Alterations in ultrasonic backscatter during exercise-induced myocardial ischemia in humans

The role of echocardiography in the non-invasive diagnosis of cardiac amyloidosis

INTRODUCTION

The diagnosis of cardiac amyloidosis (CA) is usually performed by endomyocardial biopsy; however, possible sampling errors and procedural risks such as cardiac tamponade, malignant arrhythmias and bleeding risk, limit its use. Therefore, a non-invasive diagnostic method appears to be necessary.

MATERIALS AND METHODS

Echocardiography plays an important role in this need. Conventional two-dimensional echocardiography appears able to detect some specific and distinguishing signs of cardiac amyloid infiltration.

RESULTS AND CONCLUSIONS

Of these, thickened right and left ventricular (LV) myocardium, normal or small LV cavity size in contrast to enlarged biatrial cavities, diffuse hyper-refractile 'granular sparkling' appearance and 'mismatch' ECG/ECHO are the most specific findings. The magnitude of cyclic variation recorded with integrated backscatter reflects structural changes in the myocardium. In patients with CA, this magnitude is reduced because myocardial amyloid infiltration is characterized by a reduction of number of "contractile" fibers. Other informations concerning LV dysfunction CA-related can be obtained by Tei index. Finally, new echocardiographic imaging modalities, such as tissue Doppler, Doppler-based strain, speckle tracking imaging and three-dimensional echocardiography, can provide some findings regarding the preclinical stages of LV dysfunction when other echocardiographic measurements are showing normal; however, these are unable to provide a non-invasive diagnosis of cardiac amyloidosis.

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.

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.

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.

Non-invasive quantitation of myocardial fibrosis using combined tissue harmonic imaging and integrated backscatter analysis in dilated cardiomyopathy

BACKGROUND

Echocardiographic modalities have challenged the myocardial tissue characterization, but this reliability has not reached to the clinical use. This study investigated whether combined tissue harmonic imaging (THI) and integrated backscatter analysis (IB) provide the reliable and quantitative information about myocardial fibrosis in idiopathic dilated cardiomyopathy (DCM) in comparison with myocardial biopsy findings.

METHODS

We studied 56 patients with DCM. All patients underwent left ventricular endomyocardial biopsy and IB with fundamental imaging (FI) and THI.

RESULTS

In patients with good echocardiographic image quality, excellent correlations between the percentage of area occupied by myocardial fibrosis (% fibrosis) and the mean of integrated backscatter during a cardiac cycle (m-IB) measured with FI or THI were seen, and the correlation was closer with THI compared with FI. While in patients with poor image quality the correlation between m-IB and % fibrosis was only modest with FI, but the correlation was excellent with THI. Four cut-off values of m-IB with THI obtained from receiver operating characteristic curve discriminated between % fibrosis of more and less than 25, 30, 35, and 40% with high sensitivity and specificity. Multivariate analysis revealed that m-IB with THI was an independent predictor for discrimination of the severity of myocardial fibrosis.

CONCLUSION

Combined IB and THI are a clinically applicable method and may be an alternative to myocardial biopsy in evaluating quantitatively myocardial fibrosis in DCM.

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.

Ultrasound Tissue Characterization by Integrated Backscatter for Analyzing Fluorouracil Induced Myocardial Damage

BACKGROUND

5-Fluorouracil (5-FU) cardiotoxicity is a well-known clinical phenomenon whose pathophysiology remains controversial. Cyclic variation of integrated backscatter (CVIBS) assesses acoustic properties of myocardium that may reflect both contractility and structural changes. The aim of this study was to evaluate CVIBS alterations in cancer patients under high-dose leucovorin and infusional 5-FU (HDLV5FU) chemotherapy.

METHOD

We prospectively evaluated 37 cancer patients under HDLV5FU treatment. Transthoracic echocardiography and CVIBS were performed at the 0th, 48th hours, and on day 15 of the first cycle. The parasternal long-axis view was preferred to obtain the image of integrated backscatter and mainly two regions of interest--interventricular septum (IVS) and posterior wall (PW)--were used.

RESULTS

Clinical cardiotoxicity was observed in two patients. No significant differences were detected in pre- and posttreatment conventional echocardiography evaluations. However, both the IVS (9.3 +/- 1.0 to 8.1 +/- 1.2 dB, P < 0.001) and PW (9.1 +/- 0.7 to 7.8 +/- 0.9 dB, P < 0.001) CVIBS values significantly decreased in all patients. All values were returned to pretreatment levels (9.2 +/- 0.9 dB in the CVIBS-IVS and 8.9 +/- 0.6 dB in CVIBS-PW, respectively) on day 15 after the treatments.

CONCLUSION

This study suggests that HDLV5FU may cause acute transient alterations in CVIBS values in the absence of clinical symptoms and signs of cardiotoxicity. The clinical value of CVIBS should be further studied in patients receiving 5-FU-based therapy.

Serial assessment of myocardial properties using cyclic variation of integrated backscatter in an adriamycin-induced cardiomyopathy rat model

Although adriamycin (Doxorubicin) is one of the most effective and useful antineoplastic agents for the treatment of a variety of malignancies, its repeated administration can induce irreversible myocardial damage and resultant heart failure. Currently, no marker to detect early cardiac damage is available. The purpose of this study was to investigate whether an assessment of the acoustic properties of the myocardium could enable the earlier detection of myocardial damage after adriamycin chemotherapy. Forty Wistar rats were treated with adriamycin (2 mg/kg, i.v.) once a week for 2, 4, 6 or 8 weeks consecutively. Left ventricular ejection fraction (LVEF) was calculated using M-mode echocardiography data. The magnitude of cardiac cycle dependent variation of integrated backscatter (CVIB) of the myocardium was measured in the mid segment of the septum and in the posterior wall of the left ventricle, using a real time two dimensional integrated backscatter imaging system. LVEF was significantly lower in the adriamycin-treated 8-week group than in the controls (75+/-9 vs 57+/-8%, p<0.05). Myocyte damage was only seen in the 8-week adriamycin-treated group. However, no significant changes of CVIB were observed between baseline or during follow-up in the ADR or control group. In conclusion, serial assessment of the acoustic properties of the myocardium may not be an optimal tool for the early detection of myocardial damage after doxorubicin chemotherapy in a rat model.

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.

Prediction of the no-reflow phenomenon with ultrasonic tissue characterization in patients with anterior wall acute myocardial infarction

The no-reflow phenomenon after acute myocardial infarction seems to be related to ischemic injury before reperfusion. Analyzing cardiac cycle-dependent variation of integrated backscatter (IBS) is a unique method to assess myocardial viability. In this study, the ability of ultrasonic tissue characterization with IBS to predict the no-reflow phenomenon was investigated in 90 patients with first anterior wall infarction who underwent successful primary percutaneous coronary intervention. IBS images were recorded on admission (before reperfusion), and the magnitude of the cyclic variation of IBS within the infarct zone was expressed as phase-corrected magnitude (PCM) by giving positive and negative values when it showed synchronous and asynchronous contraction, respectively. Myocardial contrast echocardiography was performed soon after reperfusion, and 21 patients showed substantial no-reflow. They had smaller PCM before reperfusion than patients without no-reflow (-1.6 +/- 1.9 vs 0.7 +/- 2.7 dB, respectively; p = 0.0002). Multivariate logistic regression analysis revealed that PCM before reperfusion and the number of Q waves were the independent predictors of no reflow. Using -1.0 dB as the cut-off point, PCM predicted no reflow with 66.7% sensitivity and 81.2% specificity. These results indicate that the analysis of myocardial IBS could predict the no-reflow phenomenon before reperfusion.

Ultrasonic analysis of anthracycline-induced myocardial damage using cyclic variation of integrated backscatter

To test the feasibility of integrated backscatter (IB) for detecting anthracycline cardiotoxicity, we performed conventional echocardiography and IB analysis. For interindividual comparison, 32 patients with non-Hodgkin's lymphoma and 14 control subjects were selected. Of the patients, 10 had been treated with doxorubicin doses of </=200 mg/m(2) (low dose), 15 with </=400 mg/m(2) (moderate dose), and 7 with >400 mg/m(2) (high dose). In intraindividual comparison, 8 patients were examined before doxorubicin therapy and at a dose of 100 mg/m(2) and 8 were examined before and at a 300-mg/m(2) dose. Cyclic variation of IB (CV-IB) was obtained at the left ventricular posterior wall, using a modified, commercially available system in M-mode format. In interindividual comparison, CV-IB in high- and moderate-dose groups was smaller. In intraindividual comparison, CV-IB decreased after treatment with 300 mg/m(2) of doxorubicin. CV-IB was affected in some patients treated with a moderate dose of doxorubicin. IB analysis may be helpful for detecting early anthracycline cardiotoxicity.

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.

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.

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.

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.

Alterations of myocardial ultrasonic tissue characterization by coronary angioplasty in patients with chronic stable coronary artery disease

We conducted a study to delineate the alterations in the cyclic changes of myocardial ultrasonic integrated backscatter (IBS) in patients receiving angioplasty for chronic coronary artery disease. Ultrasonic tissue characterization (UTC) and dobutamine stress echocardiography were performed in 43 patients before and 24 h after angioplasty, as well as before the follow-up angiography 3 months later. For segments being normokinetic with ischemic burden, the blunted amplitude and increased nadir deviation of IBS cyclic modulation recovered soon after angioplasty. For dyssynergic segments with contractile reserve, the angioplasty rebuilt the amplitude before the wall motion recovered, but corrected the nadir deviation tardily. In both circumstances, the coronary restenosis abolished the initial restoration. Those nonviable segments persistently revealed large deviations and small weighted amplitudes irrelevant to coronary lesions. The progress of myocardial ischemia, the development of wall motion dyssynergy and, then, the loss of viability, show different patterns of alterations in UTC after alleviating coronary obstructions.

Stress-induced changes in subendocardial tissue texture in hypertrophic cardiomyopathy: an echocardiographic videodensitometric study

BACKGROUND

Myocardial ischemia changes myocardial acoustic properties, inducing increase of integrated backscatter and blunting of cyclic variation of backscatter. Stress-induced subendocardial underperfusion has been demonstrated in patients with hypertrophic cardiomyopathy (HCM).

AIM

To evaluate the potential of a videodensitometric approach in assessing transmural ultrasonic tissue changes in HCM during dipyridamole infusion.

METHODS

Twenty-two patients (13 males, 50+/-12 years) with HCM underwent dipyridamole echo testing (DET). Myocardial gray levels amplitude was calculated off-line on digitized images in the left subendocardial (LV-endo), right subendocardial (RV-endo) region of the interventricular septum and posterior wall (long axis parasternal view).

RESULTS

The thickness of the interventricular septum and posterior wall was 1.9+/-0.3 and 1.17+/-2.1 cm, respectively. In the LV-endo layer, the cyclic variation was blunted during DET (rest = 37+/-14 vs. DET 27+/-20%, p < 0.02). In the RV-endo layer and posterior wall, no changes occurred. In the LV-endo layer of the septum, blunting of cyclic variation was more pronounced in the 10 patients with than in the 12 without ST-segment depression during DET (21.2+/-14.7% vs. 43.8+/-15.8, p < 0.01).

CONCLUSIONS

In HCM patients, DET induced blunting of cyclic variation without the evidence of wall motion abnormalities. This reduction was more pronounced when electrocardiographic signs of ischemia were simultaneously elicited by DET.

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.

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.

Ultrasonic tissue characterization with integrated backscatter during inotropic stimulation

Ultrasonic tissue characterization with integrated backscatter is an objective method to quantitatively define the physical state of the myocardium. To determine if backscatter imaging during inotropic stimulation could be used objectively to determine the myocardial viability and ischemia in patients with ischemic heart disease, the backscatter changes were examined in 23 patients with myocardial infarction during dobutamine stress two-dimensional (2-D) echocardiography. Coronary angiography was performed within 1 to 2 days after the stress test. The results of this study demonstrated that changes in backscatter variability correlated significantly with the wall motion changes in stress echocardiography during dobutamine infusion (p < 0.0001). In addition, it was shown that the backscatter changes were significantly different in various types of myocardial tissue. In 23 healthy control segments, the ultrasonic backscatter variability was preserved and unchanged during inotropic stimulation (p = NS). In 15 viable infarct zones, restoration or an increase in backscatter variability during low-dose dobutamine infusion was noted, this being lost when ischemia developing during high-dose dobutamine infusion (p < 0.01). In 9 nonviable infarct zones, the phase-weighted variation was usually < or = 0 and did not change significantly during inotropic stimulation, regardless of the patency of the infarct-related arteries. In 15 remote ischemic myocardial zones, the backscatter variability was preserved at the baseline level, did not change during low-dose dobutamine infusion, but decreased significantly during high-dose dobutamine stress (p < 0.01). In conclusion, dobutamine stress tissue characterization could offer an objective approach for the detection of myocardial viability and ischemia, and might be a useful adjunct to the conventional stress echocardiography.

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.

Comparison of simultaneous dobutamine echocardiography and thallium-201 stress-reinjection single-photon emission computed tomography in predicting improvement of chronic myocardial dysfunction after revascularization

Previous studies have shown that ultrasonic integrated backscatter is valuable in characterizing stunned myocardium. Recent investigations have demonstrated that resting cardiac cycle-dependent variation of integrated backscatter closely paralleled the contractile reserve in patients with chronic left ventricular ischemic dysfunction. The purpose of this study was to validate whether ultrasonic tissue characterization (UTC) compared with dobutamine stress echocardiography (DSE) and thallium-201 stress-reinjection single-photon emission computed tomography (Tl-SPECT) could predict reversible myocardial dyssynergy in patients with chronic coronary artery disease. Forty-eight patients with stable coronary artery disease underwent UTC, DSE, and Tl-SPECT simultaneously before successful coronary revascularization and were followed up with echocardiograms at rest >3 months later. Among the 58 investigated segments, the weighted amplitude, a composite parameter derived from the integrated backscatter power curve, was larger for those groups with greater functional recovery (p <0.001). For the persistent akinetic segments, the weighted amplitudes were small with large deviations of the nadir ratios that represented the asynchrony between the intramural contractile events and the global systole. Using the cut-off value 2.0 of the weighted amplitude, the sensitivity and specificity for predicting functional improvement after revascularization were both 82.8% (kappa = 0.66) and comparable to the sensitivity and specificity of DSE and Tl-SPECT. UTC, delineating the myocardial physical state and intramural contraction, can be a novel approach in predicting functional improvement of chronic dyssynergy after revascularization.

Ultrasonic tissue characterization evaluates myocardial viability and ischemia in patients with coronary artery disease

To evaluate whether or not ultrasonic tissue characterization (UTC) can detect jeopardized or salvageable myocardium in patients having chronic coronary artery disease, we studied 103 patients with sequential UTC, dobutamine stress echocardiography (DSE) and (201)thallium stress-reinjection single-photon emission computed tomography (T1-SPECT). This revealed that the weighted amplitude of the cyclic modulation of integrated backscatter was larger for the myocardium with less ischemia burden or greater viability (p<0.001). The segments with larger ischemia burden or the nonviable myocardium demonstrated the contrary result. Using the receiver-operating characteristic curve analyses to determine the cutoff value of weighted amplitude for various predictions, UTC can detect ischemia in normokinetic myocardium (kappa = 0.34 compared to DSE or T1-SPECT) and viability in dyssynergic myocardium (kappa = 0.57 compared to DSE and 0.45, to T1-SPECT). These observations show that UTC may prove useful in the identification and pathophysiological understanding of myocardial ischemia and viability.

Use of echocardiography for predicting myocardial viability in patients with reperfused anterior wall myocardial infarction

Dobutamine stress echocardiography (DSE), myocardial contrast echocardiography (MCE), and ultrasonic tissue characterization with integrated backscatter are useful methods for assessing myocardial viability in acute myocardial infarction. In this study, we compared the potential of 3 methods for predicting myocardial viability in 38 patients with reperfused anterior wall acute myocardial infarction. We performed MCE shortly after coronary reperfusion with an intracoronary injection of microbubbles. We recorded 2-dimensional integrated backscatter images at rest and, then, performed low-dose (10 microg/kg/min) DSE 3 days later. In integrated backscatter images, we placed the region of interest in the midwall of the myocardial segment to reconstruct the cyclic variation of myocardial integrated backscatter. The myocardial segment was judged viable when it showed active contraction 3 months later. Among 74 segments analyzed, 34 were judged viable. Presence of contractile response during DSE predicted segmental viability with 91% sensitivity and 78% specificity. Intense and homogenous contrast enhancement with MCE predicted viability with 82% sensitivity and 73% specificity. The presence of synchronous contraction of cyclic variation predicted myocardial viability with 79% sensitivity and 83% specificity. There were no differences in sensitivity and specificity among the 3 methods. Thus, MCE and ultrasonic tissue characterization can predict myocardial viability as accurately as DSE in patients with acute myocardial infarction. The logistics of the methods may determine clinical application.

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.

Dependence of "apparent" magnitude on the time delay of cyclic variation of myocardial backscatter

The goal of this study was to determine if the "apparent" magnitude of the cyclic variation, defined as the difference between the values of integrated backscatter at end-diastole and end-systole, was dependent on the corresponding time delay. We measured the cyclic variation in four myocardial segments of the parasternal short-axis view in 23 healthy subjects. The "apparent" magnitude, actual magnitude, and time delay were compared for each segment. Measured time delays were: 2.22+/-0.71 (lateral wall); 1.65+/-0.66 (inferior septum); and approximately 1.0 for the anterior septum and posterior wall. Segments exhibiting large time delays (> 1.0) resulted in a reversal in sign of the "apparent" magnitude of cyclic variation in one instance, and underestimated the true magnitude in both cases. Thus, estimates of the "apparent" magnitude of the cyclic variation are dependent on the associated time delay, whereas a properly defined magnitude is not.

Myocardial Perfusion Abnormalities by Intravenous Administration of the Contrast Agent NC100100 in an Experimental Model of Coronary Artery Thrombosis and Reperfusion

The aim of this study was to evaluate a second-generation echo contrast agent (NC100100) for the study of myocardial perfusion. In eight anesthetized open-chest dogs, this agent was injected intravenously under baseline conditions, during acute coronary thrombosis, and after reperfusion, using both fundamental (FI) and harmonic (HI) imaging, both continuous and intermittent imaging, and both ultrasound (US) and integrated backscatter (IBS) imaging. Contrast injections did not modify the hemodynamic parameters. With all imaging modalities, myocardial contrast enhancement (MCE) was higher with intermittent than with continuous imaging (134 vs 82 gray level/pixel using FI, P = 0.02; 62 vs 32 acoustic units using US HI, P = 0.02; and 52 vs 12 dB using IBS, P = 0.05). MCE equally increased using either US or IBS imaging. The accuracy of MCE in detecting perfusion defects during coronary occlusion and myocardial reperfusion after thrombolysis was very good (sensitivity and specificity = 93% and 95% and 89% and 93%, respectively). The extent of myocardial perfusion defects by echo contrast showed a closer correlation with microspheres using HI (r = 0.82) than FI (r = 0.53). Thus, the intravenous administration of NC100100 during intermittent HI allows myocardial perfusion abnormalities to be accurately detected during acute myocardial infarction.

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 for coronary care unit patients with acute myocardial infarction

The ultrasonic integrated backscatter of myocardium changes in infarction and ischemia. On the third day after acute myocardial infarction, 30 patients underwent ultrasonic tissue characterization from the parasternal short-axis view. With a composite parameter, the phase-weighted variation, sensitivity, specificity, and accuracy for diagnosing multivessel coronary artery disease were 84.6%, 52.9% and 66.6%, respectively. Using 67 degrees as the cutoff value for the phase deviation of the backscatter power curve, the recanalization of the infarct-related artery could be detected with a positive predictive value of 77.7% and a negative predictive value of 66.6%. Ultrasonic tissue characterization is a feasible technique for detecting the multivessel coronary artery diseases and the recanalization of infarct-related artery for patients with acute myocardial infarction. The diminished cardiac cycle-dependent variation in integrated backscatter and increased phase deviation can differentiate patent coronary arteries from those coronary arteries with anatomically significant stenoses.

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.

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.