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[The Italian Group for the Study of Streptokinase in Myocardial Infarct: Changes in surface cardiac potentials. Study
Abstract:
The electrocardiographic changes during and after the thrombolytic treatment with streptokinase (SK) were assessed by means of body surface potential mapping. The aim of the study was to identify potential patterns suggesting reperfusion and revealing possible short-term effects on the infarct size of the recanalization. We studied 23 patients enrolled in the G.I.S.S.I. trial; 11 had an anterior and 12 had an inferior myocardial infarction; 14 were treated with SK and 9 were controls. Body surface maps were recorded from 105 lead points located on the anterior thoracic surface using an automated instrument. The maps were obtained immediately before the SK infusion (or at the time of randomization in the control patients), 30, 60, 120 minutes thereafter and then 24 hours and 7 days after the onset of the infarct symptoms. In each patient the surface potential distribution at 100 msec after the end of QRS was considered and the sum of all the positive potential values was calculated (sigma ST). In addition, the potential time integrals relating to two intervals of the cardiac cycle (first 100 msec of ST and first 40 msec of QRS) were calculated at each lead point and transferred to diagrams representing the chest surface explored (isointegral map). With respect to Q-40 maps, deviation index maps were calculated as follows: the mean Q-40 map (obtained from 30 normal subjects) was subtracted from the map of each patient; the value obtained at each lead point was then divided by the standard deviation of the normal values for that point. An area where the integral values were at least 2 SD lower than normal was considered a reliable index of infarct. By considering as index of reperfusion an early peak of CPK (less than 12 hours from the onset of infarct symptoms), we divided the patients into 2 subsets: reperfused (R) and not reperfused (NR). The mean values of sigma ST at 100 msec progressively decreased in all patients from the baseline to the subsequent recordings in both control and SK groups, without significant differences; nevertheless, the highest percent reductions of sigma ST were observed only in some R patients. The maximum on the ST-100 isointegral maps also showed a similar behaviour.(ABSTRACT TRUNCATED AT 250 WORDS)