A real-time microprocessor QRS detector system with a 1-ms timing accuracy for the measurement of ambulatory HRV

Abstract

The design, test methods and results of an ambulatory QRS detector are presented. The device is intended for the accurate measurement of heart rate variability (HRV) and reliable QRS detection in both ambulatory and clinical use. The aim of the design work was to achieve high QRS detection performance in terms of timing accuracy and reliability, without compromising the size and power consumption of the device. The complete monitor system consists of a host computer and the detector unit. The detector device is constructed of a commonly available digital signal processing (DSP) microprocessor and other components. The QRS detection algorithm uses optimized prefiltering in conjunction with a matched filter and dual edge threshold detection. The purpose of the prefiltering is to attenuate various noise components in order to achieve improved detection reliability. The matched filter further improves signal-to-noise ratio (SNR) and symmetries the QRS complex for the threshold detection, which is essential in order to achieve the desired performance. The decision for detection is made in real-time and no search-back method is employed. The host computer is used to configure the detector unit, which includes the setting of the matched filter impulse response, and in the retrieval and postprocessing of the measurement results. The QRS detection timing accuracy and detection reliability of the detector system was tested with an artificially generated electrocardiogram (ECG) signal corrupted with various noise types and a timing standard deviation of less than 1 ms was achieved with most noise types and levels similar to those encountered in real measurements. A QRS detection error rate (ER) of 0.1 and 2.2% was achieved with records 103 and 105 from the MIT-BIH Arrhythmia database, respectively.

Variabilidade da frequência cardíaca e infecções pulmonares pós revascularização miocárdica

“…Recordings were made by the Polar™ Advanced S810i™ device. This device detects ECG RR intervals with a sampling frequency of 500 Hz, and time resolution of one millisecond (ms), and has already been validated 11,12 .…”

Adaptive motion artifacts reduction algorithm for ECG signal in textile wearable sensor

“…In this paper, we choose relatively high sampling frequency in ECG acquisition for future uses, and minimal low frequency range in modeling of motion artifacts from the previous researches ( [5,6]). In this point of view, frequency band of proposed motion artifacts occupies such a small portion of total frequency range that this may not be an efficient analysis in energy compactness manner.…”

“…The sampling frequency is 1,000 Hz, higher than general cases (250 ∼ 500 Hz) in ECG acquisition. This is for other feature extraction and future study like [6], such as QRS detection or HRV calculation in better time-resolution condition.…”

“…Gary M. Friesen, et al [5] compared noise sensitivity in detecting QRS mentioning that motion of ECG electrode caused electrode-skin impedance changes inducing baseline changes with its duration of 100 ∼ 500 ms. Antti Ruha, et al [6] proposed real-time QRS detector system for measuring ambulatory HRV. The motion artifacts were considered to be lower than 5 Hz sinusoidal wave and filtered using over-sampled (2 kHz) ECG signal for better timing-resolution.…”

Variabilidade da frequência cardíaca em pacientes com Distrofia Miotônica tipo 1

“…Data obtained by the Polar monitor were transferred to the computer using an interface with an infrared device for signal emission. This system detects ventricular depolarization, corresponding to the R wave on the ECG, with a sampling rate of 500 Hz and a temporal resolution of 1 millisecond 21 , validated by Loimaala et al 22 . The infrared interface was placed at a maximum distance of 8 inches and at a 15° angle to the Polar S810i…”