title: Effect of Thoracic Epidural Anesthesia on Ventricular Excitability in a Porcine Model.
abstract: Imbalances in the autonomic nervous system, namely, excessive sympathoexcitation, contribute to ventricular tachyarrhythmias. While thoracic epidural anesthesia clinically suppresses ventricular tachyarrhythmias, its effects on global and regional ventricular electrophysiology and electrical wave stability have not been fully characterized. The authors hypothesized that thoracic epidural anesthesia attenuates myocardial excitability and the proarrhythmic effects of sympathetic hyperactivity.
  
  
  
  Yorkshire pigs (n = 15) had an epidural catheter inserted (T1 to T4) and a 56-electrode sock placed on the heart. Myocardial excitability was measured by activation recovery interval, dispersion of repolarization, and action potential duration restitution at baseline and during programed ventricular extrastimulation or left stellate ganglion stimulation, before and 30 min after thoracic epidural anesthesia (0.25% bupivacaine).
  
  
  
  After thoracic epidural anesthesia infusion, there was no change in baseline activation recovery interval or dispersion of repolarization. During programmed ventricular extrastimulation, thoracic epidural anesthesia decreased the maximum slope of ventricular electrical restitution (0.70 ± 0.24 vs. 0.89 ± 0.24; P = 0.021) reflecting improved electrical wave stability. Thoracic epidural anesthesia also reduced myocardial excitability during left stellate ganglion stimulation-induced sympathoexcitation through attenuated shortening of activation recovery interval (-7 ± 4% vs. -4 ± 3%; P = 0.001), suppression of the increase in dispersion of repolarization (313 ± 293% vs. 185 ± 234%; P = 0.029), and reduction in sympathovagal imbalance as measured by heart rate variability.
  
  
  
  Our study describes the electrophysiologic mechanisms underlying antiarrhythmic effects of thoracic epidural anesthesia during sympathetic hyperactivity. Thoracic epidural anesthesia attenuates ventricular myocardial excitability and induces electrical wave stability through its effects on activation recovery interval, dispersion of repolarization, and the action potential duration restitution slope.
authors.affiliation: From the Department of Anesthesiology and Perioperative Medicine (K.H.-Q., T.T., E.A.D., K.Y., W.Z., A.M.), UCLA Cardiac Arrhythmia Center (U.B., A.M.), and UCLA Neurocardiology Research Center of Excellence, David Geffen School of Medicine (K.H.-Q., U.B., A.M.), University of California, Los Angeles (UCLA), Los Angeles, California.
authors.forename: Kimberly
authors.initials: K
authors.lastname: Howard-Quijano
authors.forename: Tatsuo
authors.initials: T
authors.lastname: Takamiya
authors.forename: Erica A
authors.initials: EA
authors.lastname: Dale
authors.forename: Kentaro
authors.initials: K
authors.lastname: Yamakawa
authors.forename: Wei
authors.initials: W
authors.lastname: Zhou
authors.forename: Una
authors.initials: U
authors.lastname: Buckley
authors.forename: Aman
authors.initials: A
authors.lastname: Mahajan
mesh_terms: D000200:Action Potentials / Q000187:drug effects; D000767:Anesthesia, Epidural / Q000379:methods*; D000779:Anesthetics, Local / Q000494:pharmacology; D000818:Animals; D002045:Bupivacaine / Q000494:pharmacology*; D004558:Electric Stimulation; D055724:Electrophysiological Phenomena / Q000187:drug effects*; D005260:Female; D006339:Heart Rate / Q000187:drug effects*; D006352:Heart Ventricles / Q000187:drug effects*; D008297:Male; D023421:Models, Animal; D013552:Swine
chemical_list: D000779:Anesthetics, Local; D002045:Bupivacaine