title: What induces the warm-up ischemia/angina phenomenon: exercise or myocardial ischemia?
abstract: BACKGROUND
  The relation of the warm-up ischemia phenomenon to the presence and intensity of initial myocardial ischemia is unclear. We sought to determine whether the warm-up ischemia phenomenon requires initial myocardial ischemia or can be induced by exercise without ischemia and whether there is a relation between the intensity of initial ischemia and the attenuation of ischemia on reexercise.
  
  
  RESULTS
  Twelve subjects with exertional myocardial ischemia performed 2 exercise ECG tests (1 and 2) at a +/-10-minute interval on 3 occasions (A, B, C) 1 month apart. A1 and A2 were symptom-limited. B1 was kept as long as A1, but its intensity was held under the ischemic threshold (heart ratexsystolic pressure at 1-mm ST depression [STD]) noted at A1. B2 was symptom-limited. C1 was also kept as long as A1 but with an intensity adjusted to maintain one-half maximum STD of A1. C2 was symptom-limited. Exercise duration of A2, B2, and C2 increased similarly compared with A1 (P=0.009). However, the ischemic threshold (x10-3) increased at A2 (23.5+/-6.0) compared with A1 (20.3+/-4.8; P<0.0001) but not at B2 (19.8+/-5.0) or C2 (21.5+/-5.8). Similarly, maximum STD adjusted to the highest heart rate-systolic pressure product common to A1, A2, B2, and C2 decreased at A2 (1.4+/-0.7 mm) compared with A1 (2.5+/-0.9 mm; P<0.0001) but not at B2 (2.7+/-0.9 mm) or C2 (2.3+/-0.9 mm).
  
  
  CONCLUSIONS
  Exercises under the ischemic threshold and of intermediate ischemic intensity increase short-term exercise capacity, but myocardial ischemia of more than moderate intensity is needed to induce the warm-up ischemia phenomenon.
authors.affiliation: Quebec Heart Institute/Laval Hospital, 2725 Chemin Ste-Foy, Ste-Foy, Quebec, Canada G1V 4G5. peter.Bogaty@med.ulaval.ca
authors.forename: Peter
authors.initials: P
authors.lastname: Bogaty
authors.forename: Paul
authors.initials: P
authors.lastname: Poirier
authors.forename: Luce
authors.initials: L
authors.lastname: Boyer
authors.forename: Jean
authors.initials: J
authors.lastname: Jobin
authors.forename: Gilles R
authors.initials: GR
authors.lastname: Dagenais
mesh_terms: D000787:Angina Pectoris / Q000175:diagnosis / Q000209:etiology* / Q000517:prevention & control; D004562:Electrocardiography; D015444:Exercise; D005080:Exercise Test; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D017202:Myocardial Ischemia / Q000175:diagnosis / Q000209:etiology* / Q000517:prevention & control; D055502:Secondary Prevention