Clinical Research Directory

Brain Blood Vessel Responses to Changes in Blood Flow

Brain blood flow will be measured during a simulated postural change test and while breathing increased levels of carbon dioxide using magnetic resonance imaging.

HYPER MIND - Hyperoxia Effects on Cerebral Hemodynamics

This study aims to better understand how short periods of exposure to high oxygen levels affect blood flow in the brain of patients who are intubated and mechanically ventilated in the Intensive Care Unit (ICU). Many ICU patients receive more oxygen than strictly necessary, and high blood oxygen levels (hyperoxemia) are very common. However, the immediate effects of short hyperoxic exposures on cerebral circulation and autoregulation remain poorly understood. In this study, patients who already require mechanical ventilation for medical reasons will undergo a brief and controlled increase in the oxygen delivered through the ventilator (FiO₂). During this time, we will continuously monitor blood flow in one of the main brain arteries using a non-invasive ultrasound technique called transcranial Doppler (TCD). The goal is to evaluate how cerebral blood flow, pulsatility, and autoregulatory capacity change during and after a short hyperoxic stimulus. No additional invasive procedures are required beyond standard ICU monitoring, except for the temporary adjustment of the ventilator's oxygen settings and arterial blood gas sampling, which are part of usual care in critically ill patients. Participation does not provide direct clinical benefit but may help improve future oxygen management in ICU patients. The study involves minimal risk, as short hyperoxic exposures are already common in routine care and will be interrupted immediately in case of any adverse event.

Brain Blood Vessel Responses to Changes in Blood Flow: Younger Cohort

Brain blood flow will be measured during a simulated postural change test and while breathing increased levels of carbon dioxide using magnetic resonance imaging.

CO2 Modulation in Endovascular Thrombectomy for Acute Ischemic Stroke

Acute ischemic stroke due to large vessel occlusion is responsible of cerebral blood flow impairment with a progressive and extensive ischemic process. Cerebral collateral circulation may preserve an ischemic penumbra that could recover providing timely reperfusion of the occluded vessel. Mechanical thrombectomy is the standard of care for anterior circulation large vessel reperfusion. Strategy to promote cerebral blood flow in collateral circulation before reperfusion is scarce and rely mainly on blood pressure maintenance. Carbon dioxide is a potent cerebral vasodilator that could enhance collateral circulation blood flow and cerebral protection before reperfusion. General anesthesia with endotracheal mechanical ventilation could be used for thrombectomy and give the opportunity to modulate and control carbon dioxide tension in the blood. This study will test the effect of moderate hypercapnia on penumbral collateral circulation before reperfusion during mechanical thrombectomy for anterior circulation acute ischemic stroke under general anesthesia.

Brain Blood Flow Responses During Exercise

Brain blood flow will be measured during exercise using magnetic resonance imaging.

Brain Blood Flow Responses During Exercise: Younger Cohort

Brain blood flow will be measured during exercise using magnetic resonance imaging.

Brain PERfusion Evaluation by Contrast-Enhanced UltraSound

The objective of the study is to assess brain tissue perfusion by contrast-enhanced ultrasound perfusion imaging (PerCEUS) in acute brain injuries. More precisely, it aims : * to evaluate the heterogeneity of brain perfusion and thus diagnose brain tissue hypoperfusion with contrast-enhanced ultrasound. * to correlate contrast-enhanced ultrasound with perfusion measurements by usual multimodal monitoring.

Study of Cerebral Vascular Reserve Using Pharmacological Testing With Acetazolamide: A Non-Inferiority Study of PET Method Compared to Conventional Reference Scintigraphy

This study compares two methods for assessing brain blood flow. PET scan will be use with a drug called Acetazolamide and compare its effectiveness to the standard scintigraphy method. The goal is to see if the PET scan is just as good as the traditional method in measuring how well the brain's blood vessels respond to the drug.

Assessment of the Relationship Between Cerebral Blood Flow and Heart Rate

The investigators will seek to determine the relationship between heart rate and middle cerebral artery (MCA) cerebral blood flow (CBF), as well as better understand the hemodynamic determinants of MCA CBF velocity. In order to manipulate heart rate, the investigators will recruit patients already scheduled for clinically indicated elective electrophysiological studies, where temporary pacing catheters placed in the right atrium can be used to artificially pace the heart at controlled rates. MCA CBF will be measured by transcranial Doppler ultrasound.

The Cerebral Microcirculation Diseases and Coronary Microcirculation Disease Study

Ischaemic heart disease (IHD) and degenerative brain disease are two major sources of death and disability affecting all countries. While the consequences of obstructive disease in major vessels supplying blood to both organs have been widely documented, less attention has been paid to disease processes affecting the microcirculation that may affect cardiac and cerebral function. Yet, over the last decade significant progress has been made in understanding the substrate of microvascular disease in both organs. In the heart, arteriolar thickening and capillary rarefaction that reduce the conductance of the microvasculature and its ability to vasodilate in response to increased myocardial oxygen demands constitute the leading cause of coronary microvascular dysfunction (CMD). In the brain, concentric hyaline thickening of deep penetrating small arteries (arteriolosclerosis) with associated fibrosis of the vessel wall constitutes the most frequent substrate for cerebral small vessel disease (CSVD). Of note, both CMD and CSVD share common risk factors, such as age, hypertension, and diabetes.3 These factors might have a common effect on the microvascular domain of cardiac and cerebral vascular beds. Although a potential link between both conditions has been hypothesized based on the similarities between pathological changes and risk factors, advance in knowledge exploring this has been hampered by lacking objective evidence of CMD and pathological brain changes indicative of CSVD in prior research studies. Thus, the relationship between CMD and CSVD is unknown. The main objective of this study was to analyse the relationship between cerebrovascular disease and CMD in patients with atherosclerotic coronary artery disease (CAD).