Abnormal Ultrasonic Tissue Characterization of the Myocardium in Children Receiving Doxorubicin for Cancer Therapy

Ultrasonic tissue characterization by integrated backscatter is a sensitive tool to detect myocardial changes related to specific diseases. Cardiotoxicity related to doxorubicin use is well known and remains a major concern. To determine if ultrasonic tissue characterization of the myocardium is abnormal in patients receiving doxorubicin, we studied the myocardium of pediatric patients receiving doxorubicin by a real-time integrated backscatter (IB) imaging system. Three values of IB parameters were averaged from the left ventricular posterior wall at the level of the tip of the mitral valve. In addition to standard echo parameters, we obtained the following IB parameters: peak, nadir, cyclic variation (CV), end-diastole, heart-rate corrected delay of nadir (Delay_c), and the ratio of CV over end-diastole. IB parameters were normalized as Z scores from multiple linear regression equations including echo wall thickness and functional indices from a normal control group of 72 children. We evaluated 27 patients at a median age of 11.6 years (1.6 years to 20.3 years) and median time of 1.7 m (2 days to 7.2 years) after a mean cumulative dose of doxorubicin of 188 ± 120 mg/m² for treatment of neoplasm. Mean (± SD) Z scores for IB variables were as follows: zPeak 0.15 ± 1.07, P = 0.47; zNadir 0.41 ± 1.16, P = 0.08; zCV -0.49 ± 0.95, P = 0.01; zEnd-diastole 0.17 ± 0.94, P = 0.38; zDelay_c 0.33 ± 0.80, P = 0.06, and zCV/Peak -0.59 ± 1.06, P = 0.009. This study shows that ultrasonic IB of the myocardium of children receiving doxorubicin is abnormal and is independent of the cumulative dosage of doxorubicin or the amount of time since the last dose.     

Abnormal left ventricular filling with increasing age reflects abnormal myocardial characteristics independent of ischemia or hypertrophy

Abnormal left ventricular (LV) filling may occur with increasing age despite apparently normal LV size and function, and is usually attributed to LV hypertrophy and coronary artery disease. The purpose of this study was to determine whether myocardial abnormalities could be identified in 67 such patients (36 men, mean age 57 +/- 9 years) whose LV hypertrophy and coronary artery disease were excluded by dobutamine echocardiography. All patients underwent gray scale and color tissue Doppler imaging from 3 apical views, which were stored and analyzed off line. Disturbances in structure and function were assessed by averaging the cyclic variation of integrated backscatter, strain rate, and peak systolic strain from each myocardial segment. Calibrated integrated backscatter (corrected for pericardial backscatter intensity) was measured in the septum and posterior wall from the parasternal long-axis view. Abnormal LV filling was present in 36 subjects (54%). Subjects with and without abnormal LV filling had similar LV mass, but differed in age (p <0.01), cyclic variation (p = 0.001), strain rate (p <0.01), and peak systolic strain (p <0.001). Multivariate logistic regression analysis demonstrated that age (p = 0.016) and cyclic variation (p = 0.042) were the most important determinants of abnormal LV filling in these apparently normal subjects.     

Effects of coronary artery occlusion and reperfusion on cardiac cycle-dependent variation of myocardial ultrasonic backscatter

We have recently reported a systematic variation in integrated ultrasonic backscatter throughout the cardiac cycle in canine hearts. This study was performed to determine whether the pattern of such variation is modified systematically by ischemia. Measurements of integrated ultrasonic backscatter in selected regions of normal, ischemic, and reperfused hearts were compared in view of known differences in systolic function of myocardium in each of these regions. Integrated ultrasonic backscatter (3-7 MHz) gated to the first derivative of left ventricular pressure was measured at the apex, midwall, and base in 10 dogs and at the apex before and during transient ischemia and reperfusion in four dogs. Quantitative integrated ultrasonic backscatter was referenced to a steel reflector. Cyclic variation of integrated ultrasonic backscatter was greatest at the apex [peak to trough variation 5.5 +/- 0.9 dB (mean +/- SE)] with the maximum near end diastole (-52.9 +/- 0.9 dB) and minimum near end systole (-58.4 +/- 1.0 dB). Variation at the apex (5.5 +/- 0.9 dB) and the midwall (4.3 +/- 0.8 dB) was greater than at the base (0.5 +/- 1.0 dB) (P less than 0.01 for either region compared with base). Left anterior descending coronary occlusion for 10 minutes in four of 10 dogs reduced variation at the apex to 0.4 +/- 1.5 dB (P less than 0.02 compared with preocclusion). Reperfusion for 2 hours restored apical cyclic variation to 3.9 +/- 1.7 dB, i.e., to values not significantly different from those before occlusion.(ABSTRACT TRUNCATED AT 250 WORDS)     

The dependence of myocardial ultrasonic integrated backscatter on contractile performance

We have recently shown that the cardiac cycle-dependent variation in myocardial ultrasonic integrated backscatter is blunted with regional ischemia in dogs. To determine if global and intramural regional myocardial contractile performance can be quantified by integrated backscatter, we analyzed ultrasonic responses after induction of increased and decreased contractility in five dogs. A recently developed analog data-acquisition system for measuring integrated backscatter in real time was used to sample radiofrequency signals gated from subepicardial or subendocardial regions. Base-line recordings of integrated backscatter, left ventricular pressure, left ventricular dP/dt, and wall thickness were made at 12 left ventricular sites for both intramural regions. Contractility was modified subsequently by either paired pacing or propranolol to produce significantly elevated or depressed values for maximum left ventricular dP/dt compared with baseline (1083 +/- 289 to 3001 +/- 570 mm Hg/sec; p less than .01 for all). The amplitude of the cyclic variation of integrated backscatter was 50% greater (arithmetically) in subendocardial than in subepicardial regions for all treatments (7.6 +/- 0.3 vs 6.0 +/- 0.5 dB, p less than .001). The maximum rate of change in integrated backscatter waveforms during isovolumetric contraction was faster with paired pacing and slower with propranolol than at baseline for all regions (56 +/- 6 to 74 +/- 6 to 82 +/- 5 dB/sec, p less than .005). The maximum rate of change in integrated backscatter also was greater in subendocardial than subepicardial regions (p less than .001). Thus, both regional and global differences in myocardial contractile performance are manifest quantitatively in integrated backscatter waveforms. We propose that the physiologic determinants of these differences may depend on regional and global variations in myofibril elastic characteristics.     

Quantitative ultrasonic tissue characterization with real-time integrated backscatter imaging in normal human subjects and in patients with dilated cardiomyopathy

We have shown previously that the physical properties of myocardium in dogs can be characterized with quantitative ultrasonic integrated backscatter and that interrogation of the tissue with ultrasound can delineate cardiac cycle-dependent changes in ultrasonic backscatter in normal tissue that disappear with ischemia and reappear with reperfusion if functional integrity is restorable. To determine whether this approach can be applied to man, we implemented an automatic gain compensation and continuous data acquisition system to characterize myocardium with quantitative ultrasonic backscatter and to detect cardiac cycle-dependent changes in real time. We developed a two-dimensional echocardiographic system with quantitative integrated backscatter imaging capabilities for use in human subjects that can automatically differentiate ultrasonic signals from blood as opposed to those obtained from tissue and adjust the slope of the gain compensation appropriately. Real-time images were formed from a continuous signal proportional to the logarithm of the integrated backscatter along each A-line. In our initial investigation, 15 normal volunteers (ages 17 to 40 years, heart rates 44 to 88 beats/min) and five patients with dilated cardiomyopathy (ages 22 to 52, heart rates 82 to 120 beats/min) were studied with conventional parasternal long-axis echocardiographic views. Diastolic-to-systolic variation of integrated backscatter in the interventricular septum and left ventricular posterior wall was seen in each of the normal subjects averaging 4.6 +/- 1.4 dB (SD) and 5.3 +/- 1.5 dB (n = 127 sites), respectively.(ABSTRACT TRUNCATED AT 250 WORDS)     

Myocardial ultrasonic tissue characterization for estimating histological abnormalities in hypertrophic cardiomyopathy: comparison with endomyocardial biopsy findings.

AIMS: In this study, we investigated the clinical usefulness of ultrasonic tissue characterization with integrated backscatter for the evaluation of myocardial histological abnormalities in comparison with endomyocardial biopsy findings in patients with hypertrophic cardiomyopathy. METHODS: Twenty patients with hypertrophic cardiomyopathy and 20 normal subjects were enrolled in this study. We measured two parameters for the ultrasonic tissue characterization with integrated backscatter: the magnitude of the cardiac-cycle-dependent variation in integrated backscatter signals (cdv-IB) and the mean value of integrated backscatter signals calibrated by the pericardium (cal-IB). These parameters were measured at both the interventricular septum and the left ventricular posterior wall. Histological findings of right ventricular endomyocardial biopsy specimens were analyzed by computer image analyzer. RESULTS: cdv-IB was significantly lower and cal-IB significantly higher in both the interventricular septum and the left ventricular posterior wall in patients with hypertrophic cardiomyopathy compared with normal subjects. In patients with hypertrophic cardiomyopathy, the degree of myocardial disarray, interstitial fibrosis, and nonhomogeneity of myocyte size showed positive correlations with cal-IB and negative correlations with cdv-IB. CONCLUSIONS: Ultrasonic tissue characterization with IB enables the noninvasive evaluation of myocardial histological abnormalities in patients with hypertrophic cardiomyopathy.     

Reproducibility of quantitative backscatter echocardiographic imaging in normal subjects.

Cyclic backscatter variation is useful in differentiating normal from ischemic and myopathic myocardium; however, there are few data on the reproducibility of clinical cyclic variation measurements. Therefore, a study using 2-dimensional and M-mode backscatter imaging was performed in 20 normal male subjects by 2 observers at an initial session and by 1 of the observers after 1 week. Cyclic variation on M-mode was calculated as the difference between the end-diastolic backscatter and the backscatter at the nadir. Two-dimensional determinations of backscatter were made using a single frame at end-diastole and one at end-systole. The cyclic change was the difference between backscatter measured in the end-diastolic and end-systolic frames. There were no statistically significant differences in analysis of variance among the grouped repeated measurements in either the interventricular septum or the posterior left ventricular wall. At the initial session, cyclic backscatter variation in the posterior wall using M-mode techniques was 5.9 +/- 1.8 dB (SD). The cyclic change in backscatter in the septal wall, using the 2-dimensional technique, was 4.3 +/- 2.4 dB. In the posterior wall, the cyclic change in backscatter was 5.7 +/- 1.7 dB. Pairwise observer correlations between repeated measurements ranged from -0.48 to 0.45. Thus, although there were no significant differences in group means on repeat measurements, repeated measurements in individual subjects were not reliably reproduced because of limited independent sampling of backscatter measurements at only 2 points in the heart cycle. Increased independent sampling and measurement from a backscatter waveform throughout the cardiac cycle may improve reproducibility of measurements.     

Ultrasonic tissue characterization with a real time integrated backscatter imaging system in normal and aging human hearts

Experimental studies have shown that variation in the magnitude of integrated ultrasonic backscatter during the cardiac cycle represents acoustic properties of myocardium that are affected by pathologic processes; however, there are few clinical studies using integrated backscatter. Forty subjects without cardiovascular disease (aged 22 to 71 years, mean 41) were studied with use of a new M-mode format integrated backscatter imaging system to characterize the range of cyclic variation of integrated backscatter in normal subjects. Cyclic variation in integrated backscatter was noted in both the septum and the posterior wall in all subjects. The magnitude of the cyclic variation of integrated backscatter and the interval from the onset of the QRS wave of the electrocardiogram to the minimal integrated backscatter value were measured using an area of interest of variable size for integrated backscatter sampling and a software resident in the ultrasound scanner. The magnitude of cyclic variation was larger for the posterior wall than for the septum (6.3 +/- 0.8 versus 4.9 +/- 1.3 dB, p less than 0.01). The interval to the minimal integrated backscatter value was 328 +/- 58 ms for the septum and 348 +/- 42 ms for the posterior wall (p = NS). There was a weak correlation between the magnitude of cyclic variation of integrated backscatter and subject age for the posterior wall (r = -0.47, p less than 0.01), but this was not significant for the septum (r = -0.21) (partially because of inability to exclude specular septal echoes) and septal endocardium.(ABSTRACT TRUNCATED AT 250 WORDS)     

Diagnostic value of integrated ultrasonic backscatter in congestive cardiomyopathy.

Congestive cardiomyopathy is a fatal myocardial disease which can be diagnosed by clinical findings, electrocardiography, roentgenography and echocardiography. Tissue characterization and pathology have been determined recently using histogram methods to analyze ultrasonographs. In this study ultrasonic backscatter analysis for differentiation of normal and diseased myocardium was tested. Two-dimensional echo data and radio frequency signals of long-axis views of the left ventricular posterior wall of 10 healthy children and 14 patients with congestive cardiomyopathy in systolic and diastolic phase were digitized online into the computer memory. Cyclic variation was obtained in the control group but no variation was detectable in myopathic hearts.     

Regional variations of ultrasonic integrated backscatter in normal and myopathicleft ventricles. A new multi-view approach

The purpose of the present study was to determine whether thecyclic variation of integratedbackscatter is measurable andquantifiable in all left ventricular walls and whether the informationobtained using both parasternal and apical transducer positionscan be used to identify changes in myocardial structure andcontractility. The cyclic variation of integrated backscatter was measuredfrom the parasternal long-axis, apical four-chamber and two-chamberviews in 26 patients with idiopathic dilated cardiomyopathy(meanage 58 ± 9 years; ejection fraction 29 ± 10%)and compared with information obtained from 30 aged-matchedhealthy volunteers. For each subject, the cyclic variation ofintegrated backscatter was calculated from 16 predeterminedregions-of-interest located within the myocardium of the basaland mid-segments of the left ventricle imaged from the long-axisview and also the basal mid and apical left ventricular segmentsimaged from the two apical views. The cyclic variation of integratedback-scatter was found to be present in 100% of the analysedregions-of-interest in healthy volunteers and in 87.5% of theanalysed regions-of-interest in patients with idiopathic dilatedcardiomyopathy. The mean value of cyclic variation of integratedbackscatter, averaged from all regions-of-interest in the idiopathicdilated cardiomyopathy group, was significantly reduced comparedto that in the healthy volunteers group (3.2 ± 2.5 dB[mean ± SD] vs 4 ± 2.9 dB, P<0.0001). Additionally,the healthy volunteers group demonstrated marked regional variabilityin the magnitude of cyclic variation of integrated backscatterwhich closely followed the regional changes in the contractilefunction of the normal heart. These regional differences inthe magnitude of the cyclic variation of integrated backscatterwere only partially retained in the idiopathic dilated cardiomyopathygroup, and suggest that a multi-view approach of the recordingof cyclic variation of integrated backscatter can be of valueto differentiate normal from myopathic myocardium and to quantifyregional differences in myocardial contractile performance throughoutthe left ventncular walls.     

On-Line Myocardial Tissue Characterization with a New Commercially Produced Software

Myocardial tissue characterization has been performed using various ultrasonic techniques, one of which is the cyclic variation of integrated backscatter, a method that analyzes the acoustic properties of the myocardium using backscattered radiofrequency signals to provide information about myocardial structure and function. Previous studies using prototype equipment have demonstrated a reduction in the cardiac cycle variation of integrated backscatter in various pathologic states. Recently, a commercially produced software package that allows online analysis of cyclic variation of integrated backscatter has been made available for testing by various investigators. To evaluate this new commercially produced software, we compared integrated backscatter results in three groups of patients: a control group; an end-stage cardiomyopathy group; and a heart transplant recipient group. Integrated backscatter of the septum and posterior walls in the parasternal long axis and 12, 3, 6, and 9 o'clock regions in the short axis was performed using a commercially produced program (Hewlett-Packard Sonos 1500). In the control group, the mean cyclic variation of integrated backscatter was 5.04 +/- 1.60 dB in the septum and did not significantly vary from the rest of the regions studied. In comparison, cyclic variation of integrated backscatter in every region studied was reduced in the cardiomyopathy and heart transplant groups. Intraobserver variability, interobserver variability, and reproducibility over a 3-month interval was found to be 6.5%, 5.7%, and 7.5%, respectively. These results indicate that: (1) online analysis of cardiac cyclic variation of integrated backscatter is possible utilizing commercially produced software; (2) results obtained are consistent with a low intraobserver and interobserver variability and are reproducible over time; and (3) as observed in the comparison between the transplant and control groups, this information may detect changes in cardiac structure even in the absence of changes in function. (ECHOCARDIOGRAPHY, Volume 13, May 1996)     

Ultrasonic tissue characterization with integrated backscatter. Acute myocardial ischemia, reperfusion, and stunned myocardium in patients

We have previously shown in studies of experimental animals that myocardium exhibits a cardiac cycle-dependent variation of integrated backscatter that reflects regional myocardial contractile performance and that is blunted promptly after arterial occlusion and recovers after reperfusion. To define the clinical utility of ultrasonic tissue characterization with integrated backscatter for detection of acute myocardial infarction and reperfusion, 21 patients (14 men and seven women) were studied in the cardiac care unit within the first 24 hours (mean time, 11.3 hours; range, 3.5-23.8 hours) after the onset of symptoms indicative of acute myocardial infarction with conventional two-dimensional and M-mode echocardiography and with analysis of integrated backscatter. The magnitude of cyclic variation of integrated backscatter was measured from several sites within acute infarct regions and normal regions remote from the infarct zone for each patient. The average magnitude of cyclic variation among all patients (n = 21) was 4.8 +/- 0.5 dB in normal regions compared with 0.8 +/- 0.3 dB in infarct regions (p less than 0.05) within the first 24 hours after the onset of symptoms. Among the patients who had two studies, 15 (mean, 7.1 days; range, 2-31 days for second study) underwent coronary arteriography to define vessel patency. In patients with vessels with documented patency (n = 10), the magnitude of cyclic variation in infarct regions increased over time from 1.3 +/- 0.6 to 2.5 +/- 0.5 dB from the initial to final study (p less than 0.05). Patients with occluded infarct-related arteries (n = 5) exhibited no significant recovery of cyclic variation (0.3 +/- 0.3-0.6 +/- 0.3 dB). A blinded analysis of standard two-dimensional echocardiographic images revealed no significant recovery of wall thickening in either group over the same time intervals. Ultrasonic tissue characterization promptly detects acute myocardial infarction and may delineate potential beneficial effects of coronary artery reperfusion manifest by restoration of cyclic variation of integrated backscatter in the presence of severe wall motion abnormalities.     

Detection of cardiac sarcoidosis using cardiac markers and myocardial integrated backscatter

BACKGROUNDS: It is not known whether cardiac markers and cyclic variations of integrated backscatter can be used to detect cardiac sarcoidosis. METHODS: We studied 62 patients with sarcoidosis affecting the lung, eyes, skin, or heart (27 patients with cardiac involvement and 35 patients without). The cyclic variation of integrated backscatter and wall thickening was evaluated in the left ventricular anterior septum and posterior wall. Plasma A-type natriuretic peptide (ANP) and B-type natriuretic peptide (BNP) concentrations and serum cardiac troponin T were also determined. RESULTS: Plasma natriuretic peptide concentrations were higher in the cardiac involvement group (ANP: 15.5 [interquartile range (IQR) 2.5-34.0] vs. 12.0 [10.0-16.5] pg/ml, P=0.25; BNP: 28.6 [5.9-141] vs. 10.1 [4.8-15.4] pg/ml, P=0.049). However, cardiac troponin T concentration was <0.01 ng/ml in all patients. Receiver-operator characteristic (ROC) analysis showed that both ANP and BNP could identify patients with high-degree atrioventricular block, ventricular tachyarrhythmias, or symptomatic heart failure (the areas under the ROC curve were 0.94 and 0.97, respectively). The cardiac involvement group could be distinguished from the noninvolvement group by combining cutoff values for the magnitude of integrated backscatter cyclic variation (5.5 dB) and wall thickening (30%), albeit only for the posterior wall. CONCLUSION: Both ANP and BNP are useful markers for identifying patients with sarcoidosis and cardiac complication(s). Moreover, evaluation of integrated backscatter cyclic variation combined with wall thickening may be of help in detecting cardiac involvement in the posterior wall.     

Recent experience with ultrasonic tissue characterization

The current effort in the research laboratory at Stanford University Medical Center attempts tissue characterization using the parameter of cyclic variation of integrated ultrasonic backscatter (CVIBS). This parameter is available using prototype equipment that concentrates on the relative change in ultrasonic backscatter rather than the absolute level of backscatter measured. The interobserver reproducibility is quite good. The magnitude of CVIBS is greater in the posterior wall than in the septum generally. There is a weak association of aging with the magnitude of CVIBS. Measurement of CVIBS in patients with uncomplicated pressure overload hypertrophy and those with hypertrophic cardiomyopathy shows values in the posterior wall to be similar for all groups; however, the values for the septum were significantly smaller in patients in both hypertrophy groups compared with normal subjects. Studies in human cardiac allografts for the recognition of acute rejection have been carried out using CVIBS. A decrease in the magnitude of this parameter during rejection, compared to the baseline level, was characteristically seen. Return to prerejection levels was not invariably seen. Among the different systems for ultrasonic tissue characterization, the current system using CVIBS has been successful in specific studies.     

Left ventricular function in normotensive young adults with well-controlled type 1 diabetes mellitus

The aim of this study was to determine whether early myocardial structural and functional systolic and diastolic alterations in asymptomatic and uncomplicated patients with type 1 diabetes mellitus (DM) could be detected using the new highly sensitive echocardiographic techniques of integrated backscatter and color Doppler myocardial imaging. Forty asymptomatic and uncomplicated patients with type 1 DM and 40 gender- and age-matched normal controls were studied. All patients were analyzed by conventional and new echocardiographic techniques (integrated backscatter and color Doppler myocardial imaging). Patients with DM showed reduced systolic function compared with controls, evidenced by significantly lower peak strain, strain rates, and cyclic variation indexes at the septum (p <0.0001, <0.01, and <0.001, respectively) and at the posterior wall level (p <0.0001, <0.0001, and <0.001, respectively). On receiver-operating characteristic curve analysis, systolic strain and the cyclic variation index showed the highest discriminating power for separating patients with DM and control subjects. Neither structural or ultrastructural nor diastolic functional abnormalities were detected. On univariate regression analysis, a significant inverse correlation was found for DM duration with conventional (E/A ratio) and unconventional (tissue Doppler imaging E/A ratio) indexes of diastolic function, in the absence of any correlation for systolic function. In conclusion, highly sensitive ultrasonic techniques demonstrate evidence of left ventricular systolic dysfunction in the early stage of type 1 DM, in the absence of ultrastructural and left ventricular diastolic functional abnormalities.     

Echocardiographic observation of acute myocarditis with systemic lupus erythematosus

Although myocarditis from a series of autopsies of patients with systemic lupus erythematosus was frequently observed, the incidence of clinically apparent myocardial dysfunction was low. A 30-year-old woman with systemic lupus erythematosus was examined by echocardiography. An acoustic densitometry was followed at the left ventricular posterior wall throughout the clinical course. A decrease in the magnitude of cyclic variation of integrated backscatter (IB) was observed before treatment. Following the combined treatment, steroid and cyclophosphamide, a repeated ultrasonic tissue characterization showed an increase in the magnitude of cyclic variation of IB. It is thought that ultrasonic tissue characterization may be a useful method to evaluate the impairment of contraction, and to follow up the clinical course of myocardial involvement in systemic lupus erythematosus.     

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.     

电磁脉冲照射前后大鼠心肌超声背向散射参数变化的研究

目的探讨电磁脉冲照射前、后SD大鼠心肌组织超声背向散射参数变化特点。方法40只二级雄性SD大鼠,单盲法随机分为辐照组和对照组,辐照组给以相应参数的电磁脉冲（EMP）照射,对照组给以假照射。分别于照射前、照射后24 h采集大鼠胸骨旁左室短轴射频图像,并测量感兴趣区心肌背向散射积分（IBS）值、心腔内血池IBS值,计算出标准化心肌背向散射积分（IBS%）,两时间点采集图像后每组各活杀10只大鼠,取心肌组织行透射电镜观察。结果EMP照射后大鼠心肌细胞水肿,细胞器改变。与对照组比较,辐照组照射24 h后左室前后壁IBS%均显著降低（P<0.01）;后壁IBS值减低（P<0.05）。辐照组前、后壁IBS及IBS%均显著降低。结论SD大鼠EMP照射后心肌IBS%值较照射前降低,IBS值有不同程度改变,提示EMP照射后心肌组织的病理学改变。     

Ultrasound integrated backscatter tissue characterization of remote myocardial infarction in human subjects

To determine whether quantitative ultrasound tissue characterization differentiates normal myocardial regions from segments of remote infarction, 32 consecutive patients with a diagnosis of previous myocardial infarction were evaluated. Images were obtained in real time with a modified two-dimensional ultrasound system capable of providing continuous signals in proportion to the logarithm of integrated backscatter along each A line. In 15 patients, adequate parasternal long-axis images that delineated both normal and infarct segments were obtained with standard time-gain compensation. Image data were analyzed to yield both magnitude and delay (electrocardiographic R wave to nadir normalized for the QT interval) of the cyclic variation of backscatter. Cyclic variation was present in 55 of 56 normal myocardial sites, averaging (mean +/- SEM) 3.2 +/- 0.2 dB in magnitude and exhibiting a mean normalized delay of 0.87 +/- 0.03. The magnitude of cyclic variation in infarct segments was significantly reduced to 1.1 +/- 0.2 dB (42 sites), and the delay was markedly increased to 1.47 +/- 0.12 (21 sites) (p less than 0.0001 for both). In 20 of 42 infarct sites, no cyclic variation was detectable. Thus, ultrasound tissue characterization quantitatively differentiated infarct segments from normal myocardium in patients with remote myocardial infarction.     

Ultrasonic myocardial tissue characterization in patients with hypertrophic cardiomyopathy and pressure-overloaded hypertrophy by backscattered energy temporal analysis.

This study measured integrated backscatter (IB) values in the subendocardium and subepicardium of patients with hypertrophy using the newly developed Backscattered Energy Temporal Analysis (BETA) system, and evaluated the differences of acoustic properties according to etiology. Twenty-one patients with hypertrophic cardiomyopathy (HCM), 16 with pressure-overloaded hypertrophy (POH), and 21 controls were studied. M-mode formatted IB images were obtained using BETA and the region of interest (ROI), automatically divided into epicardial and endocardial halves of the myocardium, was placed in the ventricular septum and posterior wall. Values for the cyclic variation of IB (CVIB) in the entire ROI and in each half of the ROI were obtained. CVIB significantly decreased in the ventricular septum in HCM and POH compared with normal subjects, but there were no significant differences between HCM and POH. In the posterior wall, the CVIB was less in the subendocardium than in the epicardium in POH, and was also less than in normal subjects (7.0+/-1.7 dB vs 8.6+/-1.9 dB and 8.8+/-2.1 dB, p<0.05, respectively). Separate ultrasonic tissue characterization of the subendocardium and subepicardium provides further etiological information of various heart diseases.