The ability of brief periods of ischaemia to protect the heart from subsequent ischaemia has been termed "ischaemic preconditioning'. In order to assess the role of adenosine receptor stimulation in this phenomenon we studied the ischaemic preconditioning effect during angioplasty in 10 control patients and in 10 patients pre-treated with 5 mg.kg-1 aminophylline, an adenosine receptor antagonist. The ischaemic response was assessed by analysis of the intracoronary electrocardiogram every 10 s during three consecutive inflations of 90 s with a reperfusion time of 180 s. The severity of transmural local ischaemia was expressed as the magnitude of the ST segment shift in relation to the time during each inflation. The control patients showed an improved tolerance to myocardial ischaemia: ST segment shift decreased from 1.42 +/- 0.49 mV at the end of the first inflation to 1.03 +/- 0.44 mV at the end of the third inflation (P < 0.001). However, in patients pre-treated with aminophylline, the ischaemic response was not significantly different during three inflations.
Conclusion: Aminophylline inhibits ischaemic preconditioning, as assessed by analysis of the intracoronary. ST segment changes during angioplasty. This suggests that ischaemic preconditioning is mediated by adenosine receptor stimulation in humans.