Manual Carotid Compression is a Viable Alternative for Reduction of Cerebral Microemboli.

BACKGROUND: Stroke is a devastating complication of cardiovascular surgeries, and the risk is particularly high for those requiring cardiopulmonary bypass (CPB). Embolic particles generated during the unclamping of the aortic cross-clamp may enter the cerebral circulation, lodging in small vessels. External manual compression of the carotid arteries is a non-invasive technique that has been proposed for cerebral protection during CPB procedures but is not widely deployed. METHODS: The aim of this study is to assess the potential for cerebral emboli reduction with carotid compression using an in vitro model. Experiments were performed with a glass aortic arch model in a mock cardiovascular circuit. Small fluorescent particles were released into the circulation with and without carotid compression, and the particles visualized in the aortic midplane. The number of particles in the aorta and arch branch vessels were counted from the images before, during and following the release of carotid compression for durations of 10, 15 and 20 s. A gamma variate function was fit to the data to describe the bolus dynamics. RESULTS: Carotid compression for 10 s reduces the number of embolic articles entering the carotid arteries by over 75%. A compression duration of 15-20 s does not result in greater particle reduction than one of 10 s. CONCLUSION: Brief compression of the common carotid arteries during cardiovascular interventions has the potential to dramatically reduce the number of cerebral emboli and should be investigated further.

The Effect of Inflow Cannula Length on the Intraventricular Flow Field: An In Vitro Flow Visualization Study Using the Evaheart Left Ventricular Assist Device.

Left ventricular assist device (LVAD) inflow cannula malposition is a significant risk for pump thrombosis. Thrombus development is influenced by altered flow dynamics, such as stasis or high shear that promote coagulation. The goal of this study was to measure the intraventricular flow field surrounding the apical inflow cannula of the Evaheart centrifugal LVAD, and assess flow stasis, vortex structures, and pulsatility for a range of cannula insertion depths and support conditions. Experimental studies were performed using a mock loop with a customized silicone left ventricle (LV) and the Evaheart LVAD. A transparent inflow cannula was positioned at 1, 2, or 3 cm insertion depth into the LV and the velocity field in the LV midplane was measured for 2 levels of LVAD support: 1800 and 2300 rpm. The LV velocity field exhibits a diastolic vortex ring whose size, path, and strength are affected by the flow conditions and cannula position. During diastole, the large clockwise midplane vortex grows, but its circulation and kinetic energy are reduced with cannula insertion depth. The counterclockwise vortex is smaller and exhibits more complex behavior, reflecting a flow split at 3 cm. Overall, the 1 cm cannula insertion depth produces the flow pattern that exhibits the least apical flow stasis and greatest pulsatility and should correlate to a lower risk of thrombus formation.