Tissue Synchronization Imaging Assesses Ventricular Systolic Asynchrony In Bundle Branch Block And Myocardial Infarction

Objective: Cardiac resynchronization therapy (CRT) has been proposed as an alternative treatment in patients with electrocardiogram delay, sever, drug-refractory heart failure. Currently, patients are selected mainly on electrocardiogram criteria. However, about 20% ~30% patients do not respond to CRT. These considerations suggest that the surface electrocardiogram may not be the optimal marker to select candidates for CRT. Tissue synchronization imaging (TSI), in new echocardiographic approaches, is superimposed on the routine two-dimensional echocardiographic images to provide visual mechanical information on the anatomical regions. TSI is a signal-processing algorithm of the tissue Doppler data to automatically detect peak positive velocity and then colorcode the time to peak velocities in green for normal timing, yellow-orange for moderate delay, and red for severe delay in time to peak of longitudinal velocity. However, TSI assessment during CRT may not be a routine procedure before standardized selection criteria have been defined. Further studies are needed to fully appreciate the clinical importance of these issues. There are three parts of the study. The first part is to assess synchrony in bundle branch block by TSI and tissue tracking (TT). The aim of it was to assess whether TSI is useful to predict synchronicity. The second part is to explore the systolic asynchrony in myocardial infarction (MI) dogs with hepatocyte growth factor (HGF) therapy by TSI, and the aim of it was to assess the synchronicity in MI dogs and the improvement of synchronicity after therapy. The third part is to assess leftventricular systolic asynchrony after myocardial infarction by TSI, and the aim was to explore the systolic asynchrony in anterior or inferior MI patients, the influence of infarction region to LV systolic asynchrony and heart function.Materials and methods:1. To observe synchronicity in 7 left bundle branch block patients (LBBB), 15 right bundle branch block patients (RBBB) and 21 normal subjects by TSI and TT. Six ventricular regional myocardia were assessed, which included basal and middle of right ventricular wall, interventricular septum and laterior. The time of systolic onset (Tonset) and the time of systolic peak (Tpeak) were measured, and then computed the difference and standard deviation of 6 segments.2. Eleven dogs were randomly divided into two groups: HGF group (n=6) and control group (n=5). Dog model of ligated proximal left anterior descending of coronary artery (LAD) was used. Within one hour after ligated, the HGF group was administered with HGF lml around ischemic areas, and the control group was administered with 0.9% of sodium chloride solution lml. After LAD ligated 4 weeks, 8 weeks, left ventricular end-systolic volume (LVESV) and left ventricular ejection fraction (LVEF) were determined by 2D echocardiography. TSI studies were performed in each group. The regional times to systolic velocity peak (Ts) were measured in 12 segments. Standard deviations of Ts (Ts-SD) and difference of Ts (Ts max-min) of all 12 segments were computed.3. Assess left ventricular systolic asynchrony after myocardial infarction by TSI: TSI was performed in 58 MI patients (30 anterior MI, 28 inferior MI) and 60 healthy volunteers. Ts were measured, Ts-SD and Ts max-min were computed.Results:1. There was no significant difference between RBBB and control group in time parameters of lateral and septum. There was significant difference between RBBB and control group in right ventricular. Standard deviation and difference inLBBB group were significant difference to RBBB and control group. Tonset and Tpeak were prolonged in LBBB group compared with normals (P<0.05).2. Compared with control group, LVESV was significantly decreased in HGF group, and it tended to decrease more with time prolonged. LVEF was significantly increased in HGF group as compared with controls, and it tended to improve more with time prolonged. Ts in the middle interventriclar septum in HGF was significant shorter than control groups (4 week 175.2±105.5ms vs 240.5±74.4ms;8 week 160.4±65.2ms vs 271.9±63.5ms). Ts-SD was prolonged in the controls compared with HGF group (8 week 75.1±20.2ms vs 38.7±6.4ms, P<0.05). When consider group factor and time factor, Ts max-min between controls and HGF group was difference.3. Ts-SD and Ts max-min were shortest in control group. The Ts-SD was significantly prolonged in the anterior MI group and inferior MI group when compared with controls (78.4±30ms, 79±22.2 ms, 21.3±7.9 ms, PO.05). Ts max-min was significantly prolonged in anterior MI group and inferior MI group when compared with controls (226.7±80.4 ms, 232.8±70.3 ms, 65.3 ±22 ms, p<0.05). Ts-SD in heart failure (HF) MI group was longer than non-HF MI group (88.3±7.7 vs 74.1±3.3, P=0.053). In MI group, Ts-SD and Ts max-min did not correlate with the duration of QRS complexes. Ts delayed in anterior segments and interventricular septum in anterior MI group (P<0.05). Ts delayed in inferior and posterior segments in inferior MI group (PO.05). Time to peak of lateral was prolonged in the MI group compared with controls (f<0.05).Conclusion:1. 2D and Q-analysis of TSI are useful to predict synchronicity, to evaluate regional wall delay and detect the latest region in systole.2. TSI is useful to assess the synchronicity in MI dogs, and after therapy systolic synchronicity tends to shorten with increasing LVESV and improving LVEF.3. Ts-SD in HF MI group is longer than non-HF MI group. Ts-SD tends to prolong with worsening heart function.4. Myocardial infarction has a significant impact on LV synchronicity. The LV systolic delay is mainly determined by the infarction regional.