Attachment of Meandering Reentrant Wave Fronts to Anatomic Obstacles in the Atrium

Abstract

Acetylcholine chloride (ACh) induces nonstationary meandering reentrant wave fronts in the atrium. We hypothesized that an anatomic obstacle of a suitable size prevents meandering by causing attachment of the reentrant wave front tip to the obstacle. Eight isolated canine right atrial tissues (area, 3.8 x 3.2 cm) were mounted in a tissue bath and superfused with Tyrode's solution containing 10 to 15 mumol/L ACh. Holes with 2- to 10-mm diameters were sequentially created in the center of the tissue with biopsy punches. Reentry was induced by a premature stimulus after eight regular stimuli at 400-ms cycle length. The endocardial activation maps and the motion of the induced reentry were visualized dynamically before and after each test lesion using 509 bipolar electrodes. In the absence of a lesion (n = 8), the induced single reentrant wave front, in the form of a spiral wave, meandered irregularly from one site to another before terminating at the tissue border. Holes with 2- to 4-mm diameters (n = 6) had no effect on meandering. However, when the hole diameters were increased to 6 mm (n = 8), 8 mm (n = 8), and 10 mm (n = 6), the tip of the spiral wave attached to the holes, and reentry became stationary. Transition from meandering to an attached state converted the irregular and polymorphic electrogram to a periodic and monomorphic activity with longer cycle lengths (101 +/- 11 versus 131 +/- 9 ms for no hole versus 10-mm hole, respectively; P < .001). Regression analysis showed a significant positive linear correlation between the cycle length of the reentry and the hole diameter (r = .89, P < .01) and between the cycle length of the reentry and the excitable gap (r = .89, P < .05). We conclude that a critically sized anatomic obstacle converts a nonstationary meandering reentrant wave front to a stationary one. This transition converts an irregular "fibrillation-like" activity into regular monomorphic activity.

Spiral Waves, Obstacles and Cardiac Arrhythmias

“…Therefore, the main objective of this work is to present a numerical study of the interaction of spiral waves with obstacles and to show the existence of different transitions due to the presence of obstacles. By considering non-excitable and partially excitable obstacles we will show that obstacles cannot only stabilize the dynamics as shown in (Ikeda et al, 1997;Kim et al, 1999;Lim et al, 2006), but also, they can act as destabilizers. In both cases and by different mechanisms, the obstacle might act as a switch between two arrhythmic regimes, in which one is less dangerous than the other.…”

“…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.…”

“…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. 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.…”

Approche multi-échelle appliqué à la modélisation de l’activité électrique du coeur

“…Par la suite, la réentrée sera pérennisée si le temps nécessaire à la circulation du front est supé-rieur à la période réfractaire partout le long du circuit. On a montré qu'un obstacle, de diamètre aussi petit que 0,6 mm, pouvait ancrer la réentrée 4 dans des cultures de tissu -bien que la dimension minimale fût dix fois plus grande dans l'oreillette du chien [11,12]. Toute modification du tissu qui augmente la probabilité de la formation d'un bloc local ou qui diminue la vitesse de propagation autour d'un obstacle sera favorable au déclenchement et au maintien de réentrées.…”