| Objective1. To observe the atrial electrophysiologic parameters changes under the condition of different distension pressures after atrium being dilated acutely for 30 minutes, such as atrial effective refractory period?AERP?, atrial effective refractory period dispersion?d AERP?, interatrial conduction time?IACT? and so on. To analysis the susceptibility of atrial fibrillation under the condition of different distension pressures after atrium being dilated for 30 minutes. Combining with the the atrial electrophysiologic parameters and the susceptibility of atrial fibrillation, to explore the mechanism of atrial electrical remodeling related to the induction and maintenance of atrial fibrillation.2. To observe the levels of atrial natriuretic peptide?ANP? and atrial natriuretic peptide precursor?N- terminal atrial natriuretic peptide, NT-pro ANP? in atrial tissue under the condition of different distension pressures after atrium being dilated for 2 hours, so as to get a further understanding about the synthesis and secretion mechanism of ANP related to atrial dilatation3. To observe the level of nitric oxide?NO?in atrial tissue under the condition of different distension pressures after atrium being dilated for 2 hours, so as to get a further understanding about the effect of acute atrial dilation on the synthesis of nitric oxide?NO?in atrial tissue.MethodsThirty-two rabbits were randomly divided into 0, 8, 12, 20 cm H2O groups and Langendorff isolated heart perfusion model was established. Interatrial septum was perforated to make sure the same hydrostatic pressure between left and right atrium. Three plastic hoses were intubated superior vena cava, inferior vena cava and one pulmonary vein respectively. Others pulmonary vessels were ligatured. Superior vena cava and pulmonary vein hose telecentric end were connected with the same pressure monitoring and maintaining equipment. Different hydrostatic pressure conditions of atrium were established by adjusting the inferior vena cava hose distal height level. The atrial electrophysiologic parameters of HRA, LRA, HLA, LLA and the inducibility of atrial fibrillation were detected after atrium being dilated for 30 minutes. The levels of atrial natriuretic peptide?ANP? and NT-pro ANP in atrial tissue under the condition of different distension pressures were detected after atrium being dilated for 2 hours by ELISA. The level of nitric oxide?NO?in atrial tissue under the condition of different distension pressures after atrium being dilated for 2 hours were also evaluated.Results1. With the progressive increasing of atrial hydrostatic pressure, the inducibility of paroxysmal atrial fibrillation and atrial fibrillation present progressively increased, and the differences between groups are significant?P<0.05?. The inducibility of persistent atrial fibrillation in 8, 12, 20 cm H2O pressure groups are significantly higher than that of 0 cm H2O pressure group?P < 0.05?, and the inducibility of persistent atrial fibrillation in 12, 20 cm H2O pressure groups are significantly higher than that of 0, 8 cm H2O pressure group?P<0.05?, but the difference between 12 and 20 cm H2O pressure groups has no significance.2. Compared with 0cm H2O atrial pressure group, the atrial effective refractory period?AERP?, left atrial effective refractory?LAERP?, right atrium effective refractory period?RAERP? in 8, 12, 20 cm H2O atrial pressure groups are significantly shortened?P<0.05?. Compared with 0cm H2O atrial pressure group, the interatrial conduction time in 12, 20 cm H2O atrial pressure groups are significantly prolonged. And only the left atrial effective refractory period dispersion?d AERP? in 20 cm H2O atrial pressure group is increased obviously?P <0.05?, when comparaed with that in 0, 8 cm H2O.3. With the progressive increasing of atrial hydrostatic pressure, the level of ANP in atrial tissue has no difference among the 0, 8, 12, 20 cm H2O four groups, and the level of NT-pro ANP in 8 cm H2O is higher than other three groups?P<0.05?. And there is no significant difference among 0, 12, 20 cm H2O in the level of NT-pro ANP.4. With the progressive increasing of atrial pressure, the level of NO in atrial tissue decreases progressively. And the level of NO in 12, 20 cmH2O groups were signifycantly higher than that in 0, 8 cm H2O groups?P<0.05?.Conclusions1. Acute atrial dilation can cause atrial electrophysiological changes. With the progressive increasing of atrial hydrostatic pressure, susceptibility of atrial fibrillation and induction rate of persistent atrial fibrillation are increased.2. Acute atrial dilation with the distension pressure below 8 cm H2O for 2 hours can increase the synthesis and secretion of NT-pro ANP.3. Acute atrial dilation with 12, 20 cm H2O for 2 hours can decrease the level of nitric oxide?NO?in atrial tissue. |
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