Spatiotemporal correlation uncovers characteristic lengths in cardiac tissue

Area of Science:

• Cardiac Electrophysiology
• Nonlinear Dynamics
• Biophysics

Background:

• Complex spatiotemporal patterns in mammalian hearts arise from period-doubling bifurcations with increased stimulation frequency.
• Understanding these dynamics is crucial for comprehending cardiac arrhythmias like fibrillation.

Purpose of the Study:

• To introduce and analyze a characteristic spatial length of cardiac activity in canine ventricular wedges.
• To investigate how this spatial length changes with stimulation frequency and during fibrillation.
• To establish a phenomenological law relating conduction velocity restitution and spatial length.

Main Methods:

• High-resolution optical mapping experiments in canine ventricular wedges.
• Spatiotemporal correlation analysis to determine characteristic spatial length.
• Mathematical modeling and nonlinear fitting of experimental data.

Main Results:

• Characteristic spatial length decreases from 40-20 cm (one-to-one response) to ~3 cm (transition to fibrillation).
• During fibrillation, the characteristic length stabilizes at ~1 cm.
• A constitutive phenomenological law was derived, linking conduction velocity restitution with spatial length, featuring a 3/2 fractional exponent.

Conclusions:

• The study quantifies a critical spatial scale in cardiac activity that characterizes transitions in electrophysiological behavior.
• The derived phenomenological law provides a framework for understanding fibrillation dynamics and improving cardiac models.
• Findings are consistent with domain size remapping necessary for realistic cardiac fibrillation modeling.