Measuring Absolute Brain Flow and Brain Microcirculation Resistance by Continuous Thermodilution

Worldwide, cerebrovascular accidents (also known as strokes) are the leading cause of acquired disability, the second-leading cause of dementia (after Alzheimer's disease) and the second-leading cause of death (but the leading cause of death among women). A mechanical thrombectomy (MT) allows the recanalization of the occluded cerebral artery during an acute ischemic stroke, by removing the blood clot with a mechanical device inserted endovascularly under image guidance. MTs are the optimal treatment for a large number of patients presenting an occlusion in an anterior artery (the internal carotid artery and the proximal segment of the middle cerebral artery). Reperfusion is considered satisfactory if the mTICI score at the end of the procedure is of mTICI 2c or mTICI 3. Despite these scores having been obtained by 71% of patients during the randomized trials, showing the superiority of MT over intravenous thrombolysis, only 27% of these patients were free of neurological deficits at 3 months . Therefore, there is a discrepancy between the high rate of macroscopic recanalization and clinical results. One hypothesis to explain this discrepancy is that despite high quality macroscopic recanalization, reperfusion of the cerebral microcirculation remains insufficient: macroscopic recanalization is not equivalent to microscopic reperfusion. This discrepancy also exists in cardiology: despite a high rate of coronary artery recanalization when patients with an ST- segment elevation myocardial infarction are in emergency care, half of these patients later exhibit coronary microvascular dysfunction. The absence of reperfusion is associated with an increased risk of cardiovascular death, recurring myocardial infarctions, cardiogenic shock and heart failure one year after the coronary recanalization for an ST-segment elevation myocardial infarction. It has been shown that continuous intracoronary thermodilution can be used to quantify coronary blood flow and the absolute value of microcirculatory resistance (in Wood units). There are not currently any tools that can quantify cerebral microcirculation immediately after an MT.

The aim of this study is to evaluate the feasibility and safety of using a pressure/temperature sensing guidewire to measure cerebral microcirculatory resistance using thermodilution in patients with a score of mTICI 2c or 3 after MT for the management of acute ischemic stroke in the anterior circulation.