By including a significant number of the hospitals in Switzerland, the AMIS Plus registry gives an accurate picture of the contemporary management of acute coronary syndromes in this country. This ongoing multicentre project, which offers the possibility of both data input and data analysis over the internet, is a useful tool to monitor current practices and to assess the impact of major randomised controlled trials and guidelines.16,17
The present analysis focused on the immediate reperfusion therapy of STEMI and its evolution over time.
The patients who underwent reperfusion, either by primary PCI or by thrombolysis, had a very similar profile. One notable difference was the delay between the onset of the symptoms and admission to hospital, which was about one hour longer for the patients who underwent primary PCI. Similar findings were described in the MIR (myocardial infarction registry) and MITRA (maximal individual therapy in acute myocardial infarction) registries9
and may be due to awareness that the beneficial effect of thrombolysis decreases with increasing pre-hospital delay.18
This effect does not apply to the same extent for primary PCI,19–21
therefore probably leading to a more liberal use of primary PCI for patients admitted late from the time of symptom onset.
The baseline characteristics were similar to the results of a previous study by Danchin and colleagues,10
which found no significant differences between the patients who underwent primary PCI and thrombolysis in terms of age, sex, and cardiovascular risk factors. The same study also showed that patients who did not undergo reperfusion were older and were admitted to hospital later. In our study, many of the differences in baseline characteristics between these patients and those who did undergo PCI or thrombolysis account for why those patients were not treated. Indeed, late arrival in hospital after symptom onset was noted to be the reason why about one half of these patients did not undergo reperfusion. Another reason stated was the unfulfilled ECG criteria, probably in relation to the higher rate of left bundle branch block and lower rate of ST segment elevation present on the initial ECG in these patients. In addition, the uncertainty of the diagnosis was also stated as a reason leading to absence of reperfusion. This may be linked, to a certain extent, to the higher proportion of women among these patients, who are known to have a higher incidence of atypical symptoms or silent myocardial infarctions than men,22–24
thus creating confusion regarding the establishment of a clear diagnosis. The higher age and therefore the higher rate of co-morbidities among these patients may also have influenced the choice of not performing reperfusion. The integration of Charlson’s index of co-morbidities in the questionnaire since 2002,25
which was not used in the present analysis, should help us in the future to clarify further why any given patient is selected not to receive reperfusion. Furthermore, the proportion of patients who did not receive reperfusion significantly decreased from 1997 to 2002 (from 44.8% to 31.4%). These results are comparable with those reported in registries that were conducted over the same period (28.8% to 44.2%).11–14
Improvement of referral networks, as well as continuing efforts to decrease pre-hospital delays, should help to further reduce the proportion of these patients.
From 1997 to 2002, there was a major increase in the proportion of patients treated by primary PCI and therefore this procedure became the preferred mode of reperfusion for STEMI in 2002. Over the same period, the use of thrombolysis has gradually decreased. Although this trend has also been observed in other studies,11,12
the AMIS Plus registry is, to our knowledge, the first to show that primary PCI has become the most frequently used means of reperfusion,11–14
certainly reflecting the impact of the results of several randomised controlled trials and guidelines for the management of STEMI,6–8
and showing that recent information is indeed being translated into clinical practice.
In AMIS Plus, the global in-hospital mortality for STEMI, regardless of whether reperfusion was carried out, was 10.1% during the six years of the study, which is comparable with that reported from NRMI 3 (national registry of myocardial infarction 3) (9.8% in 1999),10
but slightly higher than the results reported from other European and international multicentre studies (6.0–8.0%).12–14
This is probably explained by the fact that these studies either included a high proportion of academic medical centres with revascularisation facilities or had more selective inclusion criteria than in AMIS Plus (for example, excluding patients who died early in the emergency room, before admission to the coronary care unit). Moreover, our study shows a gradual decline of overall in-hospital mortality for STEMI, from 12.2% in 1997 to 6.7% in 2002 (p < 0.001). The evolution of in-hospital mortality stratified according to the reperfusion mode suggests that the decline of overall mortality during the study period was due to the simultaneous reduction of the mortality of patients who underwent PCI, as well as those who did not receive reperfusion, whereas there was no significant change in the mortality of the patients who underwent thrombolysis.
The overall in-hospital mortality during the study period associated with primary PCI and thrombolysis (4.1% and 5.7%, respectively) was similar to the results of previous registries and randomised trials.6,10,15
A regression model comparing mortality between both reperfusion modes, adjusted for the admission year, did not show that primary PCI was significantly more beneficial than thrombolysis. However, the mortality associated with primary PCI significantly decreased over the study period, whereas the mortality associated with thrombolysis did not. This discordance has already been reported previously9
and is probably due to the fact that thrombolysis has not seen major advances over the past 10 years, whereas PCI has progressed greatly over the same period with the improvement of angioplasty technique, broader use of stents and glycoprotein IIb/IIIa inhibitors, growing experience of the treating physicians, and optimisation of out of hospital and in-hospital logistics to shorten door to balloon delays.20,26–29
The multivariate analysis for predicting in-hospital mortality at admission also confirmed the benefit associated with primary PCI and thrombolysis, contrasting with the results from previous studies.10,15
Furthermore, admission year was a significant predictor, confirming the improvement in survival over the study period.
Although at the time of this study 54 of the 106 hospitals treating STEMI in Switzerland were participating in the AMIS Plus registry, the number of the participating centres varied during the study period and they may therefore not be entirely representative of all the hospitals in the country. Thus, the absolute number of patients may not give a true picture of the national incidence of myocardial infarction leading to hospital admission. This should improve over the coming years as more centres join the project.
Another limitation, which is common to all registries, is that AMIS Plus is an observational study rather than a randomised trial. Some of the baseline characteristics of the patients were not available and may thus have created unrecognised bias. Nevertheless, although the participating centres were not individually audited on site, the data management centre continuously and carefully checked the data questionnaires and queried incomplete questionnaires as needed.
Lastly, it is important to mention that, although AMIS Plus is supported by unrestricted grants from several pharmaceutical and medical device companies, the data were collected and analysed independently. The sponsoring firms had no access to the raw data.
From 1997 to 2002, the use of reperfusion for STEMI has increased progressively in Switzerland, with primary PCI becoming the preferred mode of reperfusion since 2002. This shows that the information from randomised controlled trials and guidelines is adequately reshaping daily clinical practice for the management of STEMI.6–8
Along with this progression, in-hospital mortality decreased greatly over the same period. However, about one third of the patients still did not receive reperfusion therapy in 2002. A continued effort is therefore necessary to make reperfusion available to a greater proportion of patients with STEMI, in particular to those admitted late after symptom onset.
Moreover, at a time when modern cardiology is changing rapidly, with new strategies such as transferring patients for primary PCI and evaluating facilitated PCI,21,30–33
registries such as AMIS Plus should help us to assess the applicability and effectiveness of these potential changes to come and to contribute to improved care for patients with STEMI.