Kevin O’Connor, MD
Ohara et al. conducted a post hoc analysis of data collected in the INTERRSeCT study (Identifying New Approaches to Optimize Thrombus Characterization for Predicting Early Recanalization and Reperfusion With IV Alteplase and Other Treatments Using Serial CT Angiography) to study thrombus changes in ICA or MCA occlusions following IV t-PA and whether this affected clinical outcomes. The 427 INTERRSeCT study patients underwent baseline CTA as well as repeat CTA or conventional angiogram following IV t-PA administration. The investigators compared the proximal position of the clot on baseline and repeat imaging, and if it migrated, they graded the degree of movement on a 0-3 scale with higher grades indicating more distal movement. If there was no change in proximal position, they assessed thrombus fragmentation determined by the presence of a new thrombus in a distal artery. A 90-day modified Rankin Scale score ≤2 was considered a good outcome.
Just over half of subjects had some degree of clot migration following IV t-PA (53%; n=230). Increased thrombus movement was associated with greater time from t-PA administration to reassessment in patients with proximal and distal occlusions (P<0.01, respectively). Time from IV t-PA to reassessment (per 30-minute increase) was independently associated with marked (grade 2-3 to complete recanalization) thrombus movement for patients with proximal occlusion (adjusted OR, 1.31 [95% CI, 1.15–1.50]) but not distal occlusions (adjusted OR, 1.32 [95% CI, 0.85-1.02]). Distal occlusion was independently associated with marked thrombus migration (adjusted OR, 2.35 [95% CI, 1.33-4.22]). For all patients, residual flow grade 1-2 (some contrast in thrombus versus grade 0, absence of contrast in thrombus) was independently associated with marked thrombus migration (adjusted OR, 4.13 [95% CI, 2.38-7.26]). For proximal occlusions, marked thrombus movement was associated with good outcome compared to mild-moderate (grade 0-1) movement (52% versus 27%; adjusted OR, 5.64 [95% CI, 1.72–20.01]). Marked thrombus movement was also associated with good outcome compared with no movement among distal occlusions (70% versus 56%; adjusted OR, 2.54 [95% CI, 1.21–5.51]).
Although the study was a post hoc analysis, it suggests that thrombus migration and/or fragmentation following IV t-PA is common. As marked thrombus migration included grade 2-3 movement and complete recanalization, it is not clear how much of the association between marked movement and good outcomes was due to complete recanalization. Additionally, they reported that half of their patients had one-vessel conventional angiograms as follow-up, potentially compromising evaluation of distal arteries. Future prospective studies could examine thrombus dynamics in response to IV thrombolytics with or without adjunctive agents.
