What does elevated high-sensitive troponin I in stroke patients mean: concomitant acute myocardial infarction or a marker for high-risk patients?

BACKGROUND: Acute ischemic stroke patients may occasionally suffer from concomitant acute coronary syndrome (ACS). Troponin I and T are established biomarkers to detect ACS. Recently introduced high-sensitive cardiac troponin (hs-TNI and hs-TNT) assays are increasingly used to identify ACS in stroke patients even without signs or symptoms of ACS. These new test systems very often detect elevated values of hs-troponin, although clinical relevance and consequences of elevated hs-TNI values in these patients are unclear so far. PATIENTS AND METHODS: We examined hs-TNI values in 834 consecutive ischemic stroke patients admitted to our Comprehensive Stroke Center during a 1-year period. hs-TNI was measured immediately after admission and after 3 h if initial hs-TNI was elevated above the 99th percentile of normal values (>0.045 ng/ml). Patients with elevated values were divided into two groups: (1) constant and (2) dynamic hs-TNI values. The dynamic approach was defined as a 30% rise or fall of the hs-TNI value above the critical value within 3 h. All patients received stroke diagnostic and continuous monitoring according to international stroke unit standards, including a 12-lead ECG, blood pressure, body temperature and continuous ECG monitoring, as well as regular 6-hourly neurological and general physical examination (including NIHSS scores). The cardiologists - as members of the Stroke Unit team - evaluated clinical symptoms/examination, as well as laboratory, echocardiographic and ECG findings for the diagnosis of ACS.
RESULTS: 172/834 (20.6%) patients showed elevated hs-TNI levels on admission. Patients with elevated hs-TNI values exhibited a significantly (p < 0.001) increased rate of hypertension (89 vs. 77.2%), history of stroke (24.4 vs. 14.8%), history of coronary artery disease (65.7 vs. 34.1%), history of myocardial infarction (22.1 vs. 7.6%), heart failure (12.8 vs. 5.7%) and atrial fibrillation (44.2 vs. 23.6%). 82/136 patients showed constant and 54/136 patients dynamic hs-TNI values: among the latter, 5 patients were diagnosed with ST segment elevation myocardial infarction (STEMI) and 24 with non-STEMI (NSTEMI).
CONCLUSION: Our data demonstrate that hs-TNI was elevated in about 20.6% of acute ischemic stroke patients but therapeutically relevant ACS was diagnosed only in the dynamic group. hs-TNI elevations without dynamic changes may occur in stroke patients without ACS due to different reasons that stress the heart. Therefore, we suppose that hs-TNI is a sensitive marker to detect high-risk patients but serial measurements are mandatory and expert cardiological workup is essential for best medical treatment and to accurately diagnose ACS in acute ischemic stroke patients.