Coronary anatomy.

The coronary arteries have a serpentine but interdependent relationship to one another. The left artery supplies the majority of the left ventricular myocardium irrespective of right or left arterial "dominance." A coronary artery obstruction begins to assume significance when it approaches 75% of the cross-sectional area of the vessel. Increasing degrees of stenosis impose limitations to blood flow during stress and finally even under resting conditions. Analysis of the arteriogram requires not only knowledge of normal anatomy and its variations but also appreciation of difficulties in distinguishing a normal from an abnormal artery and in quantifying the functional severity of an obvious obstruction.