Time- and frequency-domain analyses of signal-averaged electrocardiograms in patients with diabetes mellitus.

We recorded the signal-averaged electrocardiography (SAECG) of patients with diabetic retinopathy in order to clarify whether a ventricular conduction disturbance can be detected by time- or frequency-domain analysis of the SAECG. Twenty-four normal subjects (N group) and 20 patients with diabetic retinopathy [diabetes mellitus (DM) group] were studied. On time-domain analysis, the duration of the filtered QRS (f-QRS), the duration of the terminal QRS below 40 microV (LAS40) and the root-mean-square amplitude of the terminal 40 msec (RMS40) were measured. The frequency-domain analysis was performed using two windows. In each window, the ratio of the area under the spectral curve from 40 to 100 Hz was compared with that from 0 to 40 Hz and the area from 20 to 50 Hz was compared with that from 0 to 20 Hz. The LAS40 of the DM group was significantly prolonged when compared with the N group. The area ratio from 40 to 100 Hz versus 0 to 40 Hz significantly increased in the DM group when compared with the N group. These results suggest that SAECG can be used to detect abnormal electrical signals due to diabetic microangiopathy. Moreover, high frequency components of 40 to 100 Hz at the terminus of the QRS wave were most sensitive for abnormalities due to diabetic microangiopathy.