TIME-COURSE OF WARM-UP IN STABLE ANGINA

Patients with ischemic heart disease often experience angina during fi rst exercise, which does not return after a rest or reduction in the l evel of activity. Reference to this ''warm-up'' effect was included in early descriptions of angina by both Heberden and Osler. Despite this , most studies suggest the threshold for myocardial ischemia on exerci se testing is relatively constant.(1,2) Only occasional cases of resol ution of angina and electrocardiographic changes in myocardial ischemi a during standard exercise testing have been reported.(3-5) However, a warm-up effect may not be recognized in this situation because the wo rk load progressively increases with time. Evidence for warm-up has, h owever, been obtained by comparing 2 exercise tests, one with and one without earlier exercise.(6,7) The reasons for this improvement in per formance are uncertain. Possible explanations include reduced cardiac work due to peripheral vasodilation, increased myocardial perfusion re sulting from a delayed increase in coronary how or ischemic preconditi oning.(8) Knowledge of the time course of the warm-up effect would add to the understanding of this phenomenon and could give clues to possi ble mechanisms. This study assesses the time course of warm-up by comp aring hemodynamic and electrocardiographic changes during and after se quential exercise tests separated by a 10- or 30-minute rest in patien ts with stable exertional angina.