title: Effects of digoxin on acute, atrial fibrillation-induced changes in atrial refractoriness.
abstract: BACKGROUND
  Atrial fibrillation (AF) shortens the atrial effective refractory period (ERP) and predisposes to further episodes of AF. The acute changes in atrial refractoriness may be related to tachycardia-induced intracellular calcium overload. The purpose of this study was to determine whether digoxin, which increases intracellular calcium, potentiates the acute effects of AF on atrial refractoriness in humans.
  
  
  RESULTS
  In 38 healthy adults, atrial ERP was measured at basic drive cycle lengths (BDCLs) of 350 and 500 ms after autonomic blockade. Nineteen patients had been treated with digoxin for 2 weeks. After a several-minute episode of AF, atrial ERP was measured serially at alternating BDCLs. Compared with pre-AF ERPs, the first post-AF ERPs were significantly shorter in both the digoxin and the control groups (P:<0.001). The post-AF ERP at a BDCL of 350 ms shortened to a greater degree in the digoxin group (37+/-16 ms) than in the control group (20+/-13 ms, P:<0.001); similar changes occurred at a BDCL of 500 ms. During post-AF determinations of the atrial ERP, secondary AF episodes occurred significantly more often in the digoxin group (32% versus 16%; P:<0. 04).
  
  
  CONCLUSIONS
  After a brief episode of AF, digoxin augments the shortening that occurs in atrial refractoriness and predisposes to the reinduction of AF. These effects occur in the setting of autonomic blockade and therefore are more likely to be due to the effects of digoxin on intracellular calcium than to its vagotonic effects.
authors.affiliation: Division of Cardiology, Department of Internal Medicine, University of Michigan Medical Center, Ann Arbor, MI 48109-0022, USA.
authors.forename: C
authors.initials: C
authors.lastname: Sticherling
authors.forename: H
authors.initials: H
authors.lastname: Oral
authors.forename: J
authors.initials: J
authors.lastname: Horrocks
authors.forename: S P
authors.initials: SP
authors.lastname: Chough
authors.forename: R L
authors.initials: RL
authors.lastname: Baker
authors.forename: M H
authors.initials: MH
authors.lastname: Kim
authors.forename: K
authors.initials: K
authors.lastname: Wasmer
authors.forename: F
authors.initials: F
authors.lastname: Pelosi
authors.forename: B P
authors.initials: BP
authors.lastname: Knight
authors.forename: G F
authors.initials: GF
authors.lastname: Michaud
authors.forename: S A
authors.initials: SA
authors.lastname: Strickberger
authors.forename: F
authors.initials: F
authors.lastname: Morady
mesh_terms: D000284:Administration, Oral; D000319:Adrenergic beta-Antagonists / Q000008:administration & dosage; D000328:Adult; D001281:Atrial Fibrillation / Q000150:complications / Q000378:metabolism* / Q000628:therapy; D002118:Calcium / Q000378:metabolism*; D002304:Cardiac Pacing, Artificial; D002316:Cardiotonic Agents / Q000494:pharmacology; D004077:Digoxin / Q000494:pharmacology*; D004562:Electrocardiography / Q000187:drug effects; D005260:Female; D006325:Heart Atria / Q000187:drug effects; D006339:Heart Rate / Q000187:drug effects; D006801:Humans; D007262:Infusions, Intravenous; D007424:Intracellular Fluid / Q000378:metabolism; D008297:Male; D010276:Parasympatholytics / Q000008:administration & dosage; D011930:Reaction Time / Q000187:drug effects; D013617:Tachycardia, Supraventricular / Q000150:complications / Q000378:metabolism* / Q000628:therapy; D017180:Tachycardia, Ventricular / Q000150:complications / Q000378:metabolism* / Q000628:therapy
chemical_list: D000319:Adrenergic beta-Antagonists; D002316:Cardiotonic Agents; D010276:Parasympatholytics; D004077:Digoxin; D002118:Calcium