The volume of primary angioplasty procedures and survival after acute myocardial infarction

Background: There is an inverse relation between mortality from cardiovascu lar causes and the number of elective cardiac procedures (coronary angiopla sty, stenting, or coronary bypass surgery) performed by individual practiti oners or hospitals. However, it is not known whether patients with acute my ocardial infarction fare better at centers where more patients undergo prim ary angioplasty or thrombolytic therapy than at centers with lower volumes. Methods: We analyzed data from the National Registry of Myocardial Infarcti on to determine the relation between the number of patients receiving reper fusion therapy (primary angioplasty or thrombolytic therapy) and subsequent in-hospital mortality. A total of 450 hospitals were divided into quartile s according to the volume of primary angioplasty. Multiple logistic-regress ion models were used to determine whether the volume of primary angioplasty procedures was an independent predictor of in-hospital mortality among pat ients undergoing this procedure. Similar analyses were performed for patien ts receiving thrombolytic therapy at 516 hospitals. Results: In-hospital mortality was 28 percent lower among patients who unde rwent primary angioplasty at hospitals with the highest volume than among t hose who underwent angioplasty at hospitals with the lowest volume (adjuste d relative risk, 0.72; 95 percent confidence interval, 0.60 to 0.87; P<0.00 1). This lower rate, which represented 2.0 fewer deaths per 100 patients tr eated, was independent of the total volume of patients with myocardial infa rction at each hospital, year of admission, and use or nonuse of adjunctive pharmacologic therapies. There was no significant relation between the vol ume of thrombolytic interventions and in-hospital mortality among patients who received thrombolytic therapy (7.0 percent for patients in the highest- volume hospitals vs. 6.9 percent for those in the lowest-volume hospitals, P=0.36). Conclusions: Among hospitals in the United States that have full interventi onal capabilities, a higher volume of angioplasty procedures is associated with a lower mortality rate among patients undergoing primary angioplasty, but there is no association between volume and mortality for thrombolytic t herapy. (N Engl J Med 2000;342:1573-80.) (C) 2000, Massachusetts Medical So ciety.