The cathode (-) part of a pacemaker lead is defined as:

• A. The part connected directly into heart tissue
• B. The part that receives the electrical impulse after depolarization
• C. The part connected to the generator
• D. The insulated portion extending from the generator

Answer: (A)

Understanding which portion of a pacemaker lead acts as the cathode helps clarify how pacing delivers a beat. The cathode is the negative pole of the pacing circuit, and the electrode that actually delivers the stimulus to the heart is the tip that is implanted into the heart tissue. This tip electrode is the negative, active electrode; the current flows from the positive pole (the anode) toward this cathode to depolarize the myocardium.

So, the part that’s directly in contact with heart tissue is the cathode. The portion connected to the generator is the path back to the device and can be considered the return path, not the site of stimulation. The part that “receives the impulse after depolarization” describes what happens after stimulation, not the electrode delivering the pulse. The insulated portion does not conduct current at all.