Biomedical subjects

J Sholder

Publications and source records attributed to J Sholder.

5 recordsLinked to original sources

PubMed1996

Effect of pentaphasic pulse sequence as an impedance sensor on standard electrocardiographic recordings.

Two advances in cardiac pacing have resulted in an internal conflict in some pacemakers. One is the development of a standard lead physiological sensor and the other is protection from electromagnetic interference (EMI). One popular type of standard lead sensor uses sub-threshold pulses to measure intracardiac and intrathoracic impedance changes, i.e., minute ventilation. Recent clinical observations and extensive in vitro testing have verified that digital cellular phones can be troublesome. Large feedthrough capacitors (FCs), effective in blocking the EMI, will preclude sensing of the standard impedance-based signals. A variety of pulse configurations were studied that might be effective for a sensor-based impedance signal while allowing the pacemaker to continue to use large Fcs protecting them from environmental EMI. In comparison to both monophasic and biphasic pulse sequences, a pentaphasic pulse sequence was effective as an impedance sensor, still allows large FCs to function as an effective filter for environmental EMI, and would not produce artifacts on surface ECG.

Cardiac Pacing, Artificial↗

PubMed1994

A new automode switch algorithm for supraventricular tachycardias.

Patients with complete heart block on a spontaneous, or iatrogenic basis who also have recurrent supraventricular tachycardias, particularly atrial fibrillation and flutter, are often difficult to manage. Various techniques include: independently programmable maximum tracking and maximum sensor rates, limiting the maximum atrial tracking rate to the sensor response of the pacemaker, or automatically switching from DDDR to VVIR based upon the sensed atrial rate. This article will describe a mode switch algorithm that allows for an independently programmable atrial tachycardia detection rate (ATDR). This allows mode switching to occur only in response to the patient's pathological tachyarrhythmia, and not during normal upper rate response. The ATDR is based upon a filtered atrial rate, which will prevent an isolated premature beat from initiating the algorithm. In addition, the unit can be programmed to switch to either DDI, DDIR, VVI, or VVIR. Extensive event counters in the pulse generator allows the system to record and store the number of algorithm activations, the average atrial rate which triggered each mode switch, and the duration of the mode switch. These reports are accessible at each follow-up visit.

Algorithms↗

PubMed1986

A new advancement in noninvasive electrophysiology: a standard laboratory stimulator pulse coupled with an implanted pacemaker.

A new device for coupling the pulse from a standard laboratory stimulator to commercially available implanted pacemakers for use in noninvasive electrophysiology testing has been developed. When programmed to an electrophysiology mode, a 37 kHz carrier wave, generated by the programmer, maintains communication with the implanted pacemaker. Stimuli generated from a standard lab stimulator cause a break in the carrier wave and an output from the pacemaker. Cycle lengths as short as 127 msec can be attained. In addition to standard electrophysiology testing, this noninvasive electrophysiological technique can be used to fibrillate the heart to test the efficacy of automatic implantable cardioverter/defibrillators.

Electric Stimulation↗

PubMed1985

Cross-stimulation: the unexpected stimulation of the unpaced chamber.

The ability to stimulate one chamber through a lead or output circuit to the opposite cardiac chamber is termed cross-stimulation. Three examples of this phenomenon are presented. The first involves the close proximity of the atrial lead to the ventricular myocardium with ventricular capture occurring at sufficiently high outputs; the second is due to the basic design of dual unipolar pacing systems which have output circuits that share a common anode; the third is a self-limited eccentricity of one device that occurs only during the first phase of magnet-induced asynchronous pacing. The mechanism and clinical significance of these observations are discussed.

Equipment Design↗

PubMed1984

Clinical benefits of telemetered electrograms in assessment of DDD function.

The advent of telemetry of the endocardial electrogram is a new capability. It must be convenient to use if it is to gain acceptance. Our experience is still growing but already it is confirming information that was either deduced or previously only available by active invasive procedures. The potential value of the technology has only been touched upon in this presentation. We are convinced that it will grow and that its value will be further established as more physicians have an opportunity to use it and gain additional experience.

Ambulatory Care↗