The Clinical Research On The Hemodynamics And Synchronization Changes With Interruption Of Cardiac Resynchronization Therapy

OBJECTIVEAtrioventricular dyssynchrinization,interventricular dyssynchrinization and leftintraventricular dyssynchrinization are very common in the patients withmoderate and severe chronic heart failure.Which results in low efficiency of leftventricular ejection and vicious circle and is becoming a major problem inmedical treatment. Cardiac resynchronization therapy (CRT) improves heartfunction in heart failure on basis of biventricular pacing. This could increase thecardiac mechanical efficiency by correcting the atrio-ventricular dyssynchrony,inter-ventricular dyssynchrony and intra-ventricular dyssynchrony, which aregeneral conditions in patients with moderate to severe chronic heart failure(CHF). It was demonstrated in former researches that CRT could alleviateclinical symptoms, improve quality of life, and reduce hospitalization andmortality of CHF patients. Consequently, CRT has gradually become thepreferred treatment of patients with refractory CHF. It was found in somestudies the left ventricular (LV) end-diastolic and end-systolic volumes were significantly reduced at3–6months after CRT, and the reduced LV volumeswouldn’t change back to the baseline immediately after and pacemaker wasinterrupted or stopped. This indicated that CRT reduces the LV volumes not byacute hemodynamic changes but through the reverse remodeling of LV. However,there are also about30–40%CHF patients failed to reverse remodeling. So far,it is still unclear that the non-reverse remodeling CHF patients are benefittedfrom resynchronization and hemodynamic changes, and relative investigationsin acute hemodynamic changes and synchronism after CRT interruption werestill rarely reported. In this study, the hemodynamics and synchronism ofinterruption of more than6months CRT pacing will be evaluated.METHOD46CHF patients who had undergone implantation of CRT device for more than6months were enrolled in the study. The reverse remodeling and non-reverseremodeling were identified by reduction of LV end-systolic volumes≥15%. Thetwo groups underwent echocardiography, and the hemodynamic changes as wellas synchronization indexes were measured in “on” and “off” mode of CRT. Thevideo records of conventional apical4-,2-and3-chamber views were acquired,and LV synchronization indexes were analysis off-line with QLAB.Hemodynamic index: mitral regurgitation area(MRA), velocity time integral ofaortic valve(VTI-AV), velocity time integral of mitral valve(VTI-MV),maximum rising rate of left ventricular pressure(+dp/dtmax).Atrioventricular synchronization index: Left ventricular filling time/R-Rtime(LVFT/T).Interventricular synchronization index: Interventricular delay(IVD).LV synchronization index: Standard deviation of peak time of circumferential strain in12segments (PTcs-12SD), Standard deviation of peak time of radialstrain in12segments (PTrs-12SD), Standard deviation of peak time oflongitudinal strain in16segments (PTls-16SD).Hemodynamic indicators and synchrony index were compared in CRT on andoff modes.RESULT1. Non-revese remodeling group who had undergone CRT for median12months(9,18). Revese remodeling group who received CRT for median12months (9,12.5).There was no significantly difference in receiving CRT time between twogroups (P>0.05), and no significantly difference in age, sex, height, weight andblood pressure between two groups too (P>0.05).When compared to reveseremodeling group, Non-revese remodeling group had significantly smallerchanging in ΔLVESV[4.77(-11.01,8.12)vs27.54(16.79,27.54)，P<0.001], andΔLVEF[10.26(-23.18,20.14)vs23.13(12.88,36.76),P=0.005] after CRT.2. Two groups had significant worsening of MRA and VTI-AV after10minutesinterruption of CRT as compared to CRT-on mode (P<0.01). VTI-MV anddp/dtmaxmax were decline when CRT off as compare to CRT on (Non-reverseremodeling group P<0.05, reverse remodeling group P<0.01).3. CRT interruption caused worsening of LVFT/T in two groups (Non-reveseremodeling group P<0.05, revese remodeling group P<0.01). Reveseremodeling group had significant worsening of IVD (P<0.01), but Non-reveseremodeling group had no significant change after10minutes interruption ofCRT (P>0.05).4. There were no significant changes in intraventricular dyssynchrony indexsuch as PTcs-12SD,PTrs-12SD and PTls-16SD after10minutes interruption ofCRT as compared to CRT-on mode in either Non-revese remodeling group or revese remodeling group(P>0.05).CONCLUSION1. It was showed that hemodynamic index had changed after10minutesinterruption of CRT in both reverse remodeling group and non-reverseremodeling group. This suggests that patients of both groups have obtainedhemodynamic benefits continuously during CRT.2. In patients with reverse remodeling, both atrio-ventricular asynchrony andinter-ventricular asynchrony were deteriorated after10minutes interruption ofCRT. However, interruption of CRT resulted deterioration of atrio-ventricularasynchrony only in non-reverse remodeling patients, and no significant changewas found in inter-ventricular asynchrony. This indicates that reverseremodeling patients were benefitted in both atrio-ventricular andinter-ventricular synchronism during but non-reverse remodeling patients werebenefitted from atrio-ventricular synchronism only3. There is no significant deterioration of intra-ventricular asynchrony in bothreverse remodeling group and non-reverse remodeling group after10minutesinterruption of CRT. This result may be affected by many factors. Furtherresearch is needed.