Swedish, Canadian Registries: Women Less Likely to Be Reperfused After STEMI

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Among patients with ST-segment elevation myocardial infarction (STEMI), women are less likely than men to receive acute reperfusion, according to a registry study of Canadian and Swedish patients published online July 17, 2013, ahead of print in the European Heart Journal: Acute Cardiovascular Care. The disparity persists after controlling for important clinical factors, even among younger women.

Researchers led by Nina Johnston, MD, PhD, of the Karolinska Institute (Stockholm, Sweden), culled data from 36,051 STEMI patients discharged from 2004 to 2008 from 2 registries: Swedish (RIKS-HIA; n = 32,676) and Canadian (GRACE; n = 3,375).

Overall, women were less commonly reperfused in each country both before and after adjusting for age (table 1). In addition, older women were less commonly reperfused compared with younger women in both countries.

Table 1. Likelihood of No Reperfusion: Women vs. Men

While patients younger than 60 years showed the largest sex difference in treatment in Sweden, there was no overall interaction between sex, age, and country (P = 0.450). Multivariate analysis determined 3 factors independently linked with a higher likelihood of no reperfusion therapy: left bundle branch block on admission ECG, time from symptom onset to first ECG > 12 hours, and atypical symptoms at presentation. None of these factors was related to sex, though a country interaction was found with left bundle branch block (P < 0.001) with higher rates of reperfusion in Canada. Diabetes was associated with lower rates of reperfusion in both countries, but there was no interaction with sex.

Swedish women younger than 60 were less likely to receive reperfusion (OR 1.44; 95% CI 1.25-1.67) even after adjusting for left bundle block branch, atypical symptoms, late arrival, and fibrinolytic contraindication. When catheterization without revascularization was included in the analysis, the disparity was reduced (OR 1.29 (95% CI 1.10-1.51). Additionally, adjusting for symptoms other than chest pain at admission had the greatest effect on narrowing the observed sex differences in the Canadian population.

‘Biased Management’

Dr. Johnston and colleagues write that the study confirms previously hypothesized factors related to disparate use of reperfusion therapies in women. “However, what we also found was that, even after controlling for these factors, sex disparities persisted,” they observe. “The lack of interaction of these variables with sex, with the exception of age, may suggest a biased management of older women compared with men.”

Furthermore, “[t]he reasons for younger patients not to be treated according to guidelines is more puzzling than in the elderly,” the authors add. Atypical symptoms are often related to patient delay in obtaining medical attention, they write, frequently resulting in late diagnosis. In the Canadian cohort, younger women had longer prehospital delays than men, potentially indicating “that recognition of atypical symptoms among younger MI patients may be better in Sweden than Canada.”

The “study provides additional impetus for [following the most recent STEMI guidelines recommending similar management of men and women] and insight into what needs to be done to eliminate significant sex inequities in STEMI care,” Dr. Johnston and colleagues conclude. “As we have shown, commonly cited clinical factors do not entirely explain why reperfusion is being withheld, especially among younger women. Therefore, sex- and age-stratified monitoring of quality indicators and care pathways to standardize management for both sexes should be implemented in routine clinical practice.”

US Patterns Likely Different

In an e-mail communication with TCTMD, Hitinder S. Gurm, MD, of the University of Michigan (Ann Arbor, MI), said, “The large number of patients who were not reperfused is surprising. I suspect that part of this relates to the ECG being used as the gold standard.”

Since the study assessed use of reperfusion based on presenting ECG and not the final diagnosis, he added, “[i]t is possible that some of these patients had other diagnoses and the treating physicians correctly chose not to provide reperfusion therapy in this group. I would like to see data on how many patients actually presented with STEMI, had no contraindication for reperfusion, and did not get reperfusion.”

He explained that the observed gender disparities are likely due to younger women having an overall low incidence of STEMI. “It is not surprising that the diagnosis is not suspected in a small subset of the population,” Dr. Gurm observed. “I suspect that some older women are being missed due to atypical presentation.”

Because of the increased awareness of the need for timely reperfusion in the United States, Dr. Gurm said, similar patterns would not be seen here. “I would guess that the outcomes will be closer to those seen in Canada where the differences between men and women were small,” he postulated, adding that he has not seen a missed MI in his practice in the last 5 years.

Going forward, “we need to be cognizant of the fact that some women (and men) are still not getting reperfusion in Canada and Sweden,” Dr. Gurm said. “We need to study if the same thing is happening in the [United States] and if so, develop strategies to prevent that.”

Study Details

Women represented 29% of patients in Canada and 34% in Sweden. In general, Canadian patients were younger than Swedish patients, with 46% vs. 28% of the men and 25% vs. 13% of the women, respectively, younger than 60. Overall, women were older and had more risk factors including hypertension, diabetes, congestive heart failure, and previous stroke, whereas more men had a previous history of MI and prior revascularization.

 

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Source:
Johnston N, Bornefalk-Hermansson A, Schenck-Gustafsson K, et al. Do clinical factors explain persistent sex disparities in the use of acute reperfusion therapy in STEMI in Sweden and Canada? Eur Heart J: Acute Cardio Care. 2013;Epub ahead of print.

 

 

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