Background and purpose: Identification of acute ischemic stroke (AIS) cause is crucial for guidance of secondary prevention. Previous studies have yielded inconsistent results regarding possible correlations between AIS cause and thrombus composition, as assessed by semiquantitative histological analysis. Here, we performed a correlation analysis between AIS cause and AIS thrombus cellular composition and content, as assessed using quantitative biochemical assays.

Methods: Homogenates of 250 patients with AIS thrombi were prepared by mechanical grinding. Platelet, red blood cell, and leukocyte content of AIS thrombi were estimated by quantification of GP (glycoprotein) VI, heme, and DNA in thrombus homogenates. AIS cause was defined as cardioembolic, noncardioembolic, or embolic stroke of undetermined source, according to the TOAST classification (Trial of ORG 10172 in Acute Stroke Treatment).

Results: Cardioembolic thrombi were richer in DNA (35.8 versus 13.8 ng/mg, P<0.001) and poorer in GPVI (0.104 versus 0.117 ng/mg, P=0.045) than noncardioembolic ones. The area under the receiver operating characteristic curve of DNA content to discriminate cardioembolic thrombi from noncardioembolic was 0.72 (95% CI, 0.63-0.81). With a threshold of 44.7 ng DNA/mg thrombus, 47% of thrombi from undetermined cause would be classified as cardioembolic with a specificity of 90%.

Conclusions: Thrombus DNA content may provide an accurate biomarker for identification of cardioembolic thrombi in patients with AIS with embolic stroke of undetermined source.