Phase invariant signature algorithm (PISA), a new noninvasive technique, was used in the detection and quantification of
acid-induced myocardial damage in anesthetized dogs. The diagnostic capabilities of this method were compared with those of conventional electrocardiogram and
biochemical markers, MB-
creatine phosphokinase (MB-CPK) and lactic
dehydrogenase (
LDH1). Myocardial damage of varying degree was induced by injecting diluted sulphuric
acid (0.01 to 0.10 ml) into the free wall of the left ventricle. Conventional ECG, wideband ECG for PISA analysis, blood samples for
LDH1, and MB-CPK were taken before and after 15, 30, 60, and 90 min of
acid injection. The heart was removed at the end of 90 min for estimation of myocardial damage. PISA Index increased within 10-15 min of
acid injection and remained elevated for the duration of the experiment (90 min). The increase in the PISA index was directly related to the extent of myocardial damage and the amount of
acid injected. Although the conventional electrocardiogram detected large myocardial damage, it was unable to detect small myocardial damage. Also, most of initial change in conventional ECG with large myocardial damage disappeared within 90 min, while the PISA index was still elevated to the maximum level. The MB-CPK was not detected before or after myocardial damage. There was no significant change in the
LDH1 at any time after
myocardial infarction. These results suggest that the PISA technique is superior to the conventional ECG and the
biochemical markers and would be a valuable diagnostic tool in the detection and quantification of incipient as well as advanced
myocardial infarction.