Which heart of is spoken of here?
Is it The important muscular organ in most animal whose chief function is to pump the blood to nourish the body cells? 
Most likey not, because the body as a whole cannot follow an organ in itself.
The word “heart” must then be symbolic or figuratively.
It is said to stand for “the central part in general, the inside,
and so for the interior man as manifesting himself in all his various activities, in his desires, affections, emotions, passions, purposes, his thoughts, perceptions, imaginations, his wisdom, knowledge, skill, his beliefs and his reasoning, his memory and his consciousness.
Not mere outward appearances but what a person really is inside, So the Scriptures counsel:
“More than all else that is to be guarded, safeguard your heart [the whole inner man], for out of it are the sources of life.” (Prov 4:23)
In some occasions the term “heart” focuses attention on the thinking faculties,
but not in a sense that would isolate such faculties from the rest of what makes up the inner person.
Moses the Israelite told them, “Jehovah has not given you a heart [“mind,”] to know.” (De 4:39; 29:4)
Showing that at times the heart, includes the intellect
In other occasion motivation, the impelling force behind our conduct, a further vital aspect of the inner person, is represented by the “heart.”
Hebrews 4:12 explains that God’s word of promise, like a sharp sword, is able to “discern thoughts and intentions of the heart."
Jesus, too, indicated that from the heart springs the motivating force behind our conduct, whether it is good or bad.
The condition of our figurative heart is reflected in our disposition, our attitude, whether proud or humble.
All such functions, capabilities, emotions, and qualities are ascribed, not to the literal heart organ,
but to the figurative heart as representing the total inner personality.
But note that just as an ambulance, can be a lifesaver in an emergency.
But if the driver does not control the car, constantly guiding the steering wheel, that same car may easily become a deadly weapon.
Similarly, unless you safeguard your heart, you will be at the mercy of your every inner desire and impulse, and your life course will veer into disaster.