Rotor Stability Separates Sustained Ventricular Fibrillation From Self-Terminating Episodes in Humans

Abstract

Objective We mapped human ventricular fibrillation (VF) to define mechanistic differences between episodes requiring defibrillation versus those that spontaneously terminate. Background VF is a leading cause of mortality, yet episodes may also self-terminate. We hypothesized that the initial maintenance of human VF is dependent upon the formation and stability of VF rotors. Methods We enrolled 26 consecutive patients (age 64±10 years, n=13 with LV dysfunction) during ablation procedures for ventricular arrhythmias, using 64-electrode basket catheters in both ventricles to map VF prior to prompt defibrillation per IRB-approved protocol. Fifty-two inductions were attempted and 36 VF episodes were observed. Phase analysis was applied to identify bi-ventricular rotors in the first 10 seconds or until VF terminated, whichever came first (11.4±2.9 seconds to defibrillator charging). Results Rotors were present in 16 of 19 patients with VF, and in all patients with sustained VF. Sustained, but not self-limiting VF, was characterized by greater rotor stability: (1) rotors were present in 68±17% of cycles in sustained versus 11±18% of cycles in self-limiting VF (p<0.001); with (2) maximum continuous rotations greater in sustained (17±11, range 7–48) versus self-limiting VF (1.1±1.4, range 0–4, p<0.001). Additionally, biventricular rotor locations in sustained VF were conserved across multiple inductions (7/7 patients, p=0.025). Conclusions In patients with and without structural heart disease, the formation of stable rotors identifies individuals whose VF requires defibrillation from those in whom VF spontaneously self-terminates. Future work should define the mechanisms that stabilize rotors and evaluate whether rotor modulation may reduce subsequent VF risk.

Spatiotemporal Progression of Early Human Ventricular Fibrillation

“…More recent work using endocardial basket electrodes demonstrated that rotational activity is present in the vast majority of patients following induction of VF and that the stability of the rotors is larger in patients with sustained VF episodes compared to patients with self-terminating ones (19). A critical element in that study was the manual interpretation of animated sequences of phase maps.…”

“…Separately, spiral wave reentry (rotors), focal sources, and disorganized activity have been described in human VF (4–6), but the relative importance of each was unclear. Recent work in our laboratory mapped human VF and demonstrated that spiral waves, identified visually from computed phase maps, were present in the majority of patients (7). Furthermore, this study found that sustained episodes requiring defibrillation to terminate were characterized by greater spiral wave stability (7), and that ablation of VF sources increased the VF threshold in an animal model and patient with clinical VF (8).…”

Structural and Functional Bases of Cardiac Fibrillation

“…(30) However, filaments may adopt varying other shapes (e.g., L-shape, U-shape or O-shape) that may generate different patterns of activation at each surface, but still underlie a scroll wave within the three-dimensional structure of the atrial or ventricular myocardium (Figure 1). (11,31) The orientation of the filament may also change, which introduces additional complexity when it comes to attempting to track rotors in three-dimensions. Computer simulations have shown that after a certain transitional period, the filament aligns with the local fiber orientation, which provides support to the presence of intramural reentry.…”

“…(34) Sometimes they meander within specific regions of the myocardial tissue. (11) Other times, one end of a scroll wave filament (e.g., on the epicardium) may meander while the other end (i.e., on the endocardium) remains anchored. Recent data by Krummen et al underscored the importance of rotor stationarity in sustaining VF episodes that eventually require defibrillation.…”

Mechanisms Underlying AF: Triggers, Rotors, Other?

“…While rotors had been observed in animal models [70, 71] and human VF [72–74], until recently [7•, 75–78, 79•] there was little or no evidence for rotors in human AF. Several features of human AF may have contributed to difficulties in arrhythmia mapping, including low-amplitude signals [80], the practice of recording from a limited number of simultaneous electrodes during AF despite its spatial heterogeneity, the use of clinical bipolar signals during AF [81], and dependence upon activation-based analysis of AF, rather than phase mapping [82].…”