[Indications for implantable cardioverter-defibrillator].
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Clinical Trials as Topic↗
Biomedical subjects
M Niehaus
Publications and source records attributed to M Niehaus.
Interference of two common European digital cellular phones with implantable cardioverter-defibrillators.
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Arrhythmias, Cardiac↗
Atrial reentrant tachycardia after surgery for congenital heart disease: endocardial mapping and radiofrequency catheter ablation using a novel, noncontact mapping system.
BACKGROUND: The purpose of the present study was to determine the role of a novel, noncontact mapping system for assessing a variety of atrial reentrant tachycardias (ART) in patients after the surgical correction of congenital heart disease. METHODS AND RESULTS: In 14 patients, an electrophysiological study using the Ensite 3000 system was performed to assess ARTs resistant to medical treatment. Sixteen different forms of ART were inducible in the 14 patients studied. The reentrant circuit of all ARTs could be characterized and localized with respect to anatomic landmarks such as atriotomy scars, intraatrial patches/baffles, and cardiac structures. In 15 of the 16 ARTs (in 13 of the 14 patients), a target area of the reentrant circuit for radiofrequency current application (ie, an area of conduction between 2 anatomical obstacles such as surgical barriers and cardiac structures of electrical isolation) could be localized within the systemic venous atrium. Nine patients exhibited macroreentry, and 4 showed microreentry. In 12 patients, ART could be terminated by creating linear radiofrequency current lesions (75 degrees C, 180 to 390 s). Completeness of linear lesions after radiofrequency current delivery was proven by analyzing color-coded isopotential maps of atrial activation while applying atrial pacing techniques. The mean duration of the procedures was 286 minutes (range, 130 to 435 minutes); fluoroscopy time ranged from 7 to 33.8 minutes (mean, 17.4 minutes). CONCLUSIONS: In patients with ART after the surgical correction of congenital heart disease, the use of the noncontact mapping system allows for characterization of the tachycardia and guidance for effective radiofrequency current delivery.
Adolescent↗
[Usefulness of a VDD defibrillation electrode in recording atrial electrograms during atrial flutter and atrial fibrillation].
BACKGROUND: Monitoring of atrial signals improves the accuracy in identifying supraventricular tachyarrhythmias to prevent inappropriate therapies in patients with implantable cardioverter-defibrillators (ICD). Since complications due to the additional atrial lead were found in dual chamber ICD systems with 2 leads, we designed a single-pass VDD-lead for use with dual chamber ICDs. PATIENTS AND METHODS: After promising animal experiments in a German multicenter study a prototype VDD lead (single-coil defibrillation electrode with 2 additional fractally coated rings for bipolar sensing in the atrium) was temporarily used in 20 patients. Atrial and ventricular signals were recorded during sinus rhythm, atrial flutter, atrial fibrillation and ventricular tachycardia or ventricular fibrillation. Terminations of ventricular arrhythmias were performed by internal DC shock. RESULTS: The implantation of the electrode was successful in 18 of 20 patients. Mean atrial pacing threshold was 2.45 +/- 0.9 V/0.5 ms, mean atrial impedance was 215 +/- 31 Ohm. Atrial amplitudes were greater during sinus rhythm (2.7 +/- 1.6 mV) than during atrial flutter (1.36 +/- 0.28 mV, p < 0.05) or atrial fibrillation (0.92 +/- 0.29 mV, p < 0.01). During ventricular fibrillation atrial "sinus"-signals had significantly (p < 0.01) lower amplitudes than during sinus rhythm. Mean ventricular sensing was 13.3 +/- 7.9 mV, mean ventricular impedance was 577 +/- 64 Ohm. Defibrillation was successful with 20 J shock. 99.6% of P waves could be detected in sinus rhythm and 85 +/- 9.9% of flutter waves during atrial flutter. During atrial fibrillation 55% of atrial signals could be detected without modification of the signal amplifier. CONCLUSIONS: A new designed VDD dual chamber electrode provides stable detection of atrial and ventricular signals during sinus rhythm and atrial flutter. For reliable detection of atrial fibrillation modifications of the signal amplifier are necessary.
Aged↗
Prospective evaluation of catheter ablation in patients with implantable cardioverter defibrillators and multiple inappropriate ICD therapies due to atrial fibrillation and type I atrial flutter.
The high incidence of inappropriate therapies due to drug refractory supraventricular tachycardia remains a major unsolved problem of the ICD. Most of the inappropriate therapies for supraventricular tachycardia are caused by AF and type I atrial flutter with rapid ventricular response. The purpose of this prospective study was to determine the usefulness of AVN modulation or ablation for rapid AF and ablation of the tricuspid annulus-inferior vena cava (TA-IVC) isthmus for type I atrial flutter in ICD patients with frequent inappropriate ICD interventions. Eighteen consecutive patients were enrolled in this study. Twelve patients received a mean of 34 +/- 36 antitachycardia pacing (ATP) and 41 +/- 32 shock therapies for rapid AF during 49 +/- 39 months, and 6 patients a mean of 111 +/- 200 ATP and 11 +/- 8 shock therapies for type I atrial flutter during 52 +/- 37 months preceding ablation procedure. Modification of the AVN was successful in 10 (83%) of 12 AF patients, in 2 (17%) patients ablation of the AVN was performed. A complete TA-IVC isthmus block was achieved in 5 (83%) of 6 atrial flutter patients. Three (25%) AF patients had 11 +/- 24 recurrences of ATP and 0.4 +/- 1.1 shock therapies for rapid AF during 15 +/- 7 months. None of the atrial flutter patients had recurrences of inappropriate therapies for type I atrial flutter during 14 +/- 8 months, but two (33%) patients had inappropriate ICD therapies for type II atrial flutter or rapid AF. There was an overall mean incidence of 18 +/- 22 inappropriate ICD therapies per 6 months before and 4 +/- 9 per 6 months after the ablation procedure (P < 0.05). In conclusion, radiofrequency catheter modification or ablation of the AVN for rapid AF and ablation for atrial flutter type I are demonstrated to be highly effective in the majority of ICD patients with drug refractory multiple inappropriate ICD therapies.
Aged↗
Multicenter experiences with a single lead electrode for dual chamber ICD systems.
Monitoring of atrial signals improves the accuracy in identifying supraventricular tachyarrhythmias to prevent inappropriate therapies in patients with implantable ICDs. Since difficulties due to the additional atrial lead were found in dual chamber ICD systems with two leads, the authors designed a single pass VDD lead for use with dual chamber ICDs. After a successful animal study, the prototype VDD lead (single coil defibrillation lead with two additional fractally coated rings for bipolar sensing in the atrium) was temporarily used in 30 patients during a German multicenter study. Atrial and ventricular signals were recorded during sinus rhythm (SR), atrial flutter, AF, and VT or VF. The implantation of the lead was successful in 27 of 30 patients. Mean atrial pacing threshold was 2.5 +/- 0.9 V/0.5 ms, mean atrial impedance was 213 +/- 31 ohms. Atrial amplitudes were greater during SR (2.7 +/- 1.6 mV) than during atrial flutter (1.46 +/- 0.3 mV, P < 0.05) or AF (0.93 +/- 0.37 mV, P < 0.01). During VF atrial "sinus" signals had significantly (P < 0.01) lower amplitudes (1.4 +/- 0.52 mV) than during SR. The mean ventricular sensing was 13.3 +/- 7.9 mV and mean ventricular impedance was 577 +/- 64 ohms. Defibrillation was successful with a 20-J shock in all patients. In addition, 99.6% of P waves could be detected in SR and 84.4% of flutter waves during atrial flutter. During AF, 56.6% of atrial signals could be detected without modification of the signal amplifier. In conclusion, a new designed VDD dual chamber lead provides stable detection of atrial and ventricular signals during SR and atrial flutter. Reliable detection of atrial signals is possible without modification of the ICD amplifier.
Aged↗
[The importance of company interests in shaping occupational rehabilitation programs: empirical findings from company-based retraining].
The pilot project "Occupational Rehabilitation of Women Close to their Place of Residence" is orientated towards the dual system of vocational retraining by combining "on the job training" and "vocational theory in a vocational training school". Training on the job is one of the most important aspects in this programme, and data have therefore been gained from qualitative interviews with representatives of different firms. The results presented are based on the analysis of qualitative interviews with 13 employers involved in the pilot project. All interviewees underline: Training on the job alongside non-disabled persons is thought to offer good opportunities for lasting vocational integration since it enables trainees to grow accustomed to the conditions and demands of work and is thought likely to lead directly to employment. We discussed a range of mechanisms through which a societal obligation to train and/or employ disabled people could be implemented and highlighted the role of "rehabilitation services" which support the trainee by psychological, educational and social services and support the employer.
Persons with Disabilities↗
[Company approaches concerning workers with performance alterations or disablement: interview findings on the perspectives of the various parties involved].
This paper provides information about the research programme "In-plant interventions in the German car industry to increase job opportunities for employees with (severe) disabilities". The research was done in 2000 by the University of Trier and the International Research Unit for Work and Social Integration (IFASI). The purpose of the study was to capture, document, and analyse internal practices of occupational rehabilitation in five German car factories. Taking a qualitative approach, 23 persons of different company areas were interviewed, and numerous documents were analysed. The article reflects applied disability management strategies and points out success factors and barriers of inclusion.
Adult↗
Electromagnetic interference in patients with implanted pacemakers or cardioverter-defibrillators.
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Contraindications↗
Absorption and hemodynamic effects of airway administration of adrenaline in patients with severe cardiac disease.
BACKGROUND: If intravenous access cannot be attained during resuscitation of adult patients, endotracheal application of at least 2 mg of adrenaline is recommended. However, the effects of this intervention have not yet been demonstrated in adults. OBJECTIVE: To demonstrate the effects of adrenaline administered through the airways. DESIGN: Prospective clinical trial. SETTING: Operating theater at university hospital. PATIENTS: 34 patients receiving implantable cardioverter defibrillators under general anesthesia. INTERVENTION: When mean arterial pressure decreased below 80 mm Hg, 100 times the effective central intravenous dose of adrenaline (mean +/- SD, 1.3+/-0.6 mg [range, 0.7 to 3 mg]) was administered over 5 seconds into the endotracheal tube or through a bronchial catheter. Ten forced ventilations followed. MEASUREMENTS: Hemodynamic variables were recorded with a polygraph recorder. Adrenaline levels were measured in 13 patients. RESULTS: Plasma levels and arterial pressure increased in all patients (P < 0.002). Higher plasma levels (P < 0.039) and greater arterial pressure (P < 0.001) were achieved with this method than with intravenous injection. The effects of adrenaline did not differ between the two airway routes. Sustained ventricular arrhythmia did not occur. CONCLUSION: These substantial effects support the standard recommendation to consider the airways as an alternate route for at least 2 mg of adrenaline during resuscitation.
Absorption↗
Radiofrequency ablation of atrioventricular nodal reentrant tachycardia: mechanisms and recurrence rate.
Radiofrequency catheter ablation is the treatment of choice in atrioventricular nodal reentrant tachycardia. Electrophysiologic investigations in 623 patients revealed eight mechanisms of tachycardia ablation: Ablation of fast (I) or slow (II), modification of fast (III) or slow AV nodal pathways (IV), modification of both pathways (V), ablation of fast and modification of slow (VI), ablation of slow and modification of fast pathways (VII) and ablation of both pathways (VIII). The criteria of diagnosis of these eight mechanisms of tachycardia ablation are described. Follow-up showed fewer relapses in patients with ablation (0-2%) in comparison to patients with modification of a single AV nodal pathway (8-12%). Alteration of both pathways includes an increasing risk of total AV nodal block, which occurred in 7 patients (1.1%). Detailed analysis of the mechanism of catheter ablation is recommended in all patients after radiofrequency current delivery for AV nodal reentrant tachycardia to estimate the risk of relapse during follow-up or development of total AV block in the particular patient in case of a further ablation procedure.
Catheter Ablation↗
Direct suppressive effects of weak magnetic fields (50 Hz and 16 2/3 Hz) on melatonin synthesis in the pineal gland of Djungarian hamsters (Phodopus sungorus).
In many investigations performed thus far on rodents, a suppression of melatonin synthesis was observed when animals were exposed to weak magnetic fields. However, among the several issues not yet resolved is the question of whether the observed changes are caused by direct effects on the pineal gland or by indirect effects, e.g., at the level of the eyes. We, therefore, performed a series of experiments in which direct effects of weak magnetic fields were studied in isolated pineal glands of Djungarian hamsters (Phodopus sungorus). After sacrifice of animals during morning hours, pineal glands were removed and placed individually into glass chambers that were perfused with oxygenated buffer. Experiments (n = 8) lasted for 8 hr. Magnetic fields (1,623 or 50 Hz at 86 microTesla) were generated by Helmholtz coils, and were present during the entire period. In each experiment, 12 exposed, and 12 sham-exposed, pineal glands were placed individually in glass chambers, which were surrounded by identical coils. Because of the design of the coils (bifilament), and the experimental setup (black box), the experimentator was not aware which coil was activated until the results were obtained. After 3.25 hr of adaptation, melatonin production was stimulated by isoproterenol (10(-7) M) for 30 min. Eluted fractions were collected, and melatonin concentrations were measured by radioimmunoassay. Maximum melatonin production was achieved after 5-7 hr. In all experiments, maximum melatonin concentrations were lower in the exposed groups compared with the sham-exposed controls. Statistical analyses for each frequency showed significant suppressive effects at 16(2/3) Hz (P < 0.01), and 50 Hz (P < 0.00). It is concluded that the suppressive effects of magnetic fields on the synthesis of melatonin are a result of primary mechanisms at the level of the pineal gland.
Animals↗
[Guidelines for employment policies in Europe and national action plans: opportunities for people with disabilities].
The scourge of unemployment has been roundly identified throughout Europe as the most pressing social and economic problem on the current political agenda. At Luxembourg in November 1997, the European Jobs Summit brought Europe's leaders together in an historic occasion that mapped out employment guidelines for Europe. The Luxembourg Jobs Summit agreed a set of guidelines for the Member States employment policy under four pillars, employability, entrepreneurship, adaptability, and equal opportunities. One guideline referred to promoting integration of people with disabilities into working life. The Member States subsequently agreed to incorporate the Guidelines into national employment action plans. The question of this paper is, to what extent do employment guidelines and National Action Plans improve the opportunities of disabled persons? This paper seeks to establish a set of fundamental issues concerning employment and disability. Included in this analysis are recommendations in order to achieve a better presence of disabled people in National Action Plans in future.
Persons with Disabilities↗
Bimodal RR interval distribution in chronic atrial fibrillation: impact of dual atrioventricular nodal physiology on long-term rate control after catheter ablation of the posterior atrionodal input.
INTRODUCTION: Radiofrequency (RF) catheter modification of the AV node in patients with atrial fibrillation (AF) is limited by an unpredictable decrease of the ventricular rate and a high incidence of permanent AV block. A bimodal RR histogram has been suggested to serve as a predictor for successful outcome but the corresponding AV node properties have never been characterized. We hypothesized that a bimodal histogram indicates dual AV nodal physiology and predicts a better outcome after AV node modification in chronic AF. METHODS AND RESULTS: Thirty-seven patients were prospectively subdivided into two groups according to the RR histogram of 24-hour ECG monitoring. Before to RF ablation, internal cardioversion and programmed stimulation were performed. Among the 22 patients (group I) with a bimodal RR histogram, dual AV nodal physiology was found in 17 (77%) patients. Ablation significantly decreased ventricular rate with loss of the peak of short RR cycles after ablation (mean and maximal ventricular rates: 32% and 35% rate reduction, respectively; P < 0.01). In 15 patients with a unimodal RR histogram (group II), dual AV nodal physiology was found in 2 (13%), and rate reductions were 16% and 17%, respectively. At 6 months, 3 (14%) patients in group I and 6 (40%) in group II underwent elective AV nodal ablation with pacemaker implantation due to intolerable rapid ventricular response to AF. CONCLUSION: Bimodal RR interval distribution during chronic AF suggests the presence of dual AV nodal physiology and predicts a better outcome of RF ablation of the posterior atrionodal input.
Adult↗
Noninvasive diagnosis in patients with undocumented tachycardias: value of the adenosine test to predict AV nodal reentrant tachycardia.
INTRODUCTION: Patients with symptoms suggestive of paroxysmal supraventricular tachycardia (PSVT) but no tachycardia documentation often undergo diagnostic electrophysiologic study. In dual AV node physiology with AV node reentrant tachycardia (AVNRT), the anterograde fast pathway is more sensitive than the slow pathway to the effects of adenosine. The purpose of the study was to test the hypothesis that adenosine can be used as a bedside test for the diagnosis of dual AV node physiology and hence for AVNRT. METHODS AND RESULTS: During electrophysiologic study, 37 patients without prior documentation but symptoms indicative for PSVT received incremental dosages of adenosine during sinus rhythm until second-degree or greater AV block was observed. Suggestive signs of dual AV node physiology on the surface ECG (sudden jump of PQ interval > or = 50 msec) were found in 13 (76%) of 17 patients with inducible AVNRT but in only 1 (5%) of the remaining patients (P < 0.01). In the AVNRT group, the maximal increase of the PQ interval between two beats was greater (88+/-45 msec) than in the remaining 20 patients (17+/-11 msec) (P < 0.01). CONCLUSION: Careful evaluation of surface ECG during administration of adenosine helps to identify patients prone to AVNRT. The adenosine test is a valuable noninvasive adjunct in patients with undocumented palpitations suggestive of PSVT.
Adenosine↗
Urinary 6-sulfatoxymelatonin profiles in male Djungarian hamsters (Phodopus sungorus) responding and not responding to short-day photoperiods: possible role of elevated daytime levels.
The lack of endocrine and physiological responses of some Djungarian hamsters (Phodopus sungorus) to the transition from long to short photoperiods (L:D 16:8 --> L:D 8:16) has been known for a long time but is not yet understood. We investigated the role of melatonin synthesis in this context because melatonin, as part of the circadian system, may play a role in non-responsiveness. In ten responding and ten non-responding male hamsters, the urinary 24 hr 6-sulfatoxymelatonin (aMT6s) profiles under L:D 8:16 and L:D 16:8 were measured. Both short day responding and non-responding hamsters showed diurnal aMT6s excretion rhythms. Whereas responders reacted to the transition L:D 16:8 --> L:D 8:16 with a marked elevation of aMT6s excretion, in non-responders no adjustment of the melatonin rhythm to the change of the photoperiod was seen. Furthermore, under L:D 16:8 the daytime levels of aMT6s were significantly (P<0.001) lower in responders compared to non-responders whereas under L:D 8:16 these levels were higher (P<0.01). It is speculated that high daytime levels of aMT6s under long-day photoperiods in non-responders result in down-regulation of melatonin receptors of the nucleus suprachiasmaticus, the pacemaker for the pineal gland, leading to a lack of response to the transition to short-day photoperiods.
Animals↗
Growth retardation, testicular stimulation, and increased melatonin synthesis by weak magnetic fields (50 Hz) in Djungarian hamsters, Phodopus sungorus.
Male Djungarian hamsters (Phodopus sungorus; 45 animals per group) were either sham-exposed or exposed to a sinusoidal magnetic field for 56 days (Experiment 1: 50 Hz, 450 microTesla peak; max. dB/dt = 140 mTesla s(-1); 24 hrs day(-1)). Except for day 7, no effects were observed with respect to body weights during exposure. However, testicular cell numbers were significantly increased by exposure (tetraploid (4C): p=0.022; diploid (2C): p=0.039). Rectangular magnetic fields (Experiment 2: 360 microTesla; max. dB/dt = 2.5 Tesla s(-1)) caused a significant (p<0.001) but transient suppressing effect on body weights. Significant increases were also observed in testicular cell numbers (4C: p=0.034; haploid (1C): p=0.014) and in serum melatonin (p=0.001). It is concluded that weak magnetic fields may affect reproductive and physiological functions in the mammalian species tested and that the degree of these effects depends upon the fields' gradients.
Animals↗