No gender differences in long-term MI outcomes

A long-term study of more than 14,000 patients admitted to the hospital for MI over 24 years found adjusted mortality was equal for men and women. The results of this large, single-center study were published in the Oct. 30 issue of Circulation.

Sjoerd T. Nauta, MSc, and colleagues from the Thoraxcenter, Erasmus Medical Center in Rotterdam, the Netherlands, followed 14,434 consecutive patients who were admitted to their intensive care unit with a diagnosis of MI between 1985 and 2008. Of that number, 28 percent were female. The researchers intended to quantify gender-based differences, if any, in baseline characteristics, treatment, short-term mortality and long-term (20-year) mortality.

The researchers explained that women had often been underrepresented in clinical trials in the past, therefore it was possible that evidence-based strategies to treat MI might affect females differently, and women might have benefited less from improvements in treatment over the past 25 years. The researchers also noted that because most MI patients now survive to discharge, study of long-term outcomes and any related gender differences are increasingly important.

The trial included all patients over 18 years of age on first admission to the intensive coronary care unit for MI. An MI diagnosis required chest pain or equivalent symptoms with dynamic EEG changes and a serial rise to at least three times the normal value and fall in biochemical markers of cardiac necrosis. A STEMI diagnosis required ST-segment elevation greater than 0.1mV in at least two contiguous peripheral leads or greater than 0.2mV in at least two contiguous precordial leads. Patients not falling within this category were non-STEMI. There were no other inclusion or exclusion criteria.

Physicians and nurses in the coronary care unit collected data on demographic characteristics, cardiac history, risk factors, anemia and renal dysfunction. They recorded the treatment the patient received (thrombolysis and PCI). The study endpoint was all-cause mortality at 30 days and over 20 years post-hospitalization. The researchers collected survival data through municipal civil registries, which they stated are updated frequently and are highly accurate.

The authors found that on first presentation,  women were an average of five years older than the men. Compared with men, the women had higher rates of hypertension, diabetes mellitus, renal dysfunction and anemia, and were less likely to be current smokers. The women were less likely to have a cardiac history of prior MI, PCI, CABG or STEMI. As the study progressed, all patients became older on first presentation, and the increase in age was uniform for men and women. The researchers found no significant treatment disparities based on gender.

During the study period, 1,544 women and 3,708 men died. Unadjusted mortality was greater in women than men at 30 days (7 percent vs. 6 percent), but after adjustment for age and other confounders, the 30-day mortality rate equalized. There was no gender difference in 30-day mortality in subgroups based on age and diagnosis, and "borderline significant" differences in the subgroup with diabetes mellitus, suggesting that "female sex might be associated with increased 30-day mortality," the authors wrote.   

Unadjusted cumulative mortality was slightly higher in women at 20-year follow-up (71 percent for women vs. 65 percent for men) but when adjusted for age and other confounders, 20-year mortality was significantly lower for women than for men (adjusted hazard ratio 0.77 percent). The study also found improvements in outcomes over time for both men and women, reflecting that newer treatment and therapies were effective regardless of gender.

The authors addressed prior studies showing poorer outcomes for women than for men, noting that many of those studies were conducted prior to the adoption of current standard treatments, and were of shorter duration. 

"Our study was initiated in 1984, when thrombolysis became standard therapy, and extends to the present era, in which PCI became the standard therapy. ... [S[ex disparities in medical management were limited,” they wrote. “This might have contributed to relatively favorable outcomes in women compared with studies in countries where women less often receive evidence-based management."