Early reperfusion rates with IV tPA are determined by CTA clot characteristics

Abstract

Background and purpose: An ability to predict early reperfusion with IV tPA in patients with acute ischemic stroke and intracranial clots can help clinicians decide if additional intra-arterial therapy is needed or not. We explored the association between novel clot characteristics on baseline CTA and early reperfusion with IV tPA in patients with acute ischemic stroke by using classification and regression tree analysis.

Materials and methods: Data are from patients with acute ischemic stroke and proximal anterior circulation occlusions from the Calgary CTA data base (2003-2012) and the Keimyung Stroke Registry (2005-2009). Patients receiving IV tPA followed by intra-arterial therapy were included. Clot location, length, residual flow within the clot, ratio of contrast Hounsfield units pre- and postclot, and the M1 segment origin to the proximal clot interface distance were assessed on baseline CTA. Early reperfusion (TICI 2a and above) with IV tPA was assessed on the first angiogram.

Results: Two hundred twenty-eight patients (50.4% men; median age, 69 years; median baseline NIHSS score, 17) fulfilled the inclusion criteria. Median symptom onset to IV tPA time was 120 minutes (interquartile range = 70 minutes); median IV tPA to first angiography time was 70.5 minutes (interquartile range = 62 minutes). Patients with residual flow within the clot were 5 times more likely to reperfuse than those without it. Patients with residual flow and a shorter clot length (≤15 mm) were most likely to reperfuse (70.6%). Patients with clots in the M1 MCA without residual flow reperfused more if clots were distal and had a clot interface ratio in Hounsfield units of <2 (36.8%). Patients with proximal M1 clots without residual flow reperfused 8% of the time. Carotid-T/-L occlusions rarely reperfused (1.7%). Interrater reliability for these clot characteristics was good.

Conclusions: Our study shows that clot characteristics on CTA help physicians estimate a range of early reperfusion rates with IV tPA.

© 2014 by American Journal of Neuroradiology.

Figures

Fig 1.

A, M1 MCA occluded segment (white arrows) with patent proximal M1 MCA on the right and the contralateral M1 MCA (white arrowheads). B, Clot length (broken white line; segment a) and distance from M1 MCA origin to proximal clot interface (broken black line; segment b). Measurement of the contralateral M1 MCA segment is shown for reference (segment c).

Fig 2.

Residual flow on baseline CT angiography along with early reperfusion with IV tPA assessed on the first angiogram of the ipsilesional arterial tree. The top panel shows a patient with a left M1 MCA clot and no residual flow (A, grade 0 residual flow, yellow arrows, density similar to that of surrounding brain parenchyma). The first angiogram shows no recanalization (B and C). The middle panel shows a left M1 MCA clot with grade 1 residual flow (A, yellow arrows, denser than surrounding brain parenchyma). The first angiogram shows excellent reperfusion (B and C). The bottom panel shows a left M1 MCA clot with grade 2 residual flow (A, yellow arrows, hairline or streak of well-defined contrast across the partial or complete length of the clot). The first angiogram shows excellent reperfusion (B and C).

Fig 3.

Clot interface Hounsfield unit ratio calculated by measuring the Hounsfield units in a region of interest selected at the proximal and distal clot interface only in scans that are mid- to late arterial- or appropriate venous-weighted. cirHU is calculated by dividing the proximal clot interface Hounsfield unit by the distal clot interface Hounsfield unit. In A, a patient with a left M1 MCA clot has a cirHU of 1.05 while in B, a patient with a left M1 MCA clot has a cirHU of 3.21.

Fig 4.

Tree representation of a recursive partitioning model (CART) predicting early reperfusion with IV tPA. Each subgroup (rectangle) has the percentage of subjects with early reperfusion (95% confidence interval). The number of subjects reperfused/number of subjects in each subgroup is italicized below each percentage. In all, 33/192 (17.19%) patients with ICA and M1 MCA clots achieved early reperfusion. Tree end points are highlighted in red. Splitting criteria and subgroup characteristics are described along each connecting line.

Fig 5.

Clot location and length on baseline CTA along with early reperfusion (TICI 2a/2b/3) rates with IV tPA, final reperfusion (TICI 2b/3) at end of the IA procedure, and 90-day clinical outcome (mRS 0–2).