Volume, outcome, and policy.

Procedure volume is potentially important for physicians learning a new procedure and for practicing physicians to maintain proficiency. Volume standards for training are largely based on opinion. In contrast, there are substantial data showing that the volume of procedures performed by a hospital or physician in practice has an inverse relationship with clinical outcomes: higher volumes are associated with better outcomes. Increased procedure volume for implantable defibrillators has been associated with lower short-term complication rates. The controversial policy implications of these observations are discussed.