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J P Heemels

Publications and source records attributed to J P Heemels.

5 recordsLinked to original sources
PubMed1993

Accelerometer-based adaptive-rate pacing: a multicenter study. European EXCEL Study Group.

UNLABELLED: A new adaptive rate pacemaker, using an accelerometer to detect body motion as an indicator of metabolic demand, was evaluated in 13 centers located in five countries. During the study, 55 patients with a broad range of indications were implanted with the EXCEL VR single chamber pacemaker. One month evaluations were completed on a subgroup of 37 patients. The pacemaker response was optimized before discharge using a simple walking test. An "exercise test" recording feature in the programmer eliminated the need for ECG monitoring. At nominal settings, the mean (+/- SD) pacing rate increased 29 +/- 9 ppm while walking slowly and 44 +/- 11 ppm (n = 33) during a brisk walk. This information was used to optimize the parameter settings. Without further changes to the programmed settings the patients were subsequently tested 2-4 weeks postimplant with a symptom-limited treadmill test using the chronotropic assessment exercise protocol (CAEP). Mean pacing rate increased from 74.5 +/- 2.5 ppm (n = 24) at rest to 118.6 +/- 12.2 ppm (n = 21) at 3 mph/6% grade to 143.5 +/- 3.5 ppm (n = 2) at 3.8 mph/8% grade. CONCLUSION: The individual responses were proportional to the physical exertion imposed on the patients. Pacing rates were considered to be appropriate using the chronotropic response zone as a criterion for appropriate rate modulation. A simple walking test utilizing the exercise test facility, results in appropriate optimization of the pulse generator to the individual patient.

Acceleration↗
PubMed1992

Adaptive rate pacing controlled by the right ventricular preejection interval: clinical experience with a physiological pacing system.

In the Precept pacing system, the right ventricular intracardiac impedance waveform is used to evaluate either of two indicators of metabolic demand relative right ventricular stroke volume and preejection interval (PEI). PEI is known to reliably parallel contractility changes, which is reflective of physical and emotional stress. The stability and dynamic behavior of PEI were tested in ten patients with a Precept pacing system under various forms of exercise and during postural changes. Although significant patient-to-patient variability of the sensor values was observed, reflecting individual physiological differences, the chronic stability of PEI was excellent in the total device experience of 147 months. In all patients, PEI shortened significantly during bicycle ergometry from a mean value of 137.7 +/- 17.8 (range 96-162) to a mean value of 103.0 +/- 21.6 (range 92-109) (P less than 0.05). Low level bicycle exercise of short duration resulted in a prompt decrease in PEI and increase in pacing rate in all patients. There were no uniform postural responses overall, although some posture related rate changes were observed in two patients. We conclude that the first generation of a PEI based pacing system holds promise for adaptive rate pacing.

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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↗