Biomedical subjects

G Bornzin

Publications and source records attributed to G Bornzin.

3 recordsLinked to original sources

PubMed1998

Activity-controlled circadian base rate.

The current pacing rates are clustered around a fixed base rate since pacemaker patients are usually sedentary, resting, or sleeping most of the time. This fixed base rate is either too low for daytime hemodynamic support or too high for nighttime rest and recovery. Multiple Holter studies involving normal individuals have suggested that the resting base rate fluctuates during the course of the day. The circadian base rate (CBR) algorithm was designed to provide patients with a circadian change in paced resting rate and a normal rate distribution. The CBR algorithm, using a sophisticated accelerometer sensor, was developed and tested using the downloaded activity data from patients implanted with Trilogy DR+ pacemakers. Twenty-five patients (19 men, 6 women, age 72 +/- 9 years) were studied. Trilogy DR+ is able to record the detailed sensor and system behavior data for a week. During outpatient visits, the pacemaker was interrogated and the data accumulated in the pacemaker memory were downloaded. The CBR algorithm was applied to the activity variance histogram to calculate the base rate and to construct its histogram. The base rates in the CBR histogram are generally below 100 ppm with a distribution that mimics the natural sinus rate distribution of normal subjects. The CBR algorithm provides the highest daytime rates for hemodynamic support and the lowest nighttime rates for cardiac recovery, with a smoothly changing base rate modeling the normal circadian variation in heart rate.

Aged↗

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↗

PubMed1987

Constant postoperative monitoring of cardiac output after correction of congenital heart defects.

A new method has been developed that permits constant postoperative monitoring of mean and phasic cardiac output in patients after correction of congenital heart defects. A miniature ultrasound probe is attached to the adventitia of the ascending aorta at the conclusion of the operative procedure. This is connected to the monitoring equipment by means of polyurethane-covered wires that exit the chest wall through a small stab wound. The probe can easily be removed by gentle traction when the patient's condition is stable. The technique was developed, validated, and refined in extensive animal studies, and this report describes the first series of 20 consecutive human implants, performed between August 1984 and September 1985, in which the absolute cardiac output determination obtained with the ultrasound probe at the time of its application was correlated with cardiac output as measured with a standard electromagnetic flow probe. Fourteen male and six female patients (mean age 5.5 years) were studied. Operations performed included eight atrial septal defect repairs, four procedures for tetralogy of Fallot, three ventricular septal defect repairs, three stenotic valve corrections, and two Senning operations. One operative death occurred, but no complications were related to probe application or removal. The average cardiac output in the 20 patients as measured with the ultrasound probe was 2.2 +/- 1.1 L/min (range 0.67 to 5.27 L/min). This is nearly identical to the results noted with the electromagnetic flow probe, where the mean cardiac output was 2.3 +/- 1.2 L/min (range 0.7 to 6 L/min). Regression analysis revealed a high linear correlation (r = 0.9) between the two techniques. A monitor can display the cardiac output trend with 1 minute updates, which greatly enhance management of intravenous drug therapy and volume administration. In conclusion, this new extraluminal removable probe allows virtually continuous monitoring of the postoperative cardiac output after correction of congenital heart defects and should become a standard technique in the postoperative care of these patients.

Adolescent↗