Final answer:
For a patient with a left-side mastectomy, the ECG leads that would normally be placed on the left chest are shifted to the right side or below the mastectomy site and the alternative placement must be documented for accurate interpretation of the ECG.
Step-by-step explanation:
In cases where a patient has had a mastectomy on the left side, the standard placement of ECG leads for a 12-lead ECG needs to be modified to accommodate the absence of breast tissue. Normally, six electrodes are placed on the chest and four on the limbs. However, for such patients, alternative sites for the chest leads can be utilized. These alternative sites are typically located on the same horizontal plane as the standard sites but are positioned more medially or towards the right side of the chest to avoid the mastectomy site. Specifically, the leads that would normally be placed on the left chest are relocated to comparable positions on the right side or below the level of the mastectomy if possible. It's crucial to document the modified lead placement in the patient's medical record to ensure that the ECG is interpreted correctly.