The difference between fibrillations and positive sharp waves is due to tissue filtering.

Area of Science:

• Neurology
• Biomedical Engineering
• Electrophysiology

Background:

• Fibrillation potentials and positive sharp waves are distinct electromyographic waveforms with similar clinical significance.
• The underlying cause for their differing appearance has been a subject of debate, with previous hypotheses being unsatisfactory.

Purpose of the Study:

• To investigate whether electromyograph filter settings can alter the configuration of fibrillation potentials to resemble positive sharp waves.
• To explore the role of tissue filtering and electrode proximity in waveform differentiation.

Main Methods:

• Single-fiber muscle action potentials were recorded and manipulated using varying low-frequency and high-frequency filter settings on an electromyograph.
• Waveforms were analyzed after filter adjustments to observe changes in configuration from fibrillation potential to positive sharp wave appearance.

Main Results:

• Adjusting electromyograph filters from 500 Hz/20 kHz to 0.2 Hz/100 Hz transformed fibrillation potentials into positive sharp wave configurations.
• Similarly, patient-recorded fibrillation potentials (20 Hz/10 kHz) appeared as positive sharp waves when filters were changed to 0.2 Hz/500 Hz.

Conclusions:

• The study suggests that fibrillation potentials and positive sharp waves may represent the same underlying phenomenon, differentiated by the passive electrical properties of the recording environment.
• Tissue filtering and the spatial relationship between the muscle fiber and electrode are proposed as key factors influencing waveform appearance.