tPA and clot location

Q: During reperfusion therapy for acute ischemic stroke (CVA) which clots are more resistant to thrombolysis? (select one) 

 A)  proximal in the cerebrovascular arterial tree 
 B) distal in the cerebrovascular arterial tree


Answer:  A 

In acute CVA proximal sites of occlusion in the cerebrovascular arterial tree are more resistant to thrombolysis i.e. a clot in an internal carotid artery (ICA) is expected to be more resistant than middle cerebral artery (MCA). This is due to the fact that clots more proximal in CV arterial-tree tend to be bigger in size. Moreover, they may be promoting adjacent thrombosis, resulting in a very long thrombus. Another contributing factor is the relative lack of fibrin in large vessels in situ thromboses in comparison to cardiac origin fibrin-rich embolic thromboses.


#neurology
#cardiology


References: 

1.  Linfante I, Llinas RH, Selim M, et al. Clinical and vascular outcome in internal carotid artery versus middle cerebral artery occlusions after intravenous tissue plasminogen activator. Stroke 2002; 33:2066. 

2. Saqqur M, Uchino K, Demchuk AM, et al. Site of arterial occlusion identified by transcranial Doppler predicts the response to intravenous thrombolysis for stroke. Stroke 2007; 38:948. 

3. Molina CA, Montaner J, Arenillas JF, et al. Differential pattern of tissue plasminogen activator-induced proximal middle cerebral artery recanalization among stroke subtypes. Stroke 2004; 35:486.