A method for detecting myocardial abnormality by using a current-ratio mapcalculated from an exercise-induced magnetocardiogram

A method for making a current-ratio map to determine the ischaemic area of angina pectoris (AP) patients has been developed. This method uses a curren t-arrow map calculated using a QRS wave from 64-channel magnetocardiogram ( MCG) signals. The current-ratio map can be calculated from the ratio of an exercise-induced current vector to an at-rest current vector. The MCG signa ls of eight patients with angina pectoris (AP) (six patients with effort AP and two patients with variant AP) and four healthy volunteers were measure d before and after a two-step exercise test. The current-ratio maps of the six patients with effort AP showed three distinct patterns: a left-circumfl ex-artery (LCX) pattern; a right-coronary-artery (RCA) pattern; and a left- anterior-descending (LAD) pattern. The maximum current ratios of these thre e patterns differed from those of normal patterns. The patterns of two pati ents with variant AP were similar to normal patterns. Furthermore, a compar ison of the current-ratio map before and after percutaneous-transluminal-co ronary-angioplasty (PTCA) treatment indicated that the cardiac ischaemia wa s reduced in all patients. An appropriate criterion to diagnose abnormality in a patient with an ischaemic myocardial area seems to be a maximum curre nt ratio exceeding 0.4 to 0.5. Based on these preliminary results, it is be lieved that the location of an ischaemic area (the coronary artery part) ca n be estimated by using the ischaemic current-ratio map pattern.