title: Myocardial infarction and atrial fibrillation: importance of atrial ischemia.
abstract: BACKGROUND
  Myocardial infarction (MI) is associated with the development of atrial fibrillation (AF). We aimed to characterize the atrial abnormalities because of MI and determine the role of ischemia to the AF substrate.
  
  
  RESULTS
  Forty-four sheep were studied. MI was induced by occlusion of the left circumflex artery (LCX) or left anterior descending artery (LAD). Excluding 11 with fatal arrhythmias, equal groups of animals (LCX; LAD; and sham-operated) underwent sequential electrophysiology study for 45 minutes to determine atrial effective refractory periods, conduction velocity, conduction heterogeneity index, and AF inducibility. Postmortem evaluation was performed with 2,3,5 triphenyl tetrazolium chloride staining. MI resulted in greater left ventricular dysfunction (P<0.05), LA pressure (P<0.0003), and reduction in atrial effective refractory periods (P<0.0001) compared with control. 2,3,5 triphenyl tetrazolium chloride staining demonstrated that the left circumflex artery, and not the LAD, group had atrial infarction. The left circumflex artery group demonstrated the following compared with the LAD or control groups: greater slowing in atrial conduction velocity (P<0.0001 and P<0.001); increased absolute range of conduction phase delay (P<0.001 and P<0.001); increased conduction heterogeneity index (P<0.0001 and P<0.001); greater AF vulnerability (P<0.05 for both); and longer AF duration (P<0.05 for both). LAD group had modest but significant slowing in conduction velocity (P<0.01) but no change in conduction heterogeneity index or AF duration compared with control.
  
  
  CONCLUSIONS
  Left ventricular infarction, which is known to result in atrial stretch, hemodynamic change, and neurohumoral activation, contributes partially to the atrial abnormalities in MI. Atrial ischemia/infarction results in greater atrial electrophysiological changes and propensity for AF forming the dominant substrate for AF in MI.
authors.affiliation: Centre for Heart Rhythm Disorders.
authors.forename: Muayad
authors.initials: M
authors.lastname: Alasady
authors.forename: Nicholas J
authors.initials: NJ
authors.lastname: Shipp
authors.forename: Anthony G
authors.initials: AG
authors.lastname: Brooks
authors.forename: Han S
authors.initials: HS
authors.lastname: Lim
authors.forename: Dennis H
authors.initials: DH
authors.lastname: Lau
authors.forename: David
authors.initials: D
authors.lastname: Barlow
authors.forename: Pawel
authors.initials: P
authors.lastname: Kuklik
authors.forename: Matthew I
authors.initials: MI
authors.lastname: Worthley
authors.forename: Kurt C
authors.initials: KC
authors.lastname: Roberts-Thomson
authors.forename: David A
authors.initials: DA
authors.lastname: Saint
authors.forename: Walter
authors.initials: W
authors.lastname: Abhayaratna
authors.forename: Prashanthan
authors.initials: P
authors.lastname: Sanders
mesh_terms: D000200:Action Potentials; D000818:Animals; D001281:Atrial Fibrillation / Q000175:diagnosis / Q000209:etiology* / Q000503:physiopathology; D016279:Atrial Function, Left; D062185:Atrial Pressure; D004195:Disease Models, Animal; D022062:Electrophysiologic Techniques, Cardiac; D006325:Heart Atria / Q000473:pathology / Q000503:physiopathology; D006339:Heart Rate; D009203:Myocardial Infarction / Q000150:complications* / Q000175:diagnosis / Q000503:physiopathology; D012032:Refractory Period, Electrophysiological; D012307:Risk Factors; D012756:Sheep; D013997:Time Factors; D018487:Ventricular Dysfunction, Left / Q000209:etiology / Q000503:physiopathology; D016277:Ventricular Function, Left
keywords: acute coronary syndrome; atrial fibrillation; myocardial infarction; myocardial ischemia; remodeling