Ventricular Fibrillation: Spiral Wave Breakup (2D)

Ventricular fibrillation is not simply "faster" ventricular tachycardia — it is the electrical substrate turning spatially chaotic. This simulator integrates the Aliev–Panfilov reaction-diffusion model, a well-established two-variable excitable-medium equation, on a 2D finite-difference sheet of cardiac-like tissue rendered directly on canvas. Fire a planar S1 stimulus, then time a cross-field S2 stimulus into the still-refractory wake left by S1 to genuinely induce a reentrant spiral wave (rotor) through unidirectional conduction block — exactly the S1–S2 protocol used in real electrophysiology labs and computational-cardiology studies. Then tune the restitution-slope parameter (μ₁): keep it shallow and the rotor spins as a stable, organized circuit; push it steep and the same PDE spontaneously tears the spiral's arm into a shifting field of independent chaotic wavelets — the reaction-diffusion mechanism believed to underlie the transition from organized reentrant tachycardia into ventricular fibrillation. Live readouts track the S1–S2 protocol state, excited tissue fraction, wavefront count and the activation cycle length at a fixed probe point.