Pacesetter
Part of speech: noun
Definition: A person who determines the rate of action through leading.
Pacemaker
Part of speech: noun
Definition: One who sets the pace in a race, to guide the others.A set of nerves which stimulate the heart to beat.A medical implement that is used to stimulate a heart to beat by simulating the action of the natural pacemaker.
Example sentence: Under Medicare right now, I get paid to put a pacemaker in you, but I don't get paid to counsel you about end-of-life care.