High-Capacity Cardiac Signal Acquisition System for Flexible, Simultaneous, Multidomain Acquisition

Abstract

Capturing cardiac electrical propagation or electrocardiographic images demands simultaneous, multidomain recordings of electrocardiographic signals with adequate spatial and temporal resolution. Available systems can be cost-prohibitive or lack the necessary flexibility to capture signals from the heart and torso. We have designed and constructed a system that leverages affordable commercial products (Intantech, CA, USA) to create a complete, cardiac signal acquisition system that includes a flexible front end, analog signal conditioning, and defibrillation protection. The design specifications for this project were to (1) record up to 1024 channels simultaneously at a minimum of 1 kHz, (2) capture signals within the range of ± 30 mV with a resolution of 1 µV, and (3) provide a flexible interface for custom electrode inputs.We integrated the Intantech A/D conversion circuits to create a novel system, which meets all the required specifications. The system connects to a standard laptop computer under control of open-source software (Intantech). To test the system, we recorded electrograms from within the myocardium, on the heart surface, and on the body surface simultaneously from a porcine experimental preparation. Noise levels were comparable to both our existing, custom acquisition system and a commercial competitor. The cost per channel was $32 USD, totaling $33,800 USD for a complete system.

Tipping the scales of understanding: An engineering approach to design and implement whole-body cardiac electrophysiology experimental models

“…The results were two types of data: the signals themselves, captured continuously and at suitable sample rates, and the locations of the sensors relative to the cardiac anatomy, a much more static set of measurements that presented their own challenges. The result, based on decades of experience and development in our laboratory ( Macleod et al., 1896 ; Franzone et al., 1978 ; Taccardi et al., 1994 ; Khoury et al., 1995 ; Fuller et al., 2000 ; Taccardi et al., 2005 ; Taccardi et al., 2008 ; Aras, 2015 ; Aras et al., 2016 ) and from others ( Rogers et al., 2002 ; Bear et al., 2015 ; Trew et al., 2019 ), was a collection of different types of high-resolution recording arrays, including intramural multielectrode needles, epicardial socks, and torso surface strips ( Zenger et al., 2020a ; Zenger et al., 2020b ).…”

Body Surface Potential Mapping: Contemporary Applications and Future Perspectives

“…Torso surface electrogram voltages are on the order of a few (1-3) millivolts therefor electrical noise is a constant challenge, due mainly to the long connecting wires and the noise generated by other nearby electrical equipment. Analog processing of the recorded signals usually consists of buffering, amplification by a factor of 100-1000, filtering to limit the bandwidth to the physiologically relevant range, e.g., 0.2-300 Hz, and optionally to remove power line noise [93,94]. This analog processing ideally occurs as close to the electrode-tissue interface as possible, with some systems using amplifier circuits built into electrode strips such as the "Active Electrodes" from BioSemi (https://www.biosemi.com/strip_electrode.htm (accessed date 29 October 2021)) [95].…”

“…Clinical ECG systems often use a bandpass filter with an upper cutoff as low as 200 Hz. However, BSPM systems have a higher cutoff frequency in the 200 to 1000 Hz region to capture more complex high-frequency components of the ECG signals [93,94]. The cost of higher cutoff frequencies is susceptibility to noise, often requiring special care during acquisition to limit noise at the source, e.g., proper grounding of recording equipment, electrical isolation of the subject, shielding of sensitive devices, and minimizing the use of other electrical equipment during BSP signal acquisition.…”

“…Another innovation to improve signal quality is to include signal amplifiers for each electrode integrated into the strips, called 'active electrodes' by the authors [95]. Studies by other groups describe multiple strips consisting of between 4 and 12 electrodes each that connect to a variable interface system before analog processing [17,86,94,103,104]. An example recording system for experimental use is shown in Figure 4.…”

“…While older systems were limited in their recording resolution (both in time and voltage level) and number of simultaneous recording electrodes, modern systems can often record up to a thousand or more inputs at a sampling frequency of over 1000 Hz and voltage resolution in the milli to micro volt range, which is more than sufficient for most BSPM applications. Zenger et al described a hybrid system (Figure 4) based on custom-designed hardware to interface BSP electrode systems with a commercial recording system (intantech.com) initially designed for neural signals [94]. Such custom systems built for experimental use are designed to be flexible and can often record from electrode arrays on the heart surface or embedded within the cardiac tissue.…”