Microvascular Measure Gives Clues to Poor Response to Successful Thrombectomy

 You've known of 100% recovery failure after thrombectomy for a long long time! WHEN ARE YOU GOING TO DO SOMETHING ABOUT THAT?

Or just sit with your heads up your asses? That doesn't help.

Microvascular Measure Gives Clues to Poor Response to Successful Thrombectomy

Capillary bed perfusion could point to a treatment target, proof-of-concept study suggests

Microvascular hemodynamics might provide an early marker of poor recovery despite successful large-vessel thrombectomy in acute ischemic stroke, an imaging study suggested.

Poor capillary bed perfusion as indicated by relative transit time heterogeneity around the infarct on immediate post-thrombectomy perfusion MRI predicted substantial infarct progression (≥10 mL, OR 1.4 per 10% increase, 95% CI 1.0-2.0, P=0.04), with a stronger association than seen for baseline infarct volume (OR 1.1 per 1 mL, 95% CI 1.0-1.2).The microvascular measure also outperformed baseline stroke severity as an independent predictor of poor 90-day functional outcome, defined as a modified Rankin Scale score over 2 (OR 1.4 per 10% increase, 95% CI 1.0-1.9, P=0.03, vs OR 1.2 per 1-point increase on the NIH Stroke Scale, 95% CI 1.0-1.2).

In contrast, conventional post-thrombectomy perfusion parameters, such as cerebral blood flow and volume and time to maximum residue function, failed to predict outcomes, "demonstrating their insensitivity to microvascular dysfunction," reported Yannan Yu, MD, of the University of California San Francisco, at the American Society of Functional Neuroradiology meeting in Newport Beach, California.

Despite acute stroke treatment advances, "still a significant portion of the stroke patients have a bad outcome even though they have successful thrombectomy and have reperfusion of the tissue," Yu said.

While no reflow in these cases isn't well understood, animal models have shown that microvascular hemodynamic failure is one mechanism, she noted.

"In routine practice, what people get [for imaging] is maybe 24 to 48 hours after the stroke treatment, and when you evaluate no-reflow on that time point, a lot of things may have already happened," she said. "They may have late recanalization, they may have early reocclusion. ... But in this immediate post-thrombectomy MRI, we're hoping that this MRI will reflect the truth of what happened immediately after we recanalize the vessel."

The researchers aren't proposing that centers switch from their routinely done diffusion MRI to the perfusion MRI as done in this study. Rather, the findings serve as proof of concept that the microvasculature can be measured and matters in this setting.

It's one of the pieces of the puzzle to sort out what's happening to these no-reflow patients to move toward finding better treatment for them, Yu said.

"Currently our limitation is that this is a pretty small sample size. There's not a lot of analysis we can do with such a small sample size," she said. "A larger cohort will be important to validate the scientific factuality of the findings. And then after that, if we're able to validate that, I think then it could potentially become a treatment target."

The study included 47 acute ischemic stroke patients (mean 72 years, 62% women) treated for anterior circulation large vessel occlusion from 2015 through 2020 who had complete or near-complete brain tissue reperfusion (modified Thrombolysis in Cerebral Infarction score ≥2c) after thrombectomy. Participants needed to have had diffusion-weighted imaging (DWI) and dynamic susceptibility contrast perfusion MRI both pre-treatment and within 2 hours after thrombectomy as well as 24-48 hour follow-up DWI.

Among them, 43% (20 of 47) had substantial infarct progression, and the same proportion had poor functional outcomes.

Relative capillary transit time heterogeneity was calculated as the ratio of the standard deviation of mean transit time to the mean transit time of red blood cells across a capillary bed.