Search PubMed⌕ Search

Biomedical subjects

J Neuzner

Publications and source records attributed to J Neuzner.

At least 55 records · Page 3Linked to original sources
PubMed1997

Effect of the addition of an abdominal hot can cardioverter/defibrillator pulse generator on the defibrillation energy requirements in a single-lead endocardial defibrillation system.

AIMS: The effects of a cardioverter/defibrillator system with an electrically active generator can, applied without recourse to thoracotomy, have not been investigated in the abdominal position in humans. The purpose of this acute clinical study was to evaluate the defibrillation efficacy of an abdominally positioned hot can electrode in connection with a single lead endocardial defibrillation system. PATIENTS AND METHODS: Thirty consecutive patients undergoing implantation of a cardioverter/defibrillator or pulse generator replacement were enrolled in this study Each patient received an integrated, tripolar single-lead system. This was tested using an asymmetrical biphasic defibrillation waveform with constant energy delivery. Defibrillation energy, peak voltage, peak current and impedance were compared between two electrode configurations: (A) in this configuration the distal right ventricular coil was negative and the proximal coil positive; (B) in this configuration the distal right ventricular coil was negative and the proximal coil and the abdominal hot can (65 ccm), as common anode, were positive. Defibrillation threshold testing started at 15 J with stepwise energy reduction (10 J, 8 J, 5 J and 3 J) until defibrillation was ineffective. RESULTS: Compared to the single-lead configuration, the abdominal hot can configuration revealed at 17.5% reduction in defibrillation energy requirements (8.6 J +/- 4.3 J vs 10.43 J +/- 3.9 J; P = 0.041), a 15.7% reduction in peak voltage (308.6 V +/- 63 V vs 365.3 V +/- 68 V; P = 0.003), and a 21.6% reduction in impedance (41.1 omega +/- 6.3 omega vs 52.4 omega +/- 6.6 omega; P < 0.001). Peak current showed a significant increase during hot can testing of 8.2% (7.2 A +/- 1.8 A vs 7.8 A +/- 2.2 A; P = 0.16). CONCLUSION: An abdominally placed hot can pulse generator lowered defibrillation energy requirements in patients with an endocardial defibrillation lead system.

Abdominal Muscles↗
PubMed1997

Low-energy transvenous cardioversion of atrial fibrillation using a single atrial lead system.

INTRODUCTION: Clinical studies have shown that electrical conversion of atrial fibrillation (AF) is feasible with transvenous catheter electrodes at low energies. We developed a single atrial lead system that allows atrial pacing, sensing, and defibrillation to improve and facilitate this new therapeutic option. METHODS AND RESULTS: The lead consists of a tripolar sensing, pacing, and defibrillation system. Two defibrillation coil electrodes are positioned on a stylet-guided lead. A ring electrode located between the two coils serves as the cathode for atrial sensing and pacing. We used this lead to cardiovert patients with acute or chronic AF. The distal coil was positioned in the coronary sinus, and the proximal coil and the ring electrode in the right atrium. R wave synchronized biphasic shocks were delivered between the two coils. Atrial signal detection and pacing were performed using the proximal coil and the ring electrode. Eight patients with acute AF (38 +/- 9 min) and eight patients with chronic AF (6.6 +/- 5 months) were included. The fluoroscopy time for lead placement was 3.5 +/- 4.3 minutes. The atrial defibrillation threshold was 2.0 +/- 1.4 J for patients with acute AF and 9.2 +/- 5.9 J for patients with chronic AF (P < 0.01). The signal amplitude detected was 1.7 +/- 1.1 mV during AF and 4.0 +/- 2.9 mV after restoration of sinus rhythm (P < 0.001). Atrial pacing was feasible at a threshold of 4.4 +/- 3.3 V (0.5-msec pulse width). CONCLUSIONS: Atrial signal detection, atrial pacing, and low-energy atrial defibrillation using this single atrial lead system is feasible in various clinical settings. This system might lead to a simpler, less invasive approach for internal atrial cardioversion.

Acute Disease↗
PubMed1996

Safety margins: lessons from the Low Energy Endotak Trial (LEET).

The Low Energy Endotak Trial (LEET) was designed as a prospective, randomized, multicenter study to evaluate the efficacy and safety in nonthoracotomy cardioverter-defibrillator therapy with lower defibrillation energies compared to the conventional programming with devices set at maximum output. Between December 1993 and January 1996, 172 consecutive patients, undergoing implantation of a biphasic cardioverter-defibrillator with a single endocardial defibrillation lead system, were screened for study enrollment in 4 European study centers. Study inclusion criteria were defined as documented ventricular fibrillation, polymorphic ventricular tachycardia, or fast, hemodynamically unstable ventricular tachycardia, unresponsive to antitachycardia pacing and an augmented defibrillation threshold (DFT+) < or = 15 Joules (J). Patients presenting slow, pace-terminable ventricular tachycardias were excluded. Patients were randomized into 2 study arms: (1) test group patients: the first-shock energy of the implanted devices was programmed at 2 X DFT+, the second to fifth shocks at maximum output (34 J); (2) control group patients: all shocks were programmed at 34 J. Ventricular fibrillation (VF) conversion tests (first shock energy DFT+; second shock 2 X DFT+) were performed in test group patients intraoperatively, during predischarge test, and after 12 months follow-up. In the control group patients, the arrhythmia conversion tests were performed with maximum device output (34 J). Spontaneous tachyarrhythmia episodes were classified by stored intracardiac electrogram analysis, and conversion rates were compared between the 2 study groups. Of the 172 screened patients, 162 (94%) met the inclusion criteria and were enrolled in the study. The mean DFT+ was 9.6 +/- 3.2 J in the test group and 10.0 +/- 3.5 J in the control group. The success rate for the test group for a repeated arrhythmia conversion test at DFT + was 84.4% (157 of 186 induced VF episodes); the cumulative success rate for the first and the second shocks was 99.5% (185 of 186 induced episodes). In the control group, the first-shock conversion rate at 34 J was 98.8% (158 of 160 induced episodes). During a mean follow-up of 10 +/- 7 months, the first-shock conversion rate for spontaneous arrhythmia episodes was 98.5% (65 of 66 episodes) in the test group patients and 92% (69 of 75 episodes) in control group patients (p>0.05). Analyzing the pooled data of spontaneous and induced arrhythmia episodes, there were no differences regarding the first shock conversion rate between the 2 groups (test group: 98.4%; control group: 96.6%, p>0.05). The overall mortality was 3%, equally distributed in both groups. The preliminary results of this study suggest that over a 1-year period, the "2 X DFT+" safety margin was equally effective as the margin provided by a 34-J device for conversion of induced and spontaneous tachyarrhythmia episodes.

Defibrillators, Implantable↗
PubMed1996

Three-year experience with a stylet for lead extraction: a multicenter study.

INTRODUCTION: The extraction of chronically implanted and infected pacemaker and defibrillator leads is an important issue. This article describes the experience gathered between 1990 and 1994 by seven European centers regarding a locking stylet that is uniformly applicable for a wide variety of internal pacing coil diameters. This interventional locking stylet for lead extraction has an outer diameter of 0.4 mm (0.016 inches). The stylet consists of a hollow shaft in which an inner traction wire is embedded. At the tip of the inner traction wire an anchoring mechanism, which can be opened by retraction, is applied. Removal attempts were made for 150 leads, 110 in ventricular and 40 in atrial positions. RESULTS: Complete removal was possible in 122 cases (81%). Partial removal was possible in 18 cases (12%). Failure to remove the lead with the extraction stylet was experienced in 10 cases (7%). In seven patients, the leads were removed by cardiothoracic surgery; 3 defective leads were left in place. There were no serious complications associated with the procedure. None of the patients died. CONCLUSION: The experience with this extraction stylet for lead removal has shown good results. Despite a low complication rate thus far, each case for lead removal should be judged on the individual basis of benefit-to-risk ratio.

Aged↗
PubMed1996

[Catheter ablation in supraventricular tachycardia].

The first report about successful radio frequency ablation of a right-posterior-septal accessory pathway appeared in 1986. Since then, the technology of both guidable ablation catheters and radio frequency generators has been considerably improved in an initially clinical-experimental phase. At the same time, electrophysiologists were equally able to enlarge their knowledge in the field of signal characteristics of arrhythmogenic substrates. This included the discovery of action potentials of accessory pathways (preexcitation syndromes), the location of fast and slow AV node conduction (AV nodal reentrant tachycardia, AVNRT), the functional importance of the anatomical isthmus between the os of the coronary sinus, the tricuspid valve and the inferior caval vein (atrial flutter). Mapping techniques such as transient and concealed entrainment became, among others, significant tools in finding the best localization for radio frequency catheter ablation. Thus, technical development and the increased knowledge of clinical electrophysiologists resulted in firmly establishing the procedure of catheter ablation as the method of first choice in the curative treatment of supraventricular tachycardias in a potential collective of about 5 per mill of the normal population (without atrial fibrillation). Supraventricular tachycardias with a reentry mechanism in the broadest sense (> 95% of all pts. with SVT) and those with focal automaticity (< 5%) occur as atrial fibrillation or atrial flutter in about 60% of all pts. (4-6 per mill of the normal population). Manifestation of the remaining reentrant tachycardias is mainly in the form of AVNRT (retrograde conduction via the fast pathway > 90% versus uncommon type < 10%). AV reentry via accessory pathways is found in about 15%, with orthodromic conduction via the AV node (> 90%). Atrial reentrant tachycardias are rather rare (with the exception of atrial fibrillation/flutter). The literature suggests medical therapy to be successful in about 60% of these patients. Those patients who are presently proposed to receive radio frequency catheter ablation usually continue to be symptomatic despite pharmacological therapy and/or have a potential risk for sudden cardiac death due to atrial fibrillation in WPW syndrome, or rate-dependent hemodynamic compromise secondary to cardiac disease. Since 1989-1995, our laboratory had a > 93% success rate in treating 466 patients with AV reentrant tachycardia via accessory AV pathways, and in treating 398 patients with AV nodal reentrant tachycardias. Forty patients with atrial flutter and 16 patients with different atrial tachycardias (14 with focal origin, 2 reentries) were free from tachycardia in 80% after ablation. This corresponds to the literature published by other centers. Some abstracts and articles suggest that ablation of atrial fibrillation may be possible. However, there is still a lack of basic experience with view to mapping procedures and, thus, insufficient knowledge of the electrophysiological pathophysiology with regard to different cardiac diseases. As a consequence, this procedure, despite first documentation of both successful treatment and severe complications occurring in catheter ablation of atrial fibrillation, as based on the experience of the MAZE procedure, is applied in humans, at the time being, in a purely experimental setting. The only exception relates to the ablation of the AV node at accurate diagnosis for pacemaker implantation (VVIR; DDDR switch mode) which has become part of routine therapy, although, of course, atrial fibrillation itself or necessary anticoagulation cannot be abolished. Thus, our center shows a success rate of 98% in treating 117 patients by this method. First promising reports are available describing the attempt of AV node modification in the posterior nodal part with the goal of reducing the ventricular rate in atrial fibrillation.

Atrial Fibrillation↗
PubMed1995

Safety of antitachycardia pacing in patients with implantable cardioverter defibrillators and severely depressed left ventricular function.

The purpose of this study was to investigate the efficacy and safety of antitachycardia pacing (ATP) in third-generation implantable cardioverter defibrillators (ICDs) for terminating spontaneously occurring ventricular tachycardias (VTs) in patients with severely depressed left ventricular (LV) function. Ninety-one patients with active ATP were followed for 16 +/- 13 months. During this period, 775 VT episodes occurring in 36 patients were treated by ATP. The patients were divided into two groups according to their LV ejection fraction (LVEF): group A with LVEF < or = 30% (n = 20), and group B with LVEF > 30% (n = 16). There were no differences between both groups in age, gender, underlying heart disease, indication for ICD therapy, or drug therapy. The VT rates were comparable (group A: 183 +/- 16 beats/min; group B: 180 +/- 21 beats/min; P = NS). Eighty-three percent of all episodes (n = 332) in group A and 93% of the VTs (n = 443) in group B were ATP terminated (P < 0.01). Ten percent of VTs in group A were accelerated by ATP into the ventricular fibrillation zone versus 2% in group B (P < 0.01). The individual termination rate and acceleration rate per patient were comparable in both groups. All VT episodes unresponsive to ATP were converted by backup shocks. The efficacy of first-shock therapy was similar in both groups (group A: 89%; group B: 97%; P = NS). The proportion of patients who needed at least one backup shock for unsuccessful ATP was comparable in both groups (group A: 65%; group B: 56%; P = NS).(ABSTRACT TRUNCATED AT 250 WORDS)

Defibrillators, Implantable↗
PubMed1995

Programmable VT detection enhancements in implantable cardioverter defibrillator therapy.

This report describes the distribution of automatically measured values of enhanced arrhythmia detection parameters such as "rate stability" and "rate onset" in various forms of spontaneous arrhythmia episodes in patients treated with a new, third-generation, tiered therapy implantable cardioverter defibrillator (ICD). The study population consisted of 27 patients who received the Ventak PRxII cardioverter defibrillator, which provides extensive diagnostic options such as electrogram storage capabilities, and the ability to store measured values of additional arrhythmia detection parameters such as rate stability and rate onset during spontaneous arrhythmia episodes. During a follow-up period of 11.1 +/- 5.2 months, this device detected 264 arrhythmia episodes. The analysis of stored electrograms revealed 13 episodes of sinus tachycardia, 52 episodes of atrial tachyarrhythmias, and 201 episodes of monomorphic ventricular tachycardias (VTs). The mean measured values of rate stability and rate onset were: 2.2 +/- 0.9 msec, 0% in sinus tachycardias; 41.0 +/- 24.1 msec, 8.5% +/- 9.5% in atrial tachyarrhythmias; and 7.8 +/- 6.0 msec, 30.6% +/- 12.1% in monomorphic VTs. There was a wide zone of overlapping measured values for rate stability and rate onset in ventricular and nonventricular rhythms. No episode of VT showed a measured rate stability criterion > 35 msec. The subanalysis of arrhythmia episodes presenting with a heart rate < 160 beats/min revealed no episode of VT with a rate stability value > 24 msec. The calculated, rate dependent specificities for these programmed rate stability parameters in detecting VTs were 46.2% and 81.8%, respectively. The analysis of the rate onset algorithm revealed no comparable relationship between sensitivity and specificity in the detection of VTs.(ABSTRACT TRUNCATED AT 250 WORDS)

Arrhythmias, Cardiac↗
PubMed1995

[Implantable cardioverter/defibrillators with endocardial electrode systems: long-term stability of the defibrillator's effectiveness].

The vast majority of cardioverter/defibrillator implantations is performed with non-thoracotomy lead systems. The temporal stability of defibrillation energy requirements is well established for epicardial defibrillation lead systems, but not for non-thoracotomy lead systems. The defibrillation energy requirements were reevaluated in 30 patients, 13 months after implantation of a cardioverter/defibrillator with a non-thoracotomy lead system. The study patients group consisted of 4 females and 26 males; mean age 60.1 +/- 10.5 years; mean left ventricular ejection fraction was 32.2 +/- 6.2%. Coronary artery disease was the underlying heart disease in 12 patients, dilated cardiomyopathy in 15 patients, and artificial valve replacement in 3 patients. There was no clinical progression in the underlying heart disease between defibrillator implantation and control measurements; left ventricular ejection fraction was unchanged (32.2 +/- 6.2 vs. 32.3 +/- 6.4%); no changes occurred regarding patients' clinical status. In 27/30 patients the defibrillation threshold at defibrillator implantation could be reconfirmed at control measurements. The mean defibrillation energy/requirements at implantation (14.4 +/- 4.8 Joules) were unchanged compared to control measurements (14.8 +/- 4.6 Joules). A temporal stability of defibrillation energy requirements could be established for the monophasic (n = 15; 18.0 +/- 4 vs. 18.1 +/- 3.4 Joules) as well as for the biphasic waveform (n = 15; 11.1 +/- 3.4 vs. 11.5 +/- 2.9 Joules). The results of intraoperative defibrillation thresholds measurements are predictive for chronic defibrillation energy requirements in patients with non-thoracotomy lead systems.

Aged↗
PubMed1995

[Incidence of intervention-related heart valve lesions after high-frequency catheter ablation of the left-side accessory atrioventricular conduction pathways].

The aim of this study was to evaluate the incidence of valve lesions after radiofrequency catheter ablation of accessory atrioventricular pathways using the retrograde transaortic approach. Patients who presented no preexisting detectable valve lesion prior to catheter ablation and who underwent a comparable echocardiographic examination prior to and after catheter ablation were included for data analysis. From January 1991 until May 1993, 113 patients underwent radiofrequency catheter ablation of a left-sided accessory atrioventricular pathways at our institution. Fifty-nine patients were included in this study. Five patients (8.4%) developed new valve lesions after radiofrequency catheter ablation. There were two cases (3.3%) of aortic regurgitation and four cases (6.7%) of mitral regurgitation. In the majority of cases only mild valve regurgitation was detected. A hemodynamically significant valve lesion was observed in a single patient (1.6%). We speculate that the new onset of valve lesions is mostly due to catheter manipulations rather than due to tissue injury related to radiofrequency current application. Echocardiographic examinations prior to and after radiofrequency catheter ablation of accessory pathways may contribute to a further reduction in intervention-related complications.

Adult↗
PubMed1994

[The clinical significance of the ajmaline test in the noninvasive diagnosis of the Wolff-Parkinson-White syndrome].

A knowledge of electrophysiological parameters of accessory atrioventricular conduction pathways, such as effective refractory time and high conduction capacity in atrial fibrillation, make it possible to detect those patients who are at risk of life-threatening ventricular tachyarrhythmias. One criterion to identify these electrophysiological parameters is persistent pre-excitation after intravenous administration of ajmaline in Wolff-Parkinson-White (WPW) syndrome. Sensitivity and specificity of the ajmaline test in detecting patients at risk of life-threatening ventricular tachyarrhythmias were evaluated in 58 consecutive patients (22 females, 36 males; mean age 40.2 +/- 13 years) with the WPW syndrome. Pre-excitation was blocked after ajmaline in 43 patients (74%), pre-excitation persisting in 15 (26%). In 26 of the 43 patients with blocked pre-excitation the ajmaline test indicated short effective refractory time (< 270 ms) of the accessory pathway, and a high conduction capacity in 19 (minimal pre-excitation R-R interval during atrial fibrillation of < 250 ms). Sensitivity of the ajmaline test in the detection of a short refractory time was 33.3%, specificity 89.4%, while the corresponding values were 40.6% and 92.3% for the detection of accessory pathways with high conduction capacity in atrial fibrillation. These data show that the ajmaline test is not useful for estimating the electrophysiological characteristics of the accessory pathways. It is thus of only subordinate diagnostic value in predicting how much patients with the WPW syndrome are at risk of serious ventricular tachyarrhythmias.

Adult↗
PubMed1994

Effect of biphasic waveform pulse on endocardial defibrillation efficacy in humans.

Several clinical studies have proved increased defibrillation efficacy for implantable cardioverter defibrillators with biphasic pulse waveforms compared to monophasic pulse waveforms. This difference in defibrillation efficacy depends on the type of defibrillation lead system used. The influence of biphasic defibrillation pulse waveforms on the defibrillation efficacy of purely endocardial defibrillation lead systems has not yet been sufficiently examined, we, therefore studied 30 consecutive patients with drug refractory ventricular tachyarrhythmias during the implantation of a cardioverter defibrillator. After implanting an endocardial "integrated" sensing/defibrillation lead we performed a prospective randomized comparison of the defibrillation efficacy of monophasic and biphasic defibrillation waveform pulses. For endocardial defibrillation with the biphasic waveform the mean defibrillation threshold was 12.5 +/- 4.9 joules and for the monophasic waveform 22.2 +/- 5.6 joules (P < 0.0001). There was a decrease in the required defibrillation energy of biphasic defibrillation in 29/30 patients. Thus considering purely endocardial defibrillation a statistically significant and clinically relevant increase in defibrillation efficacy can be demonstrated for biphasic defibrillation waveform pulses.

Defibrillators, Implantable↗
PubMed1994

Clinical experience with a new cardioverter defibrillator capable of biphasic waveform pulse and enhanced data storage: results of a prospective multicenter study. European Ventak P2 Investigator Group.

A recently introduced cardioverter defibrillator was implanted in 162 patients with refractory ventricular tachyarrhythmias and/or aborted sudden cardiac death. The new device is capable of delivering monophasic and biphasic defibrillation waveform pulses, arrhythmia detection, and therapy in two independently programmable zones, antibradycardia and postshock pacing. Additionally, the device enhanced data logs by storing intracardiac "far-field" electrograms of spontaneous arrhythmic episodes. One hundred sixty-two patients (mean age 55.5 years; mean left ventricular ejection fraction 36%) were enrolled in this multicenter investigation; coronary artery disease was the primary cardiac disease in 63.6% of the patients, idiopathic cardiomyopathy in 23.8%. Ventricular fibrillation was present in 49.7% of the patients; 29.3% of the patients experienced ventricular fibrillation and ventricular tachycardia; monomorphic ventricular tachycardia alone was present in 19.1% of the patients. In 26 patients the device was implanted with standard epicardial defibrillation leads (mean defibrillation threshold 11.5 +/- 3.7 J). One hundred thirty-nine patients underwent testing for implantation of a nonthoracotomy system and in 136 (98%), a nonthoracotomy system could be implanted. Defibrillation thresholds with a biphasic waveform (mean 10.2 +/- 4.3 J) were lower than with a monophasic waveform (mean 17.4 +/- 5.7 J). Two patients (1.2%) died perioperatively (< 30 days). During study time period follow-up, there were 338 device discharges in 49 patients. Analysis of stored electrograms classified 25% of discharges as inappropriate and due to supraventricular tachyarrhythmias. At a mean follow-up of 10.8 months, cumulative survival from sudden cardiac death was 98.8%, and survival from all-cause mortality was 96.3%. This study demonstrates the effectiveness of a new implantable cardioverter defibrillator in preventing arrhythmic death and the superior defibrillation efficacy of biphasic waveform pulses, which results in a higher implantation rate of nonthoracotomy systems, as well as the accurate arrhythmia classification made possible by the stored electrograms.

Adolescent↗
PubMed1994

Radiofrequency catheter ablation of a concealed accessory atrioventricular pathway after heart transplantation.

Three months after orthotopic cardiac transplantation, a 46-year-old man developed paroxysmal supraventricular tachycardia. Electrophysiological investigation of the arrhythmia led to the diagnosis of an atrioventricular reentrant tachycardia involving a left lateral concealed accessory pathway. When antiarrhythmic drugs failed to suppress the arrhythmia, radiofrequency catheter ablation of the accessory pathway was performed without complication.

Atrioventricular Node↗
PubMed1994

[Subtypes of muscarinic receptors--aspects of their physiologic significance for controlling heart rate in the human].

The cDNAs for five different muscarinic cholinoceptors have been cloned. The biochemical and physiological relevance of the m1, m2 and m3 receptors is understood in many aspects. The pharmacological defined M1, M2 and M3 related to antagonists binding studies closely correspond with those cloned. We compared effects of atropine and of the subtype selective M-cholinoceptor antagonists pirenzepine and AF-DX 116 in humans. Dose- or time-response curves have been established for heart rate. Plasma samples were drawn in parallel with the effect measurements and analysed for drug concentrations. Subtype-selective radioceptor assays of the samples served to estimate the respective receptor occupancy in vivo. After low dosis of pirenzepine (M1-selective blockade) a negative chronotropic effect on heart rate could be observed. After high doses of pirenzepine or atropine (M-unselective blockade) the wellknown tachycardia appeared in parallel with occupancy of both the M2 and M3 subtypes. AF-DX 116 induced a tachycardia without a decrease of salivary flow in agreement with its selectivity profile (M2 > M1 > M3). Gastric emptying was only slightly inhibited by AF-DX 116 but nearly completely by a very high dose of pirenzepine blocking M1-, M2- and M3-cholinoceptors. The negative chronotropic effect on heart rate of a low dose of pirenzepine (M1 selective) was multi-folded by pretreatment with isoprenaline but disappeared during bicycle exercise. The implications of the functional M cholinoceptor heterogeneity in humans revealed by antagonists are discussed according to its possible importance for the control of autonomous nerve system.

Atropine↗