| The maintenance of ventricular activation sequence (VAS) and ventricular systolic synchrony (VSS) under the physiological condition depends on the special cardiac conduction system(His-Purkinje fibre, H-P), by which cardiac electrical activation is sequentially sped and ventricular synchronous systolic and diastolic process is completed. Due to the technique limitation on the implantation of pacing leads, ventricular pacing site used to be located at right ventricular apex (RVA), the earliest activation site (EAS) is always far away the physiological conduction bundle ?His-Purkinje conduction system. During RVA pacing, a counterclock alters the spatial direction and temporal process of the nomal ventricular activity and delays the conductive time of activation, so that, it induces synchronous disorders of electrical and mechanical activity between both of left and right ventricles and among the different parts of ventricular wall in a ventricle and reduces the globle VSS. It is indicated that the implanted location of ventricular lead depends on the EAS that plays an important role in alteration of VAS. The decrease of VSS due to abnormal VAS results in a negative effect to cardiac performance. Following the development and improvement on pacing engineering and implantation technique of leads, it is possible to choice the ventricular synchronous pacing mode with different pacing site combination. In the series of the present study, the purpose is to approach the effects of ventricular synchronous pacing modes with different pacing site combination on cardiac electrophysiology, myocardial mechanics and hemodynamics by animal experiment and clinical study. Accordingly, a few of ventricular synchronous pacing modes with different pacing sitecombination will be selected and evaluated, so that the better effects on hemodynamics, myocardial mechanics and cardiac working will be obtained by maintaining normal electrical mechanical activation sequence and synchrony between both of left and right ventricles and among the different parts of ventricular wall in a ventricle. As a result, it will offer an experimental foundation for the treatment of heart failure with multisite resynchronized cardiac pacing. The methods and results of our study are as follows:Part one: Study of the effects of right atria-His bundle sequential pacing on cardiac electrophysiology and hemodynamics in dogsObjective To evaluate the lead located technique and feasibility of pacing at the close to His bundle (cHisB) site, and the effects of cHisB pacing and right atria-cHisB sequential pacing (RA-cHisB) on the cardiac electrophysiology and hemodynamics in dogs. Methods A special lead was located at closed to His bundle based on the "H" wave, the QRS original vectors as similar to SNR, the shorter QRS duration compared with that of RVA pacing and the optimal pacing threshold in 20 dogs with general-anesthetized, opened chest and artificial-ventilation. The different cardiac pacing modes were composed by the cHisB site with right atrium (RA), right ventricular apex (RVA) one another. Sinus rhythm(SNR) before pacing was as self control. RA, cHisB and RVA single chamber pacing and RA-cHisB, RA-RVA dual chamber pacing (five pacing groups) were randomly performed. Every pacing mode was to capture SNR for 20 min with a recovery of physiologic parameters for 10 min, then shift another pacing mode in turn. The parameters of hemodynamics were measured simultaneously included artery pressure (AP), pulmonary artery pressure (PAP), pulmonary capillary wedge pressure (PCWP), center vein pressure (CVP), left ventricular end diastolic pressure (LVEDP), cardiac output (CO), stroke volume (SV), left ventricular stroke work (LVSW), right ventricular stroke work (RVSW), system vessel resistance (SVR) and pulmonary vessel resistance (PVR). Results The threshold of cHisB pacing12was conformed to the standard of ventricular pacing. The original vectors of the QRS complexes in cHisB pacing was similar to that in SNR. The QRS duration was shorter in c...
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