Evalution Of Left Ventricular Function In Hypertrophic Cardiomyopathy And Hypertensive Left Ventricular Hypertrophy By Velocity Vector Imaging

Background: Although both hypertrophic cardiomyopathy (HCM) and hypertensive left ventricular hypertrophy (H-LVH) are characterized with myocardial hypertrophy and impairment of myocardial function, the etiopathogenisis, history, treatment and prognosis of these two diseases are totally different. And the monitoring of myocardial function is critical determinant for clinical therapeutic decision making. Conventional two dimension echocardiography can only reflect the global heart function indirectly, and can not assess regional myocardial function directly. But in patients with H-LVH or HCM, the impairment of regional myocardial function occurs earlier than that of global heart function: Although Doppler tissue imaging and strain rate imaging can quantitatively evaluate myocardial movement in early stage, they can only be used in long-axis myocardial function evaluation due to their inherent angle dependency. But the movements of myocardium includ three directional movements (longitudinal, radial and circumferential) and twist.Velocity vector imaging (VVI) uses a tracking algorithm to estimate the myocardial movement velocity of a set of points on the contour which are traced on the two dimension echocardiographic images sequentially. This sophisticated tracking technology is not a simple "speckle tracking", but instead uses specific reference points including the motions of mitral annulus, tissue/cavity border, tissue near the border of endocardium and periodicity of the heart motion over the R-R intervals to track the movement of myocardium exactly. The velocity is displayed as a vector overlaid onto the two dimension echocardiographic image. The length of the vector indicates the magnitude of the tissue velocity, and the direction of the vector indicates the direction toward which the tissue move. The evaluation of the motion velocity and direction at a point is determined by comparing the displacement of the image data about such a point in two consecutive frames by computer automatically (velocity = displacement / time interval). Therefore VVI is an angle independent approach that allows measurement of myocardial movement velocity and deformation in both long-axis and short-axis views of the LV.Objective: Regional myocardial function in the long-axis and short-axis of the LV in patients with H-LVH or HCM are measured quantitatively by VVI. In order to investigate the clinical value of VVI in evaluation of regional myocardial contraction and relaxation function in H-LVH and HCM patients, and to find out the difference of regional myocardial function between H-LVH and HCM patients.Materials and Methods: One hundred patients and sixty healthy volunteers who were referred to our Hospital between March 2006 and January 2008 underwent echocardiography were enrolled into this study. All the subjects were divided into three groups: (1) H-LVH group (60 cases, 44 men, 16 women), mean age 49±9 years (range from 35 to 71). The diagnosis of H-LVH was based on conventional echocardiographic demonstration of a concentric hypertrophic LV in the absence of other cardiac or systemic diseases with the exception of long-term (5～15 years) hypertension history. (2) HCM group (40 cases, 27 men, 13 women), mean age 45±10 years (range from 24 to 68). The diagnosis of HCM was based on conventional echocardiographic demonstration of a symmetrical hypertrophic LV in the absence of other cardiac or systemic diseases that might lead to LVH. All studied patients exhibited normal sinus rhythm, no evidence of heart failure. Patients with diabetes mellitus, nephrosis were also excluded. (3) Control group, 60 healthy volunteers (42 men, 18 women, mean age 48±11 years, range from 22 to 73) with normal ECGs and conventional echocardiograms were served as normal control. Ultrasound machine (Sequoia 512, 2.75～4.25MHz transducer) was used to acquire two-dimensional dynamic images of apical four-chamber view, parasternal long-axis view and short-axis view of mitralis level. Images of one or two cardiac cycle loops were recorded at the beginning of end expiration, and were stored for offline analysis.Freezed images at end-diastole in VVI process. By a point-click approach, we placed some points along the LV endocardium clockwisely on a frame. The system could track the border of endocardium to obtain the velocity vector of each point automatically. Put the sample point at different segment, the velocity curve, strain curve and strain rate curve could be generated automatically, then the peak velocity (PV), peak strain (PS), and peal strain rate (PSR) of each sample point were measured. There were totally sixteen segments were analyzed in this study, including basal, middle, apical segment of postseptal wall and lateral wall at apical four-chamber view; basal, middle , apical segment of anteriorseptal wall and posterior wall at parasternal long-axis view; mitralis level segment of anteriorseptal wall, anterior wall, lateral wall, posterior wall, inferior wall and postseptal wall at short-axis view.Results: There were no significant difference of age, gender and left ventricular ejection fraction among three groups. The E/A ratio of H-LVH and HCM groups were significant lower than that of control group (P<0.05), but there was no significant difference between H-LVH and HCM.Whatever in long-axis or short-axis, the systolic PV, PS, and PSR in HCM and H-LVH were significant lower than those of the normal control (P<0.05), and the PV, PS, PSR of the postseptal, anteriorseptal and posterior wall in HCM were significant lower than those in H-LVH (P<0.05). The diastolic PV, PS, PSR of each segments in H-LVH and HCM were significant lower than those of normal contra (P<0.05)l. And the PV, PS, PSR of each segments in HCM were significant lower than those of H-LVH (P<0.05).Comparing corresponding segments of different walls in the same group, there was no significant difference of PV, PS and PSR in H-LVH(P >0.05). But in HCM, the PV, PS and PSR of the septal and posterior wall was significant lower than those of other walls (P<0.05).Conclusions: Compare to normal control group, the regional myocardial function of H-LVH and HCM patients decreased significantly, and the impairment was more serious in HCM than in H-LVH. VVI could quantitatively assess the change of myocardial function in both long-axis and short-axis without angle limited. VVI can be a new noninvasive modality for evaluation of myocardial function in clinical practice.