ISCHEMIA DETECTION AFTER MYOCARDIAL-INFARCTION - DIAGNOSTIC-VALUE OF EXERCISE-INDUCED QRS DURATION CHANGES EVALUATED BY A NEW COMPUTERIZED METHOD

A new computerized optical scanner was used to measure QRS complex dur ation during exercise stress testing, both pre- and postdischarge, as a means of ischemia detection after acute myocardial infarction. Thall ium stress testing was used as a standard of comparison. Each patient underwent predischarge exercise testing (while receiving anti-ischemic drug therapy) and a postdischarge test 1 month later (without anti-is chcmic drug therapy), as well as thallium stress testing within 4 mont hs of infarction. In the population of 68 patients, 42 of the predisch arge tests and 43 of the postdischarge tests showed an ischemic respon se of QRS prolongation. When compared with thallium testing for QRS pr olongation criteria, the sensitivity was 95% with a specificity of 77% predischarge and 89% with a specificity of 65% postdischarge. Accordi ng to ST-T criteria, only 12 of 68 patients were positive for ischemia predischarge; this number increased to 29 postdischarge (predischarge sensitivity 24% and specificity 90%, with postdischarge sensitivity 6 8% and specificity 87%), when compared with thallium testing. Measurin g QRS duration during exercise increased the sensitivity of detection of ischemic patients over that of ST-T criteria by 71% predischarge an d 21% postdischarge, with a 22-23% loss of specificity, and was appare ntly not influenced by anti-ischemic drug therapy.