Evaluation of left ventricular hypertrophy in hypertensive patients with echocardiographic myocardial videodensitometry normalized by displacement

Left ventricular hypertrophy (LVH) is an important predictor of cardiovascular morbidity and mortality. To investigate the feasibility of the myocardial grayscale intensity (GI) normalized by displacement (d) to discriminate between healthy and hypertrophic myocardium in hypertensive patients, sixty hypertensive patients and sixty age and sex-matched healthy volunteers were involved in this study. Th e peak d and the maximal GI [GI(max)] and minimal GI [GI(min)] for the middle interventricular septal (IVS) and the middle posterior wall (PW) at the level of papillary muscle were obtained from the standard parasternal long axis views using tissue tracking (TT) and videodensitometric analysis, respectively. Th e GI and the cyclic variation of GI (CVGI) normalized by d were calculated. Th e results showed that the d both for IVS and PW, the amplitude of CVGI for IVS in hypertensive patients with LVH were smaller than the ones without LVH and the normal subjects. But, the CVGI/d both for IVS and PW in hypertensive patients with LVH were all greater than the ones without LVH and the normal subjects. Moreover, the parameter, CVGI/d correlated positively with left ventricular mass index (LVMI). So, the method employed in this study, videodensitometric analysis in combination with TT allow objective and accurate determination of LVH and CVGI/d is a sensitive indicator for hypertensive patients with LVH. ©  Association of Basic Medical Sciences of FBIH. All rights reserved


Introduction
Left ventricular hypertrophy (LVH) is a common adaptation mechanism of the heart in response to a chronic pressure overload of the left ventricle in hypertensive patients, which is an important predictor of cardiovascular morbidity and mortality, such as diastolic dysfunction, sudden death and so on.[-].So, it is important to regress the LVH by antihypertensive therapy [].Echocardiography is a common approach to assess the myocardial structure and function, which can provide a quantitative evaluation of LV muscle mass and the values are near to those found at necropsy [,].Recently, myocardial tissue characterization (MTC), which is based on the hypothesis that pathological changes of myocardial structure and function result in alterations of the interaction of ultrasound with tissue [], have been exploited to characterize various abnormal pathological states, in particular to ischemic [], dilated [], and hypertrophic cardiomyopathy [,].There are two methods available for the assessment of MTC now: the analysis of the radiofrequency signal and the videodensitometry [-].Th ey allow integration of the conventional echocardiographic evaluation, and obtain specifi c acoustic properties parameters that refl ect the myocardial ultrastructural texture.Th e analysis of the radiofrequency signal is considered as gold standard which direct analyze of the raw radiofrequency signal from the transducer while videodensitometric analysis exploits methods of statistical quantifi cation of the normal echocardiographic images to determine mean gray levels of a selected region of interest (ROI) [].However, they have some common defi ciencies, such as variable attenuation eff ects because of different distances between transducer and myocardial region through the chest wall [], diff erent backscattered signal from blood as normalized reference due to the diff erent resolution of the sensor and the blood components [].To date, neither is extensively diff used in clinical practice.Th e appearance of a new echocardiographic technique integrating the analysis of regional myocardial motion, deformation and tissue characterization parameters, such as velocity, displacement, strain rate, strain and grayscale intensity, maybe change this situation, which facilitate a fast, simple, accu-rate measurement of the myocardial structural and mechanical properties at the same site and in the same cardiac cycle.In this study, we took displacement as a reference, and normalized the myocardial grayscale intensity with displacement in order to obtain an intrinsic myocardial tissue characterization parameters that are less susceptible to other factors, for example, the attenuation eff ects, the diff erent reference, the diff erent site and cardiac cycle.We aimed to investigate the feasibility of the myocardial grayscale intensity normalized by displacement to discriminate between healthy and hypertrophic myocardium in patients with hypertension.

Study population
Th e study population consisted of  hypertensive patients ( males and  females, mean age: .±.years, range: - years) who did not suff er from aortic disease, diabetes, renal disease, known coronary artery disease, previous stroke, chronic obstructive pulmonary disease.Meanwhile,  age and sex-matched normal subjects ( males and  females, mean age: .±.years, range: - years) were recruited as the control group who were absence of clinical, biochemical detection, X-ray, electrocardiographic and echocardiographic evidence of various disease.The study was approved by the local human research ethics committee and free informed consent was obtained from all the study patients.Th e blood pressure that is greater than or equal to / mmHg is diagnosed as hypertension based on the guidelines of the seventh report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure (JNC-) [].
Echocardiographic study Th e echocardiographic study was performed in all the subjects lying in left lateral decubitus position with the electrocardiography recorded simultaneously.Th e echocardiographic data were acquired using a commercially available ultrasonic system (Vivid ; General Electric Medical Systems, Milwau-kee, WI, USA) and a harmonic .-.MHz variable frequency phased array transducer.Th is ultrasonic system was equipped with a Q-analyze quantitative analysis software for the analysis of displacement (d), grayscale intensity(GI) and so on at the same site and in the same cardiac cycle (Figure ).First of all, the standard parasternal long axis view was obtained.An M-mode tracing (mm/s) was recorded for the subsequent measurements: diastolic interventricular septal thickness (DIVST), diastolic posterior wall thickness (DPWT), left ventricular end-diastolic diameter (LVEDD), left ventricular end-sistolic diameter (LVESD), left atrial end-sistolic diameter (LAESD).Th e left ventricular fractional shorting (LVFS) and left ventricular ejection-fraction (LVEF) were automatically calculated by the ultrasonic system.Th e left ventricular mass (LVM) was calculated according to the definition of the American Society of Echocardiography: LVM= .×[(LVEDD+ DVST+ DPWT) -LVEDD)] [].Th e LVM indexed for body surface area (LVMI) was calculated according to the recommendations of Devereux [,].Left ventricular hypertrophy (LVH) was defined as LVMI above  g/m in men and  g/m in women.Secondly, the tissue velocity imaging (TVI) function was FIGURE 1. Regional myocardial motion, deformation parameters and grayscale intensity measured by the ultrasonic system (Vivid 7; General Electric Medical Systems), including velocity, displacement, strain rate, strain and grayscale intensity using tissue velocity imaging, tissue tracking, strain rate imaging and videodensitometric analysis.
FIGURE 2. Measurement methods of regional myocardial displacement and grayscale intensity.The image was obtained from the parasternal long-axis view of the heart in a normal subject.A. peak displacement determined by displacement curve using tissue tracking; B. maximal and minimal grayscale intensity in the cardiac cycle determined by grayscale intensity curve using videodensitometric analysis.
activated and the TVI of fi ve cardiac cycles in the standard parasternal long axis view was stored at a frame rate of  frames per second for subsequent analysis.In this process, gains were adjusted at the minimal optimal level to minimize noise, and the filter settings were kept low ( Hz).Finally, a region of interest was placed at the middle interventricular septal (IVS) and the middle posterior wall (PW) at the level of papillary muscle for measurements of displacement (d) and grayscale intensity (GI).Adequate tracking of IVS or PW was verified and, if necessary, adjusted.Th e peak displacement, the maximal GI [GI(max)] and minimal GI [GI(min)] were obtained using tissue tracking (TT) and videodensitometric analysis, respectively (Figure ), and the cyclic variation of GI (CVGI) and the CVGI normalized by displacement were calculated.All values for each parameter were obtained by averaging measurements from three successive cardiac cycles.

Reproducibility
Intraobserver variability was assessed in  patients ( in normal subjects and  hypertensive patients) by repeating the measurements on two occasions ( days apart) under the same basal conditions.To test the interobserver variability, the measurements were performed offl ine from video recordings by a second observer who was unaware of the results of the first examination.Variability was calculated as the mean percentage error, derived as the difference between the two sets of measurements.

Statistical analysis
The values were expressed as the mean ± SD.Differences between the mean values of the two groups were analyzed by the one-way analysis of variance (ANO-VA).The linear correlation analysis was used for determining the significance of correlations between variables.Differences were considered significant at p<..SPSS version  (SPSS, Chicago, IL, USA) was used for all statistical analysis.

Cinical characteristics of hypertensive patients
As shown in   of the hypertensive patients were greater than those of the normal subjects.

Discussion
To obtain the acoustic properties of myocardium which refl ect its ultrastructural texture, MTC has been widely used in scientifi c research and clinical practice since about  years ago.Now, with the advances in digital signal processing, the clinical used equipments have allowed the MTC integrate other technical parameters, such as motion and deformation mentioned above for better assessment of myocardial structure and function.Usually, MTC may provide two types of information: one is static and consists of the absolute myocardial echo intensity that refl ects the ultrastructural myocardial changes in diff erent diseases; the other is dynamic and is related to the variations of echo intensity during the cardiac cycle which is linked to the intrinsic myocardial contractility [].
For the fi rst one, there are currently no uniform standards for the discrimination of diff erent diseases because of many factors, such as the diff erent instruments used, the diff erent attenuation eff ects, the diff erent reference chosen, the diff erent site and so on.In this study, hypertensive patients with and without LVH and the normal subjects did not diff er in GI (max), GI (min) both at IVS and PW, so it is diffi cult to discriminate the hypertensive patients with or without LVH and the normal subjects according the absolute myocardial echo intensity.For the second one, it seems to be feasible to identify the characteristics of various diseases, because of its relative independence, objectivity and fewer infl uencing factors.
It is similar to Masuyama's report [] that hypertensive patients with LVH had a smaller amplitude of CVGI for IVS than did the ones without LVH and the normal subjects in this study, but such a decrease in CVGI was not observed in the posterior wall in these patients.Th ere are several possible factors for explaining this fi nding: Th e eff ect of regional differences in the systolic wall stress, the regional diff erences in the structural changes and the asymmetric septal hypertrophy.Each factor can possible lead to the phenomenon mentioned above.In other words, CVGI alone did not always qualify for distinguishing abnormal and normal pathological states as previous study [,,].content appears to be the major determinant of regional echo intensity [].The structural changes of an increase in fi brosis of the myocardium in hypertensive patients with LVH may result in a decrease in CVGI and an insuffi cient contractility.A smaller d for IVS and PW in hypertensive patients with LVH was an illustration for the attenuated myocardial contractility.Although the magnitude of CVGI also decreased at IVS (not seen at PW) in hypertensive patients in this study, the value of CVGI/d seems to be no infl uenced, so CVGI/d is a valuable parameter for the assessment of left ventricular hypertrophy in hypertensive patients.

Conclusion
Our study demonstrate that videodensitometric analysis in combination with TT allow objective and accurate determination of LVH by providing more precise integration of information about myocardial ultrastructure and intrinsic contractility and CVGI/d is a sensitive indicator for hypertensive patients with LVH.

TABLE 2 .
Comparison of the displacement and grayscale intensity between hypertensive patients and normal subjects Legend: N, normal subjects; HP-LVH, hypertensive patients without left ventricular hypertrophy; HP+LVH, hypertensive patients with left ventricular hypertrophy; IVS, interventricular septum; PW, posterior wall; d, peak displacement; GI (max), the maximal grayscale intensity in the cardiac cycle; GI (min), the minimal grayscale intensity in the cardiac cycle; CVGI, the cyclic variation of grayscale intensity.

Table  ,
Table displays that hypertensive patients without LVH and the normal subjects did not diff er in d, GI (max), GI (min), CVGI and CVGI/d both at IVS and PW.Th e hypertensive patients with LVH had a smaller d for IVS and PW and a smaller amplitude of CVGI for IVS than did the ones without LVH and the normal subjects while the CVGI/d both for IVS and PW in hypertensive patients with LVH were all greater than the ones without LVH and the normal subjects.only CVGI/d for IVS and PW correlated positively with LVMI while there were no signifi cant correlation between CVGI/d and DIVST, DPWT, LVM and LAESD.