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Biomedical subjects

D Pfeiffer

Publications and source records attributed to D Pfeiffer.

At least 127 records · Page 7Linked to original sources
PubMed1994

[Methods, topography and mechanisms of radiofrequency ablation of AV-nodal reentry tachycardia].

Three different methods of radiofrequency catheter ablation of AV nodal reentrant tachycardia were investigated in 128 patients. Results, relapses, and complications using anterior approach (n = 15), moved catheter (n = 20), and posterior-inferior approach (n = 93) were compared. Eight mechanisms of ablation of AV nodal reentrant tachycardia were distinguished: 1) Ablation of fast pathway (n = 8), 2) of slow pathway (n = 22), 3) modification of fast (n = 12), 4) slow (n = 54), or 5) both pathways (n = 13), 6) Ablation of fast and modulation of slow pathways (n = 4), 7) ablation of slow and modulation of fast pathways (n = 12), and 8) ablation of both pathways (n = 3). The criteria of diagnosis of these mechanisms and a mapping grid of Koch's triangle were proposed. The fast pathway is located in the anterior septum in a region with identical amplitudes of atrial and ventricular deflections and the slow pathway could be found posteriorly in a more ventricular location. The anatomical location of the slow pathway differed more widely than the location of the fast pathway. The best method with lowest risk could be recommended as the ablation of the slow pathway. This method implicated the lowest incidence of complications. We observed relapses in 12 patients during control studies 30 min, 3-5 days, and 3-6 months after first ablation procedure. These arrhythmias could be ablated in a second attempt in eight and in a third procedure in four patients. With increasing experience the radiofrequency catheter ablation of AV nodal reentrant tachycardia will be the method of first choice in patients with recurrent tachycardia.

Adult↗
PubMed1994

[Adenosine in prediction of the success of radiofrequency ablation in Wolff-Parkinson-White syndrome].

Rapid bolus injection of adenosine has been shown to produce transient atrioventricular (AV) nodal block while having almost no direct effect on accessory pathway conduction. The aim of this study was to determine the efficacy of adenosine for prediction of success of catheter ablation in WPW syndrome in 31 patients (23 with preexcitation; 8 with concealed conduction) before and 30 min, 5-7 days, and 3-6 months after attempted radiofrequency catheter ablation. Before ablation 6 mg adenosine produced maximal preexcitation (QRS duration increased from 100 +/- 15 ms to 123 +/- 18 ms) in patients with manifest preexcitation, while AV block occurred in all patients (100%) with concealed conduction for 1.5 +/- 0.5 s. No patient had accessory pathway conduction unmasked by adenosine. In 30/31 (96%) of patients retrograde conduction was unchanged prior to ablation. Immediately after ablation adenosine induced AV and VA block in 29 (93%) patients. These results were also present 5-7 days and 3 months later and were confirmed by electrophysiologic study. The positive and negative predictive values are 96% and 100%, respectively. Adenosine is reliable and useful to predict short- and long-term success following radiofrequency catheter ablation.

Adenosine↗
PubMed1993

[Radiofrequency ablation of accessory pathways in pre-excitation syndrome].

Various parameters relating to the radio-frequency ablation of accessory pathways were studied in 53 patients (27 males, 26 females: mean age 38.5 [14-64] years) with a history of paroxysmal tachycardia (over 1 month to 50 years), shown to be caused by an accessory pathway (Wolff-Parkinson-White syndrome). In all patients the following values were obtained: (1) number of procedures necessary to achieve permanent blockage of the accessory pathway (1-4); (2) duration of each procedure (45-420 min); (3) duration of fluoroscopy (5-102 min); (4) number of necessary radio-frequency applications (1-48); and (5) cumulative energy per procedure. To ablate left-lateral pathways (n = 10) required fewer procedures, shorter duration per procedure, shorter fluoroscopy time, fewer current applications and less total energy than coagulation of right-sided pathways (n = 10). Those various parameters were greatest for ablation of septal and para-septal pathways (n = 9). Pathways which conducted only retrogradely (n = 15) were more difficult to ablate than those with anterograde conduction (n = 38). There were two complications. In one case a tension pneumothorax occurred after faulty puncture of the subclavian vein; in the other, the left ventricle was perforated causing an acute tamponade which required pericardiocentesis with subsequent suture closure of the perforation. It is concluded that, in principle, all accessory pathways, regardless of their conduction potential and site, can be ablated by a radio-frequency current.

Adolescent↗
PubMed1993

Enhancing biosensor performance using multienzyme systems.

Enhancing the performance of biosensors, in terms of increasing the range of analytes that may be detected, and the sensitivity and specificity of the detection event, would improve the prospects for commercializing this technology. Coupling the catalytic activities of several enzymes is one approach being used to address these issues. Sequences of enzymes, where ligand binding triggers the activation of enzymes, or where biocatalytic pre-concentration of intermediates permits augmentation of the signal, may be used. In addition, enzymatic recycling of the analyte can be used to increase the sensitivity by several orders of magnitude.

Animals↗
PubMed1993

[EGF receptor and EGF-like activity as prognostic factors in cervix cancer].

The binding of the Epidermal Growth Factor (EGF) and the amount of EGF-like activity (EGF-A) was analysed in 75 cervical carcinomas and possible clinical implications were tested. EGF-A was significantly increased in patients with metastases to the pelvic and/or para-aortic lymph nodes. The EGF-receptor (EGF-R) capacity was inversely related to the histological grade (p < 0.05) and was reduced in highly differentiated tumours. In stage I and II disease, the clinical outcome was significantly reduced, if the receptor capacity or the level of EGF-A was increased (> 100 fmol/mg protein and > 0.5 ng/mg protein, respectively). The measurement of EGF-R capacity and EGF-A provides new and additional information for the prediction of the prognosis in cervical cancer.

Biomarkers, Tumor↗
PubMed1993

Effects of antiarrhythmic drugs on epicardial defibrillation energy requirements and the rate of defibrillator discharges.

Antiarrhythmic drugs are commonly used with the implantable cardioverter/defibrillator to treat recurrent ventricular tachyarrhythmias. Since various antiarrhythmic drugs have been reported to alter defibrillation threshold, an important question is whether the device will provide adequate energy for defibrillation during long-term follow-up and to what extent antiarrhythmic drug treatment will affect defibrillation energy requirements. To answer these questions, the defibrillation thresholds were determined in 20 patients using an epicardial patch-patch lead configuration at the time of implantation and at the time of pulse generator replacement. During a mean follow-up period of 24 +/- 6 months, the defibrillation threshold increased significantly from 14.2 +/- 3.7 joules to 18.3 +/- 5.5 joules in the entire group (P < 0.05). This increase in defibrillation threshold was due to a marked elevation of defibrillation energy requirements in the subgroup of patients taking amiodarone compared with patients receiving mexiletine. Based on these results it is mandatory to retest defibrillation threshold at any time of pulse generator replacement to guarantee continued effectiveness. In particular, if amiodarone treatment is initiated after implantation of a defibrillator, it is recommended to reevaluate defibrillation threshold to ensure an adequate margin of safety.

Amiodarone↗
PubMed1993

[Non-pharmacologic treatment of pre-excitation syndromes].

Paroxysmal tachyarrhythmias due to accessory atrioventricular pathways are usually not completely suppressible with antiarrhythmic drug therapy. These patients can be treated by implantable antitachycardia pacemakers or surgical or catheter ablation of accessory pathways. The antitachycardia pacemaker offers a symptomatic treatment, which is indicated in patients with less often arrhythmias, without atrial fibrillation and with haemodynamically stable tachycardias. The surgical interruption of accessory pathways depends on thoracotomy and often the cardiopulmonary bypass. This therapy is a curative treatment, which is indicated in patients with further cardiac disease needing surgical intervention. Catheter ablation of accessory pathways with radiofrequency energy is the modern treatment. Our own experience with 12 patients with preexcitation syndrome and antitachycardia pacemakers, 50 patients with surgical interruption of accessory conduction and 63 patients with catheter ablation is referred and the results are discussed.

Adolescent↗
PubMed1992

Effects of chronic amiodarone therapy on defibrillation threshold.

In a prospective and parallel, randomized study, the long-term stability of epicardial defibrillation threshold was evaluated in 22 patients, using a patch-patch lead configuration at the time of implantation and generator replacement. The concomitant antiarrhythmic drug treatment consisted of either mexiletine (720 mg/day) or amiodarone (400 mg/day) and was administered to patients in a randomized and parallel manner. During a mean follow-up of 24 +/- 6 months, the defibrillation threshold increased significantly from 14.3 +/- 2.8 to 17.9 +/- 5.3 J (p < 0.05) for the entire patient group. The increase in the chronic defibrillation threshold was due to a marked increase in defibrillation energy needs in the subgroup of patients receiving amiodarone. Whereas no significant change in the defibrillation threshold was documented in the subgroup of patients receiving mexiletine, the mean defibrillation threshold increased from 14.1 +/- 3.0 to 20.9 +/- 5.4 J (p < 0.001) in those receiving amiodarone. In all patients with increased defibrillation thresholds, reevaluation showed a reduction in the defibrillation threshold after discontinuation of antiarrhythmic drug therapy. The only variable associated with an increase in the chronic defibrillation threshold was amiodarone treatment. These findings suggest that the defibrillation threshold should be measured at each generator replacement and in case of a change in antiarrhythmic drug treatment. In particular, if amiodarone treatment is initiated, it is recommended that the defibrillation threshold should be reevaluated to ensure an adequate margin of safety.

Amiodarone↗
PubMed1992

[Age-related differences and changes in clinical aspects and follow-up of cervix cancer since 1973].

In an attempt to clarify, whether the malignant potential of cervical cancer is age-dependent and whether this has changed in the last decade, we analysed the data from 1496 patients suffering from cervical cancer. The patients were treated between 1973 and 1988 at the second Universitäts-Frauenklinik, Lindwurmstrasse and at the Frauenklinik Grosshadern, both of the Ludwig-Maximilians-Universität München. After 1973, the total number of patients with cervical cancer decreased, whilst at the same time, the percentage of young patients increased. In the sub-group of surgically treated patients (n = 555), the percentage of patients with lymph node metastases increased after 1973. The increase in lymph node involvement was most pronounced in young patients with small tumours (stage Ib disease, 35 years of age). In this group, the percentage of lymph node involvement rose from 6.3% in 1973 to 38.6% in 1988. Lower stage disease was significantly more frequent in the young patients. Accordingly, the overall mean survival time was longer in the young patients. In the sub-group of surgically treated patients, however, when comparing equal stages, the survival time was shorter in the young patients. In small tumours (confined to the uterine cervix), pelvic lymph node involvement was more frequently seen in the younger patients. Secondary metastases developed more rapidly and significantly more often in the young patients. Our data supply evidence to indicate an enhanced malignancy of cervical cancer in young patients.

Adult↗
PubMed1992

[Wolff-Parkinson-White syndrome: regional endocardial potential and efficacy of high frequency ablation].

The aim of the study was the evaluation of results of radiofrequency (RF) catheter ablation in relation to characteristics of regional endocardial potential morphology. 418 RF current deliveries in 26 patients with anterogradely conducting left-sided accessory pathways (AP) were investigated. A large regional atrial deflection (> 1/4 of ventricular potential) prior to RF discharge is a prerequisite for ablation success using the ventricular approach. A failing or extremely short (< 10 ms) isoelectric interval between atrial and ventricular deflections of the regional potential predicts a block of the AP. A persistent block can be expected if the regional electrogram contains an AP potential and the AP block occurs early (< 5 s) during onset of RF current.

Adult↗
PubMed1992

Treatment of tachyarrhythmias in a patient with the long QT syndrome by autotransplantation of the heart and sinus node-triggered atrial pacing.

The case history of a 37-year-old woman with the long QT syndrome and drug-refractory paroxysmal ventricular tachyarrhythmias is reported. She was resuscitated eight times between 1980 and 1987. The duration of these attacks increased from a few minutes to 8 hours and the interval between them decreased from 2 years to 4 weeks. An autotransplantation was performed of the anatomically and hemodynamically normal heart. She has had normal QT intervals and has been free of tachyarrhythmias since the operation in June 1987. Because of a slow escape low atrial rhythm, she was treated with a dual-chamber pacemaker programmed in the VDD mode with a coupling interval of 15 msec. The pacemaker wires were connected to the nontransplanted atrial cuff ("atrial" wire) and the transplanted atrium ("ventricular" wire). The hemodynamic effect of the resultant sinus node-driven low atrial pacing was restoration of normal values. This is the first report of successful autotransplantation of the heart for ventricular tachyarrhythmias caused by the long QT syndrome.

Adult↗
PubMed1991

Second generation biosensors.

Enzyme-membrane electrodes using glucose oxidase in combination with peroxide detection dominate in the field of laboratory analyzers for diluted samples. Using the same indication principle, extremely fast responding glucose sensors have been fabricated by covering thin metal electrodes with a porous enzyme layer. In the second generation auxiliary enzymes and/or co-reactants are coimmobilized with the analyte converting enzyme in order to improve the analytical quality and to simplify the performance. Following this line oxidizable interferences are suppressed by using a glucose oxidase/peroxidase complex which communicates with the electrode at a low working potential. Furthermore, fluctuations of pH or buffer capacity are ineffective when using a glucose oxidase/peroxidase layer covered fluoride FET in the potentiometric glucose determination. Enzymatic recycling of the analyte and/or accumulation of intermediates increase the sensitivity by several orders of magnitude. Inclusion of NAD bound to PEG in the glucose dehydrogenase layer allows a reagentless glucose measurement.

Biosensing Techniques↗
PubMed1991

Adenovirus precipitating antibodies in the sera of brush-tailed possums in New Zealand.

Sera collected from the Australian brush-tailed possum Trichosurus vulpecula in New Zealand in 1975 and 1989 were tested for the presence of antibodies to adenovirus. Of the 231 sera tested in an agar gel diffusion test, eight (3.5%) had precipitating antibodies to the group specific antigen of mammalian adenoviruses. Available data allowed 99/231 sera to be classified as being obtained from either adult (total 62) or sexually immature (total 37) possums. From the adult animals, 4/62 (6.5%) sera were positive, while no reactive sera were detected among the 37 immature animals. The results provide evidence that natural infection by an adenovirus occurs in possums in New Zealand. Further work needs to be carried out to isolate this adenovirus to enable detailed serological and epidemiological studies to be performed. A species-specific possum adenovirus could have potential in the biological control of this species.

Journal Article↗
PubMed1990

[Enzyme liberation after electrical His bundle ablation].

The release of isoenzymes, i.e. aspartate aminotransferase (ASAT), lactic dehydrogenase (LDH), malic dehydrogenase (MDH), and of creatine kinase (CK) after electric His bundle ablation is presented. The enzyme release is increasing with the amount of energy applied during the intervention. Mitochondrial MDH and ASAT were found in six of the seven patients. Therefore, the size of myocardial necrosis by ablation can be estimated by the sequence of the release of the enzymes, and the isoenzymes, respectively.

Adolescent↗
PubMed1990

Amperometric bi-enzyme based biosensor for the detection of lactose--characterization and application.

Based on the glucose oxidase-beta-galactosidase sequence an enzyme probe for the specific determination of lactose has been developed. beta-Galactosidases from different sources have been compared, the sensor containing beta-galactosidase from Curvularia inaequalis has been characterized in respect of optimal pH, enzyme loading, apparent activity and functional stability. The response of the bi-enzyme probe depends linearly on lactose concentration between 0.02 and 3.00 mmol dm-3. The application to different milk and foodstuff samples resulted in good correlations toward enzymatic photometric (y = (0.956x-1.67) mmol dm-3) and infrared detection (y = (1.0772x-0.3909)%). Using a measuring frequency of 100 h-1 the serial imprecision is about 2% for diluted milk, urine, or foodstuff samples.

Animals↗