This is the first report from the Norwegian Myocardial Infarction Registry, providing details of the number of patients with myocardial infarction admitted to Norwegian hospitals, their treatment and the mortality rate. A total of 13,043 cases were recorded in 2013. The majority were classified as nSTEMI (70 %). Most STEMI patients received reperfusion therapy with percutaneous coronary intervention (77 %, n = 2,798), while the corresponding number for nSTEMI patients was 35 % (n = 3,179). Secondary prophylaxis with drug therapy was prescribed to a lesser degree for nSTEMI patients than for STEMI patients. The 30-day mortality rate was 10 % for the entire population, and there was no difference between health regions or between men and women.
A high proportion of patients had suffered a myocardial infarction on a previous occasion. Entries submitted to the Myocardial Infarction Registry were completed on the patient’s discharge from hospital. Consequently, we have no information relating to further patient follow-up or the outcomes of secondary prophylactic measures, but our findings may indicate that there is a need for further investment in prevention.
The European Society of Cardiology recommends early revascularisation for most patients with myocardial infarction, irrespective of the type of infarction (8, 9). The time of the first pre-hospital contact with a medical officer (GP, ambulance service, pre-hospital ECG etc.) was not recorded in the Myocardial Infarction Registry in 2013. Regrettably, the times of symptom onset, hospital admission and angiography/percutaneous coronary intervention were incompletely registered at many hospitals, particularly in cases of nSTEMI. It is therefore impossible to say what proportion of STEMI patients received reperfusion therapy with primary percutaneous coronary intervention within the recommended 90-minute time lapse from first contact with a medical officer.
The time lapse between arrival at the invasive hospital and treatment with percutaneous coronary intervention was short. The variation found between invasive hospitals may have been caused by differences in the recording procedures at the different locations. However, all hospitals stayed within the international guidelines (9). The proportion of nSTEMI patients who were offered invasive coronary examination was lower than the corresponding proportion of STEMI patients, and lower at primary admission to local hospitals than to invasive hospitals.
The guidelines recommend coronary angiography for all nSTEMI patients without counter-indications (8). These patients were older than the STEMI patients and suffered from a higher number of additional diseases. This can explain the difference to some extent, but we nevertheless feel that there is potential for improvement in offering more nSTEMI patients invasive coronary examination and treatment. It is necessary to exercise caution when interpreting variations between hospitals due to demographic differences and dissimilar distribution of functions.
Most patients suffering from myocardial infarction received secondary prophylaxis with drugs such as acetylsalicylic acid, ADP receptor inhibitors, beta-blockers, statins and ACE/AII receptor inhibitors in compliance with the European guidelines (8, 9). The proportions within each group of medication was somewhat lower in Norway than in Sweden (10), but the two countries’ myocardial infarction registries do not lend themselves to direct comparison because some of the hospitals in Sweden had registered only patients in cardiac intensive care units.
Some patients with myocardial infarction, particularly the elderly, suffer from complicated additional diseases and an increased risk of bleeding which may make the use of various types of medication difficult, especially blood platelet inhibitors. Nevertheless, there is reason to take note of the difference between STEMI patients and nSTEMI patients with respect to the proportion discharged with ADP-receptor inhibitors. This may also be associated with the lower percentage of percutaneous coronary intervention in nSTEMI cases, but the guidelines recommend ADP receptor inhibitors irrespective of whether or not percutaneous coronary intervention is performed.
In general, the 30-day mortality was low (10 %) and found to be similar across the various health regions. The results from the Myocardial Infarction Registry are comparable to the analysis of mortality following myocardial infarction that was conducted by the Norwegian Knowledge Centre for the Health Services in 2010 and 2011 (30-day mortality rate of 12.6 per cent) (11). Recently published data from the EU funded research project entitled European Health Care Outcomes, Performance and Efficiency (EuroHOPE) also demonstrate that the survival rate after myocardial infarction in Norway is higher than the European average (12).
We have refrained from giving the 30-day mortality rate per hospital because the age distribution and risk profiles of patients vary between hospitals and because the hospitals’ dissimilar patient flow procedures affected the results. Moreover, the death rate at many hospitals was very low, so that random variations would impact considerably on the reported figures.
The Myocardial Infarction Registry and the 2013 data analysis suffer from a number of limitations. Only myocardial infarctions that led to hospitalisation were recorded. We had no access to records of myocardial infarctions that did not result in hospitalisation, nor of patients who died of infarction outside of hospital.
Six hospitals failed to submit complete data. Each hospital was asked to ensure that all their cases were registered by checking their internal patient administration systems, but the Registry’s secretariat had no opportunity to check this at national or local level. It is therefore impossible to give the exact incidence of myocardial infarction in Norway. For the time being, Norwegian patient registries do not have access to comparable data for the number of admissions diagnosed with myocardial infarction in 2013.
The procedures used for recording the time of admission and invasive examination and treatment varied between hospitals. The Myocardial Infarction Registry has not had the opportunity to undertake quality control at local level of data submitted by individual hospitals. Data submitted by several hospitals in the course of the same patient’s treatment, were linked up at the Registry. This led to a certain degree of uncertainty, particularly if the same variable had been recorded differently.
When figures were collated for the different types of infarction, STEMI was given a higher priority even if recorded by only one hospital in the course of the same treatment. This may have meant that a myocardial infarction registered as STEMI at the first hospital but assessed as nSTEMI at a subsequent hospital, has been registered as STEMI. An amendment to the legislation would be desirable to enable registration of only a single record per myocardial infarction by allowing local hospitals and invasive hospitals to enter their data into the same electronic form.
Despite the above-mentioned limitations the results indicate that the majority of patients receive satisfactory treatment. The 30-day mortality rate was at a level found in comparable countries, and a high proportion of our patients received the recommended secondary prophylaxis with drug therapy. However, we identified a number of areas for improvement. In particular, the routines for invasive examination and treatment of myocardial infarctions without ST-segment elevation should be reassessed.
It is the Myocardial Infarction Registry’s objective to represent a constant source of improvement for the treatment of myocardial infarction in Norway. Complete high-quality records are essential – which is why it is important that everyone involved with the treatment of patients with myocardial infarction contribute towards this end. The Norwegian Myocardial Infarction Registry will continue its work to ensure that all hospitals introduce similar recording procedures, tighten the requirement to submit complete records and enhance its contributions to local and central quality assurance. Also, better systems must be introduced for the reporting of results and relevant quality indicators back to all hospitals.