Early identification with ultrasonic integrated backscatter of viable but stunned myocardium in dogs

Cyclic Variation of Spectral Parameters for the Differentiation of Atrial Myocardium Before and Immediately Following Radiofrequency Ablation

Radiofrequency ablation (RFA) is a common treatment of atrial fibrillation. However, current treatment is associated with a greater than 20% recurrence rate, in part due to inadequate monitoring of tissue viability during ablation. Spectral parameters, in particular cyclic variation of integrated backscatter (CVIB), have shown promise as early indicators of myocardial recovery from ischemia. Our aim was to demonstrate the use of spectral parameters to differentiate atrial myocardium before and after radiofrequency ablation. An AcuNav 10 F catheter was used to collect radiofrequency signals from the posterior wall of the left atrium of patients before and immediately after RFA for AF. The normalized power spectrum was obtained and three spectral parameters (integrated backscatter [IB], slope, and intercept) were extracted across two continuous heart cycles. Parameters were gated for ventricular end-diastole and compared before and after ablation. Additionally, the cyclic variation of each of these three parameters was generated as an average of the variation across the two recorded heart cycles. Data from 14 patients before and after ablation demonstrated a significant difference in the magnitude of the cyclic variation of integrated backscatter (9.0 vs. 6.0 dB, p < .001) and cyclic variation of the intercept (14.0 vs. 11.5 dB, p = .04). No significant difference was noted in the magnitude of the cyclic variation of the slope. Among spectral parameters gated for end-diastole, significant differences were noted in the slope (-4.39 vs. -3.73 dB/MHz, p = .002) and intercept (16.8 vs. 11.9 dB, p = .002). No significant difference was noted in the integrated backscatter. Spectral parameters are able to differentiate atrial myocardium before and immediately following ablation and may be useful in monitoring atrial ablations.

Ultrasonic Assessment of Myocardial Microstructure in Hypertrophic Cardiomyopathy Sarcomere Mutation Carriers With and Without Left Ventricular Hypertrophy

BACKGROUND

The noninvasive assessment of altered myocardium in patients with genetic mutations that are associated with hypertrophic cardiomyopathy (HCM) remains challenging. In this pilot study, we evaluated whether a novel echocardiography-based assessment of myocardial microstructure, the signal intensity coefficient (SIC), could detect tissue-level alterations in HCM sarcomere mutation carriers with and without left ventricular hypertrophy.

METHODS AND RESULTS

We studied 3 groups of genotyped individuals: sarcomere mutation carriers with left ventricular hypertrophy (clinical HCM; n=36), mutation carriers with normal left ventricular wall thickness (subclinical HCM; n=28), and healthy controls (n=10). We compared measurements of echocardiographic SIC with validated assessments of cardiac microstructural alteration, including cardiac magnetic resonance measures of interstitial fibrosis (extracellular volume fraction), as well as serum biomarkers (NTproBNP, hs-cTnI, and PICP). In age-, sex-, and familial relation-adjusted analyses, the SIC was quantitatively different across subjects with overt HCM, subclinical HCM, and healthy controls (P<0.001). Compared with controls, the SIC was 61% higher in overt HCM and 47% higher in subclinical HCM (P<0.001 for both). The SIC was significantly correlated with extracellular volume (r=0.72; P<0.01), with left ventricular mass and E' velocity (r=0.45, -0.60, respectively; P<0.01 for both), and with serum NTproBNP levels (r=0.36; P<0.001).

CONCLUSIONS

Our findings suggest that the SIC could serve as a noninvasive quantitative tool for assessing altered myocardial tissue characteristics in patients with genetic mutations associated with HCM. Further studies are needed to determine whether the SIC could be used to identify subclinical changes in patients at risk for HCM and to evaluate the effects of interventions.

Review: New approaches to the assessment of left ventricular hypertrophy

In hypertension, Left ventricular hypertrophy is initially a useful compensatory process that represents an adaptation to increased ventricular wall stress; however, it is also the first step toward the development of overt clinical disease. For this reason most international guidelines recommend the assessment of cardiac target organ damage in hypertensive patients for cardiovascular risk stratification. It is therefore of great importance to keep in mind the strengths and weakness of the different available methods for LVH assessment.

Several methods are currently available for the assessment of LVH; however the various techniques differ in cost, availability, sensitivity and specificity. Due to its wide availability and its low cost, eLectrocardiography should be part of all routine assessment of subjects with high blood pressure; however, despite its good specificity, the sensitivity for LVH detection is low. Several other methods have been proposed for LVH detection. Cardiac magnetic resonance imaging allows 3D reconstruction of the heart with high spatial resolution; however its main limitation is represented by the relatively low availability and by its costs. Echocardiography certainly represents a valuable method for the detection of LVH in hypertensive patients, due to its wide availability and its relatively low cost. The main limitations of the technique are represented by the lower spatial resolution and reproducibility in comparison with magnetic resonance. The development of new matrix-array transducers and new software for 3D reconstruction with echocardiography make this approach particularly promising for the future; in the meantime, standard echocardiography, widely available and with low cost, will probably remain the most used tool for the evaluation of left ventricular structure and function in hypertension.

Improving the reproducibility of the cyclic variation of myocardial backscatter

The goal of myocardial tissue characterization is to augment information provided by two- and three-dimensional echocardiographic imaging, Doppler blood flow and speckle- or Doppler-derived tissue motion. Tissue characterization based on the systematic variation ofbackscattered ultrasound during the cardiac cycle ('cyclic variation') appears to be effective in characterizing both focal and diffuse myocardial pathologies. Unfortunately, comparison ofresults from different laboratories is difficult because of a lack of consistency among the several reported methods of analyzing the cyclic variation data. The goals of the present work are to present an improved method of analysis and to demonstrate that apparent disagreements are attributable primarily to the distinct approaches employed by different investigators. The improved automated method for determining the magnitude of cyclic variation utilizes binomial smoothing and an average deviation method and was validated using data acquired from 23 patients. This method illustrates a systematic means for resolving differences between laboratories. This resolution facilitates future comparisons between the cyclic variation of myocardial backscatter and measurements derived, for example, from strain-related approaches.

Integrated backscatter for the assessment of myocardial viability

PURPOSE OF REVIEW

Ultrasonic tissue characterization is a non-invasive diagnostic method that uses myocardial integrated backscatter analysis to determine contractile performance and myocardial viability independent of wall motion. This review discusses recent clinical findings regarding the application of ultrasonic tissue characterization for the assessment of myocardial viability.

RECENT FINDINGS

As this technique is non-invasive, ultrasonic tissue characterization can be used to predict the patency of infarct-related arteries in patients in the early stage of acute myocardial infarction. Several recent studies have shown that this technique is useful in identifying myocardial contractile reserve. The accuracy of ultrasonic tissue characterization for predicting functional recovery after coronary reperfusion is comparable to dobutamine echocardiography and radionuclide methods. Several studies have suggested that the cyclic variation of myocardial integrated backscatter reflects myocardial viability rather than contractile reserve. The cyclic variation of integrated backscatter is associated with myocardial viability confirmed by the integrity of the microvasculature identified by contrast echocardiography. In addition, the cyclic variation of integrated backscatter better reflects myocardial viability confirmed by the integrity of cellar metabolism than contractile reserve.

SUMMARY

Ultrasonic tissue characterization with integrated backscatter is a useful non-invasive method that can provide unique information for the assessment of myocardial viability.

Comparison of Acoustic Densitometry and Dobutamine Echocardiography for an Assessment of Myocardial Viability

AIM

The aim of this study has been to compare acoustic densitometry and dobutamine echocardiography for an assessment of myocardial viability.

METHODS AND RESULTS

Thirty-four patients with coronary artery disease and dysfunctional myocardial segments, who were referred for myocardial revascularization, underwent a viability assessment using low-dose dobutamine echocardiography and acoustic densitometry. Results of the two techniques were compared to follow-up resting echocardiography. This follow-up examination was performed at a mean of 3 months after successful revascularization in order to assess the recovery of function in revascularized, initially dysfunctional segments. Echocardiography was performed in standard views using 16-segment model of the left ventricle. Viable myocardium was identified by the augmentation of systolic thickening of an abnormal segment by at least one grade during dobutamine infusion and by the value of the maximal amplitude of cyclic variation of integrated backscatter. Acoustic densitometry had the sensitivity and specificity to predict functional recovery 90% and 77%, respectively. Dobutamine echocardiography had the sensitivity and specificity to predict contractile reserve 83% and 81%, respectively. The results were statistically comparable. Concordance between these methods was 80%.

CONCLUSION

Acoustic densitometry and dobutamine echocardiography did not statistically differ in the prediction of functional recovery dysfunctional myocardial segments after revascularization.

Ultrasonic Tissue Characterization Predicts Left Ventricular Remodeling in Patients with Acute Anterior Myocardial Infarction after Primary Coronary Angioplasty

OBJECTIVES

The aim of this study was to assess the role of cyclic variation (CV) of myocardial integrated backscatter (IBS) in the prediction of left ventricular (LV) remodeling in patients with anterior acute myocardial infarction (AMI) after primary coronary angioplasty.

BACKGROUND

Some studies have shown that the CV of myocardial IBS predicts myocardial viability for patients with AMI.

METHODS

We recorded short-axis IBS images within 24 hours of angioplasty in 80 patients with anterior AMI. Two parameters were measured: the magnitude of CV and the normalized time delay (NTD). The increase in LV end-diastolic volume (LVEDV) at 4 weeks (DeltaLVEDV) was defined as LV remodeling (>20% increase from baseline).

RESULTS

Patients were divided into two groups according to LV remodeling status: the remodeling group (n = 41) and the nonremodeling group (n = 39). There was a significant difference in the magnitude of CV between the two groups (5.11 +/- 1.47 vs 5.96 +/- 189 dB, P < .05), and the NTD was significantly different in the two groups (1.57 +/- 0.31 vs 1.23 +/- 0.32, P < .0001). The correlation between the magnitude of CV and DeltaLVEDV was significant but weak (r = -0.338, P < .01). There was significant correlation between NTD and DeltaLVEDV (r = 0.443, P < .0001). Using NTD greater than 1.35 as the optimal cutoff, the sensitivity, specificity, and positive and negative predictive values to predict LV remodeling were 82%, 86%, 87%, and 80%, respectively.

CONCLUSIONS

Myocardial IBS, especially NTD, is useful for predicting LV remodeling in patients with AMI after primary coronary angioplasty.

Sensitive detection of myocardial viability in chronic coronary artery disease by ultrasonic integrated backscatter analysis

BACKGROUND

Myocardial viability is not synonymous with contractile reserve and identifiable in a significant percentage of dysfunctional myocardial segments without contractile reserve. The usefulness of ultrasonic tissue characterization by the phase-corrected magnitude of cyclic variation of integrated backscatter (MVIB) in chronic coronary artery disease is not fully validated. Thus, whether MVIB predominantly reflects the contractile reserve or myocardial viability of chronically dysfunctional myocardium was determined.

METHODS

The MVIB of severely dysfunctional interventricular septum or posterior wall was measured in 34 consecutive patients with previous myocardial infarction. Dobutamine stress echocardiography and fluorine-18 fluorodeoxyglucose positron emission tomography were used as the standards of contractile reserve and myocardial viability, respectively.

RESULTS

Among 44 dysfunctional segments, only 15 were judged as having contractile reserve and 29 were judged as not by dobutamine stress echocardiography, whereas 26 segments showed myocardial viability using fluorine-18 fluorodeoxyglucose positron emission tomography and 18 did not. MVIB was greater in segments with than in those without contractile reserve (4.7 +/- 2.2 vs -1.4 +/- 4.9 dB, P < .0001), but there was considerable overlap between the groups. On the other hand, MVIB of segments with and without myocardial viability (4.1 +/- 2.6 vs -4.3 +/- 3.3 dB, P < .0001) was distinctly different and predicted myocardial viability with a sensitivity of 92% and a specificity of 94%.

CONCLUSIONS

For patients with chronic coronary artery disease, MVIB better reflects myocardial viability than it does contractile reserve. Ultrasonic tissue characterization, in concordance with fluorine-18 fluorodeoxyglucose positron emission tomography, is a sensitive method for detecting myocardial viability.

Cyclic variation of myocardial integrated backscatter and myocardial wall thickness during percutaneous coronary angioplasty

Cyclic variation of myocardial integrated backscatter (CVIBS) and change in myocardial wall thickness (WT%) were evaluated during percutaneous transluminal coronary angioplasty (PTCA). Fourteen patients who underwent PTCA of the proximal left anterior descending (LAD) coronary artery were included in the study. PTCA was performed by inflating the balloon at the site of the LAD lesion for 1 minute. CVIBS was measured at three episodes during PTCA in the parasternal short-axis view: before the inflation, at the end of 1-minute inflation, and at the fifth-minute after deflation of the balloon. Three regions of interest were used to evaluate the three-vessel territories: mid-anteroseptal area for LAD, mid-posterolateral area for circumflex artery, and mid-inferior area for right coronary artery. The WT% was calculated in each area. In the LAD territory, CVIBS measured at the end of 1-minute inflation was lower than the values obtained before PTCA, 5.2 +/- 1.0 decibel (dB) versus 3.7 +/- 0.7 dB (P < 0.01). CVIBS magnitudes increased at the fifth-minute after the deflation back up even to higher levels than pre-PTCA values,6.1 +/- 1.0 dB versus 5.2 +/- 1.0 dB (P < 0.01). The WT% values decreased during balloon inflation but did not recover to the pre-inflation values measured at fifth-minute after deflation. In other sites, there was no change in either CVIBS or WT% values at any time studied. The observed increase in CVIBS may be an indicator of restoration of blood flow to ischemic myocardium.

Use of myocardial backscatter as a quantitative tool for dobutamine echocardiography: feasibility, response to ischemia and accuracy compared with coronary angiography

BACKGROUND

Integrated backscatter (IB) changes with ischemia, but most prior studies have involved parasternal imaging, which limited the number of evaluable segments. We sought to assess the efficacy and feasibility of IB from the apical views, and compare this to myocardial Doppler findings and wall motion analysis during dobutamine echocardiography.

METHODS AND RESULTS

Forty-one patients undergoing dobutamine echocardiography had gray scale images and color myocardial Doppler acquired in three apical views. Cyclic variation IB (CVIB), time to peak IB (tIB, corrected for QT interval) and Doppler peak velocity (PV) in the same segment at rest and peak stress were assessed offline from digital cineloops at 80-120 frames/s. Significant coronary disease was defined by quantitative angiography as > 50% stenosis. Analysis of the waveform in the apical views was feasible in 82% of segments. The backscatter curve was shown to be biphasic, with correlation of the first peak with peak tissue velocity, and significant regional variation. However, the response to normal segments was different with tissue Doppler (increased velocity) and backscatter (no change). Ischemia was associated with a lower peak tissue velocity and lower CVIB. Only resting tissue velocity and tIB (not CVIB) distinguished scar from ischemic segments. Using an optimal cutoff of < 5.3 dB at rest achieved a sensitivity of 55%, a specificity of 76% and an accuracy of 75% when compared to angiography. The same cutoff at peak achieved a sensitivity of 58%, a specificity of 80% and an accuracy of 76%.

CONCLUSIONS

CVIB and tissue velocity responses to stress are different, but both may be used to identify abnormal segments in patients with CAD. However, while measurement of CVIB is feasible in the apical views, the variability caused by anisotropy limits the accuracy of a single cutoff.

Influence of propranolol infusion on cyclic variation of myocardial integrated backscatter in hypertrophic obstructive cardiomyopathy

It has been demonstrated that cyclic variation, assessed by myocardial integrated backscatter, reflects regional myocardial contractile function. The aim of this study was to investigate the influence of administration of beta-blocker propranolol on cyclic variation in patients with hypertrophic cardiomyopathy and persistent left ventricular (LV) pressure gradient and to test the hypothesis that the reduction of LV pressure gradient would be related to the change in regional contractile function. Before and after 2 mg propranolol infusion, transthoracic echocardiography with integrated backscatter analysis was performed on 11 patients (8 men and 3 women, mean age 54 +/- 12 years old). Integrated backscatter curves were obtained from the ventricular septum and LV posterior walls. With propranolol infusion, there was a significant reduction of LV fractional shortening (0.39 +/- 0.08 to 0.34 +/- 0.09, P <.01) and LV pressure gradient (83 +/- 40 mm Hg to 42 +/- 32 mm Hg, P <.001). In the posterior wall, the magnitude of cyclic variation significantly decreased (7.1 +/- 2.2 dB to 5.6 +/- 1.8 dB, P <.01), whereas in the septum, no apparent change in this parameter was observed (5.8 +/- 2.1 dB to 4.7 +/- 1.9 dB). Our findings suggest that in this form of cardiomyopathy, (1) the posterior wall myocardium is more susceptible to negative inotropic effects than the septum; (2) the reduction of LV pressure gradient is not related to that of regional wall motion; and (3) poor response of the ventricular septum is possibly because of more severe myocardial disarray and hypertrophy.

Enhanced method for predicting left ventricular reverse remodeling after surgical repair of aortic regurgitation: application of ultrasonic tissue characterization

To predict left ventricular (LV) reverse remodeling after surgical repair of aortic regurgitation, we examined 30 patients with aortic regurgitation accompanying LV dilatation by myocardial tissue characterization with integrated backscatter method. Before and after operation, the magnitude of cyclic variation of integrated backscatter (CVIB) was obtained from anterior septum and posterior wall, and averaged value was calculated in each patient. Before operation, LV end-diastolic dimension, fractional shortening, and LV end-diastolic pressure were not significantly different between the patients with (group GR) and without (group PR) decreased LV end-diastolic dimension after operation. Under these conditions, CVIB, which was 9.6 +/- 1.0 dB from healthy volunteers, was significantly greater in group GR, 5.7 +/- 1.4 dB, than that in group PR, 3.8 +/- 0.8 dB (P =.0003). The patients with CVIB >/= 4 before operation were expected to have reverse remodeling after operation with a sensitivity of 79%, a specificity of 82%. These data indicate that preoperative CVIB from the left ventricle provides pivotal information for predicting reverse remodeling after operation for aortic regurgitation in addition to the conventional echocardiographic parameters.

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.

Assessment of normal and ischaemic myocardium by quantitative M-mode tissue Doppler imaging

This paper presents a methodology and a software package developed to quantify M-mode tissue Doppler imaging (TDI), defining a number of quantitative parameters drawn from velocity and gradient curves obtained after segmenting the myocardial wall into anatomical layers. The independent clinical predictive value of these parameters to detect motion abnormalities in the presence of ischaemia was evaluated in a comparative study between a group of 17 healthy volunteers and 18 ischaemic patients. Factor analysis and stepwise logistic regression were used to assess the independent predictive value of these parameters in detecting abnormal contractility of the basal posterior segment. The statistical analysis performed has proved that any single parameter related to the gradient intensity, particularly the maximum gradient at the moment of the "e" wave, provides meaningful clinical information, achieving a rate of correct classification of 79.1% on the same data set used for the analysis. Adding additional parameters does not improve the diagnostic performance. Further testing with different settings (stress studies, other pathologies or segments) is warranted.

Ultrasonic tissue characterization in acute myocarditis: a case report

A 25-year-old woman was admitted because of acute myocarditis. Echocardiogram revealed hypokinesis of the left ventricle with increased wall thickness, but on day 7, the wall motion normalized. Cyclic variation of myocardial integrated backscatter on day I was reduced to 1.8 dB (normal range, 2.9-5.3 dB) and normalized to 3.2 dB on day 3. The normalization of the cyclic variation of integrated backscatter in the myocardium preceded the recovery of the left ventricular wall contractility, suggesting the ability of tissue characterization to predict recovery of cardiac function.

Prognostic implication of myocardial texture analysis in idiopathic dilated cardiomyopathy

BACKGROUND AND AIM

Abnormal myocardial acoustic properties have been reported in patients with idiopathic dilated cardiomyopathy (IDC). The aim of this study was to investigate the relationship between quantitative ultrasonic textural alterations of myocardium and clinical outcome in IDC.

METHODS

Baseline clinical and echocardiographic variables were obtained from 28 patients with IDC. By using a videodensitometric approach, quantitative myocardial texture analysis was performed on images obtained from septum and posterior wall (PW). Cyclic variation (CV) index of mean gray level (MGL) was calculated according to the formula: (MGLdiast-MGLsyst)/MGLdiastx100. All patients were followed for an average of 11+/-5 months for the occurrence of cardiac death or repeated hospitalization due to worsening of heart failure.

RESULTS

During follow-up, 10 patients experienced cardiac events (6 cardiac deaths and 4 heart failure events). The CV indexes of both septum and PW were significantly lower in patients with cardiac events than those of event free patients (6.8+/-9.6% vs. 13.6+/-8.2%, P<0.05 and 5.3+/-6.4% vs.15.7+/-7.2% P<0.001, respectively). Univariate analysis defined the following variables as predictors of outcome: PW-CV index (chi2=13.0, P=0.0003), transmitral E/A ratio (chi2=12.5, P=0.0004), symptom status (chi2=8.7, P=0.003), and septum-CV index (chi2=4.7, P=0.03). Multivariate stepwise regression analysis showed that the PW-CV index (chi2=7.5, P=0.006) and E/A ratio (chi2=6.5, P=0.01) were the independent predictors of outcome. The event-free survival rate of patients with PW-CV index <11% was significantly lower than those with an index > or = 11 (35.7% vs. 92.8%, P=0,001).

CONCLUSION

The assessment of severely depressed CV index provides valuable prognostic information in patients with IDC.

Myocardial texture analysis in idiopathic dilated cardiomyopathy: prediction of contractile reserve on dobutamine echocardiography

Conventional resting echocardiography is not able to predict contractile reserve (CR) of patients with idiopathic dilated cardiomyopathy. The aim of this study was to investigate whether the videodensitometric myocardial texture analysis could predict the CR of these patients. Myocardial texture analysis was performed on echocardiographic digitized images of 27 patients with IDC through a calibrated 256 gray level digitization system. Cyclic variation (CV) index of myocardial mean gray level (MGL) was calculated according to the formula: (MGL(diast) - MGL(syst))/ MGL(diast) x 100. CR was defined as the %-change of ejection fraction by 10 microg/kg per minute dobutamine infusion. A clinical follow-up was also performed for all patients for an average of 8 +/- 3 months. CR ranged from -1.8% to 50.3%. CV index of both septum and posterior wall (PW) was the single parameter significantly correlated to CR (r = 0.69 and r = 0.77, respectively, P <.0001 for both). The mean resting CV index of septum and PW were significantly lower in patients with CR less than 17%-median value of all subjects-(5.7 +/- 5.6 vs 16.9 +/- 7.9 and 5.4 +/- 5.9 vs 16.1 +/- 6.4, respectively, P <.0001 for both). A CV index of 10% for both septum and PW yielded a sensitivity of 77% and 84%, and a specificity of 84% and 84% for predicting diminished CR, respectively. The event-free survival rate was significantly lower in patients with CR less than 17% (61.5% vs 92.8%, P <.05). The CV index of both septum and PW were also significantly lower in patients with cardiac events (13.6 +/- 8 vs 4.3 +/- 6, P <.05 and 14.7 +/- 7 vs 4.1 +/- 7, P <.01, respectively). Ultrasonic myocardial texture analysis in idiopathic dilated cardiomyopathy has a high ability to discriminate the patients with and without preserved CR, and patients with unfavorable outcome as well.

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.

Ultrasonic integrated backscatter in early assessment of myocardial injury during open heart surgery

OBJECTIVES

The recovery of cyclic variation of ultrasonic integrated backscatter in myocardial ischemia provides early assessment of myocardial injury and is useful in assessing myocardial injury during open heart surgery.

METHODS

We studied 25 patients with valvular disease undergoing cardiac surgery--7 with aortic stenosis, 7 with aortic regurgitation, 6 with mitral stenosis, and 5 with mitral regurgitation. All underwent transesophageal echocardiography (before aortic cross-clamping: T-pre and 60 minutes after aortic declamping: T-60). The short-axis view at the papillary muscle level of the left ventricle was recorded and anterior areas were assessed.

RESULTS

The magnitude of cyclic variation at T-pre and T-60 was 9.4 +/- 2.5 dB and 8.8 +/- 3.0 dB, and the ratio was 97 +/- 32%. Fractional shortening at T-pre and at T-60 was 27 +/- 7% and 20 +/- 9%, and the ratio was 79 +/- 44%. Recovery of magnitude was ahead of recovery of fractional shortening. The percent recovery of magnitude at T-60 did not correlate with aortic cross-clamping time (p = 0.91), postoperative peak creatine kinase-MB (p = 0.4), or catecholamine dosage (p = 0.13), but correlated with preoperative left ventricular mass index (p < 0.01). In patients with aortic stenosis, the percent recovery of magnitude at T-60 (66 +/- 4%) was significantly lower than in those with other types of valvular disease.

CONCLUSIONS

The recovery of magnitude of cyclic variation of ultrasonic integrated backscatter provides early assessment of myocardial injury, particularly in severely hypertrophied hearts, during reperfusion after aortic declamping in open heart surgery.

Prediction of contractile reserve by cyclic variation of integrated backscatter of the myocardium in patients with chronic left ventricular dysfunction

OBJECTIVE

To clarify whether assessment of the acoustic properties of the myocardium at rest can predict contractile reserve in patients with chronic left ventricular dysfunction.

METHODS

23 patients (mean (SD) age 63 (12) years) with chronic left ventricular dysfunction were studied. The magnitude of cardiac cycle dependent variation of integrated backscatter (CVIB) of the myocardium was measured at rest in the basal and mid segment of the septum and posterior wall of the left ventricle, using a real time two dimensional integrated backscatter imaging system. The results were compared with the percentage wall thickening and the wall motion at rest and during low dose dobutamine infusion. The wall motion was graded as normal, hypokinetic, or akinetic and contractile reserve was considered present when an akinetic or hypokinetic segment improved during dobutamine infusion.

RESULTS

The CVIB at rest correlated with per cent wall thickening at rest and during dobutamine infusion (at rest, r = 0.61, p < 0.0001, during dobutamine, r = 0.76, p < 0.0001). Of the 76 segments examined, 27 showed contractile reserve. The mean CVIB at rest was significantly greater in segments with contractile reserve than in those without (p < 0.0001). CVIB above 3 dB at rest predicted segments with contractile reserve with a sensitivity and specificity of 81% and 60%, respectively (p < 0.0001).

CONCLUSIONS

CVIB reflected not only myocardial contractility but also the functional capacity of the myocardium. It predicted segmental contractile reserve in patients with chronic left ventricular dysfunction.

Coronary artery bypass grafting on the beating heart evaluated with integrated backscatter

BACKGROUND

In beating heart coronary artery bypass grafting (CABG) the effect of ischemic insult during coronary occlusion could not be evaluated immediately. Using transesophageal echocardiography, myocardial performance can be evaluated with analysis of integrated backscatter.

METHODS

In 15 beating heart CABGs, cyclic variation (CV) of integrated backscatter of the anterior wall before, during, and after the left internal thoracic artery to left anterior descending (LAD) branch anastomosis was measured with transesophageal echocardiography. The patients were divided into two groups according to collateral vessels status (good collateral group n = 6, poor collateral group n = 9).

RESULTS

In all patients, CV increased significantly after revascularization (8.56+/-2.50 to 11.47+/-3.32 dB, p < 0.0001). During LAD occlusion, significant decrease in CV was found in patients who had poor collateral arteries. At 15 minutes of LAD occlusion, CV decreased from the preocclusion value of 7.51+/-2.21 to 3.23+/-4.03 dB (p < 0.01).

CONCLUSIONS

Measurement of CV can detect the ischemic insult during coronary occlusion and the effect of revascularization in beating heart CABG.

Studies of cardiac function and myocardial tissue characterization

The heart can be studied using ultrasound techniques. The shape of the heart, its chambers, wall thicknesses, wall tissue characteristics as well as motion of walls and valve leaflets are all diagnostic information. In addition, the blood velocity and its timing within the cardiac cycle is an important diagnostic tool. In the present paper focus will be limited to the analysis of the left ventricular function as observed with two-dimensional and three-dimensional echocardiography and the characteristics of backscattered ultrasound information from the left ventricular chamber wall. Function of the heart is often studied by observation of local wall motion or comparison of chamber volume in maximum and minimum shapes during the cardiac cycle (ejection fraction). Integrated backscatter from the wall is described in examples of cardiac transplantation and hypertrophy. Study of cyclic variation of frequency-dependent attenuation and integrated backscatter indicates that these are independent parameters.

Myocardial integrated ultrasonic backscatter in patients with dilated cardiomyopathy: prediction of response to beta-blocker therapy

BACKGROUND

Myocardial integrated backscatter (IB) imaging has been reported to be useful for ultrasonic tissue characterization and delineation of myocardial viability or fibrosis. beta-Blocker therapy has beneficial effects for patients with dilated cardiomyopathy (DCM), but there are no clear findings that indicate which patients with DCM will respond to this therapy. This study was performed to evaluate whether myocardial IB analysis can predict the response to beta-blocker therapy.

METHODS AND RESULTS

We prospectively performed echocardiographic examination with IB analysis in 29 patients with DCM (20 men, 9 women) before starting bisoprolol therapy and in 15 normal subjects. Standard echocardiographic examination and IB analysis in the left ventricular wall in the 2-dimensional short-axis view were performed and the magnitude of cyclic variation (CV) of IB and calibrated myocardial IB intensity (subtracted pericardial) were obtained from the interventricular septum and the left ventricular posterior wall. Sixteen patients responded to bisoprolol therapy and 13 did not respond after 12 months of full-dose therapy. Calibrated myocardial IB intensity was lower in responders relative to nonresponders in both the interventricular septum (responders, -20.1 +/- 3.6 dB vs nonresponders, -9.8 +/- 5.1 dB, P <.0001; controls, -20.1 +/- 4.4 dB) and posterior wall (responders, -20.6 +/- 3.6 dB vs nonresponders, -14.6 +/- 4.2 dB, P =.0002; controls, -22.7 +/- 3.3 dB). Also, the lower the myocardial intensity in the interventricular septum or posterior wall, the better left ventricular systolic function improved after beta-blocker therapy. However, CV was lower in both DCM groups than in the controls, and CV in the interventricular septum was lower in nonresponders than in responders (responders, 4.0 +/- 4.1 dB vs nonresponders, -0.8 +/- 6. 1 dB, P <.02; controls, 8.3 +/- 2.4 dB). In addition, CV in the posterior wall showed no difference between the 2 DCM groups (responders, 5.6 +/- 1.3 dB vs nonresponders, 5.1 +/- 3.5 dB, P = not significant; controls, 9.6 +/- 2.5 dB). Also, the percent fibrosis on right ventricular endomyocardial biopsy specimens showed no distinctions between these 2 groups (responders, 25.1% +/- 16.1% vs nonresponders, 24.9% +/- 15.0%, P = not significant).

CONCLUSIONS

These findings suggest that left ventricular myocardial IB data, especially IB intensity, provide useful information for predicting the response to beta-blocker therapy in patients with DCM. However, right ventricular endomyocardial biopsy findings do not appear to contribute to discriminating between the 2 groups.

Detection of residual tissue viability within the infarct zone in patients with acute myocardial infarction: ultrasonic integrated backscatter analysis versus dobutamine stress echocardiography

OBJECTIVES

The goals of this study were to analyze temporal changes in cardiac cyclic variation of integrated backscatter (CVIB) in acute myocardial infarction (AMI) and to investigate the predictive value of CVIB normalization compared with that of dobutamine stress echocardiography (DSE) in the assessment of functional recovery after revascularization.

BACKGROUND

The normal CVIB is blunted by ischemia and recovers early after reperfusion, faster than wall motion improvement. Analysis of CVIB has been widely investigated for its potential to detect viable myocardium in the early stage of infarction. No studies have compared CVIB analysis with other techniques for viability assessment in patients with acute ischemic.

METHODS AND RESULTS

Integrated backscatter images were obtained in 12 patients with AMI on days 1, 3, and 7 after admission and 1 month after revascularization. On day 7, DSE was performed in all patients. On admission, 22 of 144 segments were dyssynergic. On day 1, CVIB was abnormal in all 22 infarcted segments, on day 3, in 16, and on day 7, in only 10 infarcted segments. Eight of 10 segments nonviable by CVIB (CVIB-nonviable) were also nonrespondent by DSE; whereas 12 of 14 segments viable by DSE (DSE-viable) were also CVIB-viable. At follow-up, 10 CVIB-viable segments and 1 CVIB-nonviable segment showed functional recovery; whereas 10 of 14 DSE-viable segments showed functional recovery. Thus the positive predictive value of CVIB and DSE was 83% and 72%, respectively, with a diagnostic agreement between techniques in 77% of segments.

CONCLUSIONS

Our data suggest that the normalization in CVIB in the first week after AMI accurately predicts residual tissue viability within the infarct zone. We also observed that the initial pattern of cyclic variation may be predictive of functional recovery. Finally, we found a good correlation between the recovery of a normal CVIB in segments that were still dysfunctional and a more validated method to assess tissue viability, such as the dobutamine test.

The extracellular matrix is an important source of ultrasound backscatter from myocardium

Ultrasound tissue characterization with measurement of backscatter has been employed in numerous experimental and clinical studies of cardiac pathology, yet the cellular components responsible for scattering from cardiac tissues have not been unequivocally identified. This laboratory has proposed a mathematical model for myocardial backscatter that postulates the fibrous extracellular matrix (ECM) as a significant determinant of backscatter. To demonstrate the importance of ECM, this group sought to determine whether measurements of backscatter from the isolated ECM could reproduce the known directional dependence, or anisotropy of backscatter, from intact cardiac tissues in vitro. Segments of left ventricular free wall from ten formalin fixed porcine hearts were insonified at 50 MHz, traversing the heart wall from endo- to epicardium to measure the anisotropy of myocardial backscatter, defined as the difference between peak (perpendicular to fibers) and trough (parallel to fibers) backscatter amplitude. The tissue segments were then treated with 10% NaOH to dissolve all of the cellular components, leaving only the intact ECM. Scanning electron micrographs (SEM) were obtained of tissue sections to reveal complete digestion of the cellular elements. The dimensions of the residual voids resulting from cell digestion were approximately the diameter of the intact myocytes (10-30 microm). These samples were reinsonified after seven days of treatment to compare the anisotropy of integrated backscatter. The magnitude of anisotropy of backscatter changed from 15.4 +/- 0.8 to 12.6 +/- 1.1dB for intact as compared with digested specimens. Because digestion of the myocardium leaves only extracellular sources of ultrasonic scattering, and because the isolated ECM exhibits similar ultrasonic anisotropy as does the intact myocardium, it is concluded that there is a direct association between the ECM and the anisotropy of backscatter within intact tissue. Thus, it is suggested that ultrasonic tissue characterization represents a potentially clinically applicable method for delineating the structure and function of the ECM.

Alterations in ultrasonic backscatter during intra-aortic balloon counterpulsation support in patients with acute myocardial infarction

Alterations of ultrasonic backscatter parameters have been evident in humans with myocardial infarction or ischemia. The backscatter variability could be restored in ischemic or stunned myocardium after reperfusion. The aims of this study were to determinate changes in regional myocardial ultrasonic backscatter during intra-aortic balloon counterpulsation (IABP) support in patients with acute myocardial infarction (AMI), and to evaluate whether backscatter imaging could be a functional guide of IABP support. A total of 9 patients with AMI were investigated during IABP support with a two-dimensional (2-D) ultrasonic backscatter imaging approach for parasternal short-axis view. Coronary angiography was performed in 6 of the 9 patients. A total of 21 vessel territories were studied in different modes of IABP support: 1:1, 1:2 and standby. Restoration of cyclic variation of backscatter after IABP support was demonstrated in 10 vessel territories. Failure of restoration of cyclic variation of backscatter after IABP support was noted in 6 vessel territories with severe coronary lesions (total or nearly total occlusion) or scar tissue. No changes of the ultrasonic backscatter were found in nonischemic vessel territories with patent coronary arteries or TIMI III coronary flow. In addition, the wall motion score did not change significantly with different IABP support. These results suggest that IABP could restore the cyclic variation of backscatter in ischemic myocardium. Myocardial anisotropy may play an influential role in the alterations of ultrasonic backscatter. We propose that ultrasonic backscatter could be a noninvasively functional guide of IABP use in patients with AMI.

[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.

Real time assessment of myocardial revascularization during coronary artery bypass surgery by means of ultrasonic integrated backscatter

OBJECTIVE

The recovery of cyclic variation (CV) of ultrasonic integrated backscatter (IB) may provide a more sensitive predictor of the success of myocardial revascularization. This study was designed to elucidate the possibility of real time assessment of coronary artery bypass grafting (CABG) using CV of IB.

METHODS

We studied 10 patients (61 +/- 4 years old) with the perfused areas by stenosed or occluded LAD without myocardial infarction. There were six ischemic dysfunctional areas, and four ischemic but non-dysfunctional areas. The CV of IB was measured before and just after extracorporeal circulation (ECC). Wall motion was analyzed by segmental wall thickening during systole at the same time of the IB analysis during CABG and at 3 weeks after CABG. Those 10 areas were completely revascularized.

RESULTS

In the non-dysfunctional areas, wall thickening did not change and remained at normal values before and after ECC, and 3 weeks after CABG (31 +/- 3% 29 +/- 3% and 29 +/- 5%, respectively). The magnitude of CV of IB did not also change before and after ECC (8.0 +/- 1.6 dB and 7.8 +/- 1.3 dB). However, in the ischemic dysfunctional areas, while wall thickening did not change before and after ECC (21 +/- 5% and 20 +/- 5%), it increased and reached similar values as the non-dysfunctional regions at 3 weeks after CABG (26 +/- 7%, P < 0.01 vs. before and after ECC values). The magnitude of CV of IB increased even after ECC (3.71 +/- 0.4 dB vs. 7.4 +/- 3.5 dB, P < 0.05), and reached the same level as those in the non-dysfunctional areas. There was a significant relationship between wall thickening at 3 weeks after bypass grafting and magnitude of CV of IB after ECC (r = 0.67, P < 0.05).

CONCLUSIONS

Improvement in wall motion was gradually attained after bypass grafting. On the contrary, an increase in the magnitude of CV of IB was obtained immediately after myocardial revascularization. Our data suggest that CV of ultrasonic IB method can provide close real time information regarding the effectiveness of bypass surgery.

Ultrasonic tissue characterization in predicting residual ischemia and myocardial viability for patients with acute myocardial infarction

The identification of viable myocardium and residual ischemia in patients with acute myocardial infarction has important prognostic implications. The ultrasonic tissue characterization with integrated backscatter and dobutamine-atropine stress echocardiography were performed 8.3+/-3 days after AMI in 30 patients. After coronary angioplasty for the residual stenosis of infarct-related artery, both modalities were repeated. The parameter obtained from ultrasonic tissue characterization, phase-weighted variation, could differentiate the myocardium with residual coronary stenosis or nonviable myocardium from the viable myocardium without residual coronary stenosis (p < 0.001). Using the cutoff value of 5.8 dB, the sensitivity, specificity and accuracy for detecting viable myocardium without residual coronary stenosis were 75%, 100% and 90.2%, respectively. The phase-weighted variation of the viable infarction zone restored after the coronary stenosis was relieved. In contrast, the nonviable myocardium had a small phase-weighted variation that was irrelevant to the patency of the infarct-related artery. The ultrasonic tissue characterization may be used in identifying patients with acute myocardial infarction whose infarction zones are viable without residual ischemia.

Ultrasonic tissue characterization predicts myocardial viability in early stage of reperfused acute myocardial infarction

BACKGROUND

The aim of the present study was to characterize temporal changes in cyclic variation of ultrasonic integrated backscatter (IBS), which reflects intrinsic contractile performance, in patients with reperfused acute myocardial infarction (AMI) and to elucidate the clinical value of tissue characterization in predicting myocardial viability.

METHODS AND RESULTS

We recorded short-axis IBS images before and 3, 7, and 21 days after reperfusion in 26 patients with AMI and obtained the cyclic variation of IBS in the normal and infarct zones. When cyclic variation showed synchrony and asynchrony, we expressed its magnitude as positive and negative values, respectively, called the phase-corrected magnitude. We also measured average wall motion score (dyskinesis, 4; normal, 0) of the infarct segments. The phase-corrected magnitude was lower in the infarct zone than in the normal zone before reperfusion (0.3+/-2.5 versus 5.2+/-1.7 dB, P<.05). At day 3, the phase-corrected magnitude increased by 2.1+/-2.6 dB despite no improvement in wall motion. Improvement in wall motion was observed only at day 21. The patients with the phase-corrected magnitude of > or =2.0 dB at day 3 showed significantly lower wall motion score at day 21 than did the other patients (1.7+/-0.6 versus 2.4+/-0.5, P<.01).

CONCLUSIONS

In patients with AMI, cyclic variation of IBS is blunted during ischemia but recovers much faster after reperfusion than the improvement in wall motion. The greater phase-corrected magnitude at day 3 may be a predictor of better functional improvement.

Relation of ultrasonic tissue characterization with integrated backscatter to contractile reserve in chronic left ventricular ischemic dysfunction

Previous studies have shown that viable but stunned myocardium displays contractile reserve and exhibits cardiac cycle-dependent variations of integrated backscatter, whereas infarcted myocardium does not. The present study was designed to evaluate whether integrated backscatter imaging could be useful in identifying segments with recruitable inotropic reserve in patients with chronic left ventricular (LV) ischemic dysfunction. We studied 15 patients (mean age 59 +/- 10 years) with chronic coronary artery disease, anterior or inferior wall dysfunction, and depressed LV ejection fraction (35 +/- 12%), and 6 noncardiac control subjects (mean age 49 +/- 18 years). Cardiac cycle-dependent variations of integrated backscatter were measured in anterior and inferior segments during transesophageal echocardiography and compared with the contractile response (% wall thickening) of these segments to low doses of dobutamine (5 to 10 microg/kg/min). The average magnitude of cardiac cycle-dependent variations of integrated backscatter was greater among normally contracting segments of both patients and controls (5.67 +/- 0.88 and 5.64 +/- 2.26 dB, respectively, p = NS) than among dysfunctional segments (2.77 +/- 3.05 dB, p <0.01 vs control and remote segments). Dysfunctional segments were further categorized into those with and without dobutamine-induced contractile reserve. At baseline, systolic wall thickening was similar among segments responding to dobutamine than among those that did not (3.6 +/- 2.3% vs 2.9 +/- 1.6%, p = NS). During dobutamine, systolic wall thickening increased only in segments showing improvement in wall motion score (to 24.5 +/- 4.7%), whereas it remained unchanged in segments not responding to dobutamine (to 2.0 +/- 3.7%, p <0.01). The magnitude of resting cardiac cycle-dependent variations of integrated backscatter was larger in segments responding to dobutamine than in those with persistent dysfunction (5.31 +/- 2.06 vs 0.23 +/- 0.94 dB, p <0.01) and correlated significantly (r = 0.74, p <0.01) with systolic wall thickening during dobutamine. Our data demonstrate that resting cardiac cycle-dependent variations of integrated backscatter closely parallel contractile reserve in patients with chronic LV ischemic dysfunction. This suggests that tissue characterization with integrated backscatter could be a useful adjunct to the delineation of myocardial viability in these patients.

Echocardiography for the assessment of myocardial viability

The identification of viable myocardium in the setting of acute myocardial infarction or chronic coronary artery disease with reduced left ventricular function has important prognostic and therapeutic implications. Many noninvasive methods have been used to assess viability, and recently, dobutamine stress echocardiography has been studied for this purpose. Dobutamine stress echocardiography is a safe, accessible, and relatively inexpensive technique. Moreover, its accuracy for detecting viability approaches that of positron emission tomography and thallium scintigraphy. In addition to dobutamine stress echocardiography, other echocardiographic techniques, such as myocardial contrast echocardiography and dipyridamole stress echocardiography, are being developed to delineate viability. In the future, echocardiographic methods may identify viability with enough accuracy to allow us to better select patients for revascularization procedures when the indications are otherwise unclear.

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.

Myocardial ultrasonic tissue characterization in patients with different types of left ventricular hypertrophy: a videodensitometric approach

Although analysis of the radio frequency signal is the most accurate approach to myocardial tissue characterization, clinical diffusion has been limited because of the complex technology required. Much easier to perform, videodensitometric analysis could represent a valuable alternative. Previous works carried out on radio frequency data have shown that the absolute value of ultrasonic back scatter increases while its diastole-to-systole variation decreases in the hypertrophied myocardium. This study was aimed at clarifying whether alterations in characterization indexes of ultrasonic tissue can be detected by means of a videodensitometric approach, whether a specific type of left ventricular (LV) hypertrophy can be identified with this method, and finally what possible relationships exist between parameters of contractile function and tissue characterization indexes. Myocardial echo intensity (MEI), its cyclic variation (CV), and the dynamic relationship between myocardial signal and wall thickness variations during the cardiac cycle were assessed in 20 healthy subjects, 11 patients with essential hypertension and LV hypertrophy, 15 patients with hypertrophic cardiomyopathy, and 4 patients with primary amyloidosis. The CV was lower in the interventricular septum of patients with cardiac hypertrophy as a group, compared with that of control subjects (13.0% +/- 5.6% versus 18.8% +/- 5.5%, p < 0.001), but it was similar among patients with different types of hypertrophy. In control subjects, a significant inverse correlation was found between the progressive decrease of the myocardial signal and the parallel increase in wall thickness during systole; this correlation was lost in 60% of patients with hypertrophic cardiomyopathy and 50% of those with amyloidosis, but only in 9% of patients with essential hypertension (chi square analysis 12.68, p < 0.01). The CV was associated with systolic wall thickening (r = 0.53, p = 0.0001) and fractional shortening (r = 0.44, p = 0.0014). MEI and its CV per se cannot distinguish among different types of LV hypertrophy; however, the loss of an inverse relationship between the myocardial signal and wall thickness may suggest abnormal myocardial conditions in individual patients with the same disease or comparable wall thickness.

Influence of data processing on cyclic variation of integrated backscatter and wall thickness in stunned porcine myocardium

This study was performed to investigate the relationship between the cyclic variation of integrated backscatter and myocardial wall thickening in stunned myocardium. Different definitions of cyclic variation were evaluated to be able to compare with other studies. Ultrasound data were acquired from 10 open-chested Yorkshire pigs (25-33 kg) at baseline, during regional ischemia and during 30 min of stunning, using a broadband ultrasound transducer (3-7 MHz) sutured directly upon the left ventricular myocardial wall. Cyclic variation of integrated backscatter and myocardial wall thickening were calculated using three definitions obtained from the literature. Independent of the definition, cyclic variation of wall thickness and integrated backscatter were blunted during acute ischemia and returned transiently to or above baseline during the first minute of reperfusion, followed by a gradual decrease to a level under baseline during stunning. An early return of the cyclic variation of the integrated backscatter was not observed in pigs, independent of the data processing used. The relationship between integrated backscatter and wall thickness was maintained.

Myocardial ultrasonic tissue characterization in pediatric and adult patients with hypertrophic cardiomyopathy

BACKGROUND

Hypertrophic cardiomyopathy (HCM) has different clinical and prognostic aspects in young than in adult patients. This study was undertaken to determine whether these reported differences are reflected by changes in ultrasonic backscatter parameters and whether oral treatment with verapamil modifies backscatter variables in children with HCM.

METHODS AND RESULTS

Sixty-eight subjects underwent backscatter analysis to assess the ultrasonic myocardial reflectivity and the amplitude of the cardiac cycle-dependent variation of the backscatter power curve. Subjects were divided into four groups: 10 HCM and 23 normal subjects < 10 years old and 17 HCM and 18 normal adults. Myocardial reflectivity and amplitude of the cyclic variation were assessed in the septum and in the posterior wall of all subjects. The children with HCM were restudied after long-term oral administration of verapamil. Both children and adult patients, compared with the normal control groups, showed a significant reduction in the amplitude of the cyclic variation both in the septum and in the posterior wall. In contrast, myocardial reflectivity, although significantly increased in adult HCM patients, was unchanged in the young HCM group. Verapamil administration did not significantly alter the results in the children with HCM.

CONCLUSIONS

These data demonstrate that in young HCM patients, the ultrasonic myocardial reflectivity is normal, in contrast to the significant increase observed in adult patients affected by the same disease. This observation is in accord with the different clinical manifestations reported in young HCM patients and indicates an age-dependent difference in the echogenic structure of the hypertrophied myocardium in HCM.

Ultrasonic Tissue Characterization: Review of a Noninvasive Technique for Assessing Myocardial Viability

The determination of myocardial perfusion and myocardial viability has prognostic and therapeutic implications, particularly in the current era of percutaneous transluminal coronary angioplasty and thrombolytic therapy. Several modes of investigation, including positron emission tomography, thallium-201 scintigraphy, and nuclear magnetic resonance imaging are used to differentiate viable from nonviable myocardium. Though these noninvasive tests are useful diagnostic modalities, they are expensive, time consuming, and too cumbersome to be used in the acute setting. Expeditious distinction between viable and nonviable myocardium, during acute coronary syndromes, is of great importance since reperfusion can minimize the extent of ischemic injury and infarction. An expanding body of evidence confirms that ultrasonic tissue characterization has great potential to become a practical bedside diagnostic tool in the search for salvageable myocardium. Further clinical investigative studies would help accomplish a better understanding of the complex interaction between ultrasound and myocardium. (ECHOCARDIOGRAPHY, Volume 13, July 1996)

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)

The clinical value of blunting of cyclic gray level variation for the detection of acute cardiac rejection: a two-dimensional, Doppler, and videodensitometric ultrasound study

Aims of this study were to assess (1) whether videodensitometric analysis of myocardial gray-level variation can distinguish normal from rejecting transplanted hearts in a clinical setting and (2) whether this sign, used in combination with the other conventional two-dimensional and Doppler echocardiographic findings, might improve the accuracy of ultrasound techniques. Thirty heart transplant recipients (23 men; mean age 40 years; range 20 to 54 years) were studied in 87 different situations by endomyocardial biopsy and echocardiographic evaluation. Of the 87 situations, 37 ("rejectors") showed histologic evidence of rejection of mild (n = 17) or moderate (n = 10) severity and 50 ("nonrejectors") did not show rejection processes. Cyclic variation was decreased significantly in rejectors compared with nonrejectors in both the septum (15% +/- 10% versus 25% +/- 11%; p < 0.0001) and the posterior wall (19% +/- 10% versus 25% +/- 12%; p < 0.01). When a cutoff of 20% or greater of cyclic variation in the septal wall was taken as a positivity criterion, it yielded a 70% sensitivity and 70% specificity for identifying rejection. Sensitivity of conventional two-dimensional and Doppler echocardiographic signs was 51% and increased to 89%, increased by the videodensitometric criteria (p < 0.001). Specificity was 92% and decreased to 62% with videodensitometric criteria (p < 0.001). Overall diagnostic accuracy was 75% for conventional two-dimensional echocardiographic Doppler criteria alone and remained unchanged by the addition of videodensitometric criteria. In conclusion, blunting of cyclic gray-level variation induced by rejection is detectable with videodensitometric analysis. The clinical impact of this sign appears to be limited, because the resulting increase in sensitivity is counter-balanced by a reduced specificity compared with the currently available conventional ultrasound techniques.

Dissociation between wall thickening of normal myocardium and cyclic variation of backscatter during inotropic stimulation

The purpose of this study was to determine the relation between increased myocardial wall thickening during inotropic stimulation and quantitative acoustic properties of normal myocardium in humans. We first validated a new 2-dimensional ultrasonic backscatter imaging approach for measurement of cyclic variation in the parasternal long-axis view against conventional M-mode integrated backscatter technique in 41 patients and controls (group A). We then performed 2-dimensional ultrasonic integrated backscatter imaging in 18 patients (group B) with normal segmental function at baseline to determine the magnitude of the cyclic variation of the septum and the posterior wall before and during infusion of dobutamine (10 and 20 microgram/kg/min). Group A patients showed a close correlation of the cyclic variation obtained by the new 2-dimensional ultrasonic integrated backscatter imaging approach and the conventional M-mode technique. Group B patients had mean values of cyclic variation that remained unchanged in the septum (4.4 +/- 1.4, 4.3 +/- 1.7, and 4.8 +/- 1.6 dB at baseline and at each dobutamine stage, respectively, p = NS) and in the posterior wall (6.4 +/- 1.7, 6.4 +/- 1.8 and 6.1 +/- 1.9 dB, respectively, p = NS) despite progressive dobutamine-induced increases in percent wall thickening (septum: 38 +/- 10% to 57 +/- 17% and 68 +/- 19%, respectively, and posterior wall 42 +/- 13% to 72 +/- 20% and 77 +/- 18%, respectively; both p <0.001 vs baseline for both walls). Thus, physical properties of normal myocardium remain unchanged during inotropic stimulation.

Nuclear and echocardiographic imaging for prediction of reversible left ventricular ischemic dysfunction after coronary revascularization: current status and future directions

Modern therapy of coronary artery disease (CAD) increasingly involves interventional strategies aimed at restoring blood flow to the ischemic myocardium. The emergence of coronary artery bypass surgery, percutaneous transluminal coronary angioplasty, and more recently thrombolytic therapy, has helped to change the natural course of ischemic heart disease and contribute to the overall reduction in the mortality from both acute myocardial infarction and chronic CAD. Presumably, the beneficial effects of revascularization result from improving blood supply to dysfunctional but viable regions with subsequent improvement in regional and global left ventricular function. Over the past decade, several approaches have been proposed to predict the reversibility of left ventricular dysfunction after coronary revascularization. For the most part, these methods rely on assessment of basic cellular mechanisms that are known to play a central role in the recovery of systolic function after coronary revascularization. These include sufficient resting perfusion to provide metabolic fuels and to allow wash-out of toxic metabolites, maintain membrane integrity (which includes the ability to generate transmembrane ionic gradients and to transport energy providing substrates), preserve metabolic machinery (to allow glucose, fatty acid and oxygen consumption), and recruitable inotropic reserve. Among the available modalities, thallium imaging, positron emission tomography, and low-dose dobutamine echocardiography are currently the most frequently used in the clinical setting. All allow prediction of reversible dysfunction with a high degree of sensitivity (greater than 80%). They seem to vary, however, in terms of specificity, thallium imaging showing the lowest (50-55%) and dobutamine echocardiography the highest (80-85%) specificity. New promising modalities, such as FDG or MIBI SPECT imaging, contrast echocardiography and integrated backscatter imaging are just ahead and will likely strengthen further our ability to identify jeopardized but viable myocardium.