We found that, for each health region in Alberta, the yield of high-risk CAD increased linearly with an increase in cardiac catheterization rates and continued to do so without evidence of a plateau. This suggests that the optimal catheterization rate to detect high-risk CAD in Alberta is greater than 638.1 per 100 000 adults over age 20 among men and greater than 314.0 per 100 000 among women. Given that rates of cardiac procedures in Alberta are among the highest in Canada,6,7
our findings suggest that an optimal cardiac catheterization rate has not yet been reached in this country. These findings are of great international relevance because considerable rate differences exist across countries without evidence of optimal rates.
In comparison with other countries, Canada is considered to have a “medium” cardiac catheterization rate, similar to that of Australia, Belgium and Germany, with lower rates reported in the Netherlands, Sweden, the United Kingdom, Hungary and Poland, and the highest rates in Brazil and the United States.4,13
Our results are consistent with those of a number of previous studies of cardiac procedure rates in Canada that indirectly suggested that a significant number of patients with high-risk CAD are not being identified.14,15
In a more direct comparison, Batchelor and colleagues16
determined that the rate of catheterization after myocardial infarction in the United States was more than 2.5 times that in Canada, with US physicians identifying on average 7.4 more cases of severe CAD per 100 post-MI patients than Canadian physicians.
In a previous study of APPROACH data, a large proportion (74.2%) of the patients with high-risk CAD discovered at cardiac catheterization subsequently underwent revascularization procedures; in general, this tendency was uniform across regions.17
This finding indicates that the discovery of high-risk CAD in Alberta patients usually leads to therapeutic action (i.e., revascularization), which may in turn improve long-term prognosis.
Implicit in some of the preceding discussion is that the use of catheterization is rational and truly linked to need. In reality, this may not be the case. Decisions to perform catheterization procedures are typically made by individual physicians faced with individual patients. Such a one-on-one perspective is often blind to the perspective of population-based needs that our study has attempted to address. Furthermore, this argument could be extended to the question of whether societal investment is best aimed at sick individuals (i.e., clinical interventions) as opposed to sick populations (i.e., population-based health promotion interventions). Rose18
acknowledged the role of intervention that targets both ends of this spectrum, although he pointed out that the returns may be greater for population-based interventions. In this regard, we acknowledge that our findings need to be complemented by future work assessing the economic implications of various catheterization utilization strategies.
Our study has limitations. Because the inception point of APPROACH is cardiac catheterization, and because no reliable data on regional prevalence of CAD are available, age adjustment of catheterization rates was the only method used to account for true regional differences in prevalance of severe CAD. Also, formal assessments of the appropriateness of the catheterization procedures were not conducted. However, it has been previously shown that inappropriate use of angiography does not explain geographic variations in procedure rates.19
In conclusion, we found a linear relation between cardiac catheterization rates and the yield of high-risk CAD in all of the 17 health regions in Alberta. Increasing the current rate of use of this procedure could lead to the detection of more patients with high-risk CAD who would then potentially benefit from revascularization. Because Alberta has one of the highest rates of cardiac catheterization in Canada, and because Canada is considered to have an intermediate rate of cardiac catheterization compared with rates in other countries, these results suggest that a higher utilization rate may be required, not only in Canada but in many other countries with similar or lower catheterization rates. Whether an optimal rate of catheterization has been reached in countries with higher utilization rates (e.g., the United States) has yet to be determined, perhaps through the use of analyses similar to those presented here.
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