Ultrasonic myocardial texture versus Doppler analysis in hypertensive heart: a preliminary study

Novel methods for assessment of right heart structure and function in pulmonary hypertension

Long-term increases in pulmonary vascular resistance and pulmonary arterial pressure resulting from structural alterations and abnormal vasoreactivity of the pulmonary vasculature may lead to right ventricular (RV) remodeling. Conventional methods of assessment of RV structure and function do not provide sensitive markers of RV remodeling for prognostic information. Advances in cardiac imaging have provided the capability to obtain quantitative information on the RV structure and function. This article reviews the clinical conditions that result in PH and discusses the novel and emerging methods for the assessment of right heart structure and function in PH in infants and children.

Texture analysis in digitally-acquired echocardiographic images: the effect of JPEG compression and video storage

The analysis of texture in video-stored echocardiographic images is an established method to characterize myocardial pathologies. We investigated whether or not texture parameters calculated from video-stored images and those derived from the joint photographic expert group (JPEG) format compressed data are equivalent to those calculated from uncompressed digital images. Texture parameters were calculated using uncompressed digital data, images stored on videotape, and three forms of compressed digital data (baseline JPEG, JPEG 2000 and lossless JPEG 2000). Video storage heavily affected most texture parameters. Although first-order texture parameters derived from JPEG-compressed images were generally equivalent to those derived from the uncompressed data, several second-order parameters differed significantly. We conclude that texture of video-stored images is not comparable to that of digitally-stored images and that JPEG compression changes important second-order texture parameters. This observation should be taken into account when analyzing texture of modern image data (uncompressed or compressed) and comparing the results with earlier studies utilizing video-stored data.

Ultrasonic tissue characterization of the mouse myocardium: Successful in vivo cyclic variation measurements

BACKGROUND

Measurements of the systematic variation of backscattered ultrasonic energy from myocardium during the heart cycle (cyclic variation) have been successfully used to characterize a wide spectrum of cardiac pathologies in large animal models and human subjects. The purpose of this study was to evaluate the feasibility of extending cyclic variation measurements to the study of genetically manipulated mouse models of cardiac diseases as a method for developing further insights into the disease-altered properties of the myocardium and its characterization with ultrasound.

METHODS

Parasternal long-axis images of the heart were obtained in 9 wild-type mice under light anesthesia using a commercial imaging system with a 15-MHz nominal center frequency linear array. Images of a tissue-mimicking phantom and the mouse hearts were obtained for a series of specific receiver gains for each of a series of specific dynamic range settings. Analyses of these data formed the basis for gray-scale image calibration. Cyclic variation measurements were obtained by determining the average gray-scale value for a region of interest placed in the midmyocardium of the posterior wall for each frame acquired during 4 cardiac cycles and converting these mean gray-scale values to backscatter values expressed in decibels using the determined calibration. Results are expressed in terms of the magnitude and time delay of cyclic variation. To evaluate repeatability of these measurements the same group of mice underwent the identical imaging protocol 2 weeks after the first study.

RESULTS

The mean magnitude of cyclic variation was found to be 4.6 +/- 0.2 dB with a corresponding normalized time delay of 1.02 +/- 0.03 for data averaged over all dynamic range settings. There was no significant difference among results obtained with each of the dynamic range settings. A comparison of these results with those from data acquired 2 weeks after the initial study showed no significant difference.

CONCLUSION

This study represents the first reported measurement of cyclic variation in mice and demonstrates that reliable cyclic variation measurements can be obtained among individual animals and over different time points and, hence, forms the basis for subsequent investigations addressing specific cardiac pathologies and effects arising from myocardial anisotropy.

Cyclic variation of the myocardial integrated backscatter signal in hypertensive cardiopathy: a preliminary study

BACKGROUND

Ultrasound tissue characterization studies realized through integrated backscatter analysis with end-diastolic sampling in hypertensive cardiopathy have demonstrated that abnormalities in the left ventricular myocardial ultrasonic texture are present in extreme forms of left ventricular hypertrophy (LVH). Such abnormalities are not evident in the athlete's heart. The aim of the present study was to analyze the ultrasonic backscatter myocardial indexes both as peak end-diastolic signal intensity and as cardiac-cyclic variation in two models of LVH: hypertensive cardiopathy and athlete's heart.

METHODS

Three groups of 10 subjects each, all men of mean age (31.6+/-3.5 years), and of comparable weight and height, were analyzed. Group A comprised 10 cyclists of good professional level, while hypertensive patients were grouped in Group H. Both groups presented a comparable left ventricular mass (LVM). Group C included 10 healthy subjects acting as controls. The men with hypertension were selected on the basis of the results of ambulatory monitoring of the blood pressure according to ISH-World Health Organization guidelines (International Society of Hypertension). A 2D-color Doppler echocardiography with a digital echograph Sonos 5500 (Agilent Technologies, Andover, Massachusetts, USA), was carried out on all the subjects in the study for conventional analysis of the LVM and function. The ultrasonic myocardial integrated backscatter signal (IBS) was analyzed with an 'acoustic densitometry' module implemented on a AT echograph. The signal was also sampled with a region of interest (ROI) placed at interventricular septum and at posterior left ventricular wall level. The systo-diastolic variation of the backscatter was also considered, as cyclic variation index (CVIibs).

RESULTS

According to the inclusion criteria, the LVM was comparable in groups A and H, but it was significantly higher than group C (left ventricular mass (body surface) (LVMbs)=154.5+/-18.7 (A), 146.8+/-25.5 (H), 101.4+/-12.4 (C), p < 0.001). The end-diastolic IBS did not show significant statistical differences among the three groups. The CVI(IBS) both at septum (30.5+/-5.3 (A), 13.2+/-13.1 (H), 27.2+/-7.3(C), p < 0.002) and posterior wall level (43.7+/-9.1 (A), 16.5+/-12.1 (H), 40.7+/-9.1 (C), p < 0.001) though, was significantly lower in the hypertensive patients than in both the athletes and the control group, where the results were comparable.

CONCLUSION

A significant alteration of the myocardial CVIibs (both for septum and posterior wall) was found in the hypertensive model. This was probably the expression of an alteration in the intramural myocardial function.

Microalbuminuria, pulse pressure, left ventricular hypertrophy, and myocardial ultrasonic tissue characterization in essential hypertension

Microalbuminuria (UAE) may be considered a marker of systemic vascular dysfunction, while pulse pressure (PP) is an indicator of the stiffness of vascular conduits. Both these parameters, together with left ventricular hypertrophy (LVH), are linked to cardiovascular morbidity in hypertensive patients. The aim of this study was the analysis of the possible relationships among UAE, PP, and LVH with ultrasonic myocardial textural parameters, which are altered in hypertensives patients. A group of male (n = 70) essential hypertensive patients (mean age: 58 +/- 7 yr) was analyzed with a group of age-comparable normotensive healthy subjects as controls (n = 32). Ambulatory blood pressure monitoring (ABPM) was performed with an oscillometric monitor; UAE was measured by nephelometry. A conventional 2D-Doppler echocardiography (to analyze left ventricular mass: LVM) and a quantitative analysis of the echocardiographic digitized imaging with the use of a calibrated digitization system (to calculate the septum and the posterior wall textural parameters) were performed on all subjects. The myocardial mean gray level was calculated to derive the cyclic variation index (CVI). The CVI was significantly lower in hypertensives both for the septum (- 16.3 +/- 22.8 vs 34.7 +/- 15.3%; p < 0.001) and for the posterior wall (- 15.2 +/- 23.6 vs 38.2 +/- 15.4%; p < 0.001). A significant negative correlation was found between logUAE and the CVI of the septum (r = -0.42; p < 0.001), between the PP and the CVI of the septum (r = -0.40; p < 0.002) and between the CVI and the LVM (r = -0.38; p < 0.001). Multiple regression analysis having as dependent variable the CVI at septum level showed as significantly related independent variables: PP (p < 0.01), logUAE (p < 0.001), and LVM (p < 0.05) (multiple R: 0.76, squared multiple R: 0.57; p < 0.001). It was found that LVM, logUAE, and PP are all correlated with textural parameters, and the CVI can be considered a sensitive parameter in the identification of an abnormal myocardial texture in hypertension. A high level of arterial stiffness and the presence of vascular dysfunction in essential hypertension could participate in the determination of myocardial alterations and permit the identification of patients with the worst prognosis in terms of morbidity or mortality due to cardiovascular events.

The potential prognostic value of ultrasonic characterization (videodensitometry) of myocardial tissue in essential arterial hypertension

BACKGROUND

Left ventricular hypertrophy (LVH) and the geometric shape of the left ventricle are well-established important risk factors for cardiovascular morbidity and mortality in the hypertensive population. Videodensitometry is an alternate echocardiographic approach to the study of myocardial structural and functional alterations in essential hypertension.

OBJECTIVES

To analyze the behavior of the ultrasonic videodensitometric parameter for various subgroups of a hypertensive population; first according to the severity of LVH (group A, without LVH; group B, with mild-to-moderate LVH; and group C, with severe LVH) and second according to geometric adaptation of left ventricle to pressure-volume overload of essential hypertension (group NG, normal geometry; group CR, concentric remodeling; group CH, concentric hypertrophy; and group EH, eccentric hypertrophy).

METHODS

For 70 male, essential hypertensive patients and 32 normotensive healthy subjects matched for age (58 +/- 7 years) and sex as controls (group N) we performed ambulatory blood pressure measurements for the evaluation of 24 h mean systolic and diastolic blood pressures, conventional two-dimensional Doppler echocardiography to evaluate left ventricular performance and left ventricular mass index, and digitization of left ventricular parasternal long-axis echocardiographic images. For regions of interest selected within the septum and the posterior wall, the mean gray levels were calculated at end-systole and end-diastole. The resulting values were used to estimate the percentage cyclic variation index (CVI).

RESULTS

The results according to left ventricular mass index were CVI for septum group N 34.7 + 16.3%; group A - 0.18 +/- 16%, group B - 13 +/- 19%, and group C - 22 +/- 12% (P < 0.001); and CVI of posterior wall, group N 38.2 +/- 15.4%, group A -0.75 +/- 16%, group B -16 +/- 16% and group C -16 +/- 13% (P< 0.001). According to left ventricular geometry CVI for septum were group NG 0.6 +/- 24%, group CR 1.9 +/- 17%; group CH - 25.4 +/- 18%, and group EH -17.1 +/- 20% (P < 0.01). CVI of posterior wall were group NH -5.8 + 24%, group CR 6.4 +/- 23%, group CH -29 +/- 20%, group EH -20 +/- 21 (P < 0.01).

CONCLUSIONS

Our results demonstrate that subjects with high left ventricular masses and those with concentric hypertrophy, which have the worst prognostic impacts, have the most significant changes in CVI. Furthermore, videodensitometric findings are quite different even among the subgroups with mild-to-moderate left ventricular hypertrophy and eccentric hypertrophy. Therefore this videodensitometric approach could provide some useful information for better definition of cardiovascular risk in hypertension.