The following is a video of a coronary artery anomaly demonstrated with cardiac (heart) catheterization.  In this study, a fine tube is threaded into the heart and dye is injected to visualize the arteries.  The right and left coronary arteries provide the blood supply to the heart.  This study is normal except for a congenital variation of the left coronary artery.  Often times these arteries become clogged with fatty plaques.  If these plaques breakdown and develop ulcers a blood clot can form which blocks the artery.  When this happens a heart attack often occurs.