Mother Rotors and the Mechanisms of D600-Induced Type 2 Ventricular Fibrillation

Abstract

Background-Two types of ventricular fibrillation (VF) have been demonstrated in isolated rabbit hearts during D600 infusion. Type 1 VF is characterized by the presence of multiple, wandering wavelets, whereas type 2 VF shows local spatiotemporal periodicity. We hypothesized that a single mother rotor underlies type 2 VF. Methods and Results-One (protocol I) or 2 (protocol II) cameras were used to map the epicardial ventricular activations in Langendorff-perfused rabbit hearts. Multiple episodes of type 2 VF were induced in 22 hearts by high-concentration (Ն2.5 mg/L) D600 (protocol I). During type 2 VF, a single spiral wave (nϭ19) and/or an epicardial breakthrough pattern (nϭ11) was present in 14 hearts. These spiral waves either slowly drifted or intermittently anchored on the papillary muscle (PM) of the left ventricle. Dominant-frequency (DF) analyses showed that the highest local DF was near the PM (12.5Ϯ1.1 Hz). There was an excellent correlation between the highest local DF of these spiral waves and breakthroughs (11.8Ϯ1.7 Hz) and the DF of simultaneously obtained global pseudo-ECG (11.2Ϯ1.8 Hz, rϭ0.97, PϽ0.0001) during type 2 VF. We also successfully reproduced the major features of type 2 VF by using the Luo-Rudy action-potential model in a simulated, 3-dimensional tissue slab, under conditions of reduced excitability and flat action-potential duration restitution. Conclusions-Either a stationary or a slowly drifting mother rotor can result in type 2 VF. Colocalization of the stationary mother rotors with the PM suggests the importance of underlying anatomic structures in mother rotor formation.

Therapeutic Hypothermia (30.DEG.C) Enhances Arrhythmogenic Substrates, Including Spatially Discordant Alternans, and Facilitates Pacing-Induced Ventricular Fibrillation in Isolated Rabbit Hearts

“…17 The signals were digitized by an AxoScope with a sampling rate of 1 kHz. [15][16][17][18][19] Optical Mapping Using a 2-camera optical mapping system, epicardial activations in the anterior and posterior aspects of the hearts were simultaneously mapped. 15,16 The hearts were stained with di-4-ANEPPS, and excited with 4 light-emitting diode modules (wavelength=519±20 nm).…”

“…In a typical time-embedded phase portrait, the upstroke of the action potential corresponds to a phase ranging from −3/4π to −1/4π, roughly the light-blue color (between dark-blue and green) using color representation. 15,16,18,19 Phase mapping was performed to evaluate the wavefront characteristics, and the location and evolution of phase singularities (PSs). 20 A PS shown on the phase maps was defined as a site with an ambiguous phase surrounded by pixels exhibiting a continuous phase progression from -π to +π.…”

“…15,16,18,19 Baseline VF was defined as a stable VF that persisted for 5 min after pacing induction. Three sets of optical data and corresponding pseudo-ECG recordings were obtained during baseline VF, then the hearts were cooled to 30°C.…”

Repetitive Endocardial Focal Discharges During Ventricular Fibrillation With Prolonged Global Ischemia in Isolated Rabbit Hearts

“…In contrast, type 2 VF is associated with either a stationary or a slowly drifting mother rotor. 1,2 When tissue excitability is depressed due to global ischemia (GI), the VF phenotype is consistent with type 2 VF with a subepicardial source of rapid activation. 4 Furthermore, during prolonged (>5 min) GI, the incidence of early VF recurrence after successful defibrillation increases.…”

The Photodiode Array: A Critical Cornerstone in Cardiac Optical Mapping

“…This data is challenging to analyze and interpret, since recordings of fibrillation often have a chaotic appearance when viewed with time as the horizontal axis. Thus a variety of alternate methods have been used to gain insight into the nature of fibrillation, including dominant frequency analysis (Caldwell et al, 2007;Choi et al, 2003;Choi et al, 2006;Joel & Hsia, 2005;Moreno et al, 2005;Wu et al, 2004;Wu et al, 2006;Zaitsev et al, 2003) and mutual information (Omichi et al, 2004, Wu et al, 2005. More recently the use of a metric known as spatiotemporal entropy has been used to analyze oscillatory dynamics in cardiac and neural systems Jung et al, 2000;Himel et al, 2009).…”