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

Area of Science:

• Biomedical Engineering
• Cardiovascular Physiology
• Sensor Technology

Background:

• Accurate measurement of cardiac electrical activity is crucial for understanding heart function and diagnosing arrhythmias.
• Existing methods for recording cardiac electrograms can be invasive or lack the spatial resolution to capture localized electrical phenomena.
• The development of flexible, non-contact sensors is needed to overcome limitations of current technologies.

Purpose of the Study:

• To develop and evaluate a new flexible sensor for in vitro measurement of cardiac surface potential (Phi) and its gradient (electric near field, E).
• To assess the sensor's capability in computing local conduction velocity (theta) during cardiac depolarization.
• To determine the sensor's performance in detecting subtle cardiac activation patterns, such as those in fibrotic tissue.

Main Methods:

• Fabrication of a flexible sensor on a polyimide film with four silver electrodes.
• Implementation of non-contact recording using spacer pillars to maintain a 70 µm distance from the tissue.
• Utilizing high-resolution data acquisition (100 kHz sampling rate, 24-bit) for signal analysis.

Main Results:

• The sensor demonstrated low rms-noise (24-28 µV) and high signal-to-noise ratios (46 dB for Phi, 41 dB for E).
• Accurate measurement of maximum peak-slope (dPhi/dt: 497-561 V/s) and local activation time (LAT) was achieved.
• Real-time monitoring of Phi, E, and theta was possible at high heart rates (up to 600 beats/min).
• The technique successfully discriminated between cardiac activations separated by <1 mm and <1 ms, indicative of fibrotic tissue.

Conclusions:

• The developed flexible sensor enables precise, non-contact measurement of cardiac electrical parameters.
• This technology facilitates accurate computation of local conduction velocity and detection of complex arrhythmias.
• The sensor's flexibility, low mass, and high resolution offer significant advantages for in vitro cardiac electrophysiology studies.