Non-ST-elevation myocardial infarction in the Netherlands: room for improvement!

Improvements in early recognition and revascularisation have significantly decreased mortality after myocardial infarction in recent decades [1‐3]. This reduction in mortality, however, has been achieved especially in ST-elevation myocardial infarction (STEMI) patients. Unfortunately, the mortality rate in non-STEMI (NSTEMI) patients has not declined in recent years [4, 5].

The most recent European and American guidelines emphasise that the use of an early invasive strategy, as well as optimal medical therapy, contributes to a better long-term survival after NSTEMI (both evidence class 1, level A) [2, 3, 6]. The European guidelines even indicate them as performance measures of NSTEMI care, based on various large meta-analyses and randomised controlled trials [7, 8]. Recently, Hall et al. demonstrated that optimal use of guideline-indicated care for NSTEMI was associated with greater survival gain [9]. However, in Hall’s study the adherence rate was suboptimal, indicating that survival can potentially be improved. This recent study illustrates that large-scale monitoring of guideline-indicated care adherence is crucial to provide insight into how to improve NSTEMI care, ultimately resulting in improved survival.

The Dutch National Healthcare Institute (Zorginstituut Nederland, ZINL) advises the Dutch government with the primary objective of improving Dutch national healthcare. For this purpose, ZINL has access to all Dutch patients’ claims data in the Netherlands. The use of these claims data has been proven to reflect the real clinical data and to be correct and adequate in previous studies [10‐12]. The current study is performed in close collaboration with ZINL and aims to analyse NSTEMI care in the Netherlands and to identify modifiable performance factors that can be used to analyse and improve the quality of NSTEMI healthcare in the Netherlands.

Hospital claims are sent to patients’ insurance companies and subsequently collected in the central database of the insurance companies in the Netherlands. The use of this type of data has been validated in previous studies [11]. ZINL has access to both hospital and pharmacy claims databases and can access data at the patient level, which can be linked but is anonymous (Fig. 1).

The current study analyses NSTEMI care in the Netherlands through hospital and pharmacy claims data. The main findings can be summarised as follows: NSTEMI patients are predominantly older, male patients. The use of PCI within 4 days of hospitalisation and the prescription of complete optimal medication treatment within 30 days after NSTEMI are both modest, but both significantly reduce 1‑year mortality in these patients. Non-use of both factors is independently associated with increased mortality, which suggests that through the present study NSTEMI healthcare quality can be improved in the Netherlands.

The current call for awareness of a wider use of PCI within 4 days of admission after NSTEMI and of optimal medical treatment prescription is in line with the recommendations in the European Society of Cardiology guidelines [3]. Furthermore, it is congruent with a recently published study by Hall et al. analysing over 400,000 hospital survivors of a NSTEMI in England and Wales, in order to investigate whether improved survival is associated with the use of NSTEMI guideline-indicated treatments [9]. In this somewhat older cohort (2003–2013), Hall et al. demonstrate that guideline-indicated treatment is associated with improved survival that persisted over the longer term. An invasive coronary strategy was found to have the most comprehensive and persistent impact on survival. This is consistent with the finding of the current study that PCI treatment for NSTEMI substantially reduces 1‑year mortality with an OR of 0.42.

A potential argument for non-use of PCI in NSTEMI patients in daily practice may be that the beneficial effect of PCI is less in the elderly with more co-morbidities, and complications are more prominent in this group. Interestingly, Couture et al. found that especially in older patients with more co-morbidities a more invasive strategy should be considered [14]. With the NSTEMI cohort in our study having a similar profile and low PCI rate, this can be an important finding indicating that there is room for improvement in the Netherlands. This issue was indeed also raised in a very recent registry by Hoedemaker et al., who evaluated treatment patterns of NSTEMI patients in 23 non-PCI centres in the Netherlands. In this registry, the majority of high-risk patients underwent angiography at a non-PCI centre. Despite the guideline recommendation only a quarter of these high-risk patients were transferred to a PCI centre within 1 day [15].

Apart from early PCI, the present study also underlines the importance of implementing optimal medical treatment within 30 days after NSTEMI. Whereas Hall et al. reported on recipes at discharge, the current study reveals which medication is collected at pharmacies up to 30 days after NSTEMI. Since primary non-adherence to prescribed medication has been reported to be very common in patients with ischaemic heart disease [16], we think that the current results provide additional insight into the significance of secondary prevention medication use after NSTEMI, especially since mortality differences were already observed within the 1st year. Accordingly, a conjoint effort of cardiologists and patients is warranted to improve medication adherence after NSTEMI.

The current study confirms the findings of Hall et al. and extends them to the entire Dutch population with additional insights into the impact of secondary prevention medication truly collected at pharmacies. Interestingly, the method of data collection substantially differs between the two studies. In particular, Hall et al. reported on data gathered from national clinical audits. Data collection for audits, however, is time consuming and expensive. We want to stress the need for new effective ways of evaluating healthcare as a key element in healthcare innovation. The use of claims data has been proven to be correct and adequate in previous studies [10, 11]. National claims data provide a good representation of the ‘real world’ setting in contrast to the common single-centre registries in NSTEMI studies [17‐22]. Furthermore, such data have the following advantages: low administrative load, low costs, absence of reporting bias, and easy follow-up of patients being treated in more than one hospital.

Some limitations should nonetheless be considered when interpreting the results. First, the study uses a non-randomised design with observational data. The addition of propensity score matching, however, strengthens the results [23]. Second, this study assessed PCI treatment only in the acute phase of the infarction; an effect of PCI on mortality after the acute phase of NSTEMI was not calculated. Likewise, the effect of bypass surgery on mortality after NSTEMI was not calculated. Third, the level of clinical detail is limited, e.g. completeness of revascularisation or infarct size. Commonly used risk scores (e.g. Global Registry of Acute Coronary Events (GRACE) risk score) cannot be applied either. Potentially there could have been a bias from patients who were registered as NSTEMI but did not meet all the criteria of myocardial infarction and therefore should have been classified as having unstable angina. For our study, however, we rely on correct registration by Dutch cardiologists. Equally, the definitions used for co-morbidities are only determined through medication use prior to the infarction and not via clinical data. Likewise, clinical details on differences between male and female PCI rates are lacking in financial claims data. Fourth, although mortality data are available, the cause of death is not specified. Fifth, the pharmacy claims data only represent the collected medication, not the consumed medication. Furthermore, it remains unclear if medication was contra-indicated or not prescribed. And lastly, further randomised trials are needed to validate the healthcare benefit of PCI during hospitalisation and optimal medical treatment.

The present study analysed hospital and pharmacy claims data of more than 17,000 NSTEMI patients in the Netherlands. PCI use during hospitalisation and optimal medical treatment are both moderately applied in this patient group but are independently associated with a lower 1‑year mortality. These findings importantly suggest that attention to a wider use of PCI during hospitalisation as well as particular attention to optimal medical treatment prescription by cardiologists and medication adherence by patients may substantially improve outcome after NSTEMI.