Editing Coronary circulation (section)

===Changes in oxygen demand===
The heart regulates the amount of [[vasodilation]] or vasoconstriction of the coronary arteries based upon the oxygen requirements of the heart. This contributes to the filling difficulties of the coronary arteries.
Compression remains the same. Failure of oxygen delivery caused by a decrease in blood flow in front of increased oxygen demand of the heart results in tissue [[ischemia]], a condition of oxygen deficiency. Brief ischemia is associated with intense chest pain, known as [[Angina pectoris|angina]]. Severe ischemia can cause the heart muscle to die from hypoxia, such as during a [[myocardial infarction]].  Chronic moderate ischemia causes contraction of the heart to weaken, known as myocardial hibernation.{{citation needed|date=April 2021}}

In addition to metabolism, the coronary circulation possesses unique pharmacologic characteristics. Prominent among these is its reactivity to adrenergic stimulation.{{citation needed|date=April 2021}}