The truth and fiction in aspiration physics: may the forces be with you

Recently, a number of authors, including us, have bemoaned inaccurate nomenclature and poorly described techniques throughout the acute ischemic stroke intervention literature. Such limitations adversely affect communication and may mislead readers and researchers alike about important and fundamental features of embolectomy procedures. This is particularly true of aspiration embolectomy, which remains poorly understood as a mechanistic and physical technique. Moreover, some investigations into the technique have seemed both misguided and confusing, probably because of a conceptual disconnection between the angiography suite and the laboratory benchtop. First, we would like to focus attention on an ongoing misunderstanding about what we are actually doing during these procedures, particularly the term ‘aspiration embolectomy'. Modern aspiration embolectomy encompasses two completely separate phenomena—‘aspiration-mediated retrieval’ and ‘clot ingestion’. Although many people think that the clot is continuously sucked through the entire length of the catheter, what is actually going on during many ‘aspiration’ procedures, is retrieval , not clot ingestion. In other words, we aspirate the face of the clot into the distal tip of the embolectomy catheter. We then start pulling (ie, retrieving) the clot out of the patient using the clot-engaged aspiration catheter—exactly as with a stent retriever. The suction force within the catheter, plus any friction between the ingested clot and the distal catheter inner wall, serve to hold onto the clot while we apply a considerable retrieval force (not suction force) with our hands, all of this to counteract the friction force and pressure …