Operator Volume and Clinical Outcomes of Primary Coronary Angioplasty for Patients With Acute Myocardial Infarction

An inverse relationship between the annual number of patients treated by a hospital or physician and rates of mortality and complications has been repeatedly documented. These volume-outcome relationships have been explored in particular detail in cardiovascular medicine, including for procedures such as coronary artery bypass graft surgery and coronary angioplasty and conditions such as acute myocardial infarction. There is considerable controversy regarding how these data should be interpreted and, in particular, whether policies should be based on hospital or physician volume. In the present issue of Circulation , Vakili and associates1 present data on the effect of operator volume on the outcome of primary angioplasty for acute myocardial infarction. To place this study in context, we will first review the data on volume-outcome relationships, then assess why these relationships exist, and finally discuss what policies might be based on these findings.See p 2171 The relationship of coronary angioplasty volumes to outcome has been examined in many studies. Jollis and coworkers2 analyzed claims data from 1987 through 1990 for 217 836 Medicare beneficiaries and found an inverse relationship between mortality and the annual number of angioplasty procedures performed in a hospital. They found the volume-outcome relationship was J-shaped, ie, had a stronger inverse relationship at low angioplasty volumes than at high volumes. This study highlights several methodological issues common to all studies of volume and outcome. First, very large sample sizes are needed to provide sufficient statistical power to document a relationship between mortality and procedure volume. Second, unless a wide range of procedure volumes is examined, a real relationship between volume and outcome may be missed.The inverse relationship between hospital volume of coronary angioplasty and short-term adverse outcomes (mortality, need for emergency coronary bypass surgery) reported by Jollis and coworkers2 has been repeatedly confirmed. Kimmel …