Related Experiment Videos
Relation between transcardiac and transthoracic current during defibrillation in humans
1Department of Medicine, New York Hospital-Cornell University Medical College, NY 10021.
Circulation Research
|December 1, 1990
Summary
The current fraction traversing the heart during transthoracic defibrillation in humans is approximately 4%. This low percentage is due to parallel pathways in the thorax shunting current away from the heart.
Area of Science:
- Biomedical Engineering
- Cardiovascular Physiology
- Electrophysiology
Background:
- Transthoracic defibrillation threshold current is influenced by transcardiac current fraction (FC).
- Previous FC estimates in humans are lacking, despite theoretical values up to 45%.
Purpose of the Study:
- To quantify the transcardiac current fraction (FC) during transthoracic defibrillation in humans.
- To validate the use of voltage ratios as a surrogate for FC measurement.
Main Methods:
- Measured simultaneous transthoracic (VT) and transcardiac (VC) voltages during defibrillator testing in 10 human patients.
- Calculated the VC/VT ratio as a surrogate for FC.
- Compared direct FC measurements with VC/VT in 16 dogs.
Main Results:
- The VC/VT ratio in humans was 0.04 ± 0.03, indicating approximately 4% of transthoracic current traverses the heart.
- In dogs, direct FC measurements and VC/VT ratios were statistically equivalent (approximately 0.05).
- Parallel pathways (thoracic cage, lungs) significantly shunt current away from the heart.
Conclusions:
- The transcardiac current fraction during human transthoracic defibrillation is significantly lower than previously estimated.
- The VC/VT ratio is a valid and practical method for estimating FC in humans.
- Understanding current distribution is crucial for optimizing defibrillation efficacy.