When reading electrocardiograms, one should always be aware of the following: 1. Interpreting an ECG as indicative of ischemia or a prior infarction when the changes are due to lead placement, to body build or to other confounders such as hypertrophy, hypopotassemia or cardioactive drugs may have deleterious effects on the patient and should be avoided . 2. Interpreting an ECG as normal on one day and consistent with a prior anterior infarction on the next day is inappropriate and should also be avoided. The changes in the ECG responsible for the interpretation change are usually due to a change in the relationship of the chest leads to the heart, most often the result of a change in the placement of the chest leads.