Role of endogenous adenosine in atrial fibrillation after coronary artery bypass graft.

.‡University of Suleyman Demirel, School of Medicine, Department of Cardiovascular Surgery, Isparta,Turkey; *Cardiology Associate sof North Mississippi, North Mississippi Medical Center, Tupelo, Mississippi, USA; †University of Osmangazi, School of Medicine,Department of Cardiovascular Surgery, Eskibehir; ‡Dr. Sami Ulus Pediatric Hospital, Department of Pediatric Cardiovascular Surg ery,Ankara, TurkeySummaryBackground: Atrial fibrillation (AF) is the most commoncomplication following coronary artery bypass graft (CABG).The mechanism of AF after CABG is not well defined; how-ever, it is suggested that endogenous adenosine, released in re-sponse to tissue hypoxia, may play a mechanistic role in thesearrhythmias.Hypothesis: The purpose of this study was to examinewhether intravenous theophylline, via adenosine A1 receptorantagonism, would correct or modify new-onset early (<48 hpost CABG) atrial fibrillation in patients post CABG, andthereby implicate endogenous adenosine as an inciting agent.Methods: A prospective double-blind, placebo-controlledstudy design was applied to 385 consecutive patients withcoronary artery disease who had undergone CABG. Any pa-tient who developed AF within 48 h of the operative procedurewas randomly assigned to receive 5 mg/kg of intravenoustheophylline (Group A) or matched intravenous placebo(Group B). The patients who converted to sinus rhythm within15 min of drug administration were accepted as showing posi-tive responses.Results: Thirty patients comprised the study group. InGroup A, 8 of the 15 patients (53%) converted from AF to si-nus rhythm within 15 min of theophylline administration.One patient who converted to sinus rhythm 20 min after theo-phylline administration was accepted as showing a negativeresponse. In the placebo-treated group, no patient convertedto sinus rhythm within 15 min (p<0.007 compared withGroup A).Conclusions: The mechanism of AF after CABG is notwell defined and is probably multifactorial. However, thisstudy demonstrated that antagonism of the adenosine A1 re-ceptor can promptly convert many of these patients back to si-nus rhythm, and thereby implicates endogenously releasedadenosine in a mechanistic role for inciting early (<48 h)post-CABG AF.Key words: adenosine, atrial fibrillation, coronary artery dis-ease, coronary bypass surgery, complications, theophylline,cardiac arrhythmiaIntroductionAtrial fibrillation (AF) is the most common complicationfollowing coronary artery bypass graft (CABG).