© 1986 by European Society of Cardiology
Copyright © 1986, European Society of Cardiology
Evolution of vectorcardiographic QRS changes during myocardial infarction in dogs and their relation to infarct size
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*From the Institute of Informatics, University of Oslo, Oslo, Norway
From the Bærum Hospital, Sandvika, Norway
From the Institute of Surgical Research, Rikshospitalet, Oslo, Norway
The ability of vectorcardiographic QRS changes to quantify myocardial ischaemia and necrosis in dogs was studied. Myocardial infarction was produced in 21 anaesthetised dogs by inflating a balloon inserted into the right, left anterior descending, or left circumflex coronary artery. A Frank vectorcardiogram was recorded before and every 15–30 minutes for 10 hours after the occlusion. ST vector magnitude (ST-VM), QRS summation vectors, and QRS integral differences (QRS-VD) between the preocclusion recording and subsequent recordings were computed. Twenty four hours after occlusion two vectorcardiograms were obtained, the hearts removed, and the infarcts cut out and weighed. Four dogs were excluded from the study because of persistent arrhythmias, major conduction defects, or sudden death. In the remaining 17 dogs the QRS summation vectors rotated maximally towards the site of infarction 7 minutes after occlusion corresponding to a median minimum QRS-VD of –19 (range –2 to –29) µVs. This coincided with the maximum ST-VM, median 0.43 (range 0.12 – 0.68) mV. The QRS summation vectors subsequently rotated away from the infarct producing a median maximum QRS-VD of 20 (range 6–28) µVs. The maximum QRS-VD correlated significantly with the percentage of infarcted myocardium (r=0.82). The correlation between the early minimum QRS-VD and the maximum ST-VM was r=0.83. The QRS-VD was recomputed with a reference taken 2 or 4 hours after occlusion. The relation between maximum QRS-VD and infarct percentage was not significantly changed with the reference at 2 hours, but with the reference at 4 hours the ability to predict infarct size was lost. With a common reference representing the median of the preocclusion recordings the correlation between maximum QRS-VD and infarct percentage was r=0.60. Examination of various QRS time integrals showed that the integral from QRS beginning to QRS end produced the highest correlations with infarct percentage.
These results indicate that with a proper preinfarction reference serial assessment of QRS integral differences in the Frank vectorcardiogram can be used to quantify both the ischaemic area and the final size of a myocardial infarct and to follow the progression of the evolving infarction. This technique can therefore represent a valuable adjunct in monitoring the infarction process and in studying infarct limiting treatment in the coronary care unit.
KEYWORDS Infarct size, QRS vectors, difference vectors, ST vectors
Address for correspondence and reprints; Dr Per Grøttum, Institute of Informatics, University of Oslo, Box 1080Blindem, 0316 Oslo, Norway.