A new floating sensor array to detect electric near fields of beating heart preparations

• Published in: Biosensors & bioelectronics Vol. 21; no. 12; pp. 2232 - 2239
• Main Authors: Hofer, E., Keplinger, F., Thurner, T., Wiener, T., Sanchez-Quintana, D., Climent, V., Plank, G.
• Format: Journal Article
• Language: English
• Published: Lausanne Elsevier B.V 15-06-2006; Elsevier Science
• Subjects: Animals; Biological and medical sciences; Biotechnology; Body Surface Potential Mapping - instrumentation; Body Surface Potential Mapping - methods; Conduction velocity; Electrodes, Implanted; Electromagnetic Fields; Equipment Design; Equipment Failure Analysis; Fundamental and applied biological sciences. Psychology; Guinea Pigs; Heart Conduction System - physiology; Heart Rate - physiology; High-density electrode array; In Vitro Techniques; Methods. Procedures. Technologies; Mice; Micro mapping; Microelectrodes; Others; Transducers; Various methods and equipments; High-density electrode array; Conduction velocity; Micro mapping; Near field; Heart; Electrodes; Array; Electric field; Measurement sensor; Sensor array; In vitro
• ISSN: 0956-5663; 1873-4235
• DOI: 10.1016/j.bios.2005.11.010

A new flexible sensor for in vitro experiments was developed to measure the surface potential,
Φ, and its gradient,
E (electric near field), at given sites of the heart. During depolarisation,
E describes a vector loop from which direction and magnitude of local conduction velocity
θ can be computed. Four recording silver electrodes (14
μm
×
14
μm) separated by 50
μm, conducting leads, and solderable pads were patterned on a 50
μm thick polyimide film. The conductive structures, except the electrodes, were isolated with polyimide, and electrodes were chlorided. Spacer pillars mounted on the tip fulfil two functions: they keep the electrodes 70
μm from the tissue allowing non-contact recording of
Φ and prevent lateral slipping. The low mass (9.1
mg) and flexibility (6.33
N/m) of the sensor let it easily follow the movement of the beating heart without notable displacement. We examined the electrodes on criteria like rms-noise of
Φ, signal-to-noise ratio of
Φ and
E, maximum peak-slope recording d
Φ/d
t, and deviation of local activation time (LAT) from a common signal and obtained values of 24–28
μV, 46 and 41
dB, 497–561
V/s and no differences, respectively. With appropriate data acquisition (sampling rate 100
kHz, 24-bit), we were able to record
Φ and to monitor
E and
θ on-line from beat-to-beat even at heart rates of 600
beats/min. Moreover, this technique can discriminate between uncoupled cardiac activations (as occur in fibrotic tissue) separated by less than 1
mm and 1
ms.