MRI to assess arrhythmia and cardiomyopathies: relationship to echocardiography

Regional circumferential strain is a biomarker for disease severity in duchenne muscular dystrophy heart disease: a cross-sectional study

The aim of this study is to determine the contribution of strain ε cc in mid left ventricular (LV) segments to the reduction of composite LV circumferential ε cc in assess severity of duchenne muscular dystrophy (DMD) heart disease as assessed by cardiac magnetic resonance imaging (CMR). DMD patients and control subjects were stratified by age, LV ejection fraction, and late gadolinium enhancement (LGE) status. Tagged CMR images were analyzed for global ventricular function, LGE imaging, and composite and segmental ε cc. The relationship between changes in segmental ε cc changes and LGE across patient groups was assessed by a statistical step-down model. LV ε cc exhibited segmental heterogeneity; in control subjects and young DMD patients, ε cc was greatest in LV lateral free wall segments. However, with increasing age and cardiac disease severity as demonstrated by decreased EF and development of myocardial strain the segmental differences diminished. In subjects with advanced heart disease as evidenced by reduced LV ejection fraction and presence of LGE, very little segmental heterogeneity was present. In control subjects and young DMD patients, ε cc was greatest in LV lateral free wall segments. Increased DMD heart disease severity was associated with reduced composite; ε cc diminished regional ε cc heterogeneity and positive LGE imaging. Taken together, these findings suggest that perturbation of segmental, heterogeneous ε cc is an early biomarker of disease severity in this cross-section of DMD patients.

MRI of nonischemic cardiomyopathy

OBJECTIVE

The purpose of this article is to present current clinical and research issues in MRI evaluation of nonischemic cardiomyopathy, a diverse set of diseases, many of which have a genetic basis.

CONCLUSION

Cardiac cine MRI along with delayed myocardial enhancement MRI and other MRI techniques can provide information beyond echocardiography for tissue characterization. MRI is increasingly being used for evaluation of genetically positive, phenotypically negative patients as well as for risk stratification.

Effects of somatostatin analogues on acromegalic cardiomyopathy: results from a prospective study using cardiac magnetic resonance

OBJECTIVE

Left ventricular (LV) hypertrophy is the main finding of patients with active acromegaly at cardiac magnetic resonance (CMR). The aim of the study was to evaluate heart changes in acromegalic patients treated with somatostatin analogues (SMSA) using CMR.

DESIGN AND PATIENTS

This was a prospective study. Fourteen consecutive patients (8 women, mean age 46+/-10 yr) with untreated active acromegaly were submitted to CMR and 2D-color Doppler echocardiography before and after a 6-month SMSA course.

MEASUREMENTS

LV volume, mass (LVM) and wall thickness.

RESULTS

CMR: Mean LVM and LVM index (i) decreased from 151+/-17 g and 77+/-9 g/m2, to 144+/-24 g and 70+/-12 g/m2, respectively (p=0.047 and p<0.0001, respectively); LV hypertrophy reverted in 6 out of 10 patients (p=0.016). Systolic function, evaluated by measuring LV ejection fraction remained normal in all patients (67+/-11%). There was not a correlation between changes in LVMi and changes in serum IGF-I concentrations. However, patients with controlled disease had higher reduction of LVMi than those with uncontrolled acromegaly (DeltaLVMi, -8.2+/-4.2 vs 4.0+/-5.3 p<0.05). 2D-echo cardiography: Mean LVMi decreased from 110+/-24 g/m2 to 100+/-20 g/m2 (p=0.026); hypertrophy, revealed in 5 patients (36%) at baseline, reversed in 2 patients (p=0.500) after SMSA; abnormal diastolic function [evaluated by isovolumic relaxation time or early (E) to late of atrial (A) peak velocities ratio] found in 4 patients (29%) at the study entry, improved in a patient. Systolic function remained within the normal range in all patients during the study period.

CONCLUSIONS

CMR detects changes in LVMi in most patients with acromegaly treated with SMSA, which are more evident if the disease is controlled.

Diagnostic approaches for diabetic cardiomyopathy and myocardial fibrosis

In diabetes mellitus, alterations in cardiac structure/function in the absence of ischemic heart disease, hypertension or other cardiac pathologies are termed diabetic cardiomyopathy. In the United States, the prevalence of diabetes mellitus continues to rise and the disease currently affects about 8% of the general population. Hence, the use of appropriate diagnostic strategies for diabetic cardiomyopathy, which may help correctly identify the disease at early stages and implement suitable corrective therapies is imperative. Currently, there is no single diagnostic method for the identification of diabetic cardiomyopathy. Diabetic cardiomyopathy is known to induce changes in cardiac structure such as, myocardial hypertrophy, fibrosis and fat droplet deposition. Early changes in cardiac function are typically manifested as abnormal diastolic function that with time leads to loss of contractile function. Echocardiography based methods currently stand as the preferred diagnostic approach for diabetic cardiomyopathy, due to its wide availability and economical use. In addition to conventional techniques, magnetic resonance imaging and spectroscopy along with contrast agents are now leading new approaches in the diagnosis of myocardial fibrosis, and cardiac and hepatic metabolic changes. These strategies can be complemented with serum biomarkers so they can offer a clear picture as to diabetes-induced changes in cardiac structure/function even at very early stages of the disease. This review article intends to provide a summary of experimental and routine tools currently available to diagnose diabetic cardiomyopathy induced changes in cardiac structure/function. These tools can be reliably used in either experimental models of diabetes or for clinical applications.

Circumferential strain analysis identifies strata of cardiomyopathy in Duchenne muscular dystrophy: a cardiac magnetic resonance tagging study

OBJECTIVES

This study sought to evaluate the natural history of occult cardiac dysfunction in Duchenne muscular dystrophy (DMD).

BACKGROUND

Duchenne muscular dystrophy is characterized by progressive cardiac dysfunction and myocardial fibrosis late in the disease process. We hypothesized that left ventricular myocardial peak circumferential strain (epsilon(cc)) would decrease in DMD before global systolic functional abnormalities regardless of age or ventricular ejection fraction (EF).

METHODS

We evaluated cardiac magnetic resonance image (MRI) data from 70 DMD patients and 16 aged-matched control subjects. Standard imaging data included steady-state free precession short-axis cine stack images, cine myocardial tagged images, and myocardial delayed enhancement (MDE) (an indicator of myocardial fibrosis) sequences. Analysis was performed with QMASS (Medis Medical Imaging Systems, Leiden, the Netherlands) and HARP (Diagnosoft, Palo Alto, California) software. The DMD patient data were subdivided by age (<10 or >10 years), EF (>55% or <55%), and the presence or absence of MDE.

RESULTS

The DMD patients with normal EF had reduced epsilon(cc) at an early age (<10 years) compared with control subjects (p < 0.01). The DMD patients age >10 years with normal EF had further decline in epsilon(cc) compared with younger DMD patients (p < 0.01). There was further decline in epsilon(cc) with age in patients with reduced EF (p < 0.01) without MDE. The oldest patients, with both reduced EF and positive MDE, exhibited the lowest epsilon(cc). None of the patients had ventricular hypertrophy.

CONCLUSIONS

Myocardial strain abnormalities are prevalent in young DMD patients despite normal EF, and these strain values continue to decline with advancing age. Strain analysis in combination with standard MRI and MDE imaging provides a means to stratify DMD cardiomyopathy.

Role of cardiac magnetic resonance imaging in assessment of nonischemic cardiomyopathies

Diagnosis of nonischemic cardiomyopathy is a challenging process that influences patient morbidity and mortality. Currently, the well known World Health Organization classification has been revisited by an American Heart Association expert consensus panel. The contemporary classification is compatible with the rapid evolution in molecular genetics and evolving diagnostic tools such as cardiac magnetic resonance imaging (MRI). Magnetic resonance imaging is a robust diagnostic tool that offers various techniques to assess the function, morphology, perfusion, and scarring of myocardial tissue thus providing better understanding of the underlying causes of nonischemic cardiomyopathies. In this review, we discuss the current role of cardiac MRI in the evaluation of nonischemic cardiomyopathy, in the context of the current American Heart Association classification of these disorders.

High prevalence of cardiac hypertophy without detectable signs of fibrosis in patients with untreated active acromegaly: an in vivo study using magnetic resonance imaging

OBJECTIVE

Left ventricular (LV) hypertrophy and myocardial fibrosis are considered the main pathological features of acromegalic cardiomyopathy. The aim of the study was to evaluate the proportion of LV hypertrophy and the presence of fibrosis in acromegalic cardiomyopathy in vivo using cardiac magnetic resonance (CMR).

DESIGN AND PATIENTS

Fourteen consecutive patients (eight women, mean age 46 +/- 10 years) with untreated active acromegaly were submitted to two-dimensional (2D) colour Doppler and integrated backscatter (IBS) echocardiography and CMR.

MEASUREMENTS

LV volume, mass and wall thickness and myocardial tissue characterization (IBS and CMR).

RESULTS

On echocardiography: mean LV mass (LVM) and LVM index (LVMi) were 209 +/- 48 g and 110 +/- 24 g/m(2), respectively; hypertrophy was revealed in five patients (36%); abnormal diastolic function [evaluated by isovolumic relaxation time (IVRT) or early (E) to late or atrial (A) peak velocities (E/A ratio)] was found in four patients (29%). Systolic function evaluated by measuring LV ejection fraction (LVEF) was normal (mean 72 +/- 12%) in all patients. Six patients (43%) had increased IBS (mean 57.4 +/- 6.2%). On CMR: mean LVM and LVMi were 151 +/- 17 g and 76 +/- 9 g/m(2), respectively; 10 patients (72%) had LV hypertrophy. Contrastographic delayed hyperenhancement was absent in all patients; on the contrary, mild enhancement was revealed in one patient. Systolic function was normal in all patients (LVEF 67 +/- 11%). LVMi was not related to serum IGF-1 concentrations or the estimated duration of disease.

CONCLUSIONS

CMR is considered to be the gold standard for evaluating cardiac hypertrophy, fibrosis and systolic function. Using CMR, 72% patients with untreated active acromegaly had LV hypertrophy, which was only detected in 36% patients by echocardiography. However, cardiac fibrosis was absent in all patients irrespective of the estimated duration of disease. Although a very small increase in collagen content (as suggested by increased cardiac reflectivity at IBS), not detectable by CMR, could not be ruled out, it is unlikely that it would significantly affect cardiac function.

Cardiac MRI is Complementary to Echocardiography in the Assessment of Cardiac Masses

Despite the fact that the incidence of cardiac tumors is low, the prompt evaluation and adequate intervention of these is highly important. Although most tumors of the heart are considered histologically benign, there are significant risks associated with these "benign" tumors. These are associated with significant morbidity and mortality due to obstruction of blood flow, alterations of conduction, propagation of arrhythmias, and thromboembolism, depending on their size, location, and nature. With the advent of noninvasive imaging modalities--traditionally echocardiography; but more recently using cross-sectional imaging with cardiac computed tomography and magnetic resonance imaging--cardiac tumors can be optimally assessed providing a greater opportunity for curative treatments by cardiothoracic surgery.

Dobutamine Stress Magnetic Resonance Imaging

Measurements of left ventricular function with cardiovascular magnetic resonance (CMR) at rest and during intravenous dobutamine are useful for identifying myocardial ischemia, viability, and the risk of subsequent cardiovascular events. Without ionizing radiation, intravascular iodinated contrast administration, or acoustic window limitations, CMR has emerged as a useful adjunct to transthoracic echocardiography for assessing patients with or suspected of having coronary artery disease.