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

Echocardiographic tissue imaging evaluation of myocardial characteristics and function in cardiomyopathies

Current echocardiography techniques have allowed more precise assessment of cardiac structure and function of the several types of cardiomyopathies. Parameters derived from echocardiographic tissue imaging (ETI)-tissue Doppler, strain, strain rate, and others-are extensively used to provide a framework in the evaluation and management of cardiomyopathies. Generally, myocardial function assessed by ETI is depressed in all types of cardiomyopathies, non-ischemic dilated cardiomyopathy (DCM) in particular. In hypertrophic cardiomyopathy (HCM), ETI is useful to identify subclinical disease in family members of HCM, to differentiate HCM from other conditions causing cardiac hypertrophy and to predict cardiac events. ETI also for HCM allows addressing the mechanism behind left ventricular outflow tract obstruction and its improvement after therapeutic options. ETI provides cardiac amyloidosis with unique and specific findings such as "apical sparing." Nevertheless, ETI does not seem to provide as much information amenable to histological findings as recently emerging techniques of cardiac magnetic resonance imaging. This review introduces usefulness of ETI and some other ultrasound techniques for detecting clinical and subclinical characteristics of cardiomyopathies, focusing on DCM, HCM, and cardiac amyloidosis.

Risk Stratification of Genetic, Dilated Cardiomyopathies Associated With Neuromuscular Disorders: Role of Cardiac Imaging

The etiology of dilated cardiomyopathy (DCM) can be grouped as either genetic or nongenetic. More than 50 pathogenic genes have been described, with sarcomeric and lamin A/C mutations being the most common. Mutation carriers for genetic DCM are often asymptomatic until cardiac disease manifests with heart failure, arrhythmias, or sudden cardiac death. Preventive strategies are promising but can only be applied and tested adequately if genetic DCM can be diagnosed at an early stage. Early diagnosis of mutation carriers that may develop overt DCM requires advanced imaging techniques that can detect subtle structural and functional abnormalities. Advanced echocardiographic techniques such as tissue Doppler imaging and speckle tracking strain analysis permit early detection of functional abnormalities, whereas cardiovascular magnetic resonance techniques provide information on tissue characterization and myocardial energetics that may be altered at an early stage. Furthermore, nuclear imaging techniques provide information on cellular function (metabolism, perfusion). Once the diagnosis of overt DCM has been established, various imaging parameters such as echocardiography-based myocardial mechanics and cardiovascular magnetic resonance-based tissue characterization have shown incremental benefit to left ventricular ejection fraction in risk stratification. Further research is required to understand how imaging techniques may help to choose management strategies that could delay progression when instituted early in the course of the disease. The present article reviews the role of imaging in the risk stratification of genetic DCM in general, with specific emphasis on DCM associated with neuromuscular disorders.

Ultrasonic integrated backscatter discloses intramyocardial hemorrhage in patients with acute myocardial infarction

BACKGROUND

It has been reported that intramyocardial hemorrhage (IH) can be detected by magnetic resonance imaging (MRI) and IH correlates with the poor prognosis of acute myocardial infarction (AMI). We examined whether integrated backscatter (IBS) can disclose IH in patients with AMI. We recorded IBS images in 34 patients with AMI who underwent coronary angioplasty within 12 hours of symptom onset.

METHODS

We measured calibrated IBS (C-IB) and cyclic variation (CV) in the center of the risk area on the third day after reperfusion. C-IB was calculated as: average IBS value of risk area--average IBS value of intraventricular blood. MRI was performed within 3 days after reperfusion. Regional wall motion score index (RWMSI) was calculated as follows: sum of scores (0 - 4) in risk area/number of segments of risk area. We evaluated left ventricular function using RWMSI shortly and one month after reperfusion.

RESULTS

RWMSI in the IH group (12 cases) was significantly higher than in the non-IH group (2.3+/-0.5 vs. 1.8+/-0.6: P<0.01) one month later, while RWMSI in both groups was almost the same shortly after reperfusion. The IH group showed a significantly higher value of C-IB than the non-IH group (18.6+/-2.0 vs. 16.0+/-1.4: P<0.01), while there were no significant differences in CV values between two groups. Using 17 as a cutoff value of C-IB, C-IB can detect IH with 92% sensitivity and 91% specificity. Using both CV and C-IB, however, IH can be detected more specifically.

CONCLUSION

Ultrasonic IBS, especially C-IB, discloses intramyocardial hemorrhage in patients with reperfused AMI.

Detection of cardiac sarcoidosis using cardiac markers and myocardial integrated backscatter

BACKGROUND

It is not known whether cardiac markers and cyclic variations of integrated backscatter can be used to detect cardiac sarcoidosis.

METHODS

We studied 62 patients with sarcoidosis affecting the lung, eyes, skin, or heart (27 patients with cardiac involvement and 35 patients without). The cyclic variation of integrated backscatter and wall thickening was evaluated in the left ventricular anterior septum and posterior wall. Plasma A-type natriuretic peptide (ANP) and B-type natriuretic peptide (BNP) concentrations and serum cardiac troponin T were also determined.

RESULTS

Plasma natriuretic peptide concentrations were higher in the cardiac involvement group (ANP: 15.5 [interquartile range (IQR) 2.5-34.0] vs. 12.0 [10.0-16.5] pg/ml, P=0.25; BNP: 28.6 [5.9-141] vs. 10.1 [4.8-15.4] pg/ml, P=0.049). However, cardiac troponin T concentration was <0.01 ng/ml in all patients. Receiver-operator characteristic (ROC) analysis showed that both ANP and BNP could identify patients with high-degree atrioventricular block, ventricular tachyarrhythmias, or symptomatic heart failure (the areas under the ROC curve were 0.94 and 0.97, respectively). The cardiac involvement group could be distinguished from the noninvolvement group by combining cutoff values for the magnitude of integrated backscatter cyclic variation (5.5 dB) and wall thickening (30%), albeit only for the posterior wall.

CONCLUSION

Both ANP and BNP are useful markers for identifying patients with sarcoidosis and cardiac complication(s). Moreover, evaluation of integrated backscatter cyclic variation combined with wall thickening may be of help in detecting cardiac involvement in the posterior wall.

Occult Cardiac Contractile Dysfunction in Dystrophin-Deficient Children Revealed by Cardiac Magnetic Resonance Strain Imaging

Background— Duchenne muscular dystrophy (DMD) is an inherited disease characterized by early onset of skeletal muscle degeneration and progressive weakness. Although dilated cardiomyopathy may occur during adolescence, it is often undetected early in its course because of physical inactivity and generalized debilitation. The purpose of this study was to apply the technique of cardiac magnetic resonance (CMR) tagging to detect occult cardiac dysfunction in young subjects with DMD by measuring myocardial strain and torsion.

Methods and Results— Thirteen DMD pediatric subjects without clinically apparent heart disease and 9 age-matched healthy males were recruited. Each was scanned on a 1.5-T clinical scanner to acquire contiguous short-axis planes from the apex to the mitral valve plane and then 3 tagged images at base, midventricle, and apex. Global and segmental myocardial net twist and circumferential strain were computed with the use of 2D homogeneous strain analysis. Ventricular torsion was computed by normalizing net twist by the distance from apex to mitral valve plane. DMD patients exhibited normal left ventricular volumes and ejection fractions but manifested reduced midventricular and basal cross-sectional global circumferential strain compared with the reference group ( P <0.005). These alterations also appeared in segmental analyses in the septal, anterior, lateral, and inferior walls ( P <0.05).

Conclusions— In patients predisposed to cardiomyopathies because of dystrophinopathy, occult regional cardiac dysfunction can be diagnosed with CMR tagging. This method of strain imaging analysis may offer a sensitive approach for delineating the presence and progression of cardiovascular disease and for assessing therapies designed to modulate the onset and course of heart failure.

Lack of Prognostic Value of Normalized Integrated Backscatter Analysis of Myocardium in Patients with Thalassemia Major: A Long-Term Follow-Up Study

BACKGROUND

Patients with beta-thalassemia major often present with severe anemia and must undergo continuous transfusion therapy, consequently developing iron overload leading to hemochromatosis. Because of these the iron deposits and/or secondary structural changes, patients develop an increase in myocardial integrated backscatter (IB).

AIM

To investigate the prognostic value of analyzing acoustic quantitative properties of the myocardium in patients with beta-thalassemia major.

PATIENTS AND METHODS

Between 1989 and 1990, 38 patients (mean age: 18 years, range: 7-26, 21 males) with beta-thalassemia major and without clinical signs of cardiac failure were enrolled prospectively. All patients were on chelation therapy (desferroxiamine). To obtain quantitative operator-independent measurement of the IB signal of the left ventricular septum and posterior wall, the ultrasonic radiofrequency signal integrated values were normalized to the pericardial interface and expressed in percentage (IB%).

RESULTS

Follow-up was 122 +/- 36 months, during which 15 events (7 cardiac deaths and 8 heart failures) occurred. The event-free survival was comparable in patients with normal and abnormal IB%. Septal IB% was 33 +/- 14 in the 15 patients with events, and 33 +/- 12 in the 25 patients without events (P = ns). The %IB had no prognostic value in this population. A prognostic value was found in multivariate analysis for patient refusal/noncompliance of chelation therapy (P = 0.02, OR: 4.37, 95% CI: 1.72-16.9) and also body mass index (P = 0.04, OR: 1.2, 95% CI: 1.0-1.4).

CONCLUSION

Analysis of end-diastolic IB% of myocardium in patients with beta-thalassemia and iron overload was not predictive of adverse cardiac events during long-term follow-up in this study.

Ultrasound tissue characterization detects preclinical myocardial structural changes in children affected by Duchenne muscular dystrophy

Our goal was to identify early changes in myocardial physical properties in children with Duchenne muscular dystrophy (DMDch). Duchenne muscular dystrophy (DMD) is caused by the absence of dystrophin, which triggers complex molecular and biological events in skeletal and cardiac muscle tissues. Although about 30% of patients display overt signs of cardiomyopathy in the late stage of the disease, it is unknown whether changes in myocardial physical properties can be detected in the early (preclinical) stages of the disease. We performed an ultrasonic tissue characterization (UTC) analysis of myocardium in DMDch with normal systolic myocardial function and no signs of cardiomyopathy. Both the cyclic variation of integrated backscatter (cvIBS) and the calibrated integrated backscatter (cIBS) were assessed in 8 myocardial regions of 20 DMDch, age 7 +/- 2 years (range 4 to 10 years), and in 20 age-matched healthy controls. We found large differences in the UTC data between DMDch and controls; the mean value of cvIBS was 4.4 +/- 1.5 dB versus 8.8 +/- 0.8 dB, whereas the mean value of cIBS was 36.4 +/- 7.1 dB versus 26.9 +/- 2.0 dB (p < 10(-6) for both). In DMDch, all eight sampled segments showed cIBS mean values to be significantly higher and cvIBS mean values to be significantly lower than those in the controls. Finally, interindividual differences were greater in DMDch than in controls for both parameters.The myocardium in DMDch displays UTC features different from those in healthy controls. These results show that lack of dystrophin is commonly associated with changes in myocardial features well before the onset of changes of systolic function and overt cardiomyopathy.

Depth variation bias and interaction with gain setting in ultrasonic tissue characterization by integrated backscatter analysis

Integrated backscatter signal (IBS) has been proposed as a tool to measure cardiac fibrosis. To overcome problems associated with machine settings and attenuation of the chest wall, IBS has been expressed in relation to posterior pericardium, as a variation across cardiac cycle, or both. Depth of the reflecting structure has never been considered as a source of variability. Accordingly, we studied the effect of structure depth on IBS and examined its interaction with gain setting. Backscatter signals were recorded from plastic phantoms containing identical structures set at increasing depth and in 1 healthy volunteer using silicone spacers to modify depth, on a wide range of gain settings. In the phantom, IBS signal linearly decreased with increasing depth and nonlinearly increased with increasing gain (all r(2) > 0.97). In the healthy volunteer, results from septum were very similar to the phantom experiment. Values of septal IBS were adjusted using multiple regression coefficients for gain and depth from the phantom experiment and resulted in a near-complete offset of effect of depth and gain on septal IBS (P = not significant for both gain and depth). These assumptions were also used to compare IBS analysis between hypertensive patients and patients with hypertrophic cardiomyopathy. Thus, depth and its relation with gain should be taken into account and might be almost fully predicted. Using appropriate regression modeling may allow analysis in optimal imaging conditions, tolerating between-patient comparisons even in limited diastolic frames.

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.

Prognostic implications derived from ultrasonic tissue characterization with myocardial integrated backscatter in patients with dilated cardiomyopathy

BACKGROUND

Various clinical parameters have been reported to predict survival in patients with dilated cardiomyopathy (DCM). Myocardial ultrasonic integrated backscatter (IB) imaging has a potential to perform in vivo tissue characterization. The present study was performed to examine whether myocardial IB analysis can predict the prognosis of DCM patients.

METHODS AND RESULTS

We prospectively carried out echocardiographic examinations with IB analysis in 43 patients with DCM (31 males, 12 females) under the standard treatment. IB analysis was performed in the left ventricular wall and the calibrated (subtracting pericardial data) myocardial IB intensity (IBI) was obtained from the interventricular septum and the left ventricular posterior wall. After the follow-up (8-39 months), 31 followed a good clinical course, but eight had cardiac death, one had partial left ventriculectomy for uncontrolled heart failure and three were hospitalized for worsening heart failure. Beta-blocker responded in 27 (87%) of the 31 with good clinical course, but it did not respond in 11 among the 12 with poor course. In these 12 DCM, left ventricular fractional shortening (LVFS) was lower (good: 18+/-5%, poor: 14+/-4, P<0.03) and calibrated IBI was higher in both the septum (good: -16.4+/-5.6 dB, poor: -11.1+/-4.2 dB, P<0.006) and the posterior wall (good: -19.5+/-3.6 dB, poor: -13.8+/-5.6 dB, P<0.004). On the Cox proportional hazard model analysis, only calibrated IBI in the septum >-17 dB, the cut-off score of calibrated IBI discriminating non-responders to beta-blocker therapy in our previous report, was related to the poor outcome (chi(2)=4.43, P=0.035). The stepwise multivariate analysis revealed that both calibrated IBI in the septum>-17 dB (chi(2)=4.43, P=0.035) and LVFS<15% (chi(2)=3.89, P=0.049) were useful to predict the poor clinical outcome. The event free rate assessed by the Kaplan-Meier method was also significantly reduced in patients with calibrated IBI in the septum >-17 dB (chi(2)=6.594, P=0.01) and calibrated IBI in the posterior wall>-17 dB (chi(2)=4.215, P=0.04). However, LVFS<15% (chi(2)=3.576, not significant) did not contribute to discriminating the event free rate in the clinical course.

CONCLUSIONS

The present study demonstrated that myocardial IB intensity was higher in DCM patients who followed a poor clinical course rather than in those with a good outcome. Therefore, it is clarified that myocardial ultrasonic tissue characterization in DCM patients is useful for assessing their clinical outcome after receiving not only the standard treatment but also beta-blocker therapy.

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.