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 V₃, V₄, V₅, and V₆ were analyzed in two groups of male subjects before, during, and following treadmill exercise testing. Group A included 32 coronary artery disease (CAD) patients, with arteriographically proven > 75% obstruction of at least two main coronary arteries, and group B included 30 healthy subjects, without history or symptoms of CAD. Signal averaging and filtering techniques ware used in order to enhance the signal-to-noise ratio of the recorded ECG. The averaged QRS waveforms were filtered between 150 and 250 Hz. QRS complexes of the four leads were combined to form a “precordial average complex” (PAC). The PAC signals were examined for each subject at different stages of the exercise test and two parameters were computed: the root mean square (RMS) voltage; and the peak amplitude. The values of RMS and peak amplitudes measured at each stage of the exercise test were normalized to the values at rest. Normalized RMS (NRMS) values at peak exercise, immediately after peak exercise, and during the recovery phase were found to be higher for the healthy subjects than for the CAD group (1.17 ± 0.31 vs 0.94 ± 0.26, P < 0.008 at peak exercise, 1.13 ± 0.24 vs 0.84 ± 0.19, P < 0.001 after peak exercise, 1.08 ± 0.22 vs 0.94 ± 0.17, P < 0.007 during recovery). Cut-off NRMS value of one had a sensitivity of 81.3% and a specificity of 70.0% in differentiating CAD patients from healthy subjects in the examined groups. Normalized peak amplitude (NAMP) values exhibited similar behavior, with higher values for the healthy subjects than for the CAD group (1.23 ± 0.48 vs 0.94 ± 0.36, P < 0.03 at peak exercise, 1.20 ± 0.34 vs 0.83 ± 0.28, P < 0.001 after peak exercise, 1.10 ± 0.29 vs 0.94 ± 0.23, P < 0.02 during recovery). Specificity of 73.3% and sensitivity of 71.8% were found using a postpeak NAMP cut-off value of 1. In conclusion, the present study shows that using high frequency ECG may contribute to identifying patients with CAD. Further studies in larger groups of patients are required to better define the true predictive value of the method described for the diagnosis of CAD.