Based On The Acceleration Sensor Pacemaker Frequency Adaptive System Design And Implementation

Rate adaptive (also called rate responsive) function,which can sense people’s metabolic levels under various physiologic conditions, is a significant part of current pacemakers. It is employed to adjust pacing rate for proper cardiac output according to that sensed metabolic levels. Among those patients with pacemakers implanted in, above half of them have suffered from sinus node dysfunction along with chronotropic incompetence. In addition, some patients aren’t proper for atrium-ventricle tracking pacing, for their sinus rhythm cannot be maintained even in atriums because of atrial fibrillation or flutter. These patients’heart rates are completely decided by those pacemakers implanted in their bodies. As for the fragile patients lacking activities, the basic pacing rate can almost satisfy their metabolic demands. However, if the patients need to implement exercises frequently, they have to turn to rate adaptive function for help, which keeps carrying out real-time analysis of patients’changing metabolic levels and provide ideal pacing rate. For this reason, rate adaptive function has to a great extent compensated the cardiac chronotropic incompetence, as well as improved patients’exercise tolerance.Rate adaptive function must be accurate and prompt in sensing metabolic quantities. Multiple sets of parameters should also be designed to satisfy individual difference. In this paper, we introduce an open-loop rate adaptive algorithm based on a tri-axial accelerometer. Our algorithm evaluates the amplitude and frequency characteristics of collected acceleration, and establishes proper mapping relationships between evaluated results and target pacing rate, then self-designed quasi-exponential functions are applied to transform current pacing rates smoothly to target pacing rates in case of physical damage. After optimizing specific codes of our rate adaptive algorithm based on the developing environment of IAR Embedded Workbench, we transplant it into microcontroller MSP430FG4618and realize actual demonstration. When our algorithm is running on the MCU, accurate target pacing rate in addition to current pacing rate would be timely displayed on a peripheral LCD screen.Eventually, vibration generator tests and treadmill tests are introduced. During both tests, we adopt an Enpulse E2DR01pacemaker from Medtronic Corporation, putting it together with the accelerometer into identical activity environments. Vibration generators are able to adjust vibration frequency and amplitude, thus to provide stable and controllable acceleration signals. Vibration generator tests aim at optimizing parameters in the rate adaptive algorithm by comparing its yielded target rates with pacing rates output by that Enpulse pacemaker. While in the treadmill tests, exercise speeds as well as grades are specified. We implement contrast experiments similar to that in vibration generator tests, in order to further optimize rate adaptive parameters and verify the algorithm performance. On the other hand, some regression equations from’ACSM’s Guidelines for Exercise Testing and Prescription’are adopted to calculate metabolic equivalents, showing the metabolic equivalent series and activity estimate series share an extremely high correlation. The results provide theoretic support for our proposed algorithm. These tests indicate that our proposed rate adaptive algorithm has quick response and high accuracy, which proves to possess performance as excellent as Medtronic Enpulse E2DR01pacemakers.