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Diagnosis of transmural ischemia and infarct traditionally is based on electrocardiogram evidence of ST elevation >1 mm in two contiguous leads. However, some data suggest that the initial manifestation of transmural ischemia is prolongation of the corrected QT (QTc) interval, with ST elevation occurring later. In a prospective observational study, researchers analyzed 12-lead ECGs recorded at baseline and during balloon inflation in 74 patients undergoing elective cardiac catheterization.
Transmural ischemia induced by balloon occlusion (average total occlusion time, 40 seconds) resulted in QTc interval prolongation in 100% of patients. The QTc interval was lengthened by 32 ms, from an average maximum of 423 ms at baseline to 455 ms during …