[New method to detect late potential with fast Fourier transform analysis].

We compared a new method to detect late potential applied fast Fourier transform (FFT-LP) with the prior method of Simson (S-LP). We investigated 159 consecutive pts excluding atrial fibrillation, 102 pts with old myocardial infarction (MI) without bundle branch block (BBB), 10 pts with dilated cardiomyopathy (DCM) without BBB, normal 17 pts without BBB, 15 MI pts with BBB, 3 DCM pts with BBB, and normal 12 pts with BBB. And 102 MI pts without BBB were divided into 3 groups by S-LP, group 1 was 12 pts, of which 2 or 3 parameters of S-LP were positive, group 2 was 5 pts, of which 1 parameter of S-LP was positive, and the 3rd group was 85 pts, of which all parameters of S-LP were negative. FFT was performed in the segment from terminal 40 mesc of QRS complex to ST segment, then, the area under the curve between 20 and 50 Hz was divided by the area under the curve between 0 and 20 Hz. We called this ratio "area ratio (AR)", and examined it in each group. When the value of AR was over 20, defined as FFT-LP positive, the positive ratio was 75% (group 1), 20% (group 2), 11.9% (group 3), 0% (normal pts without BBB), 40% (MI with BBB), 8.3% (normal with BBB).(ABSTRACT TRUNCATED AT 250 WORDS)