Detection of intramyocardial scroll waves using absorptive transillumination imaging

Optical imaging using voltage-sensitive dyes has become an important tool for studying vortex-like electrical waves in the heart. Such waves, known as spiral or scroll waves, can spontaneously form in pathological ventricular myocardium, causing ventricular fibrillation and sudden death. Until recently, observations of scroll waves were limited to their surface manifestations, thus providing little information about the shape and location of their organizing center, the filament. We use computer modeling to assess the feasibility of visualizing filaments using dynamic transillumination imaging in conjunction with near-IR voltage-sensitive absorptive dyes (absorptive transillumination). We simulate transillumination signals produced by the intramural scroll waves in a realistic slab of ventricular tissue with trabeculated endocardial surface. The computations use a detailed ionic model of electrical excitation (LRd) coupled to a photon transport model for cardiac tissue. Our simulations show that dynamic absorptive transillumination data, with subsequent processing involving either amplitude maps, time-space plots, or power-of-the-dominant-frequency maps, can be used to reliably detect intramural scroll waves through the whole thickness (approximately 10 mm) of the ventricular wall. Neither variations in the thickness of the myocardial wall nor noise impeded the detection of intramural filaments.