The key finding of this nationwide retrospective cohort study was that in patients diagnosed with NSTEMI followed by PCI, an invasive evaluation (ICA) within 3 days (72 h) is achieved in a very high percentage of patients, both in PCI-centres (94%) as in non-PCI centres (87%). For the total cohort, 92% underwent ICA within 3 days, which is the time window as recommended by the Dutch ACS working group. However, when considering the latest European NSTE-ACS guidelines, the adherence rate of an early (< 24 h) invasive strategy in the Netherlands is below the class IIa recommendation of the ESC. Is should be noted that ICA within 24 h for stable NSTEMI patients (without very high-risk criteria) was downgraded from a class I to a class IIa recommendation, and therefore should be merely considered, as there is no superiority in death or non-fatal myocardial infarction in several large meta-analysis [1].

Overall adherence to the ESC guidelines showed conflicting results. In a national registry from Germany, university and academic hospitals showed the highest rate of guideline adherence, with almost 99% of the hospitals reporting immediate invasive management within 24 h in patients with NSTE-ACS [10]. Outside Europe, a nationwide registry study in China showed that hospitals had much less guideline adherence, with PCI performed within 72 h after admission in only 31% of patients with NSTE-ACS. One third of the patients with intermediate to very high risk did not undergo invasive evaluation or treatment at all [11].

Overall adherence to perform invasive coronary angiography meets the Dutch standards, although there is a variation in waiting time to PCI between the 30 Dutch PCI centres. The Dutch ACS Working Group endorses a delayed invasive strategy for NSTEMI patients, considering it both safe and acceptable [4]. Further reductions in waiting times could be achieved by sharing best practices (such as about in-hospital logistics, improvement of transfer and waiting times), which can encourage hospitals to shorten the time from diagnosis to ICA and subsequent PCI. Implementing best practices can further enhance the quality of care (i.e. patient satisfaction) for NSTEMI patients in the Netherlands.

Our secondary analysis showed that 19% of the total cohort (n = 7,124) underwent ICA in a non-PCI centre before being transported to a hospital with PCI facilities. Although guideline adherence is high even among patients who underwent local ICA in non-PCI centres (89%), this approach leads to a delay in PCI treatment. The longer waiting time in these patients is recognisable in real world. In a sub-analysis from the EARLY-ACS trial, timely angiography and revascularisation were often not achieved in transferred patients versus patients presented at hospitals with direct PCI capabilities [12]. However, it is still unknown if an early invasive strategy leads to better clinical outcomes [13, 14]. In a prospective multicentre two cohort study, the prehospital identification of patients eligible for direct transfer to PCI centres has proven feasible, leading to a reduction in hospital length of stay and healthcare costs [15]. Though transporting all NSTEMI patients to PCI centres would present significant logistical challenges for both ambulance services and catheterisation laboratories. Evidence from a prospective single-centre registry in the Netherlands indicates that only 59% of NSTEMI patients underwent PCI treatment [5]. In this registry, 23% received conservative treatment, while 18% required a CABG, suggesting a significant number of these transfers to PCI centres may have been unnecessary. Therefore, advice of a preferred admittance or a direct transfer of diagnosed NSTEMI patients to PCI centres remains a subject of ongoing debate.

Currently, no randomised clinical trials have evaluated the strategy of initial ICA at PCI versus non-PCI centres with respect to healthcare resources and costs. Reducing ambulance transports and the number of ICAs in non-PCI centres can enhance the efficiency of healthcare. Future studies have to address this issue.

An important strength of this study is the national coverage: national claim data of all health insurance companies in the Netherlands were analysed. Data from NSTEMI patients who underwent PCI were included. The validity of the use of medical claims data for quality purposes has been assessed by Van Eindhoven et al. by means of retrospective records reviews in patients with acute myocardial infarction. Baseline characteristics, diagnosis and individual medication were comparable between the national claims data and the medical records in four representative hospitals [9]. A limitation of this study is the inability to include patients’ clinical baseline characteristics, as this information was not available in the claims database. As a result, we were unable to identify NSTEMI patients who might benefit from early invasive coronary evaluation, such as those with high-risk criteria. In future, linking medical claims data with clinical data (e.g. from the Netherlands Heart Registration with Dutch Hospital Data) could provide valuable insights for identifying patients who would benefit most from early ICA and/or PCI [7]. Finally, time intervals were recorded in days, as the claims database did not provide time stamps with hour-level precision.