Spatial distribution of phase singularities in ventricular fibrillation

Background - Multiple excitation wavelets are present during ventricular fibrillation (VF). The underlying wavelet organization of VF is unclear. Phase singularities (PSs) - locations of ambiguous activation state - underlie reentry and wavelet splitting and represent the sources of VF. Understanding the mechanisms of PS formation might be important in the development of effective therapies for sudden death. Methods and Results - We performed voltage, phase, and PS mapping in fibrillating ventricles, applying an automated PS detection algorithm to optically recorded fibrillation signals. PS clustering was noted along epicardial vessels, ridges of endocardial trabeculae, and papillary muscle insertions. Microscopically, these locations correlated with areas of apposition of fibers with different angulations and intramural vessels. A total of 83.2% of PSs were formed at and meandered about these anatomic structures, which acted as stabilizers: PSs colocalizing at anatomic substrates had longer life spans than nonanatomic PS (82.46 ± 60.8 versus 40.5 ± 31.9 ms, P<0.01). The RV endocardium had a higher PS incidence than the epicardium (42.3 ± 9.2 versus 23.5 ± 11.6 PS/s, P<0.01). Autocorrelation showed that irregular behavior was spatially restricted to anatomic heterogeneities compared with other areas, which had nearly periodic behaviors. Simple spatial PS distributions underlay complex and variable activation patterns attributable to variable PS behaviors, life spans, and inter-PS interactions. Conclusions - PSs occur in a nonrandom spatial distribution and colocalize with normal anatomic heterogeneities. Varying PS behaviors and life spans but stable PS spatial distributions cause ever-changing activation patterns that characterize VF.