Effect of adenosine antagonism on metabolically mediated coronary vasodilation in humans.
OBJECTIVE
This study was performed to assess the importance of adenosine in mediating metabolic coronary vasodilation during atrial pacing stress in humans.


BACKGROUND
Numerous animal studies have examined the role of adenosine in the regulation of coronary blood flow, with inconsistent results.


METHODS
The effect of the adenosine antagonist aminophylline (6 mg/kg body weight intravenously) on coronary functional hyperemia during rapid atrial pacing was determined in 12 patients. The extent of inhibition of adenosine vasodilation was assessed using graded intracoronary adenosine infusions before and after aminophylline administration in seven patients. Coronary blood flow changes were measured with a 3F intracoronary Doppler catheter.


RESULTS
After aminophylline administration, the increase in coronary flow velocity during adenosine infusions was reduced from 84 +/- 48% (mean +/- SD) to 21 +/- 31% above control values (p < 0.001) at 10 micrograms/min and from 130 +/- 39% to 59 +/- 51% above control values (p < 0.001) at 40 micrograms/min. During rapid atrial pacing under control conditions, coronary blood flow velocity increased by 26 +/- 16%. The flow increment during paced tachycardia after aminophylline (23 +/- 10%) was unchanged from the control value, despite substantial antagonism of adenosine coronary dilation by aminophylline.


CONCLUSIONS
These data suggest that adenosine does not play an important role in the regulation of coronary blood flow in response to rapid atrial pacing in humans.
Rossen
J D
JD
Department of Internal Medicine, University of Iowa College of Medicine, Iowa City 52242.
Oskarsson
H
H
Minor
R L
RL
Talman
C L
CL
Winniford
M D
MD
D000241:Adenosine / Q000008:administration & dosage / Q000037:antagonists & inhibitors* / Q000502:physiology; D000368:Aged; D000628:Aminophylline / Q000008:administration & dosage; D001783:Blood Flow Velocity / Q000187:drug effects; D002304:Cardiac Pacing, Artificial; D002637:Chest Pain / Q000000981:diagnostic imaging / Q000503:physiopathology*; D017023:Coronary Angiography; D003326:Coronary Circulation / Q000187:drug effects; D003331:Coronary Vessels / Q000187:drug effects / Q000503:physiopathology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D014655:Vascular Resistance / Q000187:drug effects; D014664:Vasodilation / Q000502:physiology*
D000628:Aminophylline; D000241:Adenosine