Rate Responsive Pacing Using Transthoracic Impedance Minute Ventilation Sensors: A Multicenter Study on Calibration Stability

Abstract

Previous studies showed that transthoracic impedance minute ventilation (IMV), as measured by a pacemaker sensor, is closely correlated to actual minute ventilation (VE) determined by standard methods. The aim of this study was to analyze the changes in the calibration between IMV and VE at rest and during exercise over time. Fifteen patients (age 60 +/- 13 years) with Medtronic Kappa 400 pacemakers completed a baseline visit followed by two visits separated by 1 month and 1 week, respectively. In each patient, VE (L/min) was monitored at rest in the supine and sitting positions and during graded bicycle ergometer exercise using a standard cardiopulmonary metabolic gas analysis system with simultaneous recording of IMV (omega/min) using DR-180 extended telemetry monitors. Calibration at rest was defined as the ratio of IMV to VE, calculated from 1-minute average values in the supine and sitting positions. Calibration during bicycle exercise was defined as intercept (IMV value at VE = 10 L/min-typical VE value at beginning of exercise), and slope of the IMV/VE regression line. The calibration of IMV showed individual variability over time. The magnitude (absolute value) of observed fractional changes in calibration at 1 month was 0.23 +/- 0.20 (rest-supine), 0.20 +/- 0.15 (rest-sitting), 0.18 +/- 0.19 (exercise-intercept), 0.28 +/- 0.35 (exercise-slope), and 0.18 +/- 0.15, 0.15 +/- 0.09, 0.28 +/- 0.39, and 0.27 +/- 0.15, respectively, at 1 week. The magnitude of change at 1 month was not statistically different from the magnitude of change at 1 week. In conclusion, the calibration of IMV, as measured by a pacemaker sensor, versus actual VE may demonstrate variability. However, this study also suggests that the observed changes are not cumulative over time. These results have implications for patient monitoring applications using these sensors and for development of future pacemaker rate response algorithms.

Acute Evaluation of Transthoracic Impedance Vectors Using ICD Leads

“…Based on the air sensitivity data in this study it seems justified to prefer the more simplified non‐TRIAD tripolar ICD vector configuration to the other vectors. The air sensitivity, 2.70 ± 2.73 Ω/L measured from the tripolar ICD vector, was found adequate, although lower than in two previous studies 2,10 that evaluated pacemaker leads. From the data on the tripolar atrial vector in 15 patients, 10 we calculated the air sensitivity in that study to be 4.06 ± 2.60 in the supine body position 4 weeks and 5 weeks postpacemaker implant.…”

“…The air sensitivity, 2.70 ± 2.73 Ω/L measured from the tripolar ICD vector, was found adequate, although lower than in two previous studies 2,10 that evaluated pacemaker leads. From the data on the tripolar atrial vector in 15 patients, 10 we calculated the air sensitivity in that study to be 4.06 ± 2.60 in the supine body position 4 weeks and 5 weeks postpacemaker implant. Simon et al 2 studied 20 patients with a DDD pacemaker system (14 ± 10 months postimplant), and the telemetered impedance waveform was recorded simultaneously with direct volume respiration measured by a pneumotachometer.…”

Clinician’s Guide to Cardiopulmonary Exercise Testing in Adults

“…They can generate heart rates that are theoretically appropriate, at rest and during effort, for patients with chronotropic incompetence due to sick sinus syndrome or advanced atrioventricular block. 173,174 Because the chronotropic control of the working sinus node is difficult to imitate, cardiologists must evaluate the rate-response pacing rate adequately, tailoring rate-response settings for many patients. This is typically performed by use of protocols based on activities of daily living, followed by an evaluation of the pacing rate through Holter monitoring.…”

Physical activity detection in patients with intracardiac leadless pacemaker

“…11 The most common sensor used to drive rate response is the accelerometer, which rapidly detects physical motion. In conventional pacemaker systems, several rate response optimization algorithms are available, [12][13][14] and selection of these automatic algorithms makes the programming of the rate adaptive function relatively simple.…”