Spiral-wave dynamics depend sensitively on inhomogeneities in mathematical models of ventricular tissue

Abstract

Every sixth death in industrialized countries occurs because of cardiac arrhythmias such as ventricular tachycardia (VT) and ventricular fibrillation (VF). There is growing consensus that VT is associated with an unbroken spiral wave of electrical activation on cardiac tissue but VF with broken waves, spiral turbulence, spatiotemporal chaos and rapid, irregular activation. Thus spiral-wave activity in cardiac tissue has been studied extensively. Nevertheless, many aspects of such spiral dynamics remain elusive because of the intrinsically high-dimensional nature of the cardiac-dynamical system. In particular, the role of tissue heterogeneities in the stability of cardiac spiral waves is still being investigated. Experiments with conduction inhomogeneities in cardiac tissue yield a variety of results: some suggest that conduction inhomogeneities can eliminate VF partially or completely, leading to VT or quiescence, but others show that VF is unaffected by obstacles. We propose theoretically that this variety of results is a natural manifestation of a complex, fractal-like boundary that must separate the basins of the attractors associated, respectively, with spiral breakup and single spiral wave. We substantiate this with extensive numerical studies of Panfilov and Luo-Rudy I models, where we show that the suppression of spiral breakup depends sensitively on the position, size, and nature of the inhomogeneity.

Small size ionic heterogeneities in the human heart can attract rotors

“…It is well known that a rotor can be locally stabilized due to anchoring to an inexcitable obstacle (4,25,26,35), i.e., process when a rotor attaches to the boundary of such an obstacle. Later, it was shown that rotors can anchor to other types of heterogeneities: ionic heterogeneities (30,31), blood vessels (40), pectinate (42), and papillary muscles (13). Also in Refs.…”

Spiral Waves, Obstacles and Cardiac Arrhythmias

“…In general, it was shown that the presence of inhomogeneities in the medium not only stabilizes the spiral wave dynamics as shown in (Ikeda et al, 1997;Kim et al, 1999;Shajahan et al, 2007) but also might generate more complex dynamics, which implies that the presence of obstacles might induce a more dangerous arrhythmic regime than the one without the obstacle. Drift of a spiral wave had been considered only for planar boundaries (Yermakova & Pertsov, 1986) and inside circular domains (Mikhailov et al, 1994).…”

“…Examples of partially excitable obstacles are scar tissue (Starobin et al, 1996) or ionic heterogeneities (Starobin et al, 1996;Tusscher & Panfilov, 2002;Valderrábano et al, 2000), whereas examples of non excitable obstacles are arteries (Valderrábano et al, 2000) or the natural orifices in the atria (Azene et al, 2001). It has been observed that an obstacle in cardiac tissue might act as a stabilizer of spiral wave dynamics (Davidenko et al, 1992;Ikeda et al, 1997;Kim et al, 1999;Lim et al, 2006;Pertsov et al, 1993;Valderrábano et al, 2000), as it provides a transition between meandering spiral waves (Ikeda et al, 1997) or multiple spiral waves (Shajahan et al, 2007;Valderrábano et al, 2000) into a simple rotation spiral, which is attached to the obstacle. This 17 www.intechopen.com transition is clinically important because as it has been shown, fibrillation like activity changes to a tachycardia regime (Kim et al, 1999).…”

“…This 17 www.intechopen.com transition is clinically important because as it has been shown, fibrillation like activity changes to a tachycardia regime (Kim et al, 1999). The interaction of spiral waves with obstacles and its relationship with the transition between different arrhythmic regimes has been experimentally and computationally studied by different researchers (Azene et al, 2001;Comtois & Vinet, 2005;Ikeda et al, 1997;Shajahan et al, 2007;2009;Valderrábano et al, 2000). Valderrabano et al (Valderrábano et al, 2000) studied in a cardiac tissue preparation the transition between ventricular fibrillation and ventricular tachycardia due to the presence of obstacles; Ikeda et al (Ikeda et al, 1997), also considered the transition of different arrhythmic regimes due to the attachment of a spiral wave to an obstacle of minimum size.…”

“…Valderrabano et al (Valderrábano et al, 2000) studied in a cardiac tissue preparation the transition between ventricular fibrillation and ventricular tachycardia due to the presence of obstacles; Ikeda et al (Ikeda et al, 1997), also considered the transition of different arrhythmic regimes due to the attachment of a spiral wave to an obstacle of minimum size. Shajahan et al (Shajahan et al, 2007) used the Luo-Rudy and Panfilov models to study the transition of spiral turbulence to a simple rotating spiral wave due to the presence of an obstacle, which again provides a transition between different arrhythmic regimes; Xie et al (Xie et al, 2001) presented a computational study of the effects of regional ischemia on the stability of a spiral wave; Azene et al (Azene et al, 2001) carried out a computational study of the attachment and detachment of wavefronts to obstacles based on the Luo-Rudy model; Olmos (Olmos, 2010) studied the interaction of spiral waves in a particular case of the meandering regime, with rectangular obstacles. The aim in that work was to understand better necessary conditions in order to obtain attachment of the meandering spiral wave to the obstacle.…”