Comparing cardiac action potentials recorded with metal and glass microelectrodes

Machine-pulled high-impedance glass capillary microelectrode is standard fo r transmembrane potential (TMP) recordings. However, it is fragile and diff icult to impale, especially in beating myocardial tissues. We hypothesize t hat a high-impedance pure iridium metal electrode can be used as an alterna tive to the glass microelectrode for TMP recording. The TMPs were simultane ously recorded from isolated perfused swine right ventricles with a metal m icroelectrode and a standard glass microelectrode during pacing and during ventricular fibrillation. The basic morphology of TMP recorded with these e lectrodes was comparable. The action potential duration (APD) at 90% repola rization was 241 +/- 29 ms for the metal microelectrode and 236 +/- 31 ms f or the glass microelectrode with a good correlation (r = 0.99, P< 0.0001). The maximum slope value of the APD restitution curves during pacing was als o significantly correlated. One metal microelectrode and >20 glass microele ctrodes were needed per study. We conclude that, in isolated perfused swine right ventricles, the TMP recorded by the metal microelectrode is comparab le with that recorded by the glass microelectrode. Because the metal microe lectrode is more durable than the glass microelectrode, it can serve as an alternative for APD recording and for restitution analyses.