Intracellular recording from beating heart in situ using a special micropipette holder.

Use of a motion-compensated micropipette holder, which senses cardiac motion and lifts and lowers the micropipette and supporting apparatus in synchrony with the heart beat, allows for stable recording of transmembrane action potentials from subepicardial cells of an in vivo beating heart in an open-chest dog without significantly impairing cardiac hemodynamics. This technique may be used to study the effects of ischemia, hypertrophy, or pharmacologic agents on the cellular electrophysiological parameters of subepicardial ventricular cells of an in vivo beating heart.