Computerized mapping of fibrillation in normal ventricular myocardium

Area of Science:

• Cardiology
• Computational Biology
• Medical Physics

Background:

• Ventricular fibrillation (VF) is an intrinsic capability of normal ventricles exceeding a critical mass.
• The mechanisms of VF initiation and perpetuation in normal myocardium remain incompletely understood.
• The low incidence of VF in the general population suggests protective factors in healthy ventricles.

Purpose of the Study:

• To elucidate the initiation and perpetuation mechanisms of ventricular fibrillation (VF) in normal myocardium.
• To understand why VF is not more prevalent in individuals with healthy ventricles.
• To investigate the role of cardiac mass and electrical stimuli in VF dynamics.

Main Methods:

• Utilized computerized mapping with up to 512 channels for simultaneous multisite recordings.
• Processed acquired data for dynamic display of cardiac activation patterns.
• Performed mathematical analyses of activation intervals to characterize VF dynamics.

Main Results:

• VF initiation in normal ventricles can occur from a single premature stimulus during the cardiac cycle's vulnerable period, forming a figure-eight pattern.
• VF perpetuates through spontaneous wave front breakup into wavelets and subsequent wavelet intersection.
• Mathematical analysis revealed VF as a form of chaos, with transitions from ventricular tachycardia (VT) to VF via a quasiperiodic route.

Conclusions:

• VF in normal myocardium is a reentrant cardiac arrhythmia initiated by electrical stimuli.
• Reentrant wave fronts and wandering wavelets act as coupled oscillators, perpetuating VF and maintaining chaotic dynamics.
• The absence of necessary triggers in normal hearts, despite the intrinsic ability to support these oscillators, prevents frequent VF occurrence.