OBJECTIVETo observe the changes of surface ECG and cell couplings between sinoatrial node cells and myocardial cells following transplantion of pedicled autologous sinoatrial node tissue graft into the right ventricle of a canine model of complete atrioventricular block.

METHODSTen healthy dogs were randomized into transplantation group and control group. Pedicled autologous sinoatrial node tissue grafts were transplanted into the right ventricle in the transplantation group, while the sinoatrial nodes were only excised in the control group after placement of temporary myocardial pacing wires. The changes of surface ECG were observed at 1, 2, 3 and 4 weeks postoperatively. At 4 weeks, complete atrioventricular block was induced in the dogs by radiofrequency ablation of the His bundle. The heart rate of the dogs in both groups were recorded after the injection of isoproternol (ISO) from the femoral vein, and the transplanted tissue graft was observed under optical and transmission electron microscopes.

RESULTSNo significant changes occurred in the surface ECG. All the dogs showed ECG waveforms specific of complete heart block after the ablation, and the ventricular heart rates were similar between the two groups (P>0.05). The ventricular heart rate did not undergo obvious changes after ISO injection (P>0.05). The transplanted pedicled autologous sinoatrial node survived in the dogs and the sinoatrial node cells established desmosome junctions with the myocardial cells, but the number of junctions was not sufficient to support heart pacing.

CONCLUSIONDesmosome junction can occur between ventricular myocardial cells and sinoatrial node cells at the edge of transplanted pedicled autologous sinoatrial node tissue.

Animals ; Atrioventricular Block ; physiopathology ; surgery ; Cardiotonic Agents ; pharmacology ; Dogs ; Electrocardiography ; Female ; Heart Rate ; drug effects ; Heart Ventricles ; surgery ; Intercellular Junctions ; Isoproterenol ; pharmacology ; Male ; Myocardium ; cytology ; Sinoatrial Node ; cytology ; transplantation ; Tissue Transplantation ; Transplantation, Autologous

Given that current axial flow blood pumps have certain structural defects,resulting in poor performance and inferior blood compatibility,an integrated axial flow blood pump is developed,and its geometry is optimized using computational fluid dynamics method.The study also investigates the effects of different operational parameters on the performance of the blood pump and compares with experimental data to determine the optimal conditions.Additionally,the flow patterns of the blood pump are comprehensively analyzed for further revealing the internal flow phenomena,and the behavior of red blood cells in the blood flow and their response to shear stress are simulated using discrete phase model to evaluate the blood compatibility of the blood pump.The study shows that the novel blood pump performed well in terms of head.Under the optimal condition with a rotational speed of 9 000 r/min and a flow rate of 6.24 L/min,the blood pump improves the head by 16%as compared with the original structure,and reaches 25%efficiency,which can meet the physiological needs of most people.The pressure gradient and velocity gradient in most areas within the blood pump are smooth,and the internal flow patterns are generally stable,effectively avoiding the occurrence of hemolysis.The optimized blood pump can ensure high-level performance and favorable flow field characteristics while maintaining superior blood compatibility,which provides important reference for the structural optimization of axial flow blood pumps.