Cerebral Hemodynamic Changes During Cardiac Surgery: A Feasibility MR Study in Piglets
Dominik T Schulte1, Ruth O'Gorman Tuura2, Henning Richter3
1Institute for Dynamic Systems and Control, ETH Zurich, Zurich, Switzerland.
Insights
Researchers developed an MR-conditional heart-lung machine (HLM) enabling MRI during cardiopulmonary bypass (CPB). This innovation allows in vivo study of brain metabolism and perfusion during CPB in piglets, paving the way for neuroprotection strategies.
Area of Science:
- Biomedical Engineering
- Neuroscience
- Pediatric Cardiology
Background:
- Congenital heart disease necessitates surgical intervention, often involving cardiopulmonary bypass (CPB).
- Infants undergoing CPB face increased risk of white matter injury, impacting neurodevelopment, with unclear mechanisms.
- Conventional heart-lung machines (HLMs) interfere with MR imaging, hindering in vivo studies of brain changes during CPB.
Purpose of the Study:
- To develop and evaluate an MR-conditional HLM for simultaneous MR imaging and CPB in a preclinical model.
- To assess the feasibility of monitoring cerebral perfusion and metabolism during CPB within an MR scanner.
Main Methods:
- An MR-conditional HLM, including a roller pump, was developed and tested.
- Piglets underwent CPB inside an MR scanner, with cooling, rewarming, and carotid clamping.
- In vivo MR imaging (flow, diffusion, perfusion, metabolism) was performed during CPB.
Main Results:
- The MR-conditional HLM operated effectively inside the scanner without compromising imaging or pump function.
- Key brain structures were visualized without artifacts, and monitoring signals remained stable.
- MR scans indicated flow-related changes and increased lactate, suggesting metabolic stress under hypoperfusion.
Conclusions:
- Performing CPB within an MR scanner using an MR-conditional HLM is technically feasible.
- This platform enables mechanistic studies of brain injury during CPB in large-animal models.
- Future applications include identifying early markers of cerebral vulnerability and developing neuroprotective strategies.
Abstract:
Congenital heart disease often requires early surgical intervention. Cardiopulmonary bypass (CPB) is a standard procedure, but infants undergoing CPB show an increased risk of postoperative white matter injury. These injuries are associated with adverse neurodevelopmental outcomes, yet the underlying mechanisms remain poorly understood. MR imaging offers unique opportunities to study cerebral perfusion and metabolism in vivo but has not previously been feasible during CPB with a heart-lung machine (HLM) in close proximity to the patient and the MR scanner, respectively, because conventional HLMs interfere with scanner operation. To address this limitation, we developed an MR-conditional HLM and evaluated it in an in vivo piglet model, which closely mimics the neonatal brain and circulation. Unlike conventional systems, our MR-conditional roller pump can be positioned directly inside the scanner bore without compromising imaging quality or pump performance. Four trials were conducted, in which piglets were cannulated and maintained on CPB inside the MR scanner. During CPB, cooling, rewarming, and unilateral carotid clamping were performed while repeatedly acquiring MR data on flow, diffusion, perfusion, and metabolism. Crucial brain structures-including the basal ganglia, hippocampus, and internal capsule-were consistently visualized without artifacts, and no disturbances occurred in pump operation or monitoring signals. The MR scans revealed flow-related changes and a progressive increase in lactate, suggesting the onset of metabolic stress under hypoperfusion. These results demonstrate the technical feasibility of performing CPB within the MR scanner using an MR-conditional HLM. Although not sufficient to identify specific mechanisms of brain injury, this platform provides a unique foundation for mechanistic studies in relevant large-animal models. In the future, such an approach could help identify early markers of cerebral vulnerability, improve the safety of pediatric cardiac surgery, and inform the development of neuroprotective strategies for CPB and extracorporeal membrane oxygenation patients.
