Final answer:
Lead aVR is the lead that records electrical activity from a midpoint between LA/LL toward the RA.
Step-by-step explanation:
The lead that records electrical activity from a midpoint between the left arm (LA) and left leg (LL) towards the right arm (RA) is Lead aVR. An electrocardiogram (ECG) is used to measure the depolarization and repolarization of the heart's muscle tissue. The standard ECG contains various leads that capture this activity from different angles, with each lead providing unique information about the heart's electrical activity. For instance, Lead II potential captures the depolarization of ventricles as well as systolic blood pressure, while Lead aVR records activity from a different angles, represented by the QRS complex, and is followed closely by the maximum or systolic blood pressure.