This study of gender differences in the assessment, treatment, complications and survival of patients with myocardial infarction treated at all Norwegian hospitals in the period 2013 – 2014 shows that coronary angiography was carried out on fewer women than men, but when coronary stenosis was found, PCI was performed to virtually the same extent on both genders. In non-STEMI cases in particular, women were discharged from hospital with fewer secondary prophylactic drugs than men. There were few differences between men and women in the incidence of complications or in survival.
The international guidelines for treatment of myocardial infarction (24) – (26) recommend early coronary angiography for all patients with myocardial infarction. Nonetheless, this study shows that many patients, particularly those with non-STEMI, were not offered this assessment, and consequently did not have the option of PCI. This applied to more women than men. These national data from 2013 and 2014 reflect the findings described from Ullevål Hospital in the period 2006 – 2007 (22) and of Melberg et al. in 2005 (23). Similar gender discrepancies have also been published recently in a country-wide French registry study (12).
The value of invasive assessment and treatment is not as well documented for women as for men (31, 32), and this may have a bearing on the choice of treatment strategy. Greater comorbidity in women may also help to explain some of the gender differences. We did not investigate in this study whether there were differences at hospital level – different local therapy traditions may also have been of significance. It has previously been shown that more patients with myocardial infarction were invasively assessed if they were admitted to a hospital where there was the option of coronary angiography (23).
The differences cannot be explained by dissimilarities in symptoms and clinical findings in connection with suspected myocardial infarction in women and men, as only patients with the diagnosis myocardial infarction were registered in the Norwegian Myocardial Infarction Registry and hence included in this study. We find reason to stress that the guidelines of the European Society of Cardiology, which it is recommended be used in Norway, do not distinguish between women and men in their recommendations for invasive assessment and treatment of myocardial infarction (24) – (26).
Secondary prophylactic drugs such as acetylsalicylic acid, ADP receptor inhibitors and statins are important for preventing reinfarction and further atherosclerosis development and are recommended for all patients after myocardial infarction (24) – (26). The reason that some patients, particularly women with non-STEMI, still did not receive these drugs on discharge from hospital is not clear. Less use of dual platelet inhibition may be due to a lower percentage of PCI in women, but the guidelines recommend dual platelet inhibition whether PCI is carried out or not. Higher comorbidity in women, and consequently a greater risk of complications and drug side effects, may also have been of significance, particularly in connection with the oldest patients.
Most earlier studies do not show any difference in survival among women compared with men in different age groups after myocardial infarction, but some studies have shown lower survival after myocardial infarction in women, particularly in STEMI cases (15) – (21, 33, 34). A high level of invasive assessment and treatment, also for women with STEMI, may have contributed to our not finding similar gender differences in this study.
There are some limitations associated with the Norwegian Myocardial Infarction Registry and this data analysis. Only myocardial infarction that led to hospitalisation was registered. We did not have an overview of cases of myocardial infarction that did not lead to hospitalisation, or of patients who died due to myocardial infarction outside hospital. A few hospitals did not deliver complete data for the whole period. All hospitals were requested to ensure that all cases were registered via special patient administration systems, but the Norwegian Myocardial Infarction Registry was not able to check this at local level. However, the coverage compared with the Norwegian Patient Register is good. Data on the same patient from more than one hospital were linked up in the register. This led to a certain degree of uncertainty, particularly in cases of different registration of the same variable.
This country-wide study, based on reporting to the Norwegian Myocardial Infarction Registry of myocardial infarctions in Norway in 2013 – 2014, shows that there were few differences in invasive treatment, complications and survival between women and men with myocardial infarction, but that women were less often assessed with coronary angiography than men, and less often recommended secondary prophylactic medication.
The Norwegian Myocardial Infarction Registry wishes to contribute to improving the treatment of myocardial infarction in Norway. By identifying differences between Norwegian practice and accepted treatment recommendations, it is our hope to contribute to equal and good treatment of all patients with myocardial infarction.