The Effect Of Coronary Sinus Obstruction On Electrophysiologic Parameters In Normal And Globally Ischaemic Isolated Rabbit Hearts

Background and objective: Coronary sinus intervention is protective to ischemic myocardium decreasing infarct size. But the effect of coronary sinus occlusion on cardiac electrophysiology is unclear. Generally, the left ventricle pacing electrode is placed via coronary venous sinus. It is also uncertain if long-term pacing electrode maintenance exerts adverse effect on cardiac electrophysiology. Our present study was to observe the changes of ventricular effective refractory period (VERP), refractory period dispersion (RPd) and ventricular fibrillation threshold (VFT) and to assess the effect of coronary sinus occlusion on cardiac electrophysiology by graded occlusion of coronary sinus in rabbit heart Langendorff perfusion models.Materials and methods: Twenty-four New Zealand white rabbits were randomly assigned into three groups: rabbits with no coronary sinus occlusion (group A), rabbits with coronary sinus occlusion of 1mm (group B), rabbits with coronary sinus occlusion of 2mm (group C). Rabbit heart Langendorff perfusion models with continuous flow were used and global ischemic models were produced by decreasing the perfusion flow rate to 10%. Two plunged tetrapolar electrodes were inserted in the right ventricular anterior wall and left ventricular anterior wall (low right to left auricle and left to interventricular sulcus). At different time points and at three sites in right and left ventricles, ventricular diastolic threshold (VDT), ventricular relative refractory period (VRRP), VERP, RPd and VFT were measured respectively under the conditions of normal perfusion and global ischemia in every group.Results: RRP and ERP at three sites in right and left ventricles slightly increased 1 minute after ischemia when coronary sinus was not occluded, then decreased significantly (P<0.05). VFT was significantly lower than that before ischemia (P<0.05) and RPd was higher. Coronary sinus occlusion of 2mm exerted no effects on cardiac electrophysiology of both normal and ischemic ventricular myocardium (P>0.05). When coronary sinus was occluded 2mm, RRP, ERP and VFT at two sites in left ventricle increased under normal perfusion (P<0.05), but, twenty minutes after the removal of occlusion, they decreased to the levels before occlusion. Electrophysiological changes in the right ventricle were not obvious. Under the condition of global ischemia, RRP, ERP and VFT at two sites in left ventricle increased slightly but below the levels before ischemia,...