Waimei Tai, MD

Vagal A, Meganathan K, Kleindorfer DO, Adeoye O, Hornung R, and Khatri P. Increasing Use of Computed Tomographic Perfusion and Computed Tomographic Angiograms in Acute Ischemic Stroke From 2006 to 2010. Stroke. 2014

Vagal et. al analyzed a large inpatient sample database to assess the utility of different CT based modalities for acute ischemic stroke. Not surprisingly it demonstrated a rise in advanced CT modality use (CT angiogram 3.8% in 2006 to 10.% in 2010, and CT perfusion use from 0.05% in 2006 to 2.9% in 2010). 
Similarly, reperfusion therapy also increased, although growth varied by subset of patients and availability of imaging information.

For head CT alone, iv tpa use went from 3% in 2006 to 4.7% in 2010, likely to systematic effects of education campaigns and the general improvement in stroke systems of care. For patients who received CT angiogram, iv tpa use went from 10.6 to 10.4%, not much of an increase right? This is because most people agree that the use of CT angiogram is not required for the iv tpa decision. While some centers (including my own) get CT angiogram as part of the initial stroke code evaluation, we don’t necessarily use it to make the iv tpa decision. It’s helpful for thrombectomy decisions.

But where the trends reverse is in thrombectomy: use of CT angiogram meant you were more likely to get mechanical therapy from 0.9% in 2006 to 3.7% in 2010, an almost 4 fold increase.  CT perfusion showed this trend as well, going from 3.7% in 2006 to 7.4% use in 2010 (2 fold increase). This intuitively makes sense, programs that use advanced modalities often have advanced acute stroke interventions as well (they study also looked at other indicators that could predicate use: academic centers , urban settings and larger hospitals which, not surprisingly have more imaging and more acute treatments) And as in my experience, lots of proceduralists want to know if there’s a clot to pull out before they go into an emergent procedure-and this is where the CT angiogram and perfusion offers additional data for decision making.

The bigger elephant in the room is: does the mechanical thrombectomy help in the long run? This has not been addressed in any definitive randomized trial (previous studies that did a not so good job with little imaging guided patient selection is not very convincing on this at all, hence all the fuss). What we do know is that in cohort based studies (DEFUSE2) patients appropriately selected (big penumbra, small ischemic core) do well. Another CT based cohort study is ongoing (NCT01622517) but I imagine that it will show a similar result: appropriately selected patients will respond will to reperfusion therapy.

But back to the study-since CT angiogram and perfusion and its anticipated consequence-more thrombectomy-hasn’t been demonstrated to work yet, why is there a trend in increased use?

Well, doctors like more data. And if they think it’ll help in decision making and it’s available and can be billed, why not use it? Well, for one reason: technology creepdefinitely plays a part in the ballooning price tags in healthcare. Not to mention that repeated use of radiation based diagnostic modalities carry their own risk. I think studies that are ongoing will hopefully shed some light on deciding when and where we should be using expensive diagnostic tests. Until then, I can only expect that if payors will pay, we will keep using it.