Formation of virtual isthmus: new scenario of spiral wave death after decrease of excitability
I. S. Erofeev, K. I. Agladze
Laboratory of Biophysics of Excitable Systems, Moscow Institute of Physics and Technology (MIPT),
141700 Dolgoprudny, Russia
Abstract
Termination of rotating (spiral) waves or reentry is crucial
when fighting with the most
dangerous cardiac tachyarrhythmia. To increase the efficiency of the
antiarrhythmic drugs as
well as finding new prospective ones it is decisive to know the
mechanisms how they act and
influence the reentry dynamics. The most popular view on the mode of
action of the
contemporary antiarrhythmic drugs is that they increase the core of the
rotating wave
(reentry) to that extent that it is not enough space in the real heart
for the reentry to exist.
Since the excitation in cardiac cells is essentially change of the
membrane potential, it relies
on the functioning of the membrane ion channels. Thus membrane ion
channels serve as
primary targets for the substances which may serve as antiarrhythmics. At
least, the entire
group of antiarrhythmics class I (modulating activity of sodium channels)
and partially class
IV (modulating activity of calcium channels) are believed to destabilize
and terminate reentry
by decreasing the excitability of cardiac tissue. We developed an
experimental model
employing cardiac tissue culture and photosensitizer (AzoTAB) to study
the process of the
rotating wave termination while decreasing the excitability of the
tissue. A new scenario of
spiral wave cessation was observed: an asymmetric growth of the rotating
wave core and
subsequent formation of a virtual isthmus, which eventually caused a
conduction block and
the termination of the reentry.