SIGNIFICANCE OF INWARDLY DIRECTED TRANSMEMBRANE CURRENT IN DETERMINATION OF LOCAL MYOCARDIAL ELECTRICAL ACTIVATION DURING VENTRICULAR-FIBRILLATION

Citation
Fx. Witkowski et al., SIGNIFICANCE OF INWARDLY DIRECTED TRANSMEMBRANE CURRENT IN DETERMINATION OF LOCAL MYOCARDIAL ELECTRICAL ACTIVATION DURING VENTRICULAR-FIBRILLATION, Circulation research, 74(3), 1994, pp. 507-524
Citations number
43
Categorie Soggetti
Hematology,"Cardiac & Cardiovascular System
Journal title
ISSN journal
00097330
Volume
74
Issue
3
Year of publication
1994
Pages
507 - 524
Database
ISI
SICI code
0009-7330(1994)74:3<507:SOIDTC>2.0.ZU;2-R
Abstract
Ventricular fibrillation (VF) is the principal cardiac rhythm disorder responsible for sudden cardiac death in humans. The accurate determin ation of local cardiac activation during VF is essential for its mecha nistic elucidation. This has been hampered by the rapidly changing and markedly heterogeneous electrophysiological nature of VF. These diffi culties are manifested when attempting to differentiate true propagati ng electrical activity from electrotonic signals and when identifying local activation from complex and possibly fractionated electrograms. The purpose of this investigation was to test the hypothesis that the presence of a balanced inwardly and outwardly directed transmembrane c harge, obtained from the ratio of the inward to outward area under the cardiac transmembrane current curve (-/+ I-m area), could reliably di fferentiate propagating from electrotonic deflections during VF. To te st this hypothesis, we applied a recently described technique for the in vivo estimation of the transmembrane current (I-m) during cardiac a ctivation. A 17-element orthogonal epicardial electrode array was comb ined with an immediately adjacent optical fiber array to record electr ical and optically coupled transmembrane potential signals during VF. Recordings were obtained during electrically induced VF in six dogs to determine the I-m associated with activation and the time course of r epolarization, as well as unipolar electrograms and bipolar electrogra ms recorded at multiple center-to-center interelectrode distances from 0.2 to 3 mm. Propagat ing local activations were associated with the presence of an easily identified inwardly directed I-m with a balanced inward and outward charge (-/+ I-m area approximate to 1.0). Electrot onic waveforms lacked this inward I-m (-/+ I-m area approximate to 0.0 ). Normal Na+-mediated inward currents were directly demonstrated to b e responsible for some activations during VF. (Circ Res. 1994;74:507-5 24.)