Detection of thrombosis in a magnetically levitated blood pump by vibrational excitation of the impeller

The use of contactless support technology for the impeller has led to an increase in the durability of ventricular assist devices (VADs), and these have been in clinical use worldwide. However, pump thrombosis and stroke are still issues to be solved. We have developed a method for detecting the thrombosis in a magnetically levitated blood pump without the need for additional sensors or other equipment. In the proposed method, a sinusoidal current is applied to the electromagnets used for the magnetic bearing, resulting in vibration of the impeller. The phase difference between the current and displacement of the impeller increases with pump thrombosis. First, we describe the principle by which the pump thrombosis is detected. Pump thrombosis reduces the narrowest fluid gap in the pump and this gives rise to a change in the phase difference. Second, we report on experiments in which we changed the narrowest fluid gap using oriented polypropylene tape and showed that decreasing the narrowest fluid gap resulted in an increase in phase difference. For these experiments, the measurements were repeated three times for each condition. Third, we examine the relationship between the pump thrombosis and the phase difference evaluated by observations of the underside of the impeller when operating the pump with porcine blood. Since light was unable to penetrate the blood layer, the erythrocytes were removed for this observation. Only one observation was made. The results showed the phase difference rapidly increased at the same moment when the pump thrombosis was observed. This implies the proposed method has the potential to detect the early stages of pump thrombosis. Finally, in vitro experiments to detect thrombosis when using whole porcine blood in the pump were conducted. The experiment was carried out five times. To intentionally form a thrombus inside the pump, the activated clotting time was controlled to be less than 200 s. In every case, the phase difference increased by more than one degree after tens of minutes. Then, the pump was disassembled and a small amount of pump thrombosis was observed. We conclude that real-time diagnosis of pump thrombosis may be realized by measuring the phase difference without the need for additional sensors.     

Impact of turbulent blood flow in the aortic root on de novo aortic insufficiency during continuous-flow left ventricular-assist device support

Severe aortic insufficiency (AI) after implantation of continuous-flow left ventricular-assist device (LVAD) affects device performance and outcomes. However, the mechanism for the occurrence and progression of AI has not been elucidated. We investigated the impact of nonphysiological retrograde blood flow in the aortic root on AI after LVAD implantation. Blood flow pattern was analyzed in patients with and without AI (n = 3 each) who underwent LVAD implantation, by computational fluid dynamics with patient-specific geometries, which were reproduced using electrocardiogram-gated 320-slice computed tomographic images. The total volume of retrograde blood flow during one cardiac cycle (716 ± 88 mL) was higher and the volume of slow blood flow (<0.1 cm/s) (0.16 ± 0.04 cm³) was lower in patients with AI than in those without AI (360 ± 111 mL, P = .0495, and 0.49 ± 0.08 cm³, P = .0495, respectively). No significant difference in wall shear stress on the aortic valve was observed between the groups. Patients with AI had a perpendicular anastomosis at the distal ascending aorta and the simulation in the modified anastomosis model of patients with AI showed that the retrograde blood flow pattern depended on the angle and position of anastomosis. Computational fluid dynamics revealed strong retrograde blood flow in the ascending aorta and aortic root in patients with AI after LVAD implantation. The angle and position of LVAD outflow anastomosis might impact retrograde blood flow and de novo AI after LVAD implantation.     

Prognostic Significance of Hiatal Hernia in Patients with Gastric Cancer Located within the Upper-Third of the Stomach

World Journal of Surgery - Gastric cancers located within the upper-third of the stomach (UGC), especially the esophagogastric junction GC (EGJGC), have distinct clinicopathological features due to...     

Spinal cord injury following aortic arch replacement

Surgery Today - Postoperative spinal cord injury is a devastating complication after aortic arch replacement. The purpose of this study was to determine the predictors of this complication. A group...     

Predictors of postoperative early recurrence of extrahepatic bile duct cancer

Resected bile duct cancers often relapse during postoperative follow-up. The aim of this study was to detect predictors of early recurrence in patients with extrahepatic bile duct cancer. Consecutive cases (n = 162) of extrahepatic bile duct cancer in which R0 or R1 resection was achieved in Kobe University Hospital between 2000 and 2016 were divided into three groups [early recurrence (ER), within 6 months of surgery, late recurrence (LR), and no recurrence (NR)] and their clinicopathological features were compared. Twenty-two patients (14%) developed ER and 69 (43%) developed LR after surgery. The rates of lymph node metastasis and residual cancer status were similar in all three groups. Liver metastasis was more common in the ER group than in the LR group (59% vs. 32%, p = 0.02). ER had a significantly worse prognosis than LR and NR (7% vs. 44% vs. 85% at 1 year, p < 0.01, respectively). Multivariate analysis showed that age > 75 years, serum CA19-9 > 1008 U/ml and perineural invasion were independent predictors of early recurrence. High serum CA19-9 values (> 1008 U/ml) were an independent predictor of early recurrence. Neoadjuvant therapy and aggressive adjuvant therapy may be beneficial for patients who show highly elevated CA19-9 values before surgery.