Study Of Left Ventricular Asynchrony In Patients With Congestive Heart Failure By Quantitative Tissue Velocity Imaging

Background and objective Congestive heart failure (CHF) is the end-stage of various heart diseases. Because of the high morbidity and mortality, treatment of CHF to increase the survival rate remains one of the the major challenges in health care practice. Recently, with the further recognition of pathophysiological mechanism of CHF , the close relation between function of left ventricle (LV) and myocardial asynchrony has been reported. Based on this theory cardiac resynchronization therapy (CRT) was originated and the clinical benefits of CRT have been demonstrated in various studies. Corrected myocardial asynchrony, reduced mitral regurgitation, reversed remodeling, increased filling time of LV and output of heart probably play a main role in CRT . As a result, evaluation of myocardial asynchrony becomes more and more important. To assess myocardial asynchrony, the traditional methods of echocardiography are M-mode, color kinesis and so on. Because of a few sample sites and being dependent on two dimensional imaging, their use is limited. At present time, Doppler tissue imaging (DTI) provides us a simple and valuable method for assessing the myocardial asynchrony. The quantitative tissue velocity imaging (QTVI) is a new DTI method and can analyze eight segments of myocardium simultaneously along long-axis of heart, having significant advantages in assessing myocardial asynchrony.However, there is no similar study domestically yet.The purposes of this study were: (1) To evaluate the LV synchrony in normal subjects and the factors related to the time of electromechanical systole and diastole of myocardium. (2) To evaluate the LV asynchrony in patients with CHF and it's relation with function of LV, QRS duration, mitral regurgitation and remodeling. Materials and methods Forty normal subjects(20 men, 20 women; age 45 ±16 years) and forty patients with CHF(22 men, 18 women; age 47±18 years) who fulfilled the Framingham heart failure diagnostic criteria (NYHN class III-IV) were included. In CHF group, the study population consisted of 11 patients with ischemic heart diseases (excluded patients with myocardial infarction), 9 patients with hypertensive heart disease, 15 patients with dilated cardiomyopathy and 5 patients with perinatal cardiomyopathy. Echocardiography was performed including M-mode, color Doppler, pulse Doppler, DTI and QTVI. The flowing segments were investigated by QTVI: anteroseptal, posteroseptal, anterior, lateral, inferior and posterior segments at basal, middle and apical levels. The time from onset of QRS complexes to peak velocity during systole and diastole (Ts and Te) were measured. Ts and Te represent the time of electromechanical systole and diastole of myocardium respectively. The maximal difference in Ts and Te within the same wall (Intra- A Ts and Intra- A Te ) , the same segment (Inter-A Ts and Inter-A Te) and all 18 segments (Max- A Ts and Max- A Te ) of LV were calculated. Parameters of LV function and the other measured indexes included: ? Ejective fraction of LV (LVEF, along apical four-chamber view by Simpson's equation); ? Tei index ( Tei index=(a-b)/b, a: the time from the end of mitral filling flow velocity to the beginning of next of it , b: the time of aortic ejection ); (3) The mean of systolic peak velocities and early diastolic peak velocities of mitral annulus of six walls (Mean Vs and Mean Ve, along apical long-axis view, four-chamber view, two-chamber view by DTI ); ? End diastolic diameter of LV (LVEDD, along LV long-axis view by M-mode) ; (5) Spherical index of LV (LVSI, the ratio short-diameter to long-diameter, along apical four-chamber view by two-dimensional echocardiography); (6) The ratio of area of mitral regurgitation to area of left atrium (MRA/LAA, along apical four-chamber view by color echocardiography); (7) QRS duration (by electrocardiogram).Results1. Ts and Te within the same segment and the same wall of LV had no significant difference in normal subjects (P>0.05). Heart rate was correlated negatively with Te (r=-0.796, P<0.01) and not correlated with Ts. Both Ts and Te were not significantly correlated with age, systolic blood pressure , diastolic blood pressure and body surface area .2. Inter- A Ts, Inter- A Te, Intra- A Ts, Intra- A Te, Max- A Ts and Max- A Te in CHF group were significantly prolonged, compared with these parameters of the control group(P<0.05).3. In CHF group, Max- A Ts was correlated with LVEF, Mean Vs and LVEDD( R=0.644, P<0.01; R=0.727, P<0.01; R=0.766, P<0.05 ; respectively), but it was not correlated with QRS duration, LVSI and Tei index. In diastole , Max-A Te was correlated with Mean Ve and MRA/LAA (R=0.643, F<0.01; R=0.739,P<0.01; respectively) and it was not correlated with QRS duration, Tei index, LVEDD and LVSI. Conclusions1. In normal persons, the time of electromechanical systole and diastole of myocardium within different segments of LV is same. The result illustrates that systole and diastole movement is highly synchronized in LV. The time of electromechanical diastole of myocardium is influenced by HR, so HR should be taken into account in similar study.2. Asynchrony exists within the same wall and the same segment of LV in patients with CHF.3. The parameters of asynchrony of myocardium movement have close relations withfunction of LV, mitral regurgitation and remodeling of LV.4. QTVI is a rapid, noninvasive, quantitative method to detect systolic and diastolic asynchrony; it's very useful to evaluate the clinical treatment of CHF and the relative parameters can be utilized to assess the curative effects and prognosis of CRT.