The Relationship between the Supply of Cardiac Catheterization Laboratories, Cardiologists and the use of Invasive Cardiac Procedures in Northern New England

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Abstract
Objectives: Utilization rates of coronary angiography and cardiac revascularization have been found to vary between areas. This study addresses the relationship between resource supply and procedure rates. Methods: We compared the association of per capita catheterization laboratories, per capita cardiologists and multi-provider markets (where more than one hospital offers coronary angiography services) with the utilization rates for angiography and cardiac revascularization in northern New England, USA. Administrative data were used to capture invasive cardiac procedures. Small area analyses were used to create coronary angiography service areas. Linear regression methods were used to measure associations between the resource supply and utilization rates. Results: Variation in the use of invasive cardiac procedures was strongly associated with the population-based availability of catheterization facilities and multi-provider markets and unrelated to cardiologist supply or need (as reflected in the hospitalization rates for myocardial infarction). In the multivariate model, an increase of 1 catheterization laboratory per 100 000 population was associated with an increase in the angiography rate of 1.62 per 1000 population; those service areas with multi-provider markets were associated with an additional increase in the angiography rate of 1.27 per 1000 population ( R2= 0.84, P = 0.0006). There was a moderately strong relationship between the catheterization laboratories per capita and the revascularization rates ( R2 = 0.43, P = 0.029). Angiography rates were highly associated with cardiac revascularization rates: An increase in the angiography rate of 1 per 1000 population was associated with a 0.46 per 1000 increase in the cardiac revascularization rate ( R2 = 0.85, P = 0.0001). Conclusions: Our work suggests that current efforts to address variation in cardiac procedures through activities such as appropriateness criteria, guidelines and utilization review are misdirected and should be redirected towards capacity, in this case the supply of catheterization facilities.