Significance ofDiscordant STAlternans inVentricular Fibrillation

Withtheuseofepicardial mapping, we investigated theelectrical alternans oftheSTsegment during acutemyocardial ischemia andstudied thedifference inSTalternans between dogswith resultant ventricular fibrillation andthose without it. During the7-minute occlusion oftheleft anterior descending coronaryartery belowitsfirst diagonal branch, 60epicardial unipolar electrograms wererecorded simultaneously at1-minute intervals bya computerized mapping system. STalternans was foundintheeight dogs we observed. Theamplitude ofSTalternans (difference intheSTsegmentelevation oftwoconsecutive electrograms) was greater indogs withventricular fibrillation (n=4)thaninthose without it(n=4)(3.92±1.24 versus0.58±0.49 mV,p<0.05). Threeofthefourdogswithventricular fibrillation demonstrated discordant ST alternans (i.e., adjacent leads wereoutofphase). Results fromthepresent study indicate that an increased amplitude anddiscordance ofSTalternans during acutemyocardial ischemia are related toventricular fibrillation andactas indicators oftimeandspatial unevenness of ventricular repolarization. (Circulation 1990;82:2185-2189)