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Spatial and temporal organization in ventricular fibrillation
1Department of Pharmacology, SUNY Health Science Center 13210, USA.
Insights
Ventricular fibrillation (VF), a cause of sudden cardiac death, is not random but organized. New analysis reveals electrical wave organization around phase singularities in the heart.
Area of Science:
- Cardiology
- Cardiac Electrophysiology
- Computational Biology
Background:
- Ventricular fibrillation (VF) is the primary cause of sudden cardiac death.
- The precise mechanisms underlying VF have remained largely unknown.
- VF is often characterized as disorganized cardiac electrical activity.
Purpose of the Study:
- To investigate the underlying mechanisms of ventricular fibrillation.
- To determine if VF exhibits organizational properties.
- To explore quantitative analysis of VF using novel algorithms.
Main Methods:
- Utilized a "two-dimensional phase mapping" algorithm.
- Employed video imaging of voltage-sensitive dye fluorescence.
- Recorded transmembrane potential from 20,000 sites on epicardial surfaces of rabbit and sheep ventricles.
Main Results:
- VF demonstrated a significant periodic component (approx. 500 beats/min).
- Phase mapping revealed VF organization around a limited number of short-lived "phase singularities."
- Phase singularities arise from wavefront interactions with obstacles.
Conclusions:
- Cardiac fibrillation exhibits substantial temporal and spatial organization.
- VF is not a random process but a quantifiable phenomenon.
- Findings may enhance understanding of VF mechanisms in healthy and diseased hearts.
Abstract:
Ventricular fibrillation (VF) is the leading heart rhythm alteration that results in sudden cardiac death, yet the detailed mechanisms of the arrhythmia remain elusive. Fibrillation has been defined as "turbulent" cardiac electrical activity, which conjures up the idea of totally random and disorganized activation of the ventricles. I review theoretical concepts and recently published results based on a newly developed algorithm, "two-dimensional phase mapping," which demonstrates that VF is not random and may be analyzed quantitatively. The approach is based on video imaging of voltage-sensitive dye fluorescence to record transmembrane potential simultaneously from 20,000 sites on the epicardial surface of rabbit and sheep ventricles. During VF, activity shows a strong periodic component centered near approximately 500 beats/min. Phase maps reveal that VF depends on the organization of electrical waves around a small number of "phase singularities" that have relatively short lifespans and form as a result of interactions of wavefronts with obstacles in their paths. Overall, the evidence demonstrates that there is a high degree of temporal and spatial organization in cardiac fibrillation. The results may pave the way for a better understanding of the mechanisms of VF in normal, as well as in diseased, hearts.