Did referral patterns for coronary angiography change in Europe? What can we learn from Denmark?

This editorial refers to ‘Danish trends in pharmacotherapy, comorbidities, and demographics in patients referred for coronary angiography: what changed during a decade?’, by M.E. Jørgensen et al., on page 157 We congratulate Jørgensen et al.1 to the stimulating insights on the temporal trend of referral to coronary angiography (CAG). These data are based on the unique Danish system of linking nationwide administrative registers on an individual level with disease-specific registers such as the Danish Heart Register. This linkage has already provided several intriguing information.2,3 In this study, Jørgensen et al. provide data of 156 496 patients with first time CAG between 2000 and 2009. The main objective of this study is a marked increase of CAG ranging from 2.2 in 2000–01 to 3.4 CAG/1000 inhabitants/year until 2007, which corresponds to a relative increase of 61% and a further constant rate of CAG until 2009. In accordance, similar data for Europe were shown in an Italian cohort demonstrating a steep increase of CAG in patients with acute myocardial infarction.4 Though, the increase of CAG in Denmark was driven by patients in both the elective and acute setting. Surprisingly, data from the state of North Carolina in the USA show an opposing trend indicated by a decline in CAG of 24% during a similar time period.5 A potential explanation for this transatlantic discrepancy may be a much higher baseline rate of 9.1 CAG/1000 inhabitants/year in the USA. This higher number of CAG may be partially caused by counting all (and not only first time) CAG. Further interesting observations in the present study include the evolving frequencies of concomitant comorbidities in Danish patients referred to CAG. While the absolute number of comorbidities such as renal disease, liver disease, chronic obstructive pulmonary disease, and vascular disease has increased, there was a relative decrease of comorbidities. Thus, the time trends are ambiguous with regard to comorbidities, with an increased number of patients with a large burden of comorbidities but obviously also of patients without comorbidities. In accordance, data from the EUROASPIRE surveys confirm the increasing rate of comorbidities in patients with established coronary heart disease in the period from 1995 to 2007.6 The increased number of patients with more than one health problem may reflect the growing number of chronic and elderly patients. The present study enhances our knowledge about distribution patterns of comorbidities of all patients referred to CAG as previous publications have focused on patients with percutaneous coronary interventions (PCIs) in the acute setting only. For example, Fokkema et al.7 described an increase of patients with diabetes over the time in 144 039 Swedish patients undergoing PCI. While evidence for a beneficial effect of PCI in the acute setting at the beginning of the observed time period has probably induced the increased number of CAG in these patients, the parallel increase of CAG in elective patients is less clear.8,9 Augmented capacities for CAG required for interventions at the same day for acute patients may also have induced more CAG in healthier patients to rule out coronary artery disease. The safety of CAG with rare (but severe) complications may have further stimulated the use of CAG in healthier patients. It would be of interest to know more about the indications for elective CAG and compare their trends with the guidelines from the European Society of Cardiology (ESC) on myocardial revascularization. These recently updated guidelines define specific situations when CAG and subsequent PCI may provide a benefit for the patient due to symptom relief or even improvement in prognosis.10 However, the lack of comprehensive clinical data to evaluate the exact indications for referral to CAG is a limitation of the linkage of routine data. Another important information of this study by Jørgensen et al. relates to prophylactic pharmacotherapy. The use of evidence-based therapies including statins, RAS inhibitors, and acetylsalicylic acid at the time of referral to CAG steeply increased over time. Still, there is some room for further improvement in the adherence to current guidelines for the treatment of patients with atherosclerotic disease.10 While there is an ongoing discussion about the relevance of PCI compared with pharmacotherapy in elective patients, these data from clinical practice indicate that both strategies are increasingly used at the same time. Of note, an even higher usage of preventive pharmacotherapy has been observed in elective patients. One is tempted to speculate whether pharmacotherapy has prevented acute coronary events or whether this observation is related to more time in elective patients to establish pharmacotherapy. An existing literature so far has focused on pharmacotherapy after discharge of patients with acute coronary syndrome: European and US data have confirmed an increased use of preventive pharmacotherapy such as antiplatelet therapy, beta-blockers, RAS inhibitors, and statins over time.4,11,12 These data also indicate that patients undergoing coronary intervention had the highest rate of evidence-based preventive measures, suggesting a high awareness of the cardiovascular risk in patients referred to CAG.12 In conclusion, the Danish healthcare system has quickly adapted to new evidence about beneficial effects of PCI and pharmacotherapy. European healthcare systems should reinforce the joint use of both invasive and non-invasive therapeutic strategies according to the current guidelines of the ESC for myocardial revascularization for an optimal patient outcome. The authors of this study, but also other scientists in charge of population-based registries, should be encouraged to provide further data how this increase in patients referred to CAG translates into changes in the number of coronary interventions and whether the increased use of pharmacotherapy and CAG impacts on cardiac mortality over time in clinical practice.