Final answer:
In a junctional rhythm, the electrical impulse often travels away from the left leg (LL) electrode, resulting in a negative deflection in lead II on an ECG.
Step-by-step explanation:
In the context of an electrocardiogram (ECG), a junctional rhythm is an abnormal heart rhythm where the electrical impulse originates from the atrioventricular (AV) node or the area around it, rather than from the sinoatrial (SA) node. When assessing an ECG, lead II is often used, which measures the voltage between the right arm (RA) and the left leg (LL). Since the impulse in a junctional rhythm is generated at or near the AV node, the vector of depolarization could be traveling away from the LL electrode, resulting in a potentially negative deflection in lead II on the ECG.
The movement of the electrical impulse correlates with the direction of electric fields that always point away from positive source charges and toward negative ones. In the case of a junctional rhythm, the ECG may show an inversion in the usual P wave polarity when the impulse moves in the opposite direction of normal sinus rhythm.