DECREASE IN THE HIGH-FREQUENCY QRS COMPONENTS DEPENDING ON THE LOCAL CONDUCTION DELAY

The high frequency components contained in the QRS complex (HF-QRS) ar e a powerful indicator for the risk of sudden cardiac death. However, it is controversial whether conduction delay increases or decreases th e HF-QRS. In 21 anesthetized, open-chest dogs, the right atrium was co nstantly paced. A cannula was inserted into the left anterior descendi ng artery and flecainide, lidocaine or disopyramide was infused to slo w the local conduction. Sixty unipolar electrograms were recorded from the entire ventricular surface and were signal-averaged. Data were fi ltered (30-250 Hz) by using fast-Fourier transform. The HF-QRS was cal culated by integrating the filtered QRS signal. Activation time (AT; d V/dt minimum) was delayed and the HF-QRS was reduced in the area perfu sed by flecainide, lidocaine or disopyramide. The percent increase in AT closely correlated the percentage decrease in the HF-QRS; the corre lation coefficients were 0.75, 0.83 and 0.76 for flecainide, lidocaine and disopyramide infusion, respectively, (p<0.001). Decrease in the H F-QRS linearly correlated with the local conduction delay. This study proved that conduction delay decreases the HF-QRS, and that the HF-QRS is a potent indicator of disturbed local conduction.