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

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.

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.

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.

Role of echocardiography versus MRI for the diagnosis of congenital heart disease

During the last few decades, significant strides have been made in the field of noninvasive imaging for the patient with congenital heart disease. Echocardiography and MRI continue to provide improved means of anatomic and functional assessment in children and adults with congenital heart lesions. This review reports some of the recent advances in tissue Doppler, strain rate, and integrated backscatter, and highlights exciting current and future potential developments in their application. We also discuss advances in MR in evaluation of cardiac anatomy and function in congenital heart disease.