Relation between regional echo intensity and myocardial connective tissue in chronic left ventricular disease

Evaluation of right ventricular diastolic function, systolic function, and circulating galectin-3 concentrations in dogs with pulmonary stenosis

BACKGROUND

Cardiovascular diseases with increased right ventricular (RV) afterload induce RV diastolic and systolic dysfunction, and myocardial fibrosis in humans. Studies in dogs with pulmonary stenosis (PS) evaluating RV diastolic function and markers of myocardial fibrosis are lacking.

HYPOTHESIS/OBJECTIVES

Dogs with PS have echocardiographic evidence of RV diastolic and systolic dysfunction and increased serum concentrations of galectin-3 (Gal-3), a surrogate biomarker for myocardial fibrosis.

ANIMALS

Forty client-owned dogs (10 controls, 30 with PS).

METHODS

Prospective study. All dogs had systemic blood pressure measurement, serum biochemical analysis, echocardiography, and measurement of serum Gal-3 concentration performed.

RESULTS

Variables of RV diastolic function were obtained in 39/40 dogs. Trans-tricuspid flow velocity in early diastole to trans-tricuspid flow velocity in late diastole ratios (RV E/A) were lower (P < .001) in dogs with PS (median, 0.94; range, 0.62-2.04) compared to controls (1.78; 1.17-2.35). Trans-tricuspid flow velocity in early diastole to tricuspid annular myocardial velocity in early diastole ratios (RV E/e') were higher (P < .001) in dogs with PS (11.55; 4.69-28) compared to control (6.21; 5.16-7.21). Variables of RV systolic function were lower in dogs with PS (P = <.001). Serum Gal-3 concentration was higher (P = .002) in dogs with PS (285.1 pg/mL; 94.71-406.97) compared to control dogs (162.83 pg/mL; 52.3-232.82).

CONCLUSIONS AND CLINICAL IMPORTANCE

Dogs with PS have RV diastolic and systolic dysfunction, and increased Gal-3 concentrations. These findings suggest the presence of RV myocardial fibrosis in dogs with PS, which could impact clinical management.

Regulation of fibroblast proliferation by Kupffer cells and monocytes

Liver cirrhosis can be considered as an alteration of the homeostatic mechanisms that maintain cell-cell and cell-matrix interactions. The mechanisms that maintain homeostasis and, therefore, that control fibroblast proliferation and collagen synthesis, are unknown. Experiments were performed to study the role of Kupffer cells in regulating fibroblast proliferation and collagen synthesis and to study the antifibrogenic properties of colchicine. Non-parenchymal cells isolated from normal and CCl4-treated rats were cultured. The cultures from normal livers contained few fibroblasts whereas those from CCl4-treated animals contained many fibroblasts. Removal of adherent cells obtained from normal liver favoured fibroblast proliferation. The fibroblasts from normal or CCl4-treated rats were similar and contained collagens type I and type III. The results obtained suggest that normal Kupffer cells control fibroblast proliferation and that incoming monocytes stimulate fibroblast proliferation. Colchicine inhibits the entry of monocytes into the injured liver and could prevent liver fibrosis by this mechanism.

Echokardiographische Funktionsdiagnostik bei Patienten mit rheumatoider Arthritis und Kollagenosen

Cardiac manifestations were observed in patients with rheumatoid arthritis and other collagenoses. Echocardiography is a method of choice to detect pathologies in morphology and function of the heart. Pathophysiologically inflammatory alterations of the endo- as well as perimyocardium can be explained in these patients. In addition, in patients with collagenoses, the coagulation system is activated and the reactivity of the endothelium is reduced. Thus, thrombus formation at the heart valves with consecutive stenosis and/or regurgitations as well as ischemia-induced regional wall motion defects due to reduced vasodilator response of the coronary arteries can be expected. In the literature in patients with rheumatoid arthritis and other collagenoses, pericardial effusion and pulmonary hypertension are most frequently described. The echocardiographic analysis, however, is more complex due to the variability of the patient cohort. Quantification of valve defects and the analysis of wall motion and perfusion at rest and during stress is necessary to detect early changes of the diseases. The prerequisites for successful diagnostic echocardiography in these patients are the knowledge of modern echocardiographic techniques like tissue Doppler and contrast echocardiography and clinical experience with patients with rheumatoid arthritis and other collagenoses. The standardization of the echocardiographic diagnostic procedure becomes more and more important for reproducibility and comparability of the results.

Effects of chronic inflammatory bowel diseases on left ventricular structure and function: a study protocol

BACKGROUND

Experimental evidences suggest an increased collagen deposition in inflammatory bowel diseases (IBD). In particular, large amounts of collagen type I, III and V have been described and correlated to the development of intestinal fibrotic lesions. No information has been available until now about the possible increased collagen deposition far from the main target organ. In the hypothesis that chronic inflammation and increased collagen metabolism are reflected also in the systemic circulation, we aimed this study to evaluate the effects on left ventricular wall structure by assessing splancnic and systemic collagen metabolism (procollagen III assay), deposition (ultrasonic tissue characterization), and cardiac function (echocardiography) in patients with different long standing history of IBD, before and after surgery.

METHODS

Thirty patients affected by active IBD, 15 with Crohn and 15 with Ulcerative Colitis, submitted to surgery will be enrolled in the study in a double blind fashion. They will be studied before the surgical operation and 6, 12 months after surgery. A control group of 15 healthy age and gender-matched subjects will also be studied. At each interval blood samples will be collected in order to assess the collagen metabolism; a transthoracic echocardiogram will be recorded for the subsequent determination of cardiac function and collagen deposition.

DISCUSSION

From this study protocol we expect additional information about the association between IBD and cardiovascular disorders; in particular to address the question if chronic inflammation, through the altered collagen metabolism, could affect left ventricular structure and function in a manner directly related to the estimated duration of the disease.

Effects of thyroid hormones on cardiac structure: a tissue characterization study in patients with thyroid disorders before and after treatment

Experimental evidence suggests an involvement of thyroid hormones in myocardial nonmyocyte component growth. We evaluated the possible role of thyroid hormones in myocardial remodeling by ultrasonic tissue characterization (videodensitometry) in 8 hyperthyroid patients, in 10 hypothyroid patients, and in 2 patients with thyroid hormone resistance syndrome (RTH), before, 60, and 120 days after treatment (T0, T60, T120), and in 10 age-matched euthyroids. According to a previously described procedure, the derived collagen volume fraction (dCVF%, an echocardiographic index estimating the collagen content) was predicted from the pixel-level frequency distribution width (broadband, Bb) of the selected echocardiographic images. Thyrotropin (TSH), free thyroxine (FT4), and free triiodothyronine (FT3) were assessed by immunometric method. QT interval dispersion (QTd) on basal electrocardiogram was measured as a marker of dyshomogeneous ventricular repolarization. At T0, Bb and dCVF% were normal in hyperthyroid and euthyroid patients, and slightly increased in RTH patients, whereas significantly higher values were found in hypothyroids. At T60, a significant reduction in Bb was observed in hypothyroids, with nearly normal dCVF% values. This trend was confirmed at T120 with complete normalization of echoreflectivity. No echoreflectivity changes were observed in hyperthyroid and RTH patients during treatment. QTd was significantly increased in hypothyroids at T0, while no significant differences were found among groups at T60 and T120. Because the different videodeonsitometric myocardial properties observed in hypothyroid versus hyperthyroid patients correspond to an increase of dCVF%, this study suggests that thyroid hormones exert an inhibitory effect on myocardial collagen synthesis in humans.

Blood pressure-independent cardiac hypertrophy in acromegalic patients

OBJECTIVE

Acromegaly is frequently associated with an increase in left ventricular mass, even in the absence of systemic hypertension. Pathological studies on acromegalic hearts have shown an extensive interstitial fibrosis, suggesting the existence of a specific acromegalic cardiomyopathy. The aim of this study was to assess left ventricular wall structure in acromegaly by ultrasonic tissue characterization.

DESIGN AND METHODS

We studied 10 untreated acromegalic patients and 10 age-matched healthy control subjects. The echo patterns of two-dimensional long-axis end-diastolic echocardiograms were assessed by colour-scale analysis of the interventricular septum, with estimates of the mean colour scale value, the broad band (Bb) and the derived collagen volume fraction (dCVF). We also measured electrocardiographic QT interval dispersion (QTd) as a marker of dyshomogeneous ventricular repolarization.

RESULTS

Seven patients had left ventricular hypertrophy according to the sex-independent criteria; of these, two had arterial hypertension. None of our patients had echocardiographic evidence of diastolic or systolic dysfunction. All patients showed significantly increased myocardial echoreflectivity (Bb = 106.4+/-12.1 versus 79.3+/-6.5; dCVF% = 2.78+/-0.53 versus 1.58+/-0.29; P < 0.0001) and QTd (66+/-13 ms versus 54+/-8 ms, P < 0.05). A significant correlation was found between dCVF and the duration of acromegaly (r = 0.80; P = 0.005).

CONCLUSIONS

Left ventricular remodelling observed in acromegaly is not related to the presence of arterial hypertension; we hypothesize that the increased echoreflectivity and QTd are long-term consequences of cardiac hypertrophy and prolonged exposure to high levels of growth hormone and insulin-like growth factor-I.

Echocardiographic patterns of myocardial fibrosis in hypertensive patients: endomyocardial biopsy versus ultrasonic tissue characterization

Echocardiographic image texture has been demonstrated to reflect the physical properties of the tissue under examination. To evaluate the role of collagen in determining the echo pattern of the left ventricular wall, we studied nine hypertensive patients with left ventricular hypertrophy (left ventricular mass index > 125 gm/m2) and biopsy-proven different degrees of myocardial fibrosis by analyzing the echocardiographic examinations performed before the biopsy. Myocardial tissue was sampled under fluoroscopy and two-dimensional echo guidance in the interventricular septum. Collagen volume fraction (CVF; normal range up to 2%) was taken as an index of fibrosis. The echo patterns were assessed by analyzing standard two-dimensional parasternal long-axis echocardiograms recorded on videotape. Images were color-coded at 256 levels (0 = yellow, 256 = black) and digitized off-line onto a personal computer. The region of analysis was set using a selection tool (20 x 10 mm) in the general area of septum where the specimen was taken. For each selection a color-level histogram, representing the frequency distribution, was derived with estimates of the average pixel intensity (mCS), skewness (SK), kurtosis (K), and the broad band (Bb) of the echoes about the distribution. Echo-derived parameters in each patient were compared with corresponding CVF values. CVF was out of range in all patients, ranging from 2.6% to 7.6% (mean 4.3% +/- 1.6%). No correlation was found between CVF and mCS, whereas a significant correlation was found at end diastole between CVF and the parameters describing histogram morphology, respectively, SK (r = 0.73), K (r = 0.69), Bb (r = 0.72). These findings for the first time demonstrate in vivo in hypertensive patients with left ventricular hypertrophy an agreement between echo amplitude and histologically assessed collagen volume. Thus in our studied patients collagen content appears to be the major determinant of regional echo intensity, its increase resulting in a significant and progressive wider asymmetrical left shift (yellow) of the color histogram.

Increased myocardial echo density in left ventricular pressure and volume overload in human aortic valvular disease: an ultrasonic tissue characterization study

Quantitatively assessed ultrasonic backscatter is an index of ultrasonic tissue characterization directly related to morphometrically evaluated collagen in human beings. Our objective was to assess myocardial reflectivity pattern of patients with severe left ventricular hypertrophy caused by either aortic stenosis (AS) or aortic regurgitation (AR). Ten patients with AS, 10 patients with AR, and 10 closely age- and gender-matched healthy controls were studied by two-dimensional Doppler echocardiography. By using an echocardiographic prototype, we performed a radiofrequency analysis to obtain quantitative operator-independent measurements of the integrated backscatter signal of the ventricular septum and the posterior wall (integrated backscatter index: IBI, expressed in percentage). All patients with stenosis or aortic insufficiency showed a normal regional and global resting systolic function (fractional shortening: AS = 36.0 +/- 6.6 versus AR = 40.3 +/- 6.2 versus control = 40.2 +/- 8.7; p = not significant [NS]) Left ventricular mass index (Devereux's formula) was markedly increased in patients with stenosis or aortic insufficiency (AS = 199.3 +/- 18 versus AR = 208.8 +/- 60 versus control = 97.3 +/- 11 g/m2; p < 0.0001). Myocardial echo density was increased in patients with stenosis or aortic insufficiency in comparison with controls, both in the septum (IBI%: AR = 40.7 +/- 7.9 versus AS = 33.4 +/- 4.2 versus control = 23.0 +/- 6.2; p < 0.0001) and in the posterior wall (IBI%: AR = 27.1 +/- 4.3 versus AS = 23.0 +/- 2.6 versus control = 15.0 +/- 4.2; p < 0.0001). No significant correlations were found between septal and posterior wall IBI and their thickness. Abnormally increased myocardial echo density--possibly related to disproportionate collagen deposition--can be detected in patients with pressure or volume overload caused by aortic valve disease and without overt systolic dysfunction.

Influences of ultrasonic machine settings, transducer frequency and placement of region of interest on the measurement of integrated backscatter and cyclic variation

Integrated backscatter and its cyclic variation are potentially important parameters to discriminate normal from diseased myocardium. Cyclic variation of integrated backscatter is expected to be independent of machine settings. Backscatter images of swine hearts were taken using a two-dimensional backscatter system while acoustic power was varied at different time gain control (TGC) settings. Cyclic variation was measured in vivo with various acoustic power and TGC settings using different transducer frequencies. Three different regions were analyzed. For any given TGC setting, the relationship between acoustic power and integrated backscatter in vitro was linear only over a narrow range. In vivo, cyclic variation was present at all regions studied in both long- and short-axis views. However, lower acoustic power (< 15 dB) and TGC (< 20 dB), or excessive settings of acoustic power (> 35 dB) and TGC (> 50 dB), produced minimal cyclic variation. Appropriate acoustic power (20-35 dB) and TGC (30-50 dB) produced larger and more consistent cyclic, variation at the posterior region of the left ventricle. These data indicate that each region has specific, appropriate machine settings to maximize the magnitude of cyclic variation.

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)

Acoustic propagation properties of normal, stunned, and infarcted myocardium. Morphological and biochemical determinants

BACKGROUND

Identification of viable but stunned myocardium remains a major problem. Since stunned myocardium results in impairment of myocardial function without any structural damage and infarcted myocardium causes major structural disruption, we postulated that acoustic properties could distinguish between the two insults.

METHODS AND RESULTS

Anesthetized open-chest dogs underwent a total occlusion of the left anterior descending coronary artery for 15 minutes (stunned, n = 7) and 90 minutes (infarcted, n = 8), followed by reperfusion for 3 hours. Circumflex coronary artery perfusion territory (n = 15) served as normal control tissue. Regions of myocardium were quantitatively evaluated with a scanning laser acoustic microscope operating at 100 MHz and a research ultrasound system operating at 4 to 7 MHz. Four ultrasonic parameters were determined: attenuation coefficient (an index of loss per unit distance), speed of propagation, a spatial variation of propagation speed called the heterogeneity index (HI), and ultrasonic backscatter at 5 MHz (IBR5). Myocardial water, lipid, and protein contents of normal, stunned, and infarcted myocardium were also determined. The attenuation coefficient of normal myocardium (179 +/- 20 dB/cm) was significantly greater than that of stunned (136 +/- 7 dB/cm, P < .001) and infarcted (130 +/- 8 dB/cm, P < .001) myocardium. The propagation speed of normal myocardium (1597 +/- 6 m/s) was similar to that of stunned (1600 +/- 6 m/s) and significantly higher than that of infarcted (1575 +/- 7 m/s, P < .001) myocardium. The HI for specimen thicknesses of 75 to 100 microns showed an increase of 33% between normal (5.0 +/- 0.8 m/s) and stunned (7.5 +/- 2.3 m/s, P < .05) myocardium. However, for the infarcted myocardium (5.8 +/- 2.0 m/s), the HI was essentially the same as that of the normal myocardium (5.0 +/- 0.8 m/s). The IBR5 of normal (-47.1 +/- 1.0 dB) was not significantly different from that of stunned myocardium (-46.8 +/- 0.9 dB). The IBR5 of infarcted myocardium (-42.4 +/- 1.0 dB) was significantly greater than that of normal myocardium. Myocardial water and protein contents were similar in the normal and stunned myocardium. Water content in the infarcted myocardium (80.8 +/- 2%) was significantly greater (P < .05) than in the normal (72.7 +/- 1.3%), and protein content of 18.5 +/- 0.7% was significantly lower (P < .05) than the normal (21.4 +/- 0.8%). Lipid content was increased in the stunned (8.5 +/- 0.5%) and virtually absent in the infarcted myocardium (0.8 +/- 0.3%) compared with normal (5.5 +/- 0.6%).

CONCLUSIONS

We conclude that acoustic propagation properties can identify stunned and infarcted myocardium and may be related to biochemical/morphological differences.

Quantitative Echocardiography, Part 1

The quantitative applications of echocardiography in clinical practice are well known. The measurements of cardiac chamber dimensions, wall thickness, and overall performance have been uniformly adopted. An important emerging ultrasound modality known as tissue characterization of the myocardium has evolved from experimental studies to clinical investigation. The ability to quantitate myocardial acoustic properties by the measurement of integrated backscatter (in decibels) provides direct assessment of myocardial structural characteristics and contractile performance, to complement conventional two-dimensional imaging of ventricular wall motion and wall thickening. Despite the considerable amount of work that has been done, there are several areas of research that need to be further investigated before widespread clinical use of these techniques is possible. Specifically, absolute values of myocardial backscatter are not yet obtainable with the current instrumentation; only the relative change in backscatter during the cardiac cycle (cyclic variation) has been defined and employed in clinical studies. This review summarizes the principles of tissue characterization and the results of several clinical studies, specifically those carried out in patients with coronary artery disease and cardiomyopathies.

Quantification of ventricular remodeling in the tight-skin mouse cardiomyopathy with acoustic microscopy

To determine the role of ultrasonic tissue characterization for the detection of changes in myocardial architecture associated with cardiomyopathy, acoustic microscopy was performed on the hearts of 4- to 6-month-old tight-skin mice [TSK/+, C57-B10.D2 (58B)/SN strain], a model of cardiomyopathy characterized by diffuse interstitial fibrosis. Ultrasonic backscatter was measured from excised segments of left ventricular free walls of five TSK mice and five sex- and age-matched normal controls with a 50 MHz broad band focused piezoelectric transducer operated in a saline-filled water tank at room temperature. Forty-nine radio frequency (RF) lines were digitized from each specimen at 2 ns/sample. Power spectral analysis of RF data was performed and mean integrated backscatter (IB) computed. The TSK group demonstrated greater IB (-53.6 +/- 0.6 dB, n = 5) than did the control group (-56.6 +/- 0.7 dB, n = 5; p < 0.02). Myocardial collagen content determined by hydroxyproline assay increased by 11% in the TSK group (2.54 +/- 0.08 microgram/mg dry wt, n = 5) over that in controls (2.28 +/- 0.07 microgram/mg dry wt, n = 5; p < 0.05). A significant linear relationship was observed between myocardial hydroxyproline concentration and IB (r = 0.74; p < 0.02). Thus, ultrasonic tissue characterization permits sensitive detection of modest changes in the extent of interstitial fibrosis that accompany tissue remodeling in the early stages of cardiomyopathy.

Prospects for cardioreparation

The structure of the myocardium has 2 principal components, a myocytic compartment and a non-myocytic compartment that consists primarily of interstitial tissue. It appears that increased collagen production is mainly responsible for the functional consequences of structural remodelling. The concept of cardioreparation implies both a restoration of structural abnormalities and a return of cardiac function to or toward normal. In spontaneously hypertensive rats with left ventricular hypertrophy and adverse structural remodeling of the cardiac interstitium, angiotensin-converting enzyme inhibition has resulted in restoration of myocardial integrity and stiffness toward normal. Further research needs to be undertaken to identify the molecular mechanisms involved in the development of interstitial myocardial fibrosis, and reliable methods for assessing the interstitium and the changes that occur within it in clinical practice need to be developed.

Normal ultrasonic myocardial reflectivity in athletes with increased left ventricular mass. A tissue characterization study

BACKGROUND

Ultrasonic integrated backscatter of myocardial walls is directly related to the morphometrically evaluated collagen content. The integrated backscatter is also increased in hypertrophic cardiomyopathy, probably because of fiber disarray. The purpose of this study was to investigate myocardial tissue reflectivity in subjects with physiological hypertrophy caused by intense physical training and to assess the relation between the acoustic properties of myocardial tissue and left ventricular wall thickness assessed by conventional two-dimensional echocardiography.

METHODS AND RESULTS

Twenty-four young male athletes (14 professional cyclists and 10 weight lifters, all in full agonistic activity) were studied together with 10 normal age-matched controls with sedentary life. By means of a commercially available two-dimensional echocardiograph, standard measurements were obtained according to the recommendations of the American Society of Echocardiography. With a prototype implemented in our Institute, an on-line radiofrequency analysis of ultrasound signals was also performed to obtain quantitative operator-independent measurements of the integrated backscatter of the myocardial walls. The integrated values of the radiofrequency signal were normalized for the pericardial interface and expressed in percent integrated backscatter (%IB). Compared with control subjects, athletes showed greater thickness values of septum (controls, 9 +/- 1; cyclists, 14 +/- 2; weight lifters, 15 +/- 1 mm, mean +/- SD; p less than 0.01) and posterior wall (9 +/- 1, 12 +/- 2, and 12 +/- 1 mm, respectively; p less than 0.01) but similar values of %IB for both septum (23 +/- 4%, 21 +/- 7%, and 23 +/- 8%, p = NS) and posterior wall (10 +/- 2%, 9 +/- 2%, and 11 +/- 2%, p = NS). In athletes, no correlation was found between septal and posterior wall thickness and the corresponding regional myocardial reflectivity (r = 0.23, p = NS and r = 0.01, p = NS, respectively). Furthermore, we compared the quantitative ultrasonic data between two subsets of 10 athletes and 10 patients with hypertrophic cardiomyopathy and similar degrees of septal thickness (16 +/- 1 versus 17 +/- 1 mm, respectively, p = NS). Septal and posterior wall %IB results were significantly higher in patients with hypertrophic cardiomyopathy (53 +/- 13% and 36 +/- 9%, respectively) than in athletes (21 +/- 7% and 10 +/- 3%, respectively; p less than 0.01 for both).

CONCLUSIONS

We conclude that 1) endurance athletes show a normal pattern of quantitatively assessed ultrasonic backscatter despite of a marked left ventricular hypertrophy and 2) athletes and patients with hypertrophic cardiomyopathy and similar degrees of myocardial wall thickness can be differentiated on the basis of quantitative analysis of backscattered signal.

Relation between cyclic variation in echo amplitude and segmental contraction in normal and abnormal hearts

OBJECTIVE

To study the relation between cardiac systolic activity and cardiac cycle dependent variation in the ultrasound signal arising from within the myocardium.

DESIGN

Regional echo amplitude was used as a measure of the myocardial ultrasound signal. Relative echo amplitude values were assigned by standardising echo gain using the posterior parietal pericardium as an in-vivo calibration. M mode measurements of the left ventricle were used to assess cardiac systolic activity. Subjects were studied prospectively. Analysis of echo amplitude was performed by investigators who were blinded to the results of the M mode analysis. The influence of impaired left ventricular performance and abnormal wall motion were assessed.

PATIENTS

11 cardiomyopathy patients with impaired ventricular function, eight patients with severe pulmonary hypertension and reversed septal motion, and 19 healthy controls.

SETTING

All subject studies were performed at Harefield Hospital. Echo amplitude analysis was performed at the Royal Brompton Hospital.

MAIN OUTCOME MEASURES

Cyclic variation in echo amplitude was determined as the change in echo amplitude from end diastole to end systole. Additionally, an index of cyclic variation defined as the ratio of the cyclic change in echo amplitude to end diastolic echo amplitude was measured. Both cyclic variation and the cyclic variation index were analysed to see whether they correlated with left ventricular dimensions, fractional shortening, and systolic wall thickening.

RESULTS

Stepwise regression analysis showed systolic wall thickening to be the most significant independent variable that correlated with the cyclic variation index for both the septum and posterior wall (r = 0.68, p = 0.0001, septum; r = 0.69, p = 0.0001, posterior wall). The slopes and intercepts for both regression equations were similar (y = 0.005x + 0.006, septum; y = 0.006x + 0, posterior wall). Subgroup analysis showed that the healthy controls, patients with cardiomyopathy, and patients with pulmonary hypertension had similar slopes and intercepts for their individual regression equations.

CONCLUSIONS

These data support the hypothesis of a quantitative relation between the extent of cyclic variation of echo amplitude and the degree of segmental myocardial shortening, as measured by systolic wall thickening, which is not significantly influenced by location within the myocardium, left ventricular performance, or wall motion. They provide further evidence of the usefulness of quantitative analysis of myocardial echo amplitude in the study of regional myocardial function in both normal and injured myocardium.

Tissue characterization with intra-arterial ultrasound: special promise and problems

Although we are able to identify many tissue types based on the screen image in intravascular ultrasound, there is additional information in the ultrasound signal which could be of assistance in characterization and identification of tissue. Intravascular ultrasound has several special characteristics which affect tissue characterization. These include the high transducer frequency, small transducers, short and relatively uniform path to the tissue, and limited tissue types to identify. These characteristics influence the results obtained by absolute backscatter, local statistics, frequency dependent backscatter, and angle dependency of backscatter. These effects are both positive and negative, and in many cases can be observed in clinical imaging. Another area of tissue characterization which can be performed with ultrasound is measurement of arterial wall elasticity. This can be of importance in the evaluation of mechanisms of dilatation, and the potential for complications.

Ultrasonic integrated backscatter two-dimensional imaging: evaluation of M-mode guided acquisition and immediate analysis in 55 consecutive patients

We have shown previously that cardiac cycle-dependent integrated backscatter characterizes the physical state of myocardium in patients with ischemic heart disease and cardiomyopathy. In the present study the clinical applicability of M-mode guided two-dimensional integrated backscatter imaging was defined in evaluation of 55 nonselected patients. The mean amplitude of cyclic variation of integrated backscatter in normal segments (long-axis view) was as follows: basal septum, 4.2 +/- 1.3 dB (mean +/- SD; n = 27), mid-septum, 4.5 +/- 1.0 dB (n = 26), basal posterior, 4.8 +/- 1.0 dB (n = 30), and mid-posterior, 4.8 +/- 1.2 decibels (n = 27). The respective mean delay values (R wave to nadir) were as follows: 0.89 +/- 0.09, 0.84 +/- 0.09, 0.86 +/- 0.09, and 0.85 +/- 0.12. At least one cardiac cycle could be analyzed fully in 62% of patients. Limitations included technically difficult two-dimensional echocardiography, inadequate M-line orientation, technically remediable errors, or poor quality integrated backscatter images. In abnormal segments (n = 13) cyclic variation was reduced and delay was prolonged (1.2 +/- 1.1 dB and 1.21 +/- 1.1, respectively). Intraobserver and interobserver variability for amplitude measurements were modest, with respective correlation coefficients of r = 0.93; r = 0.72. The findings demonstrate that M-mode--assisted integrated backscatter is a practical approach for characterization of regional myocardial properties promptly and at the bedside in a large portion of patients with cardiac disease.

Ultrasonic tissue characterization of normal and ischemic myocardium

Cardiac ultrasonic tissue characterization is designed to use the alterations in acoustic signals from the myocardium to differentiate normal from ischemic or infarcted tissue due to their characteristic backscatter attenuation. Various approaches such as use of a gray scale, color display, or quantitative image analysis have been used for tissue characterization, but all depend on subjective assessments and are not necessarily reproducible. The most promising method has been the use of "raw" radiofrequency signals and measure changes in the ultrasonic attenuation with an index of backscatter to distinguish normal from abnormal myocardium called "integrated backscatter" (IB). Various studies have demonstrated the changes in the ultrasonic backscatter with ischemia or infarction. In this review we summarize our experience with a research prototype instrument in tissue characterization and differentiation of normal, ischemic, infarcted, and post ischemic reperfused myocardium in anesthetized open chest dogs. Currently we are investigating the role of ultrasonic tissue characterization to estimate infarct size and plan to apply these observations to patients in order to detect viable myocardium and quantitate infarct size.

In vivo quantitative ultrasonic evaluation of myocardial fibrosis in humans

The aim of this study was to assess in vivo whether the regional ultrasonic reflectivity, evaluated by a real-time integrated backscatter analysis, was related to the local content of connective tissue in human myocardium as estimated by quantitative histology of endomyocardial biopsies. Sixteen patients with presumptive diagnosis of cardiomyopathy were ultrasonically studied by means of an M-mode-based echocardiographic system with quantitative integrated backscatter analysis capabilities. A 2.25-MHz transducer was used. The integrated value of the rectified radiofrequency signal of the interventricular septum was taken as integrated backscatter index and expressed in percent normalized for the pericardial interface (assumed to be 100%). All patients also underwent multiple left ventricular endomyocardial biopsies, which were stained with Masson's trichrome and studied with the use of a computer-assisted image analysis system. The percent integrated backscatter index was significantly higher in the presence of connective tissue area greater than 20% (eight patients) versus less than 20% (eight patients): 51 +/- 25% versus 26 +/- 11%, p less than 0.05. A significant correlation (p less than 0.05, R = 0.55) was found between percent integrated backscatter index and percent connective tissue area. In vivo on-line quantitative ultrasound analysis is feasible in man and reliably identifies variations in the regional extent of fibrosis in human myocardium.

Cardiac involvement in Churg-Strauss syndrome shown by echocardiography

To define the range of cardiac involvement in the Churg-Strauss syndrome, M mode, continuous wave Doppler, and cross sectional echocardiograms were recorded in twelve patients with the disorder. The M mode recordings were digitised and the cross sectional images were recorded with standardised gain settings to determine regional myocardial echo amplitude. Left ventricular end diastolic and end systolic dimensions were increased above the normal 95% confidence interval in four patients, three of whom showed a depressed shortening fraction. Mitral regurgitation was present in six patients; this was severe enough to need valve replacement in two. Mean echo amplitude in both the septum and the posterior wall was significantly increased above normal by a mean (SD) of 4.87 (2.57) dB, suggesting the presence of myocardial fibrosis. There was no evidence of subendocardial involvement as there is in other hypereosinophilic syndromes. Mitral regurgitation is common in the Churg-Strauss syndrome. This cannot be ascribed to involvement of the cusps or chordae and it occurs even when ventricular function is well preserved. It is suggested that mitral regurgitation is caused by diffuse myocardial fibrosis.

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.

Analysis of backscattered ultrasound from normal and diseased arterial wall

Intra-arterial ultrasonic imaging has several features which affect the feasibility of clinical tissue characterization when compared with trans-thoracic ultrasound. The short distance from transducer to tissue, fluid path, high frequencies, and special characteristics of the tissues of interest all contribute to making practical tissue characterization by measurement of the backscattered signal more probable in intra-arterial imaging. The properties of backscattered ultrasound, and methods of characterizing such signals, are discussed with special reference to intra-arterial applications.

Ultrasound study of acoustic properties of the normal canine heart: comparison of backscatter from all chambers

Much effort has recently been directed toward ultrasound characterization of normal and abnormal left ventricular myocardium. The purpose of this study was to evaluate the normal acoustic properties of all four cardiac chambers as a first step toward tissue characterization of the atria and ventricles. The hypothesis was that integrated ultrasound backscatter would follow the pattern of collagen concentration in the cardiac chambers, being higher in the right side of the heart than in the left and in the atria compared with the ventricles. Seven normal canine hearts, perfusion-fixed in 10% formalin, were examined. Sections of the free walls of right and left ventricles and atria were studied in vitro with a 5 MHz transducer positioned at the focal distance from the epicardium. The radio frequency ultrasound signal energy from each specimen was derived, corrected for sample thickness and expressed as integrated backscatter, in decibel units less than the reflected energy from a stainless steel block. The backscatter was higher from the right ventricle than from the left ventricle (-64.5 +/- 1.25 [mean +/- SEM] [n = 7] versus -73.6 +/- 1.32; p less than 0.05), higher from the right atrium than from the right ventricle (-58.5 +/- 0.83 versus -64.5 +/- 1.25; p less than 0.05) and higher from the left atrium than from the left ventricle (-62.8 +/- 1.14 versus -73.6 +/- 1.32; p less than 0.05). These data show that backscatter is higher in the right ventricle than in the left ventricle and in the atria compared with the ventricles.(ABSTRACT TRUNCATED AT 250 WORDS)

Sensitive detection of the effects of reperfusion on myocardium by ultrasonic tissue characterization with integrated backscatter

We have shown recently that tissue characterization of myocardium with ultrasound reflects changes associated with contractile function throughout the cardiac cycle. To determine whether ultrasonic tissue characterization can sensitively detect the impact of ischemic injury and reperfusion on contractile properties of the heart, we studied the time course of change of backscatter after 5, 20, and 60 min of coronary occlusion followed by reperfusion in 15 dogs. The time-averaged integrated backscatter (IB) and the amplitude and phase of cyclic variation of IB (phase relative to the left ventricular pressure waveform) were measured. A novel ultrasonic index of acute injury was identified, the phase-weighted amplitude of cyclic variation, and calculated by weighting the amplitude of cyclic variation of IB with respect to the phase. We hypothesized that backscatter variables would change dramatically after occlusion and that their restitution after reperfusion would sensitively reflect the extent and time course of reversibility of ischemic injury. After coronary occlusion, segmental wall thickening decreased from approximately 55% to 5% regardless of the duration of ischemia. Changes in backscatter associated with this decrease included an increase in time-averaged IB of approximately 5 dB, a 5 dB decrease in cyclic variation, an 80 degree phase shift, and a 7 dB decrease in phase-weighted amplitude. Wall thickening after reperfusion immediately after the 5, 20, or 60 min occlusions recovered to 45%, 27%, and 12% of baseline values, respectively. Within 3 hr it recovered to 53%, 44%, and 22%. Time-averaged IB recovered initially by 89%, 61%, and 44% (all p less than .05) and continued to recover subsequently although more slowly. Ultimate recovery was virtually complete. In contrast to the rapid recovery of time-averaged IB, phase-weighted amplitude recovered initially to only 72%, 41%, and -7% of baseline (all p less than .05) and manifested slower and incomplete recovery when ischemia had been present for 20 or 60 min. After reperfusion, the time course of both cyclic variation and phase were reflected by changes in the phase-weighted amplitude. The backscatter variables assessed appear to sensitively delineate the duration, time course of recovery, and reversibility of ischemic injury in response to reperfusion. The results suggest that early recovery of time-averaged IB corresponds in part to the restoration of tissue ultrastructural integrity.(ABSTRACT TRUNCATED AT 400 WORDS)

Classification of left ventricular thrombi by their history of systemic embolization using pattern recognition of two-dimensional echocardiograms

Although one can diagnose left ventricular (LV) thrombi by two-dimensional echocardiography (2DE), the factors associated with peripheral embolization, given a 2DE with LV thrombi, have not been well delineated. Therefore we looked at 2DE and clinical variables that included texture features in the 2DE of 38 patients whose 2DE had LV thrombi and questioned these patients to see if clinical embolization had occurred in the 8.9 +/- 6.1 month (+/- SD) average follow-up period. Eight patients, four with acute myocardial infarction (AMI) and four with dilated LV and decreased LV systolic wall motion, had clinically apparent leg or brain emboli, whereas the remaining patients did not. Emboli occurred within a week of obtaining the 2DE in question. The variables considered were the age of the patient, the type of heart disease present, warfarin administration, exercise tolerance, standard M-mode measurements, LV dyssynergy by 2DE, clot size and mobility, and gray scale statistics which include run length, Sobel edge points followed by 50% gradient thresholding, gray level second-order statistics, offset 1 and gray level difference statistics, offset 1. The values of the variables were then entered into an expert system (Expert Ease) in order to achieve classification of patients into emboli versus no emboli groups, while using a minimal number of variables. The only variables that were needed included run length, long runs emphasis, gray level difference statistics (entropy, contrast, mean, and angular second moment), gray level second-order statistics (contrast), and warfarin status. When probability statistics were applied to this schema, its accuracy was predicted to be at least 96%.(ABSTRACT TRUNCATED AT 250 WORDS)

Relation of regional echo amplitude to left ventricular function and the electrocardiogram in left ventricular hypertrophy

In order to determine the relation between three manifestations of left ventricular hypertrophy--ST-T wave changes on the electrocardiogram, diastolic disturbances, and increased myocardial echo intensity--M mode and cross sectional echocardiograms were recorded in 12 normal subjects, 15 athletes, 16 patients with hypertrophic cardiomyopathy, and 42 patients with secondary left ventricular hypertrophy due to aortic stenosis (20), severe essential hypertension (8), coarctation (7), or subaortic stenosis (7). M mode echocardiograms were digitised and cross sectional echocardiograms were analysed for regional echo intensity. In patients with hypertrophy regional echo amplitude was significantly increased in mid and basal septum and posterior left ventricular wall. Patients with increased echo amplitude in any region showed a higher incidence of ST-T wave abnormalities than those without and of diastolic abnormalities--including prolongation of isovolumic relaxation time, delay in mitral valve opening with respect to minimum cavity dimension, and a reduction in peak rate of posterior wall thinning and dimension increase. There was a significant rank order correlation between median pixel count and these diastolic abnormalities. No significant differences were demonstrable in these relations between the diagnostic groups. By contrast, electrocardiographic findings, diastolic function, and pixel count were uniformly normal in athletes, although the increase in left ventricular mass was similar to that in the patients. Thus an increase in left ventricular mass alone is not responsible for repolarisation or wall motion abnormalities occurring in pathological left ventricular hypertrophy. These latter changes are, however, strongly associated with the change in myocardial properties detected as an increase in echo intensity and may be due to increased interstitial fibrosis.