The effects of caffeine on the inducibility of atrial fibrillation.
BACKGROUND
There is widespread belief that caffeine consumption is linked to atrial arrhythmias; however, there is a relative lack of systematic evidence to support the assertion. The purpose of this study was to investigate whether caffeine, in doses equivalent to daily use in the general population, alter the propensity for atrial fibrillation (AF) in an experimental model comparing normal and simulated predisposition to AF.


METHODS
Caffeine (caffeine Na benzoate, 50:50 mixture) was administered intravenously at 1, 3, and 5 mg/kg doses in dogs producing serum levels of 2 to 4, 5 to 7, and 8 to 10 microg/mL. To simulate focal AF, premature stimulation from the right superior pulmonary vein was delivered at 2x, 4x, and 10x threshold at a rate of 180/min (S(1)-S(2) = 330 milliseconds) without and then with low-level stimulation of ganglionated plexi (GP) at the entrance of the right superior pulmonary vein. The window of vulnerability (WOV), a measure of the propensity for AF inducibility, was determined by the longest coupling interval of the premature beat (S(1)-S(2)) minus the shortest S(1)-S(2), which induced AF. The cumulative WOV is the sum of the individually determined WOV.


RESULTS
At each serum level of caffeine, the cumulative WOV was lower without rather than with GP stimulation compared with control. The cumulative WOV for both the stimulated, that is, predisposed to AF, and nonstimulated, that is, normal groups, exhibited a significantly lower average as compared with that exhibited by the control group (P <or= .003-.02).


CONCLUSIONS
These findings suggest that the presence of caffeine may result in an unexpected reduction in the propensity for AF in healthy individuals and in those with a predisposition for AF (enhanced AF inducibility caused by the stimulation of the GP).
Rashid
Abdul
A
Department of Internal Medicine, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA.
Hines
Mujahid
M
Scherlag
Benjamin J
BJ
Yamanashi
William S
WS
Lovallo
William
W
D000818:Animals; D001281:Atrial Fibrillation / Q000097:blood* / Q000139:chemically induced* / Q000175:diagnosis; D002110:Caffeine / Q000097:blood* / Q000633:toxicity*; D004285:Dogs; D004305:Dose-Response Relationship, Drug; D004562:Electrocardiography / Q000187:drug effects*; D018570:Risk Assessment / Q000379:methods*; D012307:Risk Factors
D002110:Caffeine