Electrophysiological analysis of hyperkalemic cardiomyocytes using a multielectrode array system.

Area of Science:

• Cardiovascular Physiology
• Electrophysiology
• Cell Biology

Background:

• Cardiomyocyte action potentials are regulated by serum electrolytes, including sodium (Na+), potassium (K+), and calcium (Ca2+).
• Hyperkalemia, characterized by elevated blood K+ levels, poses a risk of life-threatening cardiac arrhythmias.

Purpose of the Study:

• To investigate the effects of elevated extracellular K+ concentrations on the electrophysiological properties of chick embryonic cardiomyocytes.
• To evaluate the efficacy of calcium (Ca2+) therapy in mitigating hyperkalemia-induced changes in cardiomyocyte function.

Main Methods:

• Utilized a multielectrode array system to record extracellular potentials from cardiomyocyte sheets.
• Systematically increased extracellular K+ concentrations (from 4 mM to 12 mM) to observe dose-dependent effects.
• Assessed key electrophysiological parameters including interspike interval (ISI), dV/dt, field potential duration (FPD), and conduction velocity.

Main Results:

• Increased K+ concentration (12 mM) significantly prolonged ISI (approx. 3.5x), decreased dV/dt (>5x), shortened FPD (20%), and halved conduction velocity compared to control (4 mM K+).
• Calcium therapy partially restored ISI but did not recover the slowed conduction velocity, reduced dV/dt, or shortened FPD.
• Demonstrated distinct impacts of hyperkalemia on different electrophysiological parameters, with varying responses to calcium intervention.

Conclusions:

• Hyperkalemia profoundly disrupts cardiomyocyte electrophysiology, affecting action potential timing, propagation, and repolarization.
• Extracellular Ca2+ concentration plays a role in modulating hyperkalemia's effects, but its therapeutic benefits are limited in fully restoring normal cardiac function.
• These findings enhance understanding of cardiomyocyte responses to electrolyte imbalances and inform interpretations of extracellular potential recordings.