Association of Baseline Cardiac Troponin With Acute Myocardial Infarction in Stroke Patients Presenting Within 4.5 Hours.

Background and Purpose- American Heart Association guidelines recommend obtaining baseline troponin in all patients with acute ischemic stroke. Yet, there is a paucity of data on the prevalence of baseline troponin elevation and specifically its diagnostic yield for acute myocardial infarction (AMI) in patients presenting within the time window for thrombolysis. Methods- We retrospectively analyzed 1072 consecutive patients admitted for acute ischemic stroke or transient ischemic attack, who presented within 4.5 hours of last known well (LKW). Patients who had baseline cardiac troponin I (bcTnI) obtained within 72 hours from LKW (n=525) were included in the study. Multivariable logistic regression was conducted to determine factors independently related to an elevated bcTnI (>0.04 ng/mL). We calculated the area under receiver operator curves, sensitivity, and specificity, to determine the diagnostic accuracy of (i) the bcTnI for AMI stratified by the time to assessment and (ii) the best time cutoff for obtaining bcTnI. Results- Among included subjects, the median time from LKW to the bcTnI was 3.8 hours and 113 (21.5%) subjects had an elevated bcTnI. Assessment of bcTnI within 4.5 hours from LKW was significantly more often associated with normal values as compared to assessment between 4.5 and 72 hours (61.7% versus 38.3%; P=0.001). Fifteen (2.9%) patients were diagnosed with AMI. After adjustment for pertinent confounders, time to bcTnI assessment was independently associated with AMI (odds ratio, 1.04 [95% CI, 1.02-1.07] P=0.001). When stratified by time, bcTnI assessed within 4.5 hours had a sensitivity of 25% and specificity of 83.7% for AMI, whereas bcTnI assessment between 4.5 and 72 hours was associated with a sensitivity of 90.9% and specificity of 74.8%. Conclusions- Assessment of bcTnI after 4.5 hours from LKW was associated with greater diagnostic accuracy than testing within 4.5 hours. This information may inform routine clinical practice.