Mechanisms for cardiac arrhythmias |
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Authors: | B F Hoffman K H Dangman |
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Institution: | (1) Department of Pharmacology, Columbia University, 630 West 168th Street, 10032 New York, New York, USA |
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Abstract: | Summary Possible cellular electrophysiological mechanisms for arrhythmias have been investigated through studies of isolated cardiac tissues. Records through extracellular and intracellular electrodes indicate that arrhythmias may result from either focal or non-focal mechanisms. Focal mechanisms include abnormal impulse initiation (normal or abnormal automaticity), triggering from either early or delayed afterdepolarizations and reflection, whereas the non-focal mechanisms are various forms of reentry due to circus movement. It is reasonable to assume that these mechanisms also occur in vivo. Although it is safe to identify macro-re-entry as the cause of some atrial and ventricular arrhythmias, for the most part direct proof of mechanism usually is lacking for the focal arrhythmias. If on line activation sequence mapping techniques can be developed to quickly and specifically locate arrhythmogenic foci in the in situ heart, it may be possible to use unipolar extracellular recording techniques to identify the exact cellular electrophysiological mechanisms operating within them. |
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Keywords: | Cardiac arrhythmias reentry triggering automaticity transmembrane action potentials early after-depolarizations delayed afterdepolarizing actions |
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