Recommendations for methodologic criteria (Okim and Kligfield, 1995, page 1731):
(1) Measurement of ST segment depression should be measured 60 ms after the J point.
(2) ST segment measurements should be measured to the nearest 10 µV (0.01 mV).
(3) ST segment measurement is based on deviation from isoelectric baseline.
(4) Use a standard 12 lead ECG with bipolar lead CM5.
(5) Exclude aVR, aVL and V1 from analysis.
(6) The exercise testing protocol should be the Cornell modification of the Bruce protocol.
Other methodologic issues:
(7) According to Detrano et al (1986, page 837), the leads used are: I, aVF, V2, V4 and V5.
(8) The measurements are taken at rest and after peak exercise.
(9) The ST segment depression refers to a negative deflection. I am not sure how a positive deflection in a lead would be handled (? entered as a negative value; ? entered as 0; ? select another lead not showing an elevation).
Procedure:
(1) Measure the heart rate at rest.
(2) Measure the ST segment depression in each of the 5 leads at rest in microvolts.
(3) Measure the heart rate at peak exercise.
(4) Measure the ST segment depression at the end of exercise in microvolts.
(5) Subtract the ST segment depression at rest from the ST segment depression at the end of exercise.
(6) Identify the maximal difference in ST segment depression over the 5 leads.
ST/HR index =
= (maximal difference in ST segment in microvolts) / ((exercise heart rate) – (resting heart rate))
