An automatic cardiac action potential duration meter

Abstract

The duration of a cardiac action potential (AP) is measured from the beginning of its upstroke to the end of its asymptotic repolarization phase: the end being given by a point in proportion to the AP amplitude. If the resting potential, AP amplitude, as well as the duration, alter simultaneously, frequent accurate measurements can be extremely tedious. A fully automatic AP duration meter has thus been constructed to cope with these difficulties while measuring within about 2% on a beat-to-beat basis. It is suitable either for brief sampling of AP durations when recording with microelectrodes, which may impale cells intermittently, or for continuous monitoring, as with suction electrodes on intact beating hearts in situ. For example, the device can faithfully track changes in duration during periods of regional myocardial ischemia in intact ventricles in situ while the AP alters its base line, upstroke velocity, amplitude, and duration.