title: Postexercise VO2 "Hump" phenomenon as an indicator for inducible myocardial ischemia in patients with acute anterior myocardial infarction.
abstract: OBJECTIVE
  At exercise testing with respiratory gas analysis in patients with inducible myocardial ischemia, we have occasionally observed abnormal transient oxygen uptake (VO2) components with a characteristic "Hump"-shaped morphology early after exercise, which may serve as an index for inducible ischemia. We examined this hypothesis in patients with anterior q-wave myocardial infarction in whom the accuracy to identify ischemia by exercise ECG is limited.
  
  
  METHODS
  From patients with acute anterior q-wave infarction but without clinically overt heart failure who underwent pre-discharge exercise testing, we examined patients with (Group-I, n = 30) and without (Group-N, n = 29) inducible ischemia. To identify "Hump", postexercise VO2 (up to 4 min) standardized for peak VO2 was exponentially fitted with use of peak VO2 and VO2 of 90-240 s, yielding "expected VO2". "D-curve" was obtained by subtracting "expected VO2" from measured VO2.
  
  
  RESULTS
  Although exercise-induced ST depressions more frequently appeared in Group-I (27%) than in Group-N (3%, p < 0.05), the prevalence was low. D-curve peaked later (p < 0.01) and its value was greater (p < 0.05) in Group-I than in Group-N. When "Hump" was defined to be present if D-curve peaked > or =40 s and its peak value > or =15%, it was far more frequently found in Group-I (n = 17/30) than in Group-N (n = 1/29, p < 0.01). Thus, "Hump" could diagnose inducible ischemia with a sensitivity of 57% and a specificity of 97%.
  
  
  CONCLUSIONS
  Although not highly sensitive, postexercise VO2 "Hump" with its peak occurring around 60 s after exercise is a specific marker for inducible ischemia. The identification may be useful, particularly in patients with limited accuracy of exercise ECG such as those with q-wave anterior infarction.
authors.affiliation: Department of Cardiovascular Dynamics, National Cardiovascular Center Research Institute, 5-7-1 Fujishiro-dai, Osaka, 565-8565, Japan. htakaki@res.ncvc.go.jp
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Takaki
authors.forename: Satoru
authors.initials: S
authors.lastname: Sakuragi
authors.forename: Noritoshi
authors.initials: N
authors.lastname: Nagaya
authors.forename: Shoji
authors.initials: S
authors.lastname: Suzuki
authors.forename: Yoichi
authors.initials: Y
authors.lastname: Goto
authors.forename: Takayuki
authors.initials: T
authors.lastname: Sato
authors.forename: Kenji
authors.initials: K
authors.lastname: Sunagawa
mesh_terms: D005080:Exercise Test; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009203:Myocardial Infarction / Q000150:complications*; D017202:Myocardial Ischemia / Q000175:diagnosis / Q000209:etiology* / Q000378:metabolism*; D010100:Oxygen / Q000378:metabolism*
chemical_list: D010100:Oxygen