Intracellular microelectrode recordings of 22 human right atrial tissue preparations identified specialized fibers with automaticity and conduction velocities of 0.41-0.45 m/sec.
This study provides foundational reference values for the electrophysiologic properties of human atrial contractile and specialized fibers.
The electrophysiologic properties of human atrium were studied with intracellular microelectrodes in 22 preparations of human right atrial tissue obtained at the time of corrective open heart surgery. Two types of fibers were identified: the first had electrical characteristics typical of atrial contractile cells and the second those of atrial specialized fibers. Automaticity developed only in the latter type of cell. In 36 impalements of specialized atrial fibers, resting membrane potential was -86 ± 5 mv (mean ±SD), transmembrane action potential amplitude was 102 ± 12 mv, transmembrane action potential overshoot was 16 ± 4 mv. Similar results were obtained in 49 impalements of contractile fibers. Conduction velocity measured 0.28-0.33 m/sec in contractile fibers and 0.41-0.45 m/sec in specialized atrial fibers. Action potential duration of specialized atrial fibers was linearly related to the basic cycle length between 200 and 1000 msec. At cycle lengths greater than 1000 msec the increase in action potential duration was no longer linear. There was a decrease of 58 mv in resting membrane potential of specialized atrial fibers when exposed to a tenfold increase in extracellular K + . This decrease occurred in a linear fashion in K + above 5 mM. These experiments provide reference values for future studies dealing with electrophysiology of human atrial tissue.
Gelband et al. (Wed,) conducted a other in Patients undergoing corrective open heart surgery (n=22). Intracellular microelectrode recording vs. Contractile vs specialized atrial fibers was evaluated on Electrophysiologic properties including resting membrane potential, action potential amplitude, and conduction velocity. Intracellular microelectrode recordings of 22 human right atrial tissue preparations identified specialized fibers with automaticity and conduction velocities of 0.41-0.45 m/sec.