A comparison of chronaxies for ventricular fibrillation induction, defibrillation, and cardiac stimulation: unexpected findings and their implications.

Autor: Lawo T; Medical Clinic II (Cardiology), BG University Hospital Bergmannsheil, Bochum, Germany. thomas.lawo@rub.de, Deneke T, Schrader J, Danilovic D, Wenzel B, Buddensiek M, Muegge A
Jazyk: angličtina
Zdroj: Journal of cardiovascular electrophysiology [J Cardiovasc Electrophysiol] 2009 Mar; Vol. 20 (3), pp. 307-14. Date of Electronic Publication: 2008 Oct 30.
DOI: 10.1111/j.1540-8167.2008.01319.x
Abstrakt: Introduction: A low-energy (Methods and Results: In order to learn how LEC shocks may be optimized, we used an animal model to compare the strength-duration curve for VF induction and the strength-duration curve for cardiac stimulation via the shock coil. Conventional implantable cardioverter-defibrillator (ICD) leads were implanted in 12 narcotized pigs from 20 kg to 25 kg in weight. Stimulation, VF induction, and defibrillation pulses were delivered by custom-designed stimulators at preset pulse durations and amplitudes. The corresponding hyperbolic strength-duration curves were constructed using the least-squares fit method and averaged for all the animals. The mean chronaxie for stimulation via the shock coil of 0.23 ms was significantly shorter than both defibrillation (4.8 ms) and VF induction (3.1 ms) chronaxie values. At a shock duration of 0.3 ms or less, the mean VF-induction threshold amplitude exceeded 300 V.
Conclusion: It may be reasonable to study whether LEC pulses from 0.25 ms to 0.30 ms in duration and up to 250 V in amplitude would increase therapeutic yield in VT termination without VF induction in humans. Contrary to the current belief, the discrepancy between defibrillation and stimulation chronaxie is not caused by different electrode size. We postulate that the time constant of the fast sodium channel reactivation may be the underlying reason.
Databáze: MEDLINE
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