TIME-COURSE OF WARM-UP IN STABLE ANGINA

Patients with ischemic heart disease often experience angina during first exercise, which does not return after a rest or reduction in the level 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 exercise testing is relatively constant.(1,2) Only occasional cases of resolution of angina and electrocardiographic changes in myocardial ischemia during standard exercise testing have been reported.(3-5) However, a warm-up effect may not be recognized in this situation because the work load progressively increases with time. Evidence for warm-up has, however, been obtained by comparing 2 exercise tests, one with and one without earlier exercise.(6,7) The reasons for this improvement in performance are uncertain. Possible explanations include reduced cardiac work due to peripheral vasodilation, increased myocardial perfusion resulting from a delayed increase in coronary how or ischemic preconditioning.(8) Knowledge of the time course of the warm-up effect would add to the understanding of this phenomenon and could give clues to possible mechanisms. This study assesses the time course of warm-up by comparing hemodynamic and electrocardiographic changes during and after sequential exercise tests separated by a 10- or 30-minute rest in patients with stable exertional angina.