Costochondritis (kos-toe-kon-DRY-tis) is an inflammation of the cartilage that connects a rib to the breastbone (sternum). Pain caused by costochondritis might mimic that of a heart attack or other heart conditions. Costochondritis is sometimes known as chest wall pain syndrome, costosternal syndrome or costosternal chondrodynia. Sometimes, swelling accompanies the pain (Tietze syndrome). What causes costochondritis is unclear. Treatment focuses on easing the pain while waiting for the condition to improve on its own, which can take several weeks or more.