SB-QTVW: An alternate index to differentiate between healthy and acute ischemic/infarcted patients using vector magnitude derived QT variability

Abstract

Myocardial ischemia alters ventricular repolarization through a variety of mechanisms. Studies show that QTVI, an index of QT variability, is elevated during acute ischemia and cardiomyopathy. This indicates an increased QT variability in ischemic patients. Preliminary studies from our laboratory showed that the length of vector magnitude derived QT interval varies by less than 16 ms in healthy controls, and frequently varies more than 16 ms in ischemic patients. With this study, we introduced an alternative index - QT Variability Window (QTVW), and tested the hypothesis that ischemia causes the length of resting QT intervals in vector magnitude to vary more than a QTVW of 16 ms. Results from our study support our hypothesis. Furthermore, in certain cases, our algorithm was able to differentiate between the healthy controls and acute ischemic patients using as few as 20 consecutive beats. These findings provide an alternative index, QTVW, to assess ventricular repolarization following ischemia.