Stroke: ischemic postconditioning shows encouraging but exploratory signals

An intervention when blood flow returns

Endovascular thrombectomy aims to reopen a blocked artery. But restoring flow in that artery is not always enough to restore perfusion in the small vessels. The return of blood flow can also be accompanied by what is known as ischemia-reperfusion injury.

Ischemic postconditioning involves briefly interrupting and restoring blood flow in a controlled manner just after the artery is reopened. In INSPIRE, this intervention was performed on the previously blocked arterial segment using a balloon. This is a hospital procedure, not something that can be done at home.

What the researchers measured

This secondary analysis included all 60 randomized patients in the trial. Arterial blood samples collected approximately 15 minutes after recanalization were used to examine immune cell activation and the blood’s clotting properties.

Microcirculatory transit time was assessed using angiography in 55 patients. Analyses of plasma proteins and metabolites involved only 29 patients. These small subgroups limit the strength of the conclusions.

Faster transit, without proof of better recovery

Compared with controls, patients who received postconditioning had a shorter microcirculatory transit time: 2.11 seconds versus 3.03 seconds. The researchers also report less activation of neutrophils, a type of immune cell, and coagulation findings consistent with slower clot propagation.

A longer microcirculatory transit time was associated with greater cerebral infarct growth. However, this association does not demonstrate that changing this transit time improves recovery.

According to the abstract, the parent trial had observed a reduction in infarct growth between the initial assessment and 48 hours. The magnitude of this reduction is not provided. This result should not be confused with a demonstrated reduction in disability.

Biological clues that remain tentative

The molecular analyses suggest possible pathways involving the blood-brain barrier and mitochondrial energy function. After correction for multiple comparisons, no proteins and 17 metabolites remained statistically significant.

Comparisons of the other biomarkers were not corrected for multiple testing, which increases the risk of chance positive findings. The authors therefore present these observations as hypotheses to be validated in larger studies.

What we can take away

This analysis helps explore what happens in the small vessels after a cerebral artery is reopened. It is not enough to establish that postconditioning improves recovery after a stroke.