ISC 2024 | Thrombectomy use and outcomes in patients with premorbid disability

I got interested in patients with premorbid disability, because these are patients that we encounter quite frequently in our practice. Based on population studies, we think that probably about 1 in 3 or perhaps 1 in 4 patients with stroke out there in the real world have some degree of premorbid disability, meaning that they’re already needing some help with some of their daily activities before they have their stroke. But unfortunately, we’ve not done a good job of enrolling these patients in clinical trials or even really in longitudinal studies of patients with stroke so we don’t have a good sense of how they fare with and without reperfusion therapies like thrombolysis or thrombectomy. And so people are left in their practice with a lot of uncertainty about how to deal with these patients and how to evaluate whether they’re going to have a good response to these kinds of therapies.

So we became interested in rigorously trying to evaluate what’s happening out there in the real world right now to patients that are being treated with reperfusion therapies who also happen to have some premorbid disability. Fortunately, there are several physicians out there in the real world who are actually treating these patients and offering them these therapies. So it’s offered us the opportunity to look at the data and compare that to what we have for patients without such disabilities.
So this was a really interesting collaboration that emerged thanks to the international connections we have at the Calgary Stroke Program. So the data we looked at were actually from the Czech Republic. So the Czech Republic is part of an international stroke treatment registry program called SITS and in recent years they’ve also launched their own high quality stroke treatment registry called RES-Q. We looked at data from a combination of these registries going back since, say, 2017 or so. We were looking to evaluate outcomes really in patients with premorbid disability that were captured in that registry. I’m pleased to say that we had a fairly good representation of these patients in the registry that allowed us to do some meaningful analyzes in these patients. So to give you a specific number, we had 1712 patients who had pre stroke disability, which we defined as a pre stroke modified Rankin scale score of three or more. So that’s fairly moderate pre-stroke disability at least. And we compared that to some 20,000 patients who didn’t have pre-stroke disability.

What we found was that even in this sort of registry setting which, which already comprises of patients who are receiving some sort of stroke treatment, so thrombolysis at least, or if not that then thrombectomy, it was interesting to see that the patients who had pre-stroke disability were very less likely to receive EVT. So about 10% of those with premorbid disability were getting EVT, as opposed to, say, 21% of those without. And even when they were treated, they had slower treatment times. This suggests that there are differences in access to care that are happening for these patients, potentially related to the fact that I mentioned earlier that we don’t have high quality clinical trial-based evidence to offer thrombectomy and other such therapies to these patients.

But what was interesting is that while, unsurprisingly, we found that patients with pre-stroke disability did worse than those without any disability because, you know, by definition, they’re coming in with a higher degree of preexisting disability, what was interesting to us is that we were able to show that nearly a third of those patients with pre-stroke disability actually were able to return to their pre-stroke state, meaning they didn’t end up with additional incremental disability after their stroke and after they were treated. And if you think about that, that’s really sort of the best possible outcome we could achieve for a patient with pre-morbid disability. We can’t get them better than they were before their stroke. We can only get them to the way that they were before. That’s the best possible outcome. And so it was interesting to see that the Czech team was able to get there in nearly a third of their patients. There were obviously variations in their ability to achieve that based on patient age. If you looked at the young patients, those under 65 years of age, it was nearly two thirds, 66% of patients that returned to their pre-stroke state. If you got to the oldest group that we looked at, those over 85, then the number came down to about 20%, but still about 1 in 5 patients.

And what was most interesting to us is that when we did this analysis approach called propensity score weighting, we were able to find that thrombectomy was associated with better outcomes in everybody, including those with premorbid disability. So we didn’t see what we call an interaction of treatment effect based on whether somebody had premorbid disability or not. So that was quite interesting to us as well.

This study does shed some light on that because as I said earlier, you know, the patients with pre-stroke disability that we analyzed in this registry, they got into this registry because they were already being considered by their physicians for some sort of acute stroke therapy. That’s the only way you get into these kind of stroke treatment registries. So it’s worth noting that even among those patients who are being considered for, say, intravenous thrombolysis, there’s far fewer of those with premorbid disability that end up sort of making the cut, if you will, to go on to thrombectomy. So it’s hard to say exactly how this generalizes to kind of the overall stroke population, but you’d imagine that the magnitude of exclusion is probably larger, right? Because here we already had a pre-selected population that people were interested in treating in some way, shape or form.