Significant differences in achieving risk factor targets between women and men following a heart attack

19 May 2015, Sophia Antipolis, France. There is a striking and statistically significant difference in how women and men are treated following a heart attack. These gender differences are reflected in the rate of risk factor control, which was lower in women, and in the rate of hospital readmission for a further heart attack, which was higher in women than in men.

The conclusions are reported today in an analysis of the SWEDEHEART registry in the European Journal of Preventive Cardiology.(1) This Swedish registry is one of the world's biggest ongoing statistical records in cardiac treatments and one of the few to report data on the fulfilment of secondary prevention targets and readmission rates in such a large proportion of heart attack (acute myocardial infarction, AMI) patients in a single country.(2) The present study included more than half of all patients up to 75 years of age who survived an AMI in Sweden between 2005 and 2014 and were thus eligible for secondary prevention treatment, a total of 51,620 patients examined up to 12 months post-AMI.

The findings, say the authors, indicate "substantial" potential in the secondary prevention of heart attack and control of risk factors in women, particularly in lipid (LDL cholesterol) and blood pressure control, whose target levels were both higher in women than in men.

Specifically (after statistical adjustment for patient age), lipid control (as defined by a target level of <2.5 mmol/litre) was achieved by 67.0% of men but only 63.3% of women, while target blood pressure (<140 mmHg systolic) was reached by 66.4% of men and 61.9% of women. Both these differences were statistically significant. There was no significant gender difference in the rates of smoking (56.1% women and 55.4% men).

However, there was a striking difference in the rate of cardiac readmission - with 15.5% of men and 18.2% of women requiring further hospital treatment. Incidentally, non-cardiac readmissions were found to be just as common as cardiac events, and were also more common in women (20%) than in men (14.8%).

The investigators suggest two possible explanations for the gender differences: first, a failure - by physicians or women themselves - to recognise the importance of risk factor control; and second, a greater level of drug side effects experienced by women.

However, the registry did show that over time (ie, in a comparison of 2005 and 2012 registry cohorts) there has been an overall improvement in risk factor control and a reduction in cardiac readmission. Lipid control (LDL-cholesterol <2.5 mmol/L) improved from 67.9% to 71.1%, and blood pressure control (<140 mmHg systolic) from 59.1% to 69.5%.

The investigators say that registry studies such as this "reflect real-life practice as opposed to the special setting of randomized controlled clinical trials, thereby increasing the generalizability of the results".

Commenting, first investigator Dr Kristina Hambraeus from the Falun Hospital in Sweden said: "We have learnt a great deal about acute cardiac care from this registry, especially that secondary prevention is in many ways more difficult to achieve - both for healthcare providers and patient - because the patient is often doing fine and experiencing no symptoms. The high one-year readmission rate in our study, particularly in women, emphasises how important risk factor control is after a cardiac event. However, even for the best controlled risk factor, blood pressure, we still found more than 11,000 patients were insufficiently treated one year post-AMI."

Gender differences in risk factor control emerged despite the fact that current practice guidelines are "gender neutral". "For the practising cardiologists," explained Dr Hambraeus, "women constitute a minority of their acute patients. But it is still important to keep risk factor control in focus, especially as some risk factors, such as diabetes, hypertension and smoking, seem particularly serious for women. Moreover, as short-term mortality rate decreases and more patients survive their first AMI, the need for effective secondary prevention strategies becomes increasingly important."

The results of this study confirm the results of other major registry studies in recent years, which also show a shortfall between the recommendations of guidelines in secondary prevention and real-life trends.(3) However, even though this study and others reflect changes in risk factor control, real-world data on cardiac readmissions after AMI are scarce. An association between the lower rate of risk factor control and higher rate of readmissions in women needs to be further investigated, said Dr Hambraeus.