The association between the on-site availability of cardiac procedures andthe utilization of those services for acute myocardial infarction by payergroup

Background: Prior studies have suggested that in-hospital availability may be an important determinant for the use of invasive cardiac services; howev er, whether this association is influenced by payer status remains unclear. Hypothesis: The interaction of payer status and the on-site availability of coronary arteriography is associated with increased utilization of this pr ocedure. Methods: In-hospital availability and utilization of coronary arteriography was ascertained in 275,046 patients with acute myocardial infarction (AMI) enrolled in the National Registry of Myocardial Infarction 2 from June 199 4 to April 1996. Logistic regression analyses were performed to determine t he association between the on-site availability of cardiac catheterization at the initial hospital and subsequent utilization of coronary arteriograph y. Similar analyses were performed within Medicare, Medicaid, Commercial, H ealth Maintenance Organization (HMO), and Uninsured payer groups. Results: Patients initially admitted to hospitals having onsite cardiac cat heterization facilities were almost twice as likely to receive coronary art eriography as patients admitted to hospitals without such facilities and la ter transferred out [unadjusted odds ratio (OR) = 1.69, 95% confidence inte rval (CI) 1.66-1.73, p < 0.0001; adjusted OR = 2.08, 95% CI 2.01-2.15, p < 0.0001]. Furthermore, this relationship of increased utilization with great er availability was evident within each payer group, but was highest among those with Commercial insurance and lowest among Medicaid recipients: [Comm ercial insurance (OR = 2.19, 95% CI 2.07-2.31, p <0.0001); Uninsured (OR = 1.74, 95% CI 1.57-1.92, p < 0.0001); HMO (OR = 1.67, 95% CI 1.54-1.82, p < 0.0001); Medicare 1.60, 95% CI 1.55-1.64, p < 0.0001); Medicaid (1.46, 95% CI 1.29-1.65, p < 0.0001)]. Conclusions: Our results show a strong association between in-hospital avai lability and subsequent utilization of invasive cardiac procedures followin g AMI among all patients, but the strength of these associations varied amo ng payer status.