Intra-QRS high-frequency ECG changes with ischemia. Is it possible to evaluate these changes using the signal-averaged Holter ECG in dogs?

The purpose of this experiment is to study the possibility of intra-QRS high-frequency electrocardiographic (HFECG) changes for the evaluation of and recovery from myocardial ischemia in both the time-domain and spectral-turbulence analyses on the signal-averaged ECG using the Holter ECG monitoring (Holter SAECG) system. A balloon catheter was inserted into the left anterior descending coronary artery (LAD of 8 mongrel dogs and was maintained inflated for 2 hours to occlude the LAD and then was deflated to allow for reperfusion. The cardiac signal from the three orthogonal leads of the surface ECG (X, Y, and Z) was recorded and analyzed with a Del Mar Avionics (model 459, Irvine, CA) recorder and analyzer (model 563). The Holter SAECG was assessed before the LAD occlusion phase (control), during the coronary occlusion phase (ischemia), after the reperfusion phase (recovery). To evaluate intra-QRS ECG changes in the time-domain analysis, root-mean-square (RMS) voltage of the entire QRS in 40-250 HZ (40 RMS), 100-250 Hz (100 RMS), and 150-250 Hz (150 RMS) were studied and the vector magnitude of the QRS was depicted. In the spectral-turbulence analysis and spectrocardiogram to study the discordance of the ECG wave front velocity by fast Fourier transformation analysis, the interslice correlation mean (IC mean) and interslice correlation standard deviation (IC SD), which were calculated as the mean and standard deviation of the Pearson correlation coefficient of each time slice with its neighbor, were investigated. In the time-domain analysis, the LAD occlusion by balloon catheter at ischemia produced a reduction in 40 RMS, 100 RMS, and 150 RMS, while a restoration was seen at recovery in 40 RMS and 100 RMS. In the spectral-turbulence analysis, LAD occlusion at ischemia caused a decrease in IC mean and an increase in IC SD. The waveform of the vector magnitude and the spectrocardiogram seen at control showed changes with ischemia and was restored at recovery with the coronary reperfusion. It was thought possible to capture the intra-QRS HFECG changes that occur during myocardial ischemia and recovery from it in the time-domain analysis and spectral-turbulence analysis on the Holter SAECG system in spite of the limitation of this methodology. To evaluate myocardial ischemia and recovery, this method should be useful clinically.