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More than half of all patients with coronary artery disease exhibit an improvement in performance following their first exercise test—the warm up phenomenon.
The warm up phenomenon, first described more that 50 years ago in patients with effort angina, refers to the improved performance exhibited by more than half of all patients with coronary artery disease following their first exercise test.1
There are several potential causes of the warm up phenomenon including: (1) an improvement in oxygen supply, which, in turn, may be caused by stenosis dilation, collateral recruitment or myocardial perfusion redistribution; (2) a reduction in oxygen consumption caused by an adaptive down regulation or stunning of regional myocardial contractile function in the ischaemic region; and (3) a form of myocardial adaptation to ischaemia akin to ischaemic preconditioning.
MECHANISMS OF ADAPTATION TO EXERCISE INDUCED ISCHAEMIA
It has been shown that in patients with a single lesion of the left anterior descending coronary artery, great cardiac vein flow is similar during the first and second exercise stress test, thus suggesting that the warm up phenomenon is not accompanied by an increase in total myocardial blood flow.2 These findings have been recently confirmed by Bogaty and colleagues,3 who showed that the attenuation of myocardial ischaemia observed with repeated exercise is not accounted for by an improvement in myocardial perfusion as determined by single photon emission computed tomography (SPECT) thallium-201 imaging. Unfortunately, both studies do not allow us to rule out the possibility that …