title: Comparison of symptom-limited and low level exercise tolerance tests early after myocardial infarction.
abstract: OBJECTIVE
  This study was conducted to determine the diagnostic yield and risks of a symptom-limited treadmill exercise test before hospital discharge.
  
  
  BACKGROUND
  Currently, predischarge low level and 6-week symptom-limited exercise treadmill tests are recommended for risk stratification after myocardial infarction. However, few data exist on the safety and value of a predischarge symptom-limited exercise test.
  
  
  METHODS
  We utilized a modified Bruce protocol starting at 1.7 mph and 0 grade with 3-min stages in 150 consecutive patients 6.4 +/- 3.1 days after myocardial infarction. Each exercise test was interpreted for duration, symptoms and ST segment changes at the low level (70% of predicted heart rate) and symptom-limited end point.
  
  
  RESULTS
  There were no complications related to the symptom-limited exercise tests. The test results were positive in only 23% of the patients at the low level end point, but were positive in 40% of the patients at the later symptom-limited end point (p < 0.001). During a mean follow-up period of 15 +/- 5 months in 138 patients (92%), 50 patients (36%) had a cardiac event. Of the patients with a cardiac event, significantly more (p < 0.001) had a positive exercise test at the symptom-limited end point (31 vs. 16 patients). Five patients with a negative and 14 patients with a nondiagnostic symptom-limited exercise test had an event.
  
  
  CONCLUSIONS
  In patients with uncomplicated myocardial infarction, we demonstrated the safety of an early symptom-limited treadmill exercise test. Symptom-limited exercise tests will identify more patients with inducible ischemia who are at risk of future cardiac events and who may benefit from early intervention.
authors.affiliation: Division of Cardiology, University of Texas Health Science Center-San Antonio 78284.
authors.forename: A
authors.initials: A
authors.lastname: Jain
authors.forename: G H
authors.initials: GH
authors.lastname: Myers
authors.forename: P M
authors.initials: PM
authors.lastname: Sapin
authors.forename: R A
authors.initials: RA
authors.lastname: O'Rourke
mesh_terms: D004562:Electrocardiography; D005080:Exercise Test; D017079:Exercise Tolerance / Q000502:physiology*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D009203:Myocardial Infarction / Q000175:diagnosis* / Q000453:epidemiology; D011237:Predictive Value of Tests; D012307:Risk Factors; D012449:Safety; D013997:Time Factors