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Biomedical subjects

M Kleinert

Publications and source records attributed to M Kleinert.

At least 19 recordsLinked to original sources
PubMed1979

Spectral properties of atrial and ventricular endocardial signals.

The spectral energy distributions of signals picked up by endocardial, atrial and ventricular electrodes have been investigated. The results show similar spectral distributions for P-waves and QRS-complexes with maximum spectral densities at frequencies between 10 and 30 Hz.

Adult↗
PubMed1978

Clinical experience with a new transvenous atrial lead.

Although systems using atrial pacemakers offer potential clinical advantages for many patients now receiving ventricular devices, atrial systems have been used in less than 1% of the implantations of permanent pacemakers. The unavailability of clinically successful, easily positioned atrial leads is regarded as the most significant factor in the underutilization of atrial pacing systems. A permanent transvenous atrial lead has been developed and has performed well in 16 months of evaluation in 28 patients. Acute thresholds for voltage at a pulse width of 1 msec ranged from 0.40 v to 2.0 v (average, 1.1 v). Acute peak-to-peak amplitudes of the atrial electrogram were notably high, ranging from 2.5 mv to 7.5 mv (average, 5.1 mv) as measured oscilloscopically. Intermittent failure of sensing occurred in three patients during the period immediately after implantations. Spontaneous dislodgment of the lead from the right atrial appendage occurred in two patients. Atrial sensing and pacing functions remained intact in the first case, and no revision was performed. The lead was repositioned in the second patient and has remained in good position. No complications relating to the lead have been noted in the remaining patients.

Adult↗
PubMed1977

[One year experiences with a new atrial lead (j-version) in 53 patients (author's transl)].

The new atrial leads (J-version) of type Medtronic 6991, of which we implanted endocardially a total of 53 between April 1975 and May 1976, are characterized by properties, as, up to now, were exclusively to be seen in the so-called flange electrodes of ventricular position. 1. The tined J-leads were easily to introduce and required only an average of 5 minutes to position into the right appendage. 2. Moreover, these atrial leads guaranteed an anatomic stable anchorage with a dislodgement ratio of less than 6% (3 of 53). 3. Additionally, the action voltages sensed the J-shaped electrodes showed themselves averaging 5.2 mV of very high amplitude. Up to this time comparable results could not be achieved neither by other atrial leads nor techniques of their emplacement. The intraatrial voltage thresholds exceeded, as described before, the intraventricular ones by two to three times. In spite of this, no exit block was seen in 34 cases with atrial pacing systems, not even during an observation time of maximal 13 months. Therefore, the tined J-leads fulfill all requirements of a suitable atrial electrode.

Aged↗
PubMed1977

[Comparative studies of thresholds after implantation of pacemaker leads of different size (author's transl)].

Within the first 14 days after implantation, thresholds were measured at three transvenous pacemaker electrodes with different surface areas. It should be verified, 1. to what extent a correlation existed between maximal threshold increase and electrode surface, 2. how electrode impedance and 3. how the amplitudes of the R-wave voltages developed. The results were: At initial implantation, thresholds were all the lower the smaller the electrode-surface area was. On overage, 9-10 days after implantation the highest thresholds were reached. Thereby, in small surface area electrodes the threshold-increase factor was greater than in larger ones. In all cases the current threshold increase exceeded that one for voltage thresholds. 14 days later, thresholds had dropped again compared to the maximum. And this decrease was depending on the electrode-surface area also. The electrode impedance decreased after implantation to rise later on once more to 80-88% of the original value. The magnitude of the detected R-wave was independent on electrode-surface area. Indeed, using small surface electrodes, signal reductions up to 50% could be found. But 14 days later they reached again 80-95% of the initial amplitude. The key finding there is that when applying small surface-area electrodes and presuming suitable initial thresholds it seems to be possible to connect low-output pacemakers (output 5,4 V and impluse duration 0.25 ms or 4 V at 0.5 ms) to those electrodes. By this reduction of the safety margin, a considerable increase in pacemaker lifetime could be achieved.

Electrocardiography↗
PubMed1977

[First clinical experiences with a new transvenous endocardial screw-in lead (author's transl)].

From November 1976 to January 1977 a total of 10 patients were served with a new transvenous endocardial screw-in lead. In every 5 cases the lead was anchored in the right atrium respectively in the right ventricle. The lead presented itself by good biomechanical (flexibility, tension resistance) and bioelectrical properties. Because of its constructural features it was to insert easily and without any complication. Moreover, it could be placed anatomically stable by choice either in the right atrium or ventricle.

Aged↗
PubMed1976

[Possibilities of pacing the heart by transmediastinal retrocardially inserted leads (author's transl)].

Based upon experiences with 14 patients the clinical feasibility of transmediastinal retrocardial stimulation of the heart, of the left atrium as well as in one case of the left ventricle, is reported. Principally both can be stimulated by thus introduced pacemaker electodes. Thus on the one hand thresholds and consequently pulse effectivity appear to be a function of the electrode distance from the myocardium, whilst on the other hand the transmediastinal retrocardial thresholds are initially rather high in analogy to the majority taken from the atrial endocardial surface. Nevertheless, the transmediastinal retrocardial technique is possibly applicable for permanent cardiac pacing. However, additional tests about this are still necessary.

Aged↗
PubMed1976

Special pacemaker catheter techniques. The transmediastinal placement of sensing electrodes.

The clinical utilization of atrial programmed pacemakers is limited by the lead systems available for sensing of atrial activity. The endocardial method of lead placement is burdened by a dislodgement rate of up to 30 per cent. Alternatively, the patient must submit to the risks of a thoracotomy. Thirty-one patients have been treated with a transmediastinally, retrocardially positioned atrial detector electrode. In 20 patients (65 per cent) the detector performed as desired with no postimplant revision. In 11 patients (35 per cent) corrective measures were required primarily to correct lead placement; seven of these were corrected under local anesthesia merely by pulling the catheter. Spontaneous lead dislocation occurred in four patients. Four patients (13 per cent) underwent remediastinoscopy due to cranial displacement of the detector electrode with a resulting decrease in atrial potential to less than 0.5 mV. For technical reasons, the lead placements were performed without the benefit of x-ray illumination, with only an ECG check of the posterior atrial wall, and this may account for the relatively high incidence of revision. Transmediastinal placement of sensing electrodes presents a practicable alternative to methods presently used.

Adult↗
PubMed1976

[Experiences with 87 permanent atrial electrodes of various types and emplacement technics].

Between March 1972 and December 1975 87 atrial leads were implanted into 85 patients. In 37 cases the transmediastinal retrocardial approach was preferred. In all the other cases the electrodes were introduced transvenous endocardially. The results showed: 1. There exist techniques of atrial lead emplacement which, when applying suitable lead designs, guarantee an anatomic stable positioning either on the left or in the right atrium. Especially the new transvenous J-shaped electrodes of type Medtronic TJL can be positioned easily. The dislodgement ratio of these leads amounts of only 6%. 2. Retro- as well as intracardially very high action voltages were found. The ones sensed by the J-tip-electrodes from the endocardial surface of the right appendage even run up to 5,4 mV. 3. In spite of relatively high initial thresholds, no exit block was seen in any of the 34 cases, in whom atrial leads were inserted transvenous endocardially for permanent atrial pacing.

Adult↗