Temporal Resolution of Stimulation Threshold: A Tool for Electrophysiologic Analysis

Electrical stimulation of cardiac cultures with closed-loop control permits the determination of threshold in real time. The temporal response of stimulation threshold and underlying cell membrane excitability is valuable information for understanding the complex electrophysiologic processes within cardiac cells and can aid in understanding the mechanisms and effects of pharmaceuticals or other stimuli. This work presents the temporal response of stimulation threshold measured using HL-1 cardiac myocytes when exposed to changes in temperature and extracellular potassium concentration. These changes mimic systemic alteration of excitability and conditions that can result from ischemia in the heart. The results demonstrate the efficacy of stimulation threshold as a physiologic indicator and illustrate transient effects with both fast and slow time constants that can be resolved using a system that determines stimulation threshold in real time