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Biomedical subjects

B Lüderitz

Publications and source records attributed to B Lüderitz.

At least 415 records · Page 23Linked to original sources
PubMed1982

Therapeutic pacing in tachyarrhythmias by implanted pacemakers.

Termination of tachyarrhythmias by electrical stimulation has been demonstrated by clinical and experimental evidence. Implantable devices for repetitive use in long-term therapy are so far not readily available. Twelve patients with drug resistant ventricular (3) or supraventricular (accessory pathway (2), atrial flutter (3), junctional tachycardia (3), supraventricular tachycardia (1) tachyarrhythmias are reported in whom, after electrophysiological analysis of the individual tachycardia, a specially designed stimulation system was implanted. Cardiac pacing was performed in the right atrium or ventricle. Stimulation rate was in the range of 150-1016/min. In automatic ECG-controlled devices (2 patients), the number and length of cardiac cycles served as parameters for discharging the stimulation circuit. In 10 patients the antitachycardia-pacemaker was in use as a patient-activated or externally triggered device or as a fixed rate unit. After pacemaker implantation we observed a significant decrease in incidence and/or duration of tachycardic episodes in all patients. In two patients atrial pacing (80 and 90/min) suppressed tachycardias completely. Additional antidysrhythmic drug therapy was necessary in 11 out of our 12 patients. It is concluded that cardiac stimulation with implanted antitachycardia pacemakers can be an efficient long-term antitachyarrhythmic therapy in selected patients.

Adolescent↗
PubMed1982

Electrophysiology and indications for pacing in the '80's.

Newer electrophysiological studies have improved our understanding of the pathogenesis of cardiac arrhythmias. Bradycardias originate either from a dysfunction of impulse formation in the sinoatrial node or from a disturbed conduction of the impulse. Different pathogenetic mechanisms are discussed as causes of tachyarrhythmias: circus movement (re-entry) is primarily due to pathological changes in conduction and refractoriness. Focal impulse formation results from local disturbances of depolarization and repolarization of the cell membrane: increased automaticity, abnormal automaticity, triggered activity. Symptomatic bradycardias still represent the standard indication for cardiac pacing particularly with implantable pacemakers. Based on clinical electrophysiology, various types of pacemakers are available at present: atrial triggered and atrial pacing pacemakers, AV-sequential pacemakers, ventricular demand-pacemakers, stand-by pacemakers, and fixed rate pacemakers. The multiprogrammability of newer pacemaker devices is a very useful tool in avoiding secondary interventions. For antitachycardia pacemaker therapy there are essentially three methods in use: 1. overdrive pacing to prevent re-entry phenomena and automaticity and also to suppress tachyarrhythmias based on increased or abnormal automaticity; 2. competitive stimulation for termination of tachycardias by means of single impulses; and 3. rapid atrial stimulation to convert atrial flutter into atrial fibrillation and consequently to normal sinus rhythm. In very rare cases rapid ventricular stimulation is mandatory. The positive results achieved with temporary stimulation methods have led to the development of permanent (implantable) antitachycardia pacemakers for long-term therapy, which have proven to be a low-risk alternative in drug-resistant tachyarrhythmias.

Anti-Arrhythmia Agents↗
PubMed1981

[The sick sinus syndrome. What causes it?].

The basic disorder in sinoatrial disease is a functional and/or anatomical defect in the sinus node and the atrium respectively. The clinical feature includes palpitations, angina pectoris, heart failure, giddiness and systemic emboli. Associated diseases are coronary heart disease, hypertension, diphtheria, myocarditis or rheumatic fever. Diagnosis is primarily made by clinical symptoms and conventional or long term ECG-monitoring. However, impaired sinus node function including sinusbradycardia, sinus arrest, sinoatrial block and the bradycardia-tachycardia syndrome cannot easily be assessed, when rhythm disturbances are occurring intermittently, as the recording of electrical activity of sinus node pacemaker cells is not available in man. Therefore methods of provocative atrial stimulation (rapid atrial stimulation, premature atrial stimulation) have been developed for (indirect) estimation of sinus node recovery time and sinoatrial conduction time. Treatment depends on symptoms. In most cases implantation of an electric pacemaker is mandatory since drug treatment usually is unsatisfactory. The natural history of the sinoatrial disease is imperfectly known but probably covers 5--10 years.

Electrocardiography↗
PubMed1981

[Value and risk of programmed ventricular stimulation in patients with chronic recurrent ventricular tachycardia (author's transl)].

Chronic recurrent ventricular tachycardias represent potentially life-threatening cardiac arrhythmias. We used programmed ventricular stimulation for diagnosis, therapy and control of antiarrhythmic therapy in 17 patients with recurrent ventricular tachycardia. Ventricular tachycardia could be reproducibly induced in 15 patients by programmed stimulation, QRS morphology and rate being comparable to the spontaneously occurring tachycardia. Programmed stimulation was repeated under antiarrhythmic drug therapy. Over a follow-up period of 8 months (3--13 months), the results of the acute electrophysiologic study seem to be predicting oral long-term antiarrhythmic drug therapy. Application of programmed stimulation is associated with potential risks: induction of "non-clinical" more frequent tachycardia: 3/17 pat. = 18%; acceleration of the rate of tachycardia while trying to interrupt it: 5/17 pat. = 30%; necessity of DC-cardioversion: 6/17 pat. = 35%. Despite these risks, programmed ventricular stimulation offers substantial improvement of diagnosis and control of therapy of severely symptomatic patients with suspected or documented ventricular tachycardia and/or fibrillation.

Adult↗
PubMed1980

Effects of tocainide on ectopic impulse formation in isolated cardiac tissue.

The effect of tocainide on enhanced automaticity if Purkinje fibers was studied under the influence of epinephrine (0.2 microgram/ml) by means of intracellular recordings with microglass electrodes. In the presence of tocainide 5 microgram/ml and 10 microgram/ml cycle length of enhanced automaticity was increased in the range of 10.6% and 34.9% and in the range of 26.3% and 108.7% respectively. Repetitive impulse formation in ventricular myocardium was generated by creating a potential difference in a papillary muscle mounted in a partition chamber. One chamber was connected to ground, the potential of the other chamber could be changed in the range of 0 to 500 mV. By progressively increasing the voltage difference across the papillary muscle repetitive rhythmic impulse formation was induced. The threshold voltage gradient increased in the presence of tocainide (100 microgram/ml) from--285 to--335 mV. The results suggest that tocainide is suitable to suppress arrhythmias due to enhanced automaticity of Purkinje fibers.

Action Potentials↗
PubMed1980

Comparison of myocardial potassium and thallium flux as studied by tracer methods.

Although myocardial scintigraphy with 201thallium is widely applied in humans, the behavior of thallium at the cellular level is still under discussion. We compared the transmembrane fluxes of potassium and thallium in the isolated papillary muscle of guinea pigs. A qualitative conformity exists between potassium and thallium fluxes with respect to heart rate and temperature. Quantative comparison revealed a decreased flux rate of thallium for efflux when compared with potassium. The time dependence of thallium influx indicates that thallium scintigraphy of the myocardium reflects mainly an extracellular distribution.

Animals↗