Influence of preload, afterload, and contractility on myocardial ultrasonic tissue characterization with integrated backscatter

Ultrasound tissue characterization does not differentiate genotype, but indexes ejection fraction deterioration in becker muscular dystrophy

The aims of the study were, first, to assess whether myocardial ultrasound tissue characterization (UTC) in Becker muscular dystrophy (BMD) can be used to differentiate between patients with deletions and those without deletions; and second, to determine whether UTC is helpful in diagnosing the evolution of left ventricular dysfunction, a precursor of dilated cardiomyopathy. Both cyclic variation of integrated backscatter and calibrated integrated backscatter (cIBS) were assessed in 87 patients with BMD and 70 controls. The average follow-up in BMD patients was 48 ± 12 mo. UTC analysis was repeated only in a subgroup of 40 BMD patients randomly selected from the larger overall group (15 with and 25 without left ventricular dysfunction). Discrimination between BMD patients with and without dystrophin gene deletion was not possible on the basis of UTC data: average cvIBS was 5.2 ± 1.2 and 5.5 ± 1.4 dB, and average cIBS was 29.9 ± 4.7 and 29.6 ± 5.8, respectively, significantly different (p < 0.001) only from controls (8.6 ± 0.5 and 24.6 ± 1.2 dB). In patients developing left ventricular dysfunction during follow-up, cIBS increased to 31.3 ± 5.4 dB, but not significantly (p = 0.08). The highest cIBS values (34.6 ± 5.3 dB, p < 0.09 vs. baseline, p < 0.01 vs BMD patients without left ventricular dysfunction) were seen in the presence of severe left ventricular dysfunction. Multivariate statistics indicated that an absolute change of 6 dB in cIBS is associated with a high probability of left ventricular dysfunction. UTC analysis does not differentiate BMD patients with or without dystrophin gene deletion, but may be useful in indexing left ventricular dysfunction during follow-up.

The diastolic function to cyclic variation of myocardial ultrasonic backscatter relation: the influence of parameterized diastolic filling (PDF) formalism determined chamber properties

Myocardial tissue characterization represents an extension of currently available echocardiographic imaging. The systematic variation of backscattered energy during the cardiac cycle (the "cyclic variation" of backscatter) has been employed to characterize cardiac function in a wide range of investigations. However, the mechanisms responsible for observed cyclic variation remain incompletely understood. As a step toward determining the features of cardiac structure and function that are responsible for the observed cyclic variation, the present study makes use of a kinematic approach of diastolic function quantitation to identify diastolic function determinants that influence the magnitude and timing of cyclic variation. Echocardiographic measurements of 32 subjects provided data for determination of the cyclic variation of backscatter to diastolic function relation characterized in terms of E-wave determined, kinematic model-based parameters of chamber stiffness, viscosity/relaxation and load. The normalized time delay of cyclic variation appears to be related to the relative viscoelasticity of the chamber and predictive of the kinematic filling dynamics as determined using the parameterized diastolic filling formalism (with r-values ranging from .44 to .59). The magnitude of cyclic variation does not appear to be strongly related to the kinematic parameters.

Bayesian parameter estimation for characterizing the cyclic variation of echocardiographic backscatter to assess the hearts of asymptomatic type 2 diabetes mellitus subjects

Previous studies have shown that effective quantification of the cyclic variation of myocardial ultrasonic backscatter over the heart cycle might provide a non-invasive technique for identifying the early onset of cardiac abnormalities. These studies have demonstrated the potential for measurements of the magnitude and time delay of cyclic variation for identifying early onset of disease. The goal of this study was to extend this approach by extracting additional parameters characterizing the cyclic variation in an effort to better assess subtle changes in myocardial properties in asymptomatic subjects with type 2 diabetes. Echocardiographic images were obtained on a total of 43 age-matched normal control subjects and 100 type 2 diabetics. Cyclic variation data were generated by measuring the average level of ultrasonic backscatter over the heart cycle within a region of interest placed in the posterior wall of the left ventricle. Cyclic variation waveforms were modeled as piecewise linear functions, and quantified using a novel Bayesian parameter estimation method. Magnitude, rise time and slew rate parameters were extracted from models of the data. The ability of each of these parameters to distinguish between normal and type 2 diabetic subjects, and between subjects grouped by glycated hemoglobin (HbA1c) was compared. Results suggest a significant improvement in using measurements of the rise time and slew rate parameters of cyclic variation to differentiate (P < 0.001) the hearts of patients segregated based on widely employed indices of diabetic control compared to differentiation based on the magnitude of cyclic variation.

Quantitative analysis of the magnitude and time delay of cyclic variation of myocardial backscatter from asymptomatic type 2 diabetes mellitus subjects

Early detection of diabetic patients at high risk for developing diabetic cardiomyopathy may permit effective intervention. The goal of this work is to determine whether measurements of the magnitude and time delay of cyclic variation of myocardial backscatter, individually and in combination, can be used to discriminate between subgroups of individuals including normal controls and asymptomatic type 2 diabetes subjects. Two-dimensional parasternal long-axis echocardiographic images of 104 type 2 diabetic patients and 44 normal volunteers were acquired. Cyclic variation data were produced by measuring the mean myocardial backscatter level within a region-of-interest in the posterior wall, and characterized in terms of the magnitude and normalized time delay. The cyclic variation parameters were analyzed using Bayes classification and a nonparametric estimate of the area under the receiver operating characteristic (ROC) curve to illustrate the relative effectiveness of using one or two features to segregate subgroups of individuals. The subjects were grouped based on glycated hemoglobin (HbA1c), the homeostasis model assessment for insulin resistance (HOMA-IR) and the ratio of triglyceride to high-density lipoprotein cholesterol (TG/HDL-C). Analyses comparing the cyclic variation measurements of subjects in the highest and lowest quartiles of HbA1c, HOMA-IR and TG/HDL-C showed substantial differences in the mean magnitude and normalized time delay of cyclic variation. Results show that analyses of the cyclic variation of backscatter in young asymptomatic type 2 diabetics may be an early indicator for the development of diabetic cardiomyopathy.

Very early stage detection of acute myocardial infarction by harmonic ultrasonic integrated backscatter

To study the very early diagnosis of acute myocardial infarction (AMI) by harmonic imaging ultrasonic integrated backscatter (IBS). Thirty normal persons, 68 cases with AMI, of whom 28 cases were at the very early stage of acute myocardial infarction (in 2 h), and 40 cases with acute myocardial infarction (in 2 to 12 h) were examined by IBS and the cyclic variation of integrated backscatter (CVIB) with HP-5500 ultrasonic system in different segment (the segment of myocardial infarction and no myocardial infarction). In the segment of AMI of the very early stage (in 2 h) the IBS (dB) is much higher than that of the segment of no AMI (18.7 versus 8.3), p < 0.001, the CVIB (dB) are lower (6.1 versus 7.6), p < 0.001. But at that time there are no obvious changes in ECG. In the other 40 cases with AMI in 2 to 12 h, IBS in the segment of AMI is obviously higher than the normal person and no infarction segment in the same heart (21.3:8.3, 20.2:8.5) p < 0.05, but CVIB (dB) is obviously lower than the normal person and no infarction segment in the same heart (5.8:7.6, 5.9:9.4) p < 0.05 the changes of the ultrasonic is coincidence with ECG. IBS (dB) are very obvious just as in ECG. The result demonstrates that ultrasonic tissue characterization with harmonic imaging integrated backscatter can be used for diagnosis in the very early stage of AMI, and can judge the segment range of AMI and function of the whole heart.

Effect of preload reduction on sonographic myocardial integrated backscatter

PURPOSE

Sonographic myocardial tissue characterization with integrated backscatter (IBS) is affected by both structural and functional properties of the myocardium. The aim of the present study was to investigate the effect of preload reduction by hemodialysis (HD) on IBS measurements.

METHODS

Fifty-two patients on maintenance HD underwent echocardiography before and after a routine HD session. Measurements included the variation of IBS during the cardiac cycle (CV-IBS) and calibrated IBS (cal-IBS).

RESULTS

After HD, there were significant reductions in left ventricular end-diastolic and end-systolic dimensions and left atrial diameter. There was a reduction in stroke volume and LV ejection fraction consistent with a reduction in preload. Furthermore, CV-IBS was significantly lower after HD (7.9 +/- 2.2 versus 6.9 +/- 1.8 dB, 7.0 +/- 2.1 versus 6.2 +/- 1.9 dB, and 9.0 +/- 2.6 versus 8.1 +/- 2.0 dB [p < 0.01], respectively, in the left anterior, lateral, and inferior wall of the ventricle). Cal-IBS remained unchanged after dialysis compared with baseline. CV-IBS and ultrafiltration volume were significantly correlated.

CONCLUSION

HD leads to a decrease in CV-IBS that appears to be preload-dependent. This finding is in concordance with diminished left ventricular performance during HD.

Patients with a hypertensive response to exercise have impaired systolic function without diastolic dysfunction or left ventricular hypertrophy

OBJECTIVES

We sought to determine if a hypertensive response to exercise (HRE) is associated with myocardial changes consistent with early hypertensive heart disease.

BACKGROUND

An HRE predicts the development of chronic hypertension (HT) and may reflect a preclinical stage of HT.

METHODS

Patients with a normal left ventricular (LV) ejection fraction and a negative stress test were recruited into three matched groups: 41 patients (age 56 +/- 10 years) with HRE (>210/105 mm Hg in men; >190/105 in women), comprising 22 patients with (HT+) and 19 without resting hypertension (HT-); and 17 matched control subjects without HRE. Long-axis function was determined by measurement of the strain rate (SR), peak systolic strain, and cyclic variation (CV) of integrated backscatter in three apical views.

RESULTS

An HRE was not associated with significant differences in LV mass index. Exercise performance and diastolic function were reduced in HRE(HT+) patients, but similar in HRE(HT-) patients and controls. Systolic dysfunction (peak systolic strain, SR, and CV) was significantly reduced in HRE patients (p < 0.001 for all). These reductions were equally apparent in patients with and without a history of resting HT (p = NS) and were independent of LV mass index and blood pressure (p < 0.01).

CONCLUSIONS

An HRE is associated with subtle systolic dysfunction, even in the absence of resting HT. These changes occur before the development of LV hypertrophy or detectable diastolic dysfunction and likely represent early hypertensive heart disease.

Analysis of transmural trends in myocardial integrated backscatter in patients with progressive systemic sclerosis

Cardiac involvement in progressive systemic sclerosis (PSS) is common and has a strong negative impact on the prognosis, especially when autoantibodies are present. To determine whether ultrasonic tissue characterization can detect early ultrastructural changes in the sclerodermal myocardium, we analyzed the transmural heterogeneity in myocardial integrated backscatter (THIB). "A-THIB" was defined as the absolute difference in integrated backscatter between the left (subendocardial) and right (subepicardial) ventricular halves of the myocardium in the septum and posterior wall, and was measured in 11 patients with PSS and 10 age- and sex-matched healthy participants. A-THIB in patients with PSS was higher than that in healthy participants (1.3 +/- 1.3 vs 4.0 +/- 1.4 dB for the septum and 1.1 +/- 0.7 dB vs 2.8 +/- 0.4 dB for the posterior wall; mean +/- SD, respectively, P <.0005). Septal A-THIB was higher in patients with PSS with than without anti-Scl70 or antinucleolar antibodies (3.2 +/- 1.1 vs 5.0 +/- 1.0 dB, P =.0165). Early changes in the myocardium of patients with PSS, possibly related to increased interstitial collagen deposition, can be detected by quantitative analysis of THIB.

Assessment of menopause-induced myocardial changes by integrated backscatter during inotropic stimulation and atropine injection

Estradiol has been considered as an L-type calcium channel blocker in animal studies. The concentration of estradiol decreases after menopause. Therefore, we hypothesized that human myocardial functional changes developed after menopause, and those changes could be evaluated through the use of cyclic variation of integrated backscatter (CVIBS). A total of 16 patients with menopause (native and surgical menopause), follicular stimulating hormone > 40 IU/L and estradiol < 20 pg/mL underwent dobutamine stress IBS examination (study group). Another 12 women with normal menstruation, follicular stimulating hormone < 40 IU/L and estradiol > 20 pg/mL were enrolled as a control group. All patients had a low likelihood of coronary artery disease and negative results of dobutamine stress echocardiography and (201)thallium scintigraphy. To avoid the phenomenon of anisotropy, the amplitude and phase of IBS were acquired only in the midanteroseptal segment from the parasternal short axis view. The baseline amplitudes of CVIBS differed between the control and study groups (5.9 +/- 1.2 dB vs. 8.1 +/- 2.1 dB; p = 0.007). The amplitudes during low-dose (20 microg/kg-min) and peak-dose (40 microg/kg-min) dobutamine infusion were also different between these 2 groups (5.7 +/- 0.9 dB vs. 8.4 +/- 1.7 dB; p < 0.001; 6.0 +/- 1.0 dB vs. 7.7 +/- 2.4 dB; p = 0.026). However, there were no significant differences in amplitudes between these two groups after atropine injection (control group 4.5 +/- 1.2 dB, study group 5.3 +/- 1.0 dB; p = NS). No significant differences of phase were found either at baseline or under dobutamine infusion between the two groups. Multivariate linear regression analysis showed that only menopause status associated significantly with the amplitudes at different doses of dobutamine infusion (p < 0.05). In conclusion, human myocardial functional changes are observed by CVIBS after menopause. Postmenopausal women have higher values of amplitude than premenopausal women. These phenomena persist during low and peak doses of dobutamine infusion, but are abolished by atropine injection.

Influence of contractility on myocardial ultrasonic integrated backscatter and cyclic variation in integrated backscatter

To evaluate the effects of left ventricular contractility on the changes of average image intensity (AII) of the myocardial integrated backscatter (IB) and cyclic variation in IB (CVIB), 7 adult mongrel dogs were studied. The magnitude of AII and CVIB were measured from myocardial IB carves before and after dobatamine or propranolol infusion. Dobutamine or propranolol did not affect the magnitude of AII (13.8 +/- 0.7 vs 14.7 +/- 0.5, P > 0.05 or 14.3 +/- 0.5 vs 14.2 +/- 0.4, P > 0.05). However, dobutamine produced a significant increase in the magnitude of CVIB (6.8 +/- 0.3 vs 9.5 +/- 0.6, P < 0.001) and propranolol induced significant decrease in the magnitude of CVIB (7.1 +/- 0.2 vs 5.2 +/- 0.3, P < 0.001). The changes of the magnitude of AII and CVIB in the myocardium have been demonstrated to reflect different myocardial physiological and pathological changes respectively. The alteration of contractility did not affect the magnitude of AII but induced significant change in CVIB. The increase of left ventricular contractility resulted in a significant rise of the magnitude of CVIB and the decrease of left ventricular contractility resulted in a significant fall of the magnitude of CVIB.

Dipyridamole stress ultrasonic myocardial tissue characterization in patients with Kawasaki disease

Dipyridamole stress integrated backscatter (IBS) was used for evaluation of myocardial ischemia or damage in 31 children with coronary artery lesions caused by Kawasaki disease, in comparison with thallium-201 myocardial imaging. All patients underwent echocardiography at rest and after dipyridamole stress at the anterior interventricular septum, posterior wall (PW), and inferior wall (INF). At rest, no significant difference was seen in cyclic variation (CV) of IBS in the regions with normal or abnormal distribution on Tl-201 imaging. But in the regions showing abnormal distribution after stress, CV decreased significantly. A delayed study after stress showed the recovery of CV to the level at rest in all patients. Sensitivity of abnormal cyclic variation integrated backscatter was 75% in the PW and 91% in the INF, and specificity was 91% in the PW and 90% in the INF, compared with the results of thallium-201 imaging. Dipyridamole stress IBS can provide sensitive detection of myocardial ischemia or damage in Kawasaki disease.

Transmural heterogeneity of myocardial integrated backscatter in diabetic patients without overt cardiac disease

It is important to detect early changes in diabetic myocardium, because some diabetic patients suffer from diabetic cardiomyopathy, especially those with poorer glycemic control or hypertension (HT). To clarify whether ultrasonic tissue characterization can noninvasively detect ultrastructural changes in diabetic myocardium, we analyzed the transmural heterogeneity in myocardial integrated backscatter (THIB) in 20 diabetic patients and 16 normal subjects. THIB was defined as the absolute value of difference of integrated backscatter between the endocardial and epicardial half of the myocardium. THIB in diabetic patients was significantly greater than that in normal subjects. In diabetic patients, there was a significant correlation between glycosylated hemoglobin and THIB, and the greater THIB was shown in patients with HT compared with those without HT. Early changes in the myocardium, related to increased interstitial collagen deposition or other occult cardiomyopathic changes, may be detected on the basis of quantitative analysis of THIB in diabetic patients.

Ultrasonic integrated backscatter coefficient profiling of human coronary arteries in vitro

A theoretical formulation for the profile of the integrated backscatter coefficient (IBC) is derived. This new formulation is based on a theoretical treatment by Chen et al. [1]. It includes correction for the diffraction of the ultrasonic beam and correction for the non-ideal nature of the reference signal. The inclusion of these correction factors permits accurate quantitative profiling of the IBC over the transducer focal zone. Experimental measurements are first performed on well-calibrated vessel-equivalent phantom materials and subsequently on human coronary arteries in vitro. A spherically focused 50.0 MHz f/1.83 transducer is used. IBC profiles are shown for three samples that are representative of early, mid, and advanced atherosclerotic coronary disease. The IBC profiles clearly differentiate the arterial tissues. However, variation between samples with histologically confirmed intimal thickening (N = 24) was large. The mean IBC (+/- 1 standard deviation), in (Sr.mm)-1, for media, adventitia, and thickened intima were 3.86 x 10(-3), 1.53 x 10(-2), and 2.24 x 10(-2), respectively. The mean IBC of thickened intima is larger than previous measurements obtained from femoral arteries, and the mean IBC for media and adventitia layers are lower, reflecting differences in tissue composition between coronary and femoral vessels.

Prevention of doxorubicin (adriamycin)-induced cardiomyopathy by simultaneous administration of angiotensin-converting enzyme inhibitor assessed by acoustic densitometry

The purpose of our study has to determine the myocardial protective effects of the angiotensin-converting enzyme (ACE) inhibitor temocapril (TEM, 7 mg/kg/day) simultaneously administered with doxorubicin (Adriamycin). Twenty male Sprague-Dawley rats were intraperitoneally administered a cumulative dose of 15 mg/kg of doxorubicin (each dose of 1.0 mg/kg x 15) for 3 weeks, and divided into TEM-untreated and -treated rats. Seven control rats were injected with saline intraperitoneally. Body weight, hemodynamics, and echocardiographic measurements including quantitative analysis of ultrasonic integrated backscatter (IB) were obtained for 12 weeks after treatment. Finally, rats were killed for histopathologic study. At 6 weeks, end-diastolic left ventricular diameter (LVD) and percentage fractional shortening (%FS) were similar in TEM-treated and TEM-untreated rats, but cyclic variation of IB (dB) significantly decreased in TEM-untreated rats (7.3 +/- 1.2; control rats, 9.7 +/- 0.9; p < 0.01). At 12 weeks, %FS decreased in TEM-untreated rats (26.1 +/- 6.1%: TEM-treated rats, 34.2 +/- 6.2; p < 0.05), and calibrated IB (dB) in TEM-untreated rats (15.5 +/- 0.5) increased as compared with that in TEM-treated rats (12.1 +/- 0.7; p < 0.01). Interstitial collagen accumulation increased in TEM-untreated rats and was inhibited in treated rats. Simultaneous administration of TEM with doxorubicin was beneficial in preventing doxorubicin-induced myocardial damage, and myocardial tissue characterization was useful for the early detection of myocardial damage and the assessment of therapy.

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.

Ultrasonic tissue characterization in patients with dilated cardiomyopathy: comparison with findings from right ventricular endomyocardial biopsy

AIM

The clinical usefulness of integrated backscatter (IB) imaging was compared with right ventricular endomyocardial biopsy for assessing myocardial damage in patients with dilated cardiomyopathy (DCM).

METHODS

We examined 15 patients with DCM and 20 healthy controls. In addition to the conventional M-mode echocardiographic parameters, we determined the cyclic variation in IB values (CV-IB) obtained from parasternal short axis views of the left ventricle just under the transducer for both the interventricular septum (IVS) and the left ventricular posterior wall (PW). The per cent fibrosis area (%) and the transverse diameter of myocytes (microm) were measured in right ventricular endomyocardial biopsy specimens by computer image analysis. To analyze the relationship between pathological findings and CV-IB, we divided patients into four subgroups on the basis of the pathological characteristics of endomyocardial biopsy specimens as follows: degeneration dominant group (n = 5), fibrosis dominant group (n = 5), dilated phase hypertrophic cardiomyopathy (n = 2), and mixed type (n = 3).

RESULTS

CV-IB in the IVS and the PW was lower in patients with DCM (8.8 +/- 2.9, 8.3 +/- 2.7 dB, respectively) than in normal subjects (14.4 +/- 2.9, 13.6 +/- 2.6 dB, respectively). Biopsy findings showed a mean per cent fibrosis area of 24.0 +/- 12.3%, and a mean myocyte diameter of 14.3 +/- 2.9 microm in patients with DCM. CV-IB was correlated with both of these findings: per cent fibrosis area (r = -0.56 in IVS, r = -0.56 in PW) and myocyte diameter (r = 0.67 in IVS, r = 0.71 in PW). CV-IB was decreased in all DCM subgroups compared with normal subjects, but there was no significant difference between subgroups.

CONCLUSIONS

CV-IB was correlated with both the extent of fibrosis in myocardial tissue and the myocyte diameter. These findings suggest that ultrasonic tissue characterization is a good indicator of the severity of fibrosis and myocyte atrophy in patients with DCM.

[Characterization of myocardial tissue by ultrasound: backscatter]

One of the most important goals in Cardiology is to identify, noninvasively, the normal as well as pathological changes in structure and function of myocardial tissue in order to recognize their etiology and severity. Ultrasonic Tissue Characterization is an approach to define the physical state of the heart by the analysis of the pathological changes that modify cardiac tissue physical properties, therefore generating an ultrasonic signal alteration. Among the most practical types of analysis of this data is the acoustic parameters measurement, and measurements based on integrated backscatter have been utilized the most. Backscatter is the ultrasonic quantification reflected back to the transducer, therefore emanating from myocardial structures or "scatterers". This method has been used to study many patients with hypertrophy, cardiomyopathies, cardiac allograft rejection. But is the investigation of myocardial ischemia-viability one of the most clinically relevant applications because of the importance of selecting, non-invasively, and at a relatively low cost those patients with coronary artery disease in whom myocardial asynergy is noted by conventional echocardiography and/or angiography. The magnitude of alterations in backscatter measurements such as the cyclic variation of integrated backscatter are markers of myocardial viability and could better identify patients who stand to benefit the most revascularization procedures.

Myocardial tissue characterization in heart failure by real-time integrated backscatter

OBJECTIVE

Differentiation between normal and abnormal physical state of the myocardium, not possible with conventional echocardiography, so far could be done with integrated backscatter (IBS) as a research tool only.

METHODS

This study investigates myocardial texture analysis with new commercially available real time IBS in 12 normal individuals and in 18 patients with severe left ventricular dysfunction due to coronary artery disease (CAD) in 8 and dilated cardiomyopathy (DCM) in 10 patients. Analysis of IBS amplitude and cyclic variation (dB) in the parasternal long and short axis view of the septum and the posterior wall were measured and corrected with IBS curve of the blood to get absolute values.

RESULTS

Compared to normal individuals patients with left ventricular dysfunction had a reduced myocardial cyclic variation (P<0.0001), which correlated to regional systolic wall thickening (r=0.64, P=0.001) and global shortening fraction (r=0.62, P<0.01). Although systolic wall thickening in the posterior wall was lower in CAD patients (% thickening, 11.9+/-10 vs. 21.9+/-8, P=0.004), absolute cyclic variation was reduced in both, CAD and DCM patients in the same order of magnitude. However, the higher maximal IBS amplitude in the posterior wall observed in CAD when compared to DCM patients (13.2+/-4.4 vs. 9.2+/-2.4 dB; P=0.002) indicate fibrosis or scar. The dissociation between cyclic variation and systolic wall thickening could implicate hybernating myocardium.

CONCLUSION

Real-time IBS has progressed from research to routine as a tool to obtain additional and valuable information to conventional echocardiography in daily practice.

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.