Coronary Arteries

Your heart cannot use the blood inside its own chambers, so it has a dedicated supply. Two arteries branch off the aorta within an inch of the heart, ahead of the brain and kidneys, and wrap around the outside like a crown.

In practical terms there are three main roads. The left anterior descending feeds the front wall and the largest share of the pumping chamber. The circumflex curls to the side and back. The right coronary artery supplies the bottom wall and, in most people, the heart's natural pacemaker. These vessels are only two to four millimeters across, about the width of a coffee stirrer, so losing even a millimeter matters.

Unlike other arteries, they fill mainly while the heart relaxes between beats. A racing heart shortens that filling time precisely when the muscle needs more fuel, which is why exertion brings on symptoms.

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