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R Van Mechelen

Publications and source records attributed to R Van Mechelen.

5 recordsLinked to original sources
PubMed1999

Results from the use of a preshaped lead for single-pass VDD/DDD stimulation.

Main criticisms about single-pass VDD stimulation in patients with AV block and normal sinus node function concern atrial undersensing in a lead with floating atrial electrodes, and loss of AV synchrony if sinus node dysfunction develops after implantation. We evaluated the concept of a preshaped single-pass lead designed to place the atrial ring electrodes in a constant position close to, or in contact with, the atrial wall. A preshaped lead (Model 2775, Medtronic Inc.) was implanted in 14 patients and followed for up to 2 years. Mean P wave amplitudes (PWAs) were 3.1 mV at implantation, 1.2 mV at predischarge, and 1.3 mV after 12 months. In all patients, minimal PWAs were well above maximal atrial sensitivity of the pacemaker in all body positions during the complete follow-up; atrial undersensing was not observed. Effective atrial stimulation was possible in all patients at implantation (mean stimulation threshold 2.5 V at 0.50 ms), in 11 patients on the first day after implant (mean stimulation threshold 0.22 ms at 5.0 V), in 10 patients after 1 month (mean stimulation threshold 0.57 ms at 5.0 V), and in 10 patients after 1 year (mean stimulation threshold 0.65 ms at 5.0 V). Intermittent phrenic nerve stimulation could be provoked in six patients. In conclusion, the concept of a preshaped single-pass lead facilitated implantation, improved atrial sensing performance, and allowed atrial stimulation in some patients. Still, further improvements are necessary to decrease the atrial stimulation thresholds to acceptable values in all patients.

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PubMed1991

Impedance measurements in the human right ventricle using a new pacing system.

A promising new pacemaker that provides on-line measurements of right ventricular (RV) impedance was evaluated in ten patients with symptomatic second- or third-degree atrioventricular (AV) block. We tested the assumption that if changes in RV impedance represented changes in RV stroke volume (SV), conditions known significantly to affect RV SV should be accompanied by significant changes in RV impedance. One week after pacemaker implantation, RV impedance was measured noninvasively during normal respiration in the supine (baseline), left lateral, right lateral, sitting, and standing positions. In addition, all patients performed a Valsalva maneuver test. The amplitude of the impedance signal was different during in- and expiration in every body position studied. At baseline, the amplitude of the signal was 18.80 +/- 2.24 mm; in the right lateral position 16.75 +/- 3.24 mm (P = 0.04) and 17.80 +/- 2.35 mm in the left lateral position (P = 0.04). The amplitude of the signal in the sitting position was 16.65 +/- 2.89 mm (P = 0.07) and in the standing position 16.95 +/- 3.44 mm (P = 0.11). The most impressive change in amplitude was noted during performance of the Valsalva maneuver. During this test the amplitude decreased to 13 +/- 2.81 mm and rose to 20 +/- 2.66 mm (P = 0.002) afterwards. These results strongly support the assumption that changes of RV impedance as measured by this catheter represent changes in RV SV. This new pacing system is the first pacemaker that reports on the hemodynamic response of every heartbeat by measuring RV impedance.

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PubMed1988

Atrial capture detection with endocardial electrodes.

A new method of evoked response detection, previously demonstrated in the ventricle, has been studied in the atrium at the time of routine pacemaker implant in 16 patients. The atrial evoked response was readily detectable in all patients due to excellent recovery from poststimulus polarization. In six patients, as experimental threshold-tracking pacemaker was used to automatically verify atrial capture and to generate strength-duration curves. It is concluded that this pacing technique is both simple and reliable, and that automatic atrial threshold tracking is feasible.

Atrial Function↗
PubMed1985

Late purulent pacemaker pocket infection caused by staphylococcus epidermidis: serious complications of in situ management.

The pathophysiology of late pacemaker pocket infection is poorly understood. We report three cases of late infection caused by Staphylococcus epidermidis. Despite initial local conservative management ultimate removal of the entire pacing system was required. In late pacemaker pocket infection we recommend initial removal of the entire pacing system and replacement on the contralateral side. When retrieval of the lead system requires open-heart surgery epicardial wires should be placed.

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