Abstract 3651: Higher Prevalence of Unstable Angina Compared to Non-ST Elevation MI in Women Is In Part Explained By Smaller MI Size
Introduction Prior studies that included patients (pts) with non-ST elevation myocardial infarction (NSTEMI) and unstable angina (UA) reported a higher prevalence of UA rather than NSTEMI in women than men. We hypothesized that the higher prevalence of UA in women is in part due to smaller MI’s, and therefore women are less likely to meet the traditional criteria for MI based on CK or CK-MB.
Methods We performed a retrospective analysis of consecutive Emergency Department chest pain pts admitted for exclusion of myocardial ischemia over 6 year period. All pts underwent serial testing for CK, CK-MB, myoglobin, and TnI. Pts with ST elevation MI (n=230) or who did not have an 8 hour TnI (n=225) were excluded. Pts were separated into categories based on peak CK (upper limit of normal 200 U/L) and CK-MB (8 ng/mL)-> minor damage: elevated TnI with normal CK or CK-MB; small MI: peak CK 200 – 499 U/L (1–2.5 x NL) or MB 8 –39.9 mg/mL (1–5 x NL); and large MI: CK>500 U/L (>2.5 x NL) or MB>40 ng/mL (>5 x NL).
Results From 06/96 through 12/02, 1,286 pts were admitted from the ED and were diagnosed with NSTEMI, of whom 676 were men (53%) and 610 were women (47%). Peak CK (median 290 U/L vs 195 U/L) and CK-MB (median 53 ng/mL vs 34 ng/mL) were significantly higher for men compared to women (p<0.05). Using elevated CK-MB rather than TnI to define MI, 44% of women compared to 36% of men (p=0.006) had small MIs and were diagnosed by TnI only, and thus would not have met traditional CK-MB criteria for MI. When elevated CK was used to define MI, the differences were even greater; only 1/3 of men had small MIs; in contrast, 1/2 of women would have been considered to have UA rather than MI.
Conclusions Women have smaller MIs compared to men. The use of less sensitive cardiac markers in prior studies likely contributed to higher prevalence of UA found in women. This information provides interesting insight into the varied presentation in women compared with men with NSTEMI.