Assessment Of Left Ventricle Twist In Apical Hypertrophic Cardiomyopathy Using Velocity Vector Imaging

Objective: To assess left ventricular twist (LVtwist) function in the patients with apical hypertrophic cardiomyopathy (AHCM) using velocity vector imaging(VVI).Methods:1 Object: The cardiomyopathy group consisted of 15 patients(10 males, age 28–62years, mean 46.20±13.47 years) who had been previously diagnosed with apical hypertrophy cardiomyopathy (a ratio of apical to left ventricular posterior wall≥1.3) in our hospital. The diagnosis of apical hypertrophy cardiomyopathy (AHCM) was based on medical history, clinical signs and symptoms, and noninvasive procedures (echocardiography, Doppler, electrocardiogram [ECG]) without hypertension, coronary heart disease and aortic stenosis. These diseases may lead to ventricular wall hypertrophy. The control group consisted of 15 normal subjects (10males, age 27–59 years mean 48.87±11.14 years) who had no organic disease based on physical examination, electrocardiogram and echocardiography, and had no risk factors for hypertension or coronary heart disease.2 Echocardiography: Short-axis and long-axis echocardiographic recordings were obtained in the supine left lateral position with ultrasound equipment (Sequoia 512, Siemens, 4V1C probe, 2.25–4.25MHz, with Syngo US workplace). The short-axis plane included: the basal level (mitral valve level), the mid level (papillary muscle level), and the apical level (LV apex). The long-axis plane consisted of apical four-chamber, two-chamber and three-chamber views. To obtain the best frame rate, the ultrasound window was narrowed so that it only included the chamber heart structures to be observed, and processing settings were selected that enhanced temporal resolution. The images were obtained by three-beat cycle. The images were stored while the subjects held their breath and were analyzed offline. Left ventricular diastolic longitudinal length was measured at apical four-chamber view. Left ventricular ejection fraction(EF), end-diastolic volume(EDV), end-systolic volume(ESV), and stroke volume(SV) were assessed by Simpson's biplane method. And isovolumic relaxation time(IVRT) were obtained by pulsed-wave Doppler.3 VVI data analysis: Signal processing software(Syngo US workstation) was used to analyze the stored echocardiographic images. The initial step was the selection of a reference plane from the short-axis view. Then, a manual trace of the endocardial border was performed from a still frame image at an intermediate time in diastole, and this outline was automatically tracked throughout the cardiac cycle. We selected six separate locations on the endocardium for automatic tracking: anterior interventricular septum, anterior wall, lateral wall, posterior wall, inferior wall, and posterior interventricular septum. Tracings were accepted only when the VVI visual display mode identified myocardial borders accurately throughout the cardiac cycle. The following parameters were measured using VVI: peak rotational angle(ProtA), peak rotation rate(ProtR), circumferential strain(CS) and circumferential strain rate(CSR) in systole; peak untwisting velocity(Pun-twV) and untwisting rate (unTwR) in diastole; and peak untwisting angle at the end of isovolumic relaxation. We also obtained a rotation angle map and strain map. Clockwise rotation was defined as a negative value and counterclockwise rotation was a positive value. LVtwist(?) was defined as the net difference between the apical and basal angles of rotation. LVtor was calculated as LVtwist divided by ventricular diastolic longitudinal length between the LV apex and the mitral valve plane: LVtor(?/mm) = LVtwist/LV diastolic longitudinal length. The unTwR was calculated from the following formula: (LVtwist-S?LVtwist-IVRT)/LVtwist-S×100%/IVRT, where LVtwist-S was referenced to the maximal LVtwist at the end of systole, and LVtwist-IVRT was defined as maximal LVtwist at the end of isovolumic relaxation. Our study analyzed parameters from the LV endocardial and epicardial surface.Results:1 Table I comparison left ventricular function in the two groups. Left ventricular end-diastolic volume(EDV), end-systolic volume(ESV), and stroke volume(SV) were decreased in the AHCM group; LVEF in the AHCM group was higher, but there was no statistics difference between the two groups .2 Table II comparison of cardiac twist parameters. LVtwist, LVtor and rotation velocity in the AHCM group were higher than the control group, LVtwist and LVtor of subendocardial myocardium differed significantly from the parameters in the control group(P<0.01). The unTwR decreased in the AHCM group(P<0.01).3 Table III comparison part of left ventricular twist parameters. Compared with the control group, the rotation degree, rotation velocity were increased as peak untwisting velocity reduced at the basal level in AHCM. But there was no significant differences(P>0.05). In the AHCM group, the apical endocardial rotation degree was significantly higher than the control group, epicardial rotation velocity and untwisting velocity were significantly lower than the control group(P<0.05).4 Table IV comparison circumferential strain and circumferential strain rate parameters. Circumferential strain were lower in the AHCM group except of endocardium at the base level. The CS of middle and apical epicardium was significantly reduced(P<0.05). There was no significant difference in endocardial strain rate, the circumferential strain rate of middle and apical epicardium reduced significantly(P<0.05).Conclusion:1 In the AHCM group the pattern of LVtwist was normal(apex counterclockwise, base clockwise). Left ventricular end-diastolic volume (EDV), end-systolic volume(ESV), and stroke volume(SV) were decreased (P<0.01). In subendocardial myocardium LVtwist and LVtor were increased as the unTwR was reduced in the AHCM group(P<0.05). Rotation velocity of apical subepicardial myocardium increased, the peak untwisting velocity reduced(P<0.05).2 The ability of Circumferential direction deformation decreased in the apical regional myocardium, especially in subepicardial myocardium.3 VVI technology could easily and accurately evaluate the torsion of ventricle in apical hypertrophic cardiomyopathy patients. AHCM patients were found twist incompatibility between subendocardial and subepicardial myocardium.