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Electromechanical delay in the intact dog heart
International Journal of Cardiology
|October 1, 1985
Summary
A new computer method accurately measures electromechanical delay, the time between Q-wave onset and left ventricular pressure rise. This method reveals electromechanical delay is largely independent of heart rate, except at very high rates.
Area of Science:
- Cardiovascular Physiology
- Biomedical Engineering
- Computational Methods
Background:
- Electromechanical delay (EMD) is a critical parameter in cardiac function.
- Accurate measurement of EMD is essential for understanding cardiac mechanics and disease.
- Existing methods for EMD determination may have limitations.
Purpose of the Study:
- To develop and validate a novel computer-based method for determining electromechanical delay.
- To assess the influence of various hemodynamic factors on electromechanical delay.
Main Methods:
- A computer method was developed to calculate electromechanical delay from Q-wave onset to left ventricular systolic pressure rise.
- The method was validated in 86 heart catheterization sessions on 56 anesthetized beagle dogs.
- Hemodynamic parameters including heart rate, contractility, preload, and afterload were manipulated.
Main Results:
- The mean basal electromechanical delay was 22 ± 4 msec.
- Increasing heart rate from 90 to 240 bpm significantly prolonged electromechanical delay (21 ± 5 to 33 ± 14 msec, P < 0.001).
- Electromechanical delay generally changed independently of heart rate, but shortened with positive inotropic effects or increased presystolic fiber length.
Conclusions:
- The developed computer method provides a reliable means for measuring electromechanical delay.
- Electromechanical delay is primarily influenced by factors other than heart rate, such as contractility and preload.
- Understanding these influences is crucial for clinical assessment and therapeutic interventions in cardiovascular conditions.