Origins of spiral wave meander and breakup in a two-dimensional cardiac tissue model

We studied the stability of spiral waves in homogeneous two-dimensional car diac tissue using phase I of the Luo-Rudy ventricular action potential mode l. By changing the conductance and the relaxation time constants of the ion channels, various spiral wave phenotypes, including stable, quasiperiodica lly meandering, chaotically meandering, and breakup were observed. Stable a nd quasiperiodically meandering spiral waves occurred when the slope of act ion potential duration (APD) restitution was <1 over all diastolic interval s visited during reentry; chaotic meander and spiral wave breakup occurred when the slope of APD restitution exceeded 1. Curvature of the wave changes both conduction velocity and APD, and their restitution properties, thereb y modulating local stability in a spiral wave, resulting in distinct spiral wave phenotypes. In the LR1 model, quasiperiodic meander is most sensitive to the Na+ current, whereas chaotic meander and breakup are more dependent on the Ca2+ and K+ currents. (C) 2000 Biomedical Engineering Society. [S00 90-6964(00)00807-9]