ANALYSIS OF HIGH-FREQUENCY QRS POTENTIAL DURING EXERCISE TESTING IN PATIENTS WITH CORONARY-ARTERY DISEASE AND IN HEALTHY-SUBJECTS

High resolution ECG Waveforms from leads V-3, V-4, V-5, and V-6 were a nalyzed in two groups of male subjects before, during, and following t readmill exercise testing. Group A included 32 coronary artery disease (CAD) patients, with arteriographically proven > 75% obstruction of a t least two main coronary arteries, and group B included 30 healthy su bjects, without history or symptoms of CAD. Signal averaging and filte ring techniques were used in order to enhance the signal-to-noise rati o of the recorded EGG. The averaged QRS waveforms were filtered betwee n 150 and 250 Hz. QRS complexes of the four leads were combined to for m a precordial average complex'' (PAC). The PAC signals were examined for each subject at different stages of She exercise test and two para meters were computed: the root mean square (RMS) voltage; and the peak amplitude. The values of RMS and peak amplitudes measured at each sta ge of the exercise test were normalized to the values at rest. Normali zed RMS (NRMS) values at peak exercise, immediately after peak exercis e, and during the recovery phase were found to be higher for the healt hy subjects than for the CAD group (1.17 +/- 0.32 vs 0.94 +/- 0.26, P < 0.008 at peak exercise, 1.13 +/- 0.24 vs 0.84 +/- 0.19, P < 0.002 af ter peak exercise, 1.08 +/- 0.22 vs 0.94 +/- 0.17, P < 0.007 during re covery). Cut-off NRMS value of one had a sensitivity of 81.3% and a sp ecificity of 70.0% in differentiating CAD patients from healthy subjec ts in the examined groups. Normalized peak amplitude (NAMP) values exh ibited similar behavior, with higher values for the healthy subjects t han for the CAD group (1.23 +/- 0.48 vs 0.94 +/- 0.36, P < 0.03 at pea k exercise, 1.20 +/- 0.34 vs 0.83 +/- 0.28, P < 0.001 after peak exerc ise, 1.10 +/- 0.29 vs 0.94 +/- 0.23, P < 0.02 during recovery). Specif icity of 73.3% and sensitivity of 71.8% were found using a postpeak NA MP cut-off value of 1. In conclusion, the present study shows that usi ng high frequency ECG may contribute to identifying patients with CAD. Further studies in larger groups of patients are required to better d efine the true predictive value of the method described for the diagno sis of CAD.