Termination of ventricular fibrillation in dogs by depolarizing a critical amount of myocardium

A computer modeling tool for comparing novel ICD electrode orientations in children and adults

“…The critical mass hypothesis was then used to define metrics for intrapatient comparison of defibrillation "success" in different electrode configurations. 15,17,26 Note that this approach is not intended to calculate the actual DFT which would be recorded in clinical study, but to establish a yardstick by which the intrathoracic field strength over the myocardium can be compared given differing electrode configurations. The critical mass hypothesis proposes that a defibrillation shock will be successful if it produces a threshold voltage gradient over a "large" fraction of the myocardial mass, rendering it transiently inexcitable.…”

“…The criteria used in this study was a voltage gradient of 5 V/cm generated over 95% of the myocardium, values which have been accepted in the literature as a reasonable predictor of successful defibrillation. 26 As the computed electrical field in our simplified model scaled linearly with the potential difference applied to the defibrillation electrodes, once the potential distribution for nominal voltages was calculated, the defibrillation voltage meeting this threshold could be simply computed.…”

Defibrillation Shock Amplitude, Location and Timing

“…It is enough to defibrillate only a certain amount of the fibrillating myocardium and the arrhythmia in the rest of the myocardium is not enough to continue the fibrillation. This hypothesis is called the "Critical Mass" hypothesis (Zipes et al, 1975). Moreover, it is not enough only to terminate the arrhythmia, but also it is important to avoid reinitiation of the fibrillation .…”

Estudio de los efectos electrofisiológicos de la modificación local de la temperatura en un modelo experimental de corazón aislado mediante un electrodo específico de alta densidad con modulación térmica

“…Se han utilizado preparaciones experimentales in situ [Zipes et al 1975, Aupetit et al 1993, Chorro et al 1996, Dorian y Newman 1997, Kwan et al 1998], modelos de corazón aislado [Curtis 1998, Witkowski et al 1998, Wolk et al 1999, láminas de tejido miocárdico o preparaciones con cultivos celulares de miocitos [Tovar and Jones 1997].…”

“…Los estudios planteados han sido numerosos, tales como el análisis de los mecanismos de inicio y cese [Cha et al 1994], la interferencia de los procesos fibrilatorios mediante técnicas de sobreestimulación, la demostración de ventanas excitables ("gaps") durante la arritmia [Kirchhof et al 1993, Kenknight et al 1995], el papel de la masa miocárdica en la perpetuación del proceso fibrilatorio [Garrey 1914, Zipes et al 1975], los efectos desfibrilatorios o protectores de los fármacos [Wiener y Rosenblueth 1946, Zhou et al 1992, Dorian y Newman 1993, Wolk et al 1999] o la eficacia de las técnicas desfibrilatorias [Zhou et al 1993, Dillon y Kwaku 1998, Dalzell 1998], entre otros.…”