What percent of cardiac output goes to the coronaries?

• A. 10%
• B. 5%
• C. 15%
• D. 20%

Answer: (B)

Understanding how much of the heart’s output feeds its own muscle helps you remember coronary physiology: at rest, about five percent of cardiac output goes to the coronary arteries. If cardiac output is around 5 liters per minute, that’s roughly 250 milliliters per minute supplying the myocardium. The coronary vessels dilate to meet oxygen demand, so absolute flow increases with activity, but the share of total cardiac output devoted to the coronaries stays in the same general range. The other options (about 10%, 15%, or 20%) would imply far higher resting coronary flow than is typical.