title: Heterogeneity of left ventricular signal characteristics in response to acute vagal stimulation during ventricular fibrillation in dogs.
abstract: Studies have shown that long-term vagal stimulation is protective against ventricular fibrillation; however, the effects of acute vagal stimulation during ventricular fibrillation in the normal heart have not been investigated. We examined the effects of acute vagal stimulation on ventricular fibrillation in a canine model. In 4 dogs, we induced 30-second periods of ventricular fibrillation by means of intraventricular pacing. During 2 of the 4 periods of fibrillation that we analyzed, vagal stimulation was delivered through electrodes in the caudal ends of the vagus nerves. Noncontact unipolar electrograms were recorded from 3 ventricular regions: the basal septum, apical septum, and lateral free wall. We then computed the most frequent cycle length, mean organization index, and mean electrogram amplitude for each region. During fibrillation, vagal stimulation shortened the most frequent cycle lengths in the basal septum (P=0.02) and apical septum (P=0.0001), but not in the lateral wall (P=0.46). In addition, vagal stimulation significantly reduced the mean organization indices in the apical septum (P <0.001) and lateral wall (P <0.001), but not in the basal septum (P=0.19). Furthermore, vagal stimulation raised the mean electrogram amplitude in the basal septum (P <0.01) but lowered it substantially in the apical septum (P=0.00005) and lateral wall (P=0.00003). We conclude that vagal stimulation acutely affects the characteristics of ventricular fibrillation in canine myocardium in a spatially heterogeneous manner. This nonuniformity of response may have implications with regard to manipulating the autonomic system as a means of modifying the substrate for ventricular dysrhythmias.
authors.affiliation: Division of Cardiology, Texas Heart Institute at St. Luke's Episcopal Hospital, Houston, Texas 77030, USA.
authors.forename: Alireza
authors.initials: A
authors.lastname: Nazeri
authors.forename: MacArthur A
authors.initials: MA
authors.lastname: Elayda
authors.forename: Lubomir
authors.initials: L
authors.lastname: Dragnev
authors.forename: Christopher M
authors.initials: CM
authors.lastname: Frank
authors.forename: Jihong
authors.initials: J
authors.lastname: Qu
authors.forename: Valtino X
authors.initials: VX
authors.lastname: Afonso
authors.forename: Abdi
authors.initials: A
authors.lastname: Rasekh
authors.forename: Mohammad
authors.initials: M
authors.lastname: Saeed
authors.forename: Jie
authors.initials: J
authors.lastname: Cheng
authors.forename: Mossaab
authors.initials: M
authors.lastname: Shuraih
authors.forename: Ali
authors.initials: A
authors.lastname: Massumi
authors.forename: Mehdi
authors.initials: M
authors.lastname: Razavi
mesh_terms: D000818:Animals; D002304:Cardiac Pacing, Artificial; D004195:Disease Models, Animal; D004285:Dogs; D022062:Electrophysiologic Techniques, Cardiac; D005583:Fourier Analysis; D006329:Heart Conduction System / Q000503:physiopathology*; D013997:Time Factors; D055536:Vagus Nerve Stimulation; D014693:Ventricular Fibrillation / Q000209:etiology / Q000503:physiopathology / Q000628:therapy*; D016277:Ventricular Function, Left