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Defibrillation causes immediate cardiac dilation in humans.
Erin Sylvester1, Eric Johnson, Paul Hess
1The University of Memphis, Memphis, Tennessee 38152, USA.
Journal of Cardiovascular Electrophysiology
|August 2, 2003
Summary
Defibrillation causes immediate ventricular dilation in humans, indicating a rapid relaxation of the heart muscle. This study provides the first evidence of this mechanical response following defibrillation.
Area of Science:
- Cardiology
- Cardiac Electrophysiology
- Medical Imaging
Background:
- Previous research on isolated heart tissue identified excitation and deexcitation as key defibrillation mechanisms.
- This study investigates the mechanical response of the human heart to defibrillation.
Purpose of the Study:
- To provide the first evidence in humans of cardiac deexcitation immediately following defibrillation.
- To track the heart's mechanical response to defibrillation using echocardiography.
Main Methods:
- Seven human subjects receiving an implantable cardioverter defibrillator (ICD) were studied.
- Two-dimensional echocardiography was used to measure ventricular chamber geometry before and after defibrillation.
- Ventricular fibrillation and defibrillation were induced approximately three times per subject.
Main Results:
- Immediately after defibrillation, both right and left ventricular chambers showed significant dilation.
- Fractional area increase was observed in the right ventricle (1.58 +/- 0.25) and left ventricle (1.10 +/- 0.06).
- Peak dilation occurred at 194 +/- 114 milliseconds post-defibrillation.
Conclusions:
- Defibrillation induces a rapid increase in ventricular chamber area due to myocardial relaxation.
- This suggests that defibrillation synchronizes cardiac cells to a deexcited state in humans.