QUANTIFICATION OF MYOCARDIUM AT RISK AND DETECTION OF REPERFUSION BY DYNAMIC VECTORCARDIOGRAPHIC ST SEGMENT MONITORING IN A PIG OCCLUSION-REPERFUSION MODEL

Objective: The aim was to investigate whether continuous computerised vectorcardiographic monitoring of absolute spatial ST vector magnitude (ST-VM) and of spatial ST change vector magnitude (STC-VM) during cor onary occlusion could be used to estimate the size of myocardium at ri sk; and also to test whether reperfusion could be distinguished from s ustained occlusion by continuous monitoring of ST vector alterations. Methods: Computerised vectorcardiographic monitoring via Frank leads w as applied in a closed chest occlusion-reperfusion pig model. Coronary occlusion over 24 h was produced in 20 animals by injecting a 2 mm ba ll into the left anterior descending coronary artery (n = 7), the righ t coronary artery (n = 8), and the left circumflex coronary artery (n = 5). Another 31 pigs were reperfused by retraction of the ball after 30 (n = 10), 60 (n = 15), or 90 (n = 6) min of left anterior descendin g artery occlusion. The extent of the myocardium at risk was measured by autoradiography. Results: Seven animals were excluded. Irrespective of occluded coronary artery the relative parameter STC-VM over the fi rst 30 min of occlusion correlated closely with area at risk, that is, the mean STC-VM between 10 and 30 min of occlusion (r = 0.78 p<0.001) . The absolute parameter ST vector magnitude (ST-VM) did not reflect i schaemia in 16/44 animals and did not correlate significantly with are a at risk. The weight of myocardium at risk (MAR) was predictable from STC-VM: MAR weight (measured) = 0.97 X MAR weight (predicted)+0.26 (g ), r = 0.81, p<0.001. STC-VM decline rate, time to STC-VM plateau, and cumulated sum plots of STC-VM were all able to distinguish reliably b etween reperfused animals and those with permanent occlusion. A parado xical increase in STC-VM - ''reperfusion peak'' - was detected in 17/3 1 (55%) of the animals. This phenomenon was related to large amount of myocardium at risk or to a long occlusion time. Conclusion: Dynamic v ectorcardiographic ST monitoring provides adequate estimation of myoca rdium at risk and enables detection of reperfusion in experimental myo cardial ischaemia.