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D Woodson

Publications and source records attributed to D Woodson.

4 recordsLinked to original sources
PubMed1998

The patient alert system--pilot study of built-in warning systems for pacemakers.

Malfunction of a pacing system can be life-threatening for a pacemaker-dependent patient. It would be desirable for implantable pulse generators to have a built-in automatic warning system capable of alerting the patient as soon as a potentially dangerous disorder is detected. In this study, seven patients (mean age, 72.6 +/- 10.7 years) with slow, chronic atrial fibrillation underwent implantation of a dual-chamber pulse generator with a custom-made "alert electrode" connected to the atrial port of the pulse generator to stimulate the underlying pectoral muscle. The muscle was temporarily stimulated while the pacemaker was in VVIR mode. The lowest amplitude sufficient to alert the patient (perception threshold) was 1.6 +/- 0.58 V at 0.45 ms during implantation and 1.2 +/- 0.5 V at 0.45 ms chronically. In a second phase, alerts outside of the office were issued using a special software routine capable of delivering stimuli at programmable date and time.

Aged↗
PubMed1990

A new feature for control of inappropriate high rate tracking in DDDR pacemakers.

A limitation of current DDD and DDDR pacemakers is the inability to distinguish between inappropriate high rate atrial sensed events that are physiologically appropriate to track (e.g., elevated sinus rates resulting from exercise, emotional responses, etc.) and those that are physiologically inappropriate to track (e.g., paroxysmal atrial dysrhythmias, myopotentials, retrograde conduction, etc.). The sophistication of sensing circuitry is not yet sufficiently advanced to permit a pacemaker to distinguish appropriate atrial events by morphology. The addition of an independent sensor to a DDD pacemaker (i.e., DDDR) gives more information about the patient's condition, especially with respect to exercise. This information can be used to judge the appropriateness of a high sensed atrial rate, and to modulate the pacemaker's response. If the sensor input is below a specified level, indicating lack of exercise, the DDDR can track sensed atrial events only to a tolerably low limit-the conditional ventricular tracking limit (CVTL). Wenckebach-type behavior ensues at the CVTL until the sensor input increases, indicating that exercise is occurring, or until the sensed atrial rate decreases. If the sensor input indicates exercise, the DDDR pacemaker can track up to the programmed maximum rate. Two DDDR systems have been developed that incorporate this feature; one based on temperature, the other on activity. Currently the CVTL is set at a value about 30 ppm above the pacing rate, as a compromise to support emotional needs not seen by the sensor. Improved sensors could cause the decision to raise the tracking limit (i.e., recognition of physiological need for higher rates) to be more accurate, perhaps making the CVTL proportional to the sensor signal.

Atrioventricular Node↗