The following ECG changes may occur in healthy subjects during the treadmill exercise test

  PR, QRS and QT intervals shorten.

  P wave amplitude (height) increases.

  J point depression may be observed.

  PR segment may be downsloping in inferior leads.



ST segment elevation observed during treadmill exercise test

  is less frequent than ST segment depression.

  is NOT accepted as a sign of ischemia IF observed in leads having q or Q waves.

  generally denotes to ischemia in the related segments of the myocardium:

      - ST elevation in anterior leads suggest myocardial ischemia in anterior wall, which is the LAD region.

      - ST elevation inferior leads suggest ischemia in the inferior or posterior myocardium, which may be

        the RCA or Cx region.

  By contrast, observation of ST segment depression during treadmil exercise test is not related

      to any specific myocardial territory.



T wave changes observed during treadmill exercise test

  T wave is the most labile component of ECG and may even show changes with hyperventilation.

  If a T wave which is negative before test becomes positive during the test ( pseudonormalization),

      it is not generally accepted as a sign of ischemia.



To accept ST segment changes (either ST elevation or ST depression) as significant,
ST changes observed during a treadmil exercise test should be >

  at least 1 mm or more.

  observed in at least 3 consecutive beats.

  observed in at least 2 contiguous leads (example: I and II, II and III, I and III, I and aVL, C2 and C3,

      C3 and C4, C4 or       C5, etc.)

  Upsloping ST segment depression is NOT accepted as a sign of ischemia.

  ST segment depression suggesting ischemia must be either horizontal or downsloping.

  For ST segment changes to be significant, they need not to be solely observed during exercise.

      ST segment changes arising immediately after the exercise (in the recovery period) also suggest

      myocardial ischemia.



In the presence of the following, even if the patient has normal coronary arteries
ST segment depression may still be observed during treadmill exercise test

  Digoxin or Digitoxin use

  Left ventricular hypertrophy

  Dilated or hypertrophic cardiomyopathy

  Wolff-Parkinson-White (WPW) syndrome

  Mitral valve prolapse

  Significant aortic or mitral valve insufficiency

  Significant aortic valve stenosis

  Anemia

  Hypokalemia

  Uncontrolled hypertension



Observation of bidirectional ventricular tachycardia (VT) during treadmill exercise test

  Observation of bidirectional VT or polymorphic VT suggest the diagnosis of CPVT.

  Although observation of bidirectional VT during exercise test is typical for CPVT,

      only one third of the patients with CPVT show such changes.

  Even if bidirectional VT is not observed during treadmil exercise test, a progressive increase in

      ventricular arrhythmias during the test should also suggest the presence of CPVT.

  Ventricular arrhythmias generally arise at a heart rate of 110-130/minute. At first, they are seen as

      ventricular premature contractions. As the exercise progresses ventricular bigeminy,

      ventricular couplet, bidirectional or polymorphic VT are also expected to be seen.

      When the treadmill is stopped, these arrhythmias are also expected to diminish progressively.

  In patients with CPVT, the resting ECG is generally normal.



Reference

  Braunwald's Heart Disease 2008; 8th ed.



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