RESUMO
OBJECTIVE: To 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. METHODS: Ten 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. RESULTS: No 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. CONCLUSION: Desmosome junction can occur between ventricular myocardial cells and sinoatrial node cells at the edge of transplanted pedicled autologous sinoatrial node tissue.
