Late fields in magnetcardiography and late potentials in electrocardiography after acute myocardial infarction

A high specificy and a high positive prediction has been reached in risk st ratification for sudden cardiac death after acute myocardial infarction (AM I) by combining multiple methods. But sensitivity and negative prediction a re still not satisfying. There are the same physiological processes underly ing magnetcardiography (MCG) and electrocardiography (ECG). Nevertheless, t he signals in each method contain different information. Methods: We studied the cardiac magnetic fields in 50 patients after AMI an d in 32 probands and calculated the magnetic late field (LF), according to Simsons late potential (LP) analysis. We defined normal values, according t o the 95 % confidence interval of the probands (QRS < = 97 ms, RMS > = 0.6, LAS < 25 ms). Results: We compared the results of LF and LP analysis regarding pathologic -nonpathologic and found 76 % of the patients with the same results in both methods. Four patients had magnetic signals with low amplitude in the ST s egment in contrast to the ECG result, while 6 patients with a "LP positive" diagnosis based on RMS and LAS only, did not show LF. In addition, we have found the magnetic QRS complex to be shorter than the electrical one. Discussion: In general the results of LF measurement are similar to the one s of LP measurement. Presumably, there are intracardial currents, which are not detectable by EGG, Further studies are needed to evaluate the prognost ic value in patient at high risk for cardiac arrhythmias.