Biomedical subjects

G A Bornzin

Publications and source records attributed to G A Bornzin.

3 recordsLinked to original sources

PubMed2000

Enhanced rate response algorithm for orthostatic compensation pacing.

Upon orthostatic stress after a period of rest, the heart rate increases rapidly to maintain cardiac output and minimize the fall in arterial pressure. Pacemaker patients are often prone to a deficient response to orthostatic stress. This may cause lightheadedness and, in rare patients with autonomic dysfunction, syncope. To alleviate these undesirable consequences, an enhanced rate response algorithm was developed using an accelerometer. The pacemaker generates two signals from its accelerometer: instantaneous activity level (Act) and long-term change in activity level (ActVar). Low values of both Act and ActVar indicate a resting state. An increase in Act while ActVar remains low indicates the onset of motion after prolonged rest. Upon detecting this transition, the algorithm increases the pacing rate to a programmable orthostatic compensation rate for a programmable duration. A taped-on pacemaker with this algorithm was evaluated in three healthy women and two healthy men, 36 +/- 8 years of age. Electrocardiogram and ventricular pacing pulses were recorded by a 24-hour ambulatory system. Each trigger of the orthostatic compensation rate was verified against a > 10 beats/min increase in heart rate, a response classified as appropriate. The overall specificity of the algorithm among the five subjects was 78%. The nocturnal specificity (10 PM to 7 AM) was 98%, considerably higher than during daytime (72%). In conclusion, a pacing algorithm to alleviate orthostatic stress was developed, which was highly specific during the night hours.

Acceleration↗

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↗

PubMed1994

Adjusting heart rate during sleep using activity variance.

UNLABELLED: In order to mimic the natural decrease in heart rate that occurs during sleep, an algorithm was devised to decrease the base rate to a programmable sleep rate. The algorithm was developed using activity and sinus rate data obtained from 18 normal subjects ranging in age from 22-80 years. The data were recorded in the event record of a "taped-on" pacemaker. The surface ECG signal was used to inhibit a pacer programmed to VVI at 45 ppm. The ECG documented the sinus rate while the accelerometer-based activity signals were recorded in an event record. An algorithm was used to estimate the smoothed acceleration variance every 26 seconds. The activity variance was stored in a histogram. RESULTS: The lower 7/24ths of the histogram entries were primarily attributable to sleep. If the activity variance was entered into the lower 7/24ths of the histogram and the accelerometer reading was below rate responsive threshold, the base rate was switched to sleep rate. Using least mean squares to estimate optimal slope, base rate, and sleep rate, the root mean square error between activity derived heart rate and sinus rate was 12 beats/min. CONCLUSION: This study supports using an estimate of activity variance to automatically decrease pacing rate below programmed base rate. This decrease may be actuated during an afternoon nap or nighttime sleep.

Adult↗