.8% in applications. It increased with increasing block time and decreased over time during the observation period. Block time in successful burns followed by persistent block was shorter than in those followed by CIC resumption (12 +/- 6 vs 33 +/- 12 s, P<0.0001). A negative correlation between block time and resumption time was found (r = - 0.57, P<0.001). Patients with permanent pacemakers had a higher incidence of acute CIC resumption than those without pacemakers (5/7 vs 29/117, P = 0.007). The AFL recurrence rate was 4.8% during a mean follow-up period of 21 +/- 8 months. Our results suggest that acute CIC resumption may be a potential risk for clinical AFL recurrence during long-term follow-up., Conclusions: Acute CIC resumption in common AFL ablation varies in terms of incidence and time course. Block time has a predictive value for acute CIC recovery. Observation time can be shortened if block time is short. With longer block time, it is essential to observe for a longer period in order to minimize CIC resumption.

The objective of this study was to pace via a coronary vein to avoid interfering with the tricuspid valve prosthesis function. Pacing leads were inserted into the posterior cardiac vein in a 68-year-old woman (patient 1), and in the great cardiac vein and the right auricle in a 32-year-old woman (patient 2). In patient 1 the stimulation threshold was 1.8 V at implant and stabilized at 3.0 V at the 24-month follow-up. In patient 2 the ventricular pacing threshold was 1.2 V at implant and stabilized at 0.7 V at the 24-month follow-up. The cardiac output at rest increased 43% during atrioventricular synchronous pacing compared to ventricular pacing. Long-term stable ventricular pacing via the coronary venous system was obtained.

Background: Biventricular pacing using a pacemaker lead located epicardially on the left ventricle, introduced via the coronary sinus to a coronary vein, and one pacemaker lead located endocardially at the apex of the right ventricle can resynchronize the contraction of the left ventricle. Approximately 30-50% of patients with severe heart failure have left bundle branch block indicating asynchronous contraction of the left ventricle. These patients can have a significant haemodynamic benefit from biventricular pacing., Material and Methods: The methods for implanting the leads are described. Biventricular pacemakers were implanted in five patients., Results: Acceptable low thresholds for pacing the left ventricle were achieved. Resynchronization of the contraction of the left ventricle was demonstrated by using colour tissue Doppler measurements. The mechanisms for the haemodynamic benefit of biventricular pacing are discussed on the basis of our data. The first patient has been followed for 12 months. He has a lasting improvement in functional capacity from class IV to class II, marked reduction of the left ventricular size, and improvement of the left ventricular ejection fraction from 15% to 38%., Interpretation: The results are promising for patients who, because of lack of donor hearts and age criteria, often cannot be offered heart, transplantation.

Background: Atrial flutter and atrial fibrillation are among the most common heart rhythm disturbances in the population, with an assumed prevalence of 1-2%. About 40,000-60,000 Norwegians endure such rhythm disorders, with an increasing occurrence in the elderly population., Material and Methods: Surface ECG remains the corner-stone for the clinical diagnosis. We describe the various mechanisms, clinical presentation, and diagnosis based on modern invasive electrophysiological methods of atrial flutter., Results: The available therapeutic modalities for conversion during episodes and prophylaxis with drugs, various pacing techniques, DC conversion and surgical therapy are discussed., Interpretation: Radiofrequency catheter ablation is the only available method to cure the patient in a gentle manner.

Background: The anatomical structure of atrial flutter is now well recognized, and treatment with radiofrequency catheter ablation (RFA) is established. Several recording and ablation techniques can be applied., Material and Methods: An increasing number of patients have been treated with RFA at the Arrhythmia Centre at Haukeland University Hospital over the last six years. During the two-year period 1999 and 2000, a total of 108 procedures were performed for atrial flutter in a total of 84 patients. A total of 543 RFA procedures for various forms of re-entry tachycardias were performed during the same period; hence, atrial flutter comprised about 20% of RFA procedures. Altogether 71 men and 14 women with a mean age of 57 +/- 12 years were treated. The mean history of atrial flutter had a duration of nine years, maximum 43 years with several hospital admissions, drug trials, overdrive pacing and DC conversion until they were ultimately cured with RFA., Results: The success rate during first time treatment was 96.5%. No serious complications were observed., Interpretation: RFA should be the treatment of first choice in patients with recurrent or incessant atrial flutter.

During electrophysiological investigation of 22 patients with VT or aborted sudden cardiac death, arterial and RV pressures were measured. The time courses of mean arterial pressure (MAP), RV pulse pressure (RVPP), RV pulse pressure integral (RVPPI), and maximum right ventricular dP/dt (RV dP/dtmax) were followed during the first 15 seconds after VT induction. Compared to basal (preinduction) conditions, the RVPPI decreased by 41+/-10% (mean +/- SD) after 10-15 seconds of VT in 11 patients with stable VT and by 75+/-8% in 11 patients with unstable VT (MAP < 60 mmHg 15 s after VT onset). RVPP decreased by 13+/-11% after 10-15 seconds of VT in the stable VT group and by 50+/-16% in the unstable VT group. For RV dP/dtmax, these decreases were 4+/-22% in the stable VT group and 37+/-24% in the unstable VT group. There was a good correlation between percent decrease in MAP and percent decrease in RVPPI, RVPP, and RV dP/dtmax at 5-10 seconds (r = 0.86, 0.81, and 0.73, respectively) and 10-15 seconds (r = 0.84, 0.82, and 0.69, respectively) after VT onset. There was hardly any overlap of distributions of the individual values with the RVPPI parameter between the two VT groups. Comparing and correlating the percent decrease in mean arterial pressure with the RVPPI, RVPP, and RV dP/dtmax during induced VT, RVPPI demonstrated the most significant and specific changes in discriminating stable from unstable rhythms. However, by comparing RVPPI and RVPP using the area under the receiver operating characteristic curves, there was no significant statistical difference between the two parameters. By integrating rate criteria, electrogram signal analysis, and RVPPI or RVPP as a hemodynamic criterion, detection and treatment algorithms could improve the performance of future implantable defibrillators and avoiding shocks in VTs that can be terminated by antitachycardia pacing.

Automatic atrial tachycardias often originate from the ostia of the pulmonary veins. P-wave morphology during tachycardia may indicate from which pulmonary vein the tachycardia originates. Two patients with pulmonary vein tachycardias demonstrating atypical P-wave morphology were investigated. One of the patients had a tachycardia with two different cycle lengths. P-wave morphology was evaluated in 12-lead ECGs from two patients with incessant atrial tachycardia, during tachycardia and sinus rhythm. Their tachycardias were successfully ablated at the mouth of the right upper pulmonary vein. Previous studies have demonstrated a positive or negative P-wave configuration in lead aVL originating from this area and a change from a biphasic P-wave in V1 during sinus rhythm to a positive P-wave configuration during tachycardia. Neither of our two patients had such a change in lead V1. One our patients had two tachycardias with different cycle lengths originating from the same area. It is concluded that if an atrial tachycardia with P-wave morphology resembling that of sinus rhythm cannot be located to the right atrium, its origin may be the right upper pulmonary vein.

With the aid of an algorithm for automatic pacing threshold (T) measurement in the atrium and ventricle, downloadable into implanted Thera pacemakers (Medtronic Inc.), we studied T evolution during lead maturation, T variation during activities of daily living, and various types of beat-to-beat T variations in three tined bipolar leads: 5.6-mm2 steroid-eluting (Medtronic Inc. models 4524 atrial-J [n = 8] and 4024 ventricular [n = 8]), 1.2-mm2 steroid-eluting (Medtronic Inc. models 5534 atrial-J [n = 9] and 5034 ventricular [n = 9]), and 8-mm2 without steroid (Intermedics models 432-04 atrial-J [n = 7] and 430-10 ventricular [n = 7]). The leads were implanted in 24 consecutive patients with intact AV conduction (required by the algorithm) and followed for up to 13-25 months after implantation. Since the algorithm determined pulse width Ts at different amplitudes that, depending upon T level, could range from 0.5 to 5.0 V, we invented a methodology for conversion of pulse width Ts into voltage Ts at 0.5 ms, to pool and present T data on a universal scale. Frequent, high resolution T measurements revealed details on the lead maturation process that we divided into three stages: initial T subsiding, first wave of T peaking, and a new, quicker or slower, T rise. Although there were notable differences in duration and magnitude of T peaking on the individual basis, differences between the three lead types and between the atrium and ventricle were demonstrable. The 1.2-mm2 leads exhibited less T peaking than their predecessors 5.6-mm2 leads and excellent positional stability, whereas 8-mm2 leads demonstrated the most intensive T peaking and highest mean chronic T values. T changes during activities of daily living showed some tendencies-higher T during night and lower T during exercise--yet with a number of exceptions. The overall magnitude of daily T fluctuations was < 0.2 V in all but one lead, and 50% daily voltage safety margin would be sufficient. A 100% voltage safety margin may be inadequate for a 1-year period during the chronic phase (after 6 months of implantation). A scheme for calculation of pulse width safety margins equivalent to voltage safety margins is given. Some leads can exhibit very large beat-to-beat T variations before, during, and after T peaking, and prospective algorithms for automatic T measurement should verify T values through more than 1-2 captured beats to obviate a great underestimation of the T providing consistent capture. T dependence upon pacing rate was negligible. Consistent-capture hysteresis may, in conjunction with lead instability, be as much as 0.25 V. Therefore, it is better to use an incremental approach from below to T level during automatic T measurements.

A new generation of tined steroid-eluting leads featuring 1.2-mm2 distal electrodes (CapSure Z, Medtronic Inc., Minneapolis MN, USA) has the potential to reduce battery current drain and enhance pulse generator longevity by means of high pacing impedance and low pacing threshold. Forty patients aged 50-87 years (mean 72.4 years) were implanted with 33 ventricular (models 4033 and 5034) and 30 atrial-J (models 4533 and 5534) leads with 1.2-mm2 electrodes. Low pacing outputs, mainly in the range from 1 V/0.20 ms to 1.6 V/0.36 ms with > or = 3:1 pulse width safety margins (PWSM) applied, were instituted at 3-6 months of implantation and adjusted at subsequent follow-up controls according to changes in thresholds. Cumulative follow-up period of low outputs was 1,512 months (24 months per lead, range 9-36 months), which involved 3.43 follow-up controls per lead (range 2-5). During follow-up, pulse width thresholds (PWTs) at the used amplitudes did not change in 55.5% of the leads; PWTs increased by < or = 100% in 36.5%, by 101%-200% in 1.6%, and by > 200% in 6.3% of the leads. Changes in PWT that would apparently exceed 3:1 PWSM over a 1-year period occurred in one atrial lead where even the nominal 3.5 V/0.4-ms output would not be effective and in one ventricular lead in the aftermath of an acute myocardial infarction (300% PWT rise at 1.6 V). Based on the present observations, pacemaker dependent patients require > or = 4:1 PWSM and other patients > or = 3:1 PWSM with output pulse widths < or = 0.60 ms and annual pacemaker clinic visits. Calculated battery current drain and anticipated longevity associated with a variety of pacing outputs and impedances are provided, compared, and discussed. Correlation between acute and chronic pacing impedances and pacing thresholds was weak, implying that a systematic intraoperative pacing site optimization cannot contribute significantly to the extension of average battery longevity.

Pacing threshold is affected by many factors. A pacing system able to confirm capture at each beat and automatically adjust its output close to the actual pacing threshold is highly desirable. This study evaluates the safety and efficacy of the Autocapture function of the Pacesetter Microny SR+. One hundred thirteen patients were recruited from 16 centers in 7 European countries and followed up for 1 year. All pacemakers were implanted with Pacesetter's low polarization, bipolar leads. The key feature of Autocapture is the immediate delivery of a 4.5 V safety backup pulse 62.5 ms after any ineffective ongoing low output pulse. Holter recordings confirmed total reliability of this feature without any exit block. The measured evoked response (ER) signal was stable over time. Acute and chronic pacing thresholds measured by VARIO and Autocapture tests correlated (r > 0.79) over the period of the study. The incidence of backup pulses was 1.1% during pacing. With Autocapture programmed ON, the overall total current consumption was 4.1 microA for VVI and 5.0 microA for VVIR pacing. This study proved that the Autocapture safely and reliably regulates the pacemaker's output according to the prevailing threshold thus providing maximum patient safety and prolonging service life.

The aim of the study was to investigate pacing impedance (PI) behavior in ambulatory patients. Eighteen atrial and 18 ventricular tined steroid eluting leads with 1.2-mm2 and 5.6-mm2 electrodes were implanted in 20 patients. At 9-27 months after implantation PI was measured automatically by means of additional algorithms downloaded via telemetry links into implanted Thera pulse generators. PI was determined based on the voltage drop on the output capacitor during the 5 V-1 ms pacing impulse, at the programmable sampling rates from 1 second to 30 minutes. The study examined in particular: (1) PI trends and variations associated with different breathing patterns, body postures, provocative maneuvers, bike exercise, and during 24 hours; (2) impact of pacing rate and AV-delay on PI; (3) correlation between PI variability and pacing threshold, lead configuration, absolute PI value, age, gender, disease, and cardiac chamber. The most important findings were: (1) large PI variations of up to 450 omega were observed in properly functioning leads, (2) PI variability exhibited a weak negative correlation with pacing thresholds as if electrode positional stability was not a major factor underlying PI variations, (3) unipolar and bipolar PI variations were equivalent to each other (correlation factor = 0.93) implying that PI was mostly dependent on the circumstances around the lead tip.

We have developed an algorithmic method for automatic determination of stimulation thresholds in both cardiac chambers in patients with intact atrioventricular (AV) conduction. The algorithm utilizes ventricular sensing, may be used with any type of pacing leads, and may be downloaded via telemetry links into already implanted dual-chamber Thera pacemakers. Thresholds are determined with 0.5 V amplitude and 0.06 ms pulse-width resolution in unipolar, bipolar, or both lead configurations, with a programmable sampling interval from 2 minutes to 48 hours. Measured values are stored in the pacemaker memory for later retrieval and do not influence permanent output settings. The algorithm was intended to gather information on continuous behavior of stimulation thresholds, which is important in the formation of strategies for programming pacemaker outputs. Clinical performance of the algorithm was evaluated in eight patients who received bipolar tined steroid-eluting leads and were observed for a mean of 5.1 months. Patient safety was not compromised by the algorithm, except for the possibility of pacing during the physiologic refractory period. Methods for discrimination of incorrect data points were developed and incorrect values were discarded. Fine resolution threshold measurements collected during this study indicated that: (1) there were great differences in magnitude of threshold peaking in different patients; (2) the initial intensive threshold peaking was usually followed by another less intensive but longer-lasting wave of threshold peaking; (3) the pattern of tissue reaction in the atrium appeared different from that in the ventricle; and (4) threshold peaking in the bipolar lead configuration was greater than in the unipolar configuration. The algorithm proved to be useful in studying ambulatory thresholds.

A VDD pacing system with bipolar single-pass leads, were implanted in 36 consecutive patients (average age 72 +/- 2 years) with high degree atrioventricular block and normal sinus node function. At implant the atrial signal amplitude was 2.6 +/- 0.2 mV measured by a pacing system analyser (PSA), 1.8 +/- 0.1 mV measured peak-to-peak from the telemetered calibrated electrogram, and 1.3 +/- 0.1 mV measured from the sensing threshold. At one month follow-up the peak-to-peak amplitudes (mV) of the telemetered atrial electrograms were not significantly different measured continuously during resting supine with quiet breathing (1.4 +/- 0.1), sitting (1.6 +/- 0.2), standing (1.5 +/- 0.1), arm swinging (1.4 +/- 0.2), hyperventilation (1.3 +/- 0.1), Valsalva manoeuvre (1.4 +/- 0.1), and treadmill exercise (1.9 +/- 0.6). The telemetered atrial electrogram amplitude and the atrial sensing threshold varied between 1.2 +/- 0.09 mV and 1.8 +/- 0.1 mV, and between 0.95 +/- 0.07 mV and 1.3 +/- 0.01 mV, respectively at 0.5, 1, 3, 6 and 12 months follow-up, but the changes were statistically non-significant. The Event Summary showed sensing of 98% to 99% of the atrial events at the different follow-up periods.

To raise pacing impedance and reduce battery current drain, new tined steroid-eluting leads were developed with 1.2-mm2 hemispherical electrodes, instead of conventional 5-8 mm2. Twenty-two unipolar J-shaped atrial leads and 25 unipolar ventricular leads (models 4533 and 4033, respectively) were implanted in 33 consecutive patients and followed for a mean of 25 months (range 18-29). Handling characteristics of atrial leads were found favorable. The leads slipped easily into the right atrial appendage and were easy to position. Handling characteristics of ventricular leads were satisfying, but more efforts had to be applied to cross the tricuspid valve. Special care was taken to avoid perforation of the myocardium due to the small lead tip. Following implantation, four ventricular and one atrial lead exhibited instability of pacing thresholds that resolved spontaneously within 1-3 days of implantation. Except for this, no lead malfunctioned. The reoperation rate was zero. The mean electrogram amplitudes of 15 mV (ventricle) and 4 mV (atrium), and the mean chronic pacing threshold of 0.085 ms at 1.6 V (app. 0.43 V at 0.5 ms) were comparable with the best values seen in the literature on passive fixation leads. The rest of the electrophysiological parameters were enhanced: mean pacing impedances were 984 omega (acute) and 900 Q (chronic), mean slew rates 3.26 V/s (ventricle) and 1.75 V/s (atrium), mean acute voltage threshold at 0.5 ms was 0.25 V, mean current and energy thresholds calculated at 0.5 ms were 260 microA and 32 nJ (acute) and 478 microA and 103 nJ (chronic). The electrical characteristics of these leads provide for increased pacemaker longevity in combination with substantial safety margins for pacing and sensing.

The main disadvantages of bipolar pacing leads have traditionally been related to their relative thickness and stiffness compared to unipolar leads. In a new "drawn filled tube" plus "coated wire" technology, each conductor strand is composed of MP35N tubing filled with silver core and coated with a thin ETFE polymer insulation material. This and parallel winding of single anode and cathode conductors into a single bifilar coil resulted in a bipolar lead (ThinLine, Intermedics) with a body diameter and flexibility similar to unipolar leads. The lead is tined, polyurethane, with the cathode and the anode made of iridium-oxide-coated titanium (IROX). The slotted 8-mm2 cathode tip is coated with polyethylene glycol, a blood soluble material. We present the clinical evaluation results from four pacemaker clinics, where 47 leads (23 atrial-J model 432-04 and 24 ventricular model 430-10) were implanted in 25 patients and followed for up to 2 years. The lead handling characteristics were found to be very satisfactory. Electrical parameters of the leads were measured at implant and noninvasively on postoperative days 1, 2, 21, 42, and months 3, 6, 12, and 24. Mean chronic pulse width thresholds at 2.5 V were 0.14 +/- 0.05 ms in the atrium and 0.10 +/- 0.02 ms in the ventricle, pacing impedances 443 +/- 104 omega and 520 +/- 241 omega, while median electrogram amplitudes were > or = 3.5 mV and > or = 7 mV, respectively. Pacing impedances and thresholds were found to be slightly but statistically significantly higher in unipolar than in bipolar configuration--the findings are explainable by the lead construction. One of 47 leads failed 3 weeks after implant; the conductors were short circuited due to an error during the manufacturing process. We conclude that the new lead thus far has demonstrated appropriate mechanical and electrical characteristics.