Exercise-induced ischaemia protects against left ventricular dysfunction during a subsequent ischaemic episode
Kelion AD., Banning AP., Webb T., Gardner M., Ormerod OJM.
Introduction. The "warm-up" effect in some patients with angina may represent ischaemic preconditioning. We investigated whether protection occurs against ischaemic left ventricular (LV) dysfunction and subsequent stunning. Methods. 16 patients (age 63±7y, 15 male) with 3-vessel coronary disease and normal resting LV function underwent 2 symptom-limited supine bicycle exercise tests 30min apart. Patients had practice tests and stopped antianginal medication. Equilibrium gated radionuclide ventriculography (RNV) was performed; regional ejection fractions (REFs) were calculated for 9 LV segments. Results. Exercise time and maximal ST depression were the same for each test, but the onset of angina was delayed by 1.7min during test 2, whilst a higher rate-pressure product was reached before angina or 1mm ST depression occurred (P<0.01 for all). Heart rate and BP during equivalent RNV acquisitions were comparable between tests. LV segments whose REF fell during test 1 ("ischaemic") showed a reduced ischaemic response during test 2, with no increase in post-exercise stunning (Figure, left panel). "Nonischaemic" segments responded similarly to each test (Figure, right panel). (Graph Presented) Conclusion. Exercise-induced ischaemia causes immediate impairment and persistent stunning of some LV segments. With further exercise, dysfunction is less marked. This may represent ischaemic preconditioning.