Unstable angina in the context of high sensitive troponins: still a marker of high risk? A comparison of outcomes with adjudicated type 1 myocardial infarction

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Abstract Funding Acknowledgements Type of funding sources: None. Background Unstable angina (UA), considered historically a marker of high risk, has rarely been studied in the high sensitive troponin era. We sought to characterise this population and determine short and medium term outcomes for UA who did not have elevated high sensitive troponins and compared this to adjudicated type 1 MI and the global population of suspected ACS. Method We conducted a post-hoc analysis of 2 prospective cohort studies of suspected acute coronary syndrome in 2 hospitals in the northwest of England. (n=3018) We used a symptom scoring system to diagnose unstable angina. Type 1 MI was diagnosed by blinded, independent physician adjudication according to 3rd universal criteria for MI. Follow-up was 100% complete for all patients to 1 year. Results 185 and 259 were adjudicated as suffering from UA and NSTEMI respectively. We restricted our analysis to 158 patients with UA with high sensitive troponin T (Roche elecsys) ≤14ng/l (≤99th percentile). Compared to NSTEMI population UA cohort were younger (59 vs 74, p<0.002), had a lower incidence of hypertension (56% vs 69%, p= 0.009), had lower risk scores (TIMI 2 vs 3, p=0.001, GRACE 97.5 vs 140, p<0.0001, HEART 4 vs 7, p<0.0001) and had lesser ECG abnormalities ( ST depression >1mm, 5% vs 15.6%, p=0.001, T wave flattened, biphasic or inverted 24% vs 47.8%, p<0.0001). Type 1 MI to 30 days and 1 year in the UA cohort was 1.9% and 3.1% respectively compared to a repeat type 1 MI in the NSTEMI cohort of 0.8% and 2.4% respectively. Only 1 (0.8%) all cause death was recorded within one year in the unstable angina cohort as opposed to 36 (14.4%) in the NSTEMI group. Revascularisation rates were unsurprisingly lower in the UA cohort to 30 days compared to NSTEMI cohort (table 1) Conclusion Unstable angina, in the high sensitive troponin era is associated with a small early and medium term risk of myocardial infarction. Risk of medium-term MACE is much lower compared to patients with confirmed type 1 myocardial infarction.