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Decrease in the high frequency QRS components depending on the local conduction delay
T Watanabe1, M Yamaki, H Tachibana
1First Department of Internal Medicine, Yamagata University School of Medicine, Japan. tewatana@med.id.yamagata-u.ac.jp
Insights
Conduction delays decrease high-frequency QRS components (HF-QRS), a marker for sudden cardiac death risk. This study confirms HF-QRS reduction indicates disturbed local cardiac conduction.
Area of Science:
- Cardiology
- Electrophysiology
- Medical Signal Processing
Background:
- High-frequency QRS components (HF-QRS) are linked to sudden cardiac death risk.
- The relationship between cardiac conduction delay and HF-QRS levels remains debated.
Purpose of the Study:
- To investigate the impact of slowed local cardiac conduction on HF-QRS.
- To determine if HF-QRS can serve as an indicator of impaired ventricular conduction.
Main Methods:
- Utilized 21 dogs with induced cardiac conduction delays via flecainide, lidocaine, or disopyramide infusion.
- Recorded 60 unipolar electrograms from the ventricular surface.
- Analyzed filtered (30-250 Hz) QRS signals using fast-Fourier transform to calculate HF-QRS and activation time (AT).
Main Results:
- Conduction delay, measured by increased AT, significantly reduced HF-QRS in the affected area.
- A strong positive correlation was observed between increased AT and decreased HF-QRS (r=0.75-0.83, p<0.001).
- The reduction in HF-QRS was linearly related to the degree of local conduction delay.
Conclusions:
- Local cardiac conduction delay demonstrably decreases HF-QRS.
- HF-QRS is a sensitive indicator of disturbed local cardiac conduction and potential arrhythmia substrate.
Abstract:
The high frequency components contained in the QRS complex (HF-QRS) are a powerful indicator for the risk of sudden cardiac death. However, it is controversial whether conduction delay increases or decreases the HF-QRS. In 21 anesthetized, open-chest dogs, the right atrium was constantly paced. A cannula was inserted into the left anterior descending artery and flecainide, lidocaine or disopyramide was infused to slow the local conduction. Sixty unipolar electrograms were recorded from the entire ventricular surface and were signal-averaged. Data were filtered (30-250 Hz) by using fast-Fourier transform. The HF-QRS was calculated by integrating the filtered QRS signal. Activation time (AT; dV/dt minimum) was delayed and the HF-QRS was reduced in the area perfused by flecainide, lidocaine or disopyramide. The percent increase in AT closely correlated the percentage decrease in the HF-QRS; the correlation coefficients were 0.75, 0.83 and 0.76 for flecainide, lidocaine and disopyramide infusion, respectively, (p<0.001). Decrease in the HF-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.