title: Coronary reserve and exercise ECG in patients with chest pain and normal coronary angiograms.
abstract: BACKGROUND
  Coronary vasodilator reserve is reduced in some patients with a history of chest pain and angiographically normal coronary arteries. ECG changes suggestive of myocardial ischemia during exercise also can be demonstrated in a subset of these patients.
  
  
  RESULTS
  We have investigated the correlation between coronary vasodilator reserve, assessed with 13N-labeled ammonia and positron emission tomography, and the ECG during exercise stress in 45 patients with a history of chest pain, angiographically normal coronary arteries, and a negative ergonovine test. ST segment depression on the ECG during exercise was present in 29 of 45 patients. Mean resting left ventricular blood flow was 1.04 +/- 0.22 ml.min-1.g-1; it increased to 1.32 +/- 0.47 ml.min-1.g-1 (p less than 0.01 versus baseline value) during atrial pacing and to 2.52 +/- 0.96 ml.min-1.g-1 (p less than 0.01 versus baseline value) after dipyridamole (0.56 mg/kg i.v.). No regional flow defects could be demonstrated in any patient during pacing or after dipyridamole. Myocardial flows after dipyridamole, however, did not show a normal frequency distribution (Kolmogorov-Smirnov test), and two patient populations could be identified. Twenty-nine (67%) patients had a mean left ventricular flow of 3.02 +/- 0.33 ml.min-1.g-1 after dipyridamole (range, 2.13-5.46 ml.min-1.g-1), and 14 (33%) patients had a mean flow of 1.48 +/- 0.29 ml.min-1.g-1 (range, 1.06-2.04 ml.min-1.g-1, p less than 0.01 versus the "high-flow group").
  
  
  CONCLUSIONS
  Approximately one third of patients in our series showed a reduced coronary vasodilator reserve. Although 12 of 14 patients in the "low-flow group" had ST segment depression during exercise stress, 16 of 29 patients in the high-flow group also had ST segment depression during exercise stress. Therefore, despite a good sensitivity (86%) in identifying patients with a blunted increment of coronary flow, the ECG response during exercise stress appears to have a rather low specificity (45%). This suggests that factors other than reduced coronary reserve and myocardial ischemia may play a role in the genesis of the ST segment depression in these patients.
authors.affiliation: Consiglio Nazionale delle Ricerche Institute of Clinical Physiology, University of Pisa, Italy.
authors.forename: P G
authors.initials: PG
authors.lastname: Camici
authors.forename: R
authors.initials: R
authors.lastname: Gistri
authors.forename: R
authors.initials: R
authors.lastname: Lorenzoni
authors.forename: O
authors.initials: O
authors.lastname: Sorace
authors.forename: C
authors.initials: C
authors.lastname: Michelassi
authors.forename: M G
authors.initials: MG
authors.lastname: Bongiorni
authors.forename: P A
authors.initials: PA
authors.lastname: Salvadori
authors.forename: A
authors.initials: A
authors.lastname: L'Abbate
mesh_terms: D000328:Adult; D000368:Aged; D002637:Chest Pain / Q000145:classification / Q000000981:diagnostic imaging / Q000503:physiopathology*; D017023:Coronary Angiography; D003326:Coronary Circulation; D004562:Electrocardiography; D005080:Exercise Test; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009590:Nitrogen Radioisotopes; D005082:Physical Exertion; D012016:Reference Values; D014055:Tomography, Emission-Computed; D014664:Vasodilation / Q000502:physiology*
chemical_list: D009590:Nitrogen Radioisotopes