The absence of high-frequency QRS changes in the presence of standard electrocardiographic QRS changes of old myocardial infarction

Background This study compares the high-frequency QRS components (HF-QRS) i n patients with and without standard electrocardiogram (ECG) changes indica tive of old myocardial infarction (MI). Previous studies have indicated tha t patients with an old MI differ in their HF-QRS compared with healthy subj ects. The HF-QRS has been reported to be decreased during acute coronary oc clusion and increased after reperfusion. However, there is controversy abou t the appearance of HF-QRS after the acute phase of MI. Methods A total of 154 patients were included, 57 with and 97 without QRS c hanges of old MI on the standard EGG. The patients with old MI were divided into subgroups on the basis of the MI location indicated by the standard E GG. Signal-averaged ECGs from the 12 standard leads were recorded. The root -mean-square values of the HF-QRS were determined within two frequency band s: 150 to 250 Hz and 80 to 300 Hz. Results There was a large interindividual variation in HF-QRS in patients w ithout MI as well as in those with different MI locations. There were no si gnificant differences between the groups in the summed HF-QRS of all 12 lea ds or in the pattern of lead distribution of the HF-QRS. Not even the patie nts with the greatest QRS changes of old MI could be differentiated from th ose without any changes of old MI on the standard EGG. The results were the same in both analyzed frequency bands. Conclusions This study shows, contrary to previous studies, that analysis o f HF-QRS cannot differentiate between patients with and without old MI.