Evaluation On Left Ventricular Intra-cardiac Flow Field Before And After Temporary Interruption Of Pacemaker In Mid-to-long-term Cardiac Resynchronization Therapy Patients By Vector Flow Mapping

Objectives This study was to evaluate left ventricular systolic function and intra-cardiacflow field before and after temporary interruption of pacemaker in mid-to-long-termcardiac resynchronization therapy patients by vector flow mapping. And to investigate therelationship between left ventricular vortex indices and ventricular function.Methods In this study,45patients who were enrolled more than6months after CRTpacemaker implantation in Xi Jing Hospital of the Fourth Military Medical Universityfrom July in2012to February in2013.CRT before surgery,the patients with end-stageCHF were screened in strict accordance with “Proposal of Cardiac resynchronizationtherapy in chronic heart failure”which newly revised in2009China.According to theconventional transthoracic echocardiography Simpson’s biplane measurement of leftventricular end-systolic volume (LVESV) after6months compared with the preoperativereduced proportion (ΔESV) greater than15%of the responses were divided into group of32patients (22males,10females) and non-response group of13patients (8males,5females), aged34to74years, mean (57±11) years of age.The study excluded thefollowing situations: The patients who are pacemaker-dependent and those exist risks after the pacemaker was closed; The patients who intolerant pacemaker turned off, during theperiod of the study need to re-open the BVP; Severe arrhythmias (eg: significantarrhythmia, premature beat, Ⅲ degree atrioventricular block, etc.), ischemic heart disease,valvular heart disease, congenital heart disease, pericardial disease, aortic regurgitation inthe amount of more than,hemodynamic status is not stable patients; With poor acousticwindow, color Doppler flow in patients with poor image quality; The patients whounderstand risk after turning off the pacemaker.,and does not agree to close thepacemaker.Then turn off the pacemaker when avoid the risk and get the patients’permission. Echocardiographic examination was carried out after10min interruption ofCRT with ALOKA alpha10ultrasonic diagnostic system，followed by measurement ofleft ventricle （LV）, left ventricular ejection fraction (LVEF), the maximal riserates of left ventricular pressure (+Dp/Dtmax), aortic supravalvularflow velocity time Integral (VTI-AV),and the mitral regurgitant volume (MRV), area (MRA).Afterwards, Left ventricular blood fiow vector image acquisition by using VFMsoftware. Mitral valve closing moment (MVC), aortic opening moment (AVO), aortic flowvelocity peak moment (AVP),aortic closing moment (AVC) were measured as four timepoints to measure the center position of longitudinal (VD),diameters (DLand DH), area(VA) and flow volume (FV) of vortex. And with further, to measured the flow volumechange rate of (FV-CR%) and the area change rate (VA-CR%) during the period of timefrom aortic valve opening to aortic flow velocity peak, and observe their evolutioncharacteristics. Results Compared those indices before closing pacemaker with them after10minutes ofclosing, In responded group,AV-VTI and LVDp/Dtmax are all decreased (P<0.05);Andseverity of mitral regurgitation were worsened than the status before CRT interruption;According to the results of VFM analysis, when during IVC, the moving distance ofvortex center towards the basal level decreased, the attenuation of VA and FV aggravated;when during ejection, the moving distance of vortex center towards basal outflow tractdecreased either, but the decrease extent of VA and FV were less than the pacingstatus(P<0.05).FV-CR%and VA-CR%are both decreased during the period of time fromaortic valve opening to aortic flow velocity peak (P<0.01).However, in non-respondedgroup, none of the regular parameters changed after the interruption except AV-VTI, andonly moving distance of VD lessened after the interruption,the rest of the VFMparameters had no significant difference.And the response of group LVEF and VA-CR%were positively correlated,before and after pacemaker closed correlation coefficients were(r=0.632, p <0.01; r=0.654, p <0.05).Conclusion There were significant worseningeffects on intra-ventricular hemodynamics and flow field characteristics when temporarilyinterrupted the pacemaker in mid-to-long-term CRT patients,especially in patients whoresponded to CRT.The changes could be easily and objectively analyzed by VFMtechnique; and the results indicated the necessity of continuous CRT in thosepatients.VFM technology can objectively and effectively reflect the changes of leftventricular systolic blood flow characteristics before and after pacemaker interrupted，aswell as the correlation between left ventricular function.And those results indicated the necessity of continuous CRT in patient of mid-to-long-term both responded andnone-responded. VFM technology has potentially significant value in the evaluationprocess CRT therapy.