Shintaro Katahira

Oesophageal mucosal blood flow changes after thoracic endovascular stent graft implantation using a novel sensor probe

OBJECTIVES Secondary aorto-oesophageal fistula is a rare, lethal complication occurring after thoracic endovascular aneurysmal repair. The cause of secondary aorto-oesophageal fistula is unknown, but a reduction in local oesophageal mucosal blood flow (OMBF) may be a basis for such a devastating sequela. Our study aims to develop a novel blood flow sensor probe to detect changes in OMBF after thoracic stent graft implantation in an experimental swine model. METHODS A novel laser Doppler flowmetry sensor probe incorporating an optical fibre sensor within a nasogastric tube was developed using microelectromechanical system technology. OMBF was measured at various levels using this sensor probe, to test its feasibility before and after thoracic endovascular stent graft implantation covering Th4-Th8 vertebral levels in 6 swine. RESULTS In the middle oesophagus (Th5-Th7), where the aorta was covered with a stent graft, the measured OMBFs were significantly decreased after thoracic endovascular stent graft implantation than those of baseline (8.6 ± 2.7 vs 18.4 ± 7.9 ml/min/100 g, P < 0.0001), followed by a plateau period for at least 2 h after stent grafting (8.7 ± 3.3 ml/min/100 g, P < 0.0001 vs baseline). OMBFs in the upper (Th1-Th3) and lower (Th9-Th11) oesophagus, where the aorta was not covered with a stent graft, were unaffected by thoracic endovascular stent grafting. CONCLUSIONS The novel laser Doppler flowmetry sensor probe was useful to monitor precise changes of OMBF in a swine model, demonstrating a significant reduction in OMBF after thoracic endovascular stent graft implantation.

Contraction support for the right ventricle by a shape memory alloy fibered artificial myocardium

Mechanical cardiac support by using artificial organs improves the circulatory condition in the patients with heart failure. However, the thrombotic and bleeding complications might be caused by the use of these artificial prosthetic internal organs because of their direct attachment with blood. We have been developing an implantable artificial myocardial assist device that can support the natural ventricular contraction from outside of the heart. A shape memory alloy fiber was employed for the implantable design of the myocardial assistance. In this study, we focused on the right ventricular assist by the artificial myocardium using shape memory alloy fibers. We fabricated a prototype of the right ventricular contraction support based on the hinge mechanism design with shape memory fibered actuators. Fundamental characteristics of the contractile effects of the design, as well as its deformation, were examined, and the hemodynamic changes were investigated in the acute animal experiments. As a result, the supporting depth from the ventricular wall increased to be 35 mm, and the volumetric assistance showed around 50 mL incremental assist by the changes in the displacement of the actuator.