Prototype of an Ambulatory Long-Term ECG Monitoring System for Real Time Detection of QRS Complex and T Wave End Based on FPGA

Abstract

A prototype of an ambulatory long-term ECG monitor was developed for the simultaneous acquisition and storage of 3 quasi-orthogonal leads, and its real-time processing for the beat-to-beat detection of QRS complex and T-wave end for the measurement of heart rate and RT interval. The prototype has as its core a Field Programmable Gate Array (FPGA) of Xilinx Artix-7 embedded in a CMOD-A7 development board, it also controls and communicates with an ADS1294 circuit for the acquisition of the simultaneous ECG leads (D1, aVF, V2) and a micro-SD memory for the storage of these leads and the heart rate and RT interval beat-to-beat values. The prototype has a bandwidth of 200 Hz delimited by a digital FIR filter, a minimum CMRR of 112 dB at 60 Hz, a resolution of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$0.76\ \mu\mathrm{V}$</tex> and an average current consumption of 85 mA which allows a minimum battery life of 36 hours. The evaluation of the QRS complex and T-wave end detection algorithms implemented in the FPGA was performed with 10 records of the QT database. For the QRS complex detection the accuracy was of 97.8%. For the T-wave end the measurement error was of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$5.14\pm 7.07\ \text{ms}$</tex> , which was within the tolerance limits for deviations with respect of the manual measurements made by the CSE experts.