AIMTo evaluate the effects of atria-His bundle sequential pacing on cardiac electrophysiology and heamodynamics in dogs.

METHODSIn 20 opening chest anesthetized dogs, platinum electrodes were fixed at the epicardium of right atria (RA) and the right ventricular apex (RVA) respectively, pacing right atria and the right ventricle. A special lead was located at His bundle (based on a optical "H" wave and narrow duration of the QRS complexes recorded in ECG), pacing His bundle. Cardiac electrophysiology and hemodynamics parameters were compared in the different pacing models RA(AAI, RVA-(VVI), HisB-(VVI) single chamber pacing and RA-RVA(DDI), RA-HisB(DDI) dual chamber pacing.

RESULTSThe threshold of His B pacing is similar to that of RVA pacing. Cardiac output (CO) is increased in pacing of RA(AAI), His B-(VVI) and RA-His B(DDI). It is increased by 29.64% in pacing of RA-His B(DDI) (P < 0.01) and by 0.25% (P > 0.05) in pacing of RA-RVA(DD1) While CO is decreased by 5.41% in RVA-VVI) pacing (P > 0.05). SV, LVSW and RVSW of RA-HisB(DDI) pacing are superior to those in RVA-VVI) and RA-RVA(DDI) pacing.

CONCLUSIONRight atria-His bundle sequence pacing significantly improves cardiac function compared with the other model pacing because it maintains normal physiological electronic activity sequence and systolic synchrony. It will be adapted to clinical application.