Cardiovascular magnetic resonance: applications in daily practice

Over the last 10 years, the development of newer pulse sequences and applications in new clinical areas has enabled cardiovascular magnetic resonance to emerge as a powerful tool for the physicians to both diagnose and guide treatments of various cardiac pathologies. The greatest strengths of cardiovascular magnetic resonance include the assessment of ischemia and viability, evaluation of nonischemic cardiomyopathies, including myocarditis, pericardial disease, congenital heart disease, and tissue characterization of cardiac masses.     

Role of cardiac MRI in nonischemic cardiomyopathies

Cardiac magnetic resonance (CMR) with its higher spatial resolution is considered the gold standard for evaluating ventricular mass, volumes, and ejection fraction. CMR can be used for accurate diagnosis of several conditions, especially cardiomyopathies. The purpose of this article is to review the utility of CMR in the diagnosis and management of nonischemic cardiomyopathies. We have reviewed both common and rare types of nonischemic cardiomyopathies in detail and elaborated on the specific CMR findings in each. We believe that CMR is an invaluable tool, not only in differentiating nonischemic from ischemic cardiomyopathy, but also in aiding the accurate diagnosis and management of the subtype of nonischemic cardiomyopathy. CMR should routinely be integrated in the diagnostic workup of various cardiomyopathies.     

The emerging clinical role of cardiovascular magnetic resonance imaging

Starting as a research method little more than a decade ago, cardiovascular magnetic resonance (CMR) imaging has rapidly evolved to become a powerful diagnostic tool used in routine clinical cardiology. The contrast in CMR images is generated from protons in different chemical environments and, therefore, enables high-resolution imaging and specific tissue characterization in vivo, without the use of potentially harmful ionizing radiation.CMR imaging is used for the assessment of regional and global ventricular function, and to answer questions regarding anatomy. State-of-the-art CMR sequences allow for a wide range of tissue characterization approaches, including the identification and quantification of nonviable, edematous, inflamed, infiltrated or hypoperfused myocardium. These tissue changes are not only used to help identify the etiology of cardiomyopathies, but also allow for a better understanding of tissue pathology in vivo. CMR tissue characterization may also be used to stage a disease process; for example, elevated T2 signal is consistent with edema and helps differentiate acute from chronic myocardial injury, and the extent of myocardial fibrosis as imaged by contrast-enhanced CMR correlates with adverse patient outcome in ischemic and nonischemic cardiomyopathies.The current role of CMR imaging in clinical cardiology is reviewed, including coronary artery disease, congenital heart disease, nonischemic cardiomyopathies and valvular disease.     

Walking with Gianluca Di Bella during the development of clinical cardiac imaging

Cardiac magnetic resonance imaging (MRI) for the diagnosis and management of many cardiac diseases has been established in clinical practice. It provides anatomic and functional information and is the most precise technique for quantification of ventricular volume, function and mass. Among cardiac MRI sequences used in clinical practice, delayed contrast enhancement is an accurate and reliable method used in the diagnosis of ischemic and nonischemic cardiomyopathies. In addition, new technology applied in echocardiographic imaging has permitted quantification of myocardial deformations with 2-dimensional strain imaging (longitudinal, circumferential and radial strain). Cardiac MRI and echocardiography therefore both play a crucial role in the diagnosis and management of cardiovascular disease. Dr. Di Bella and colleagues have defined the roles of cardiac MRI and echocardiography in many clinical and experimental settings.     

Multimodality Imaging Assessment of Myocardial Fibrosis

Myocardial fibrosis, seen in ischemic and nonischemic cardiomyopathies, is associated with adverse cardiac outcomes. Noninvasive imaging plays a key role in early identification and quantification of myocardial fibrosis with the use of an expanding array of techniques including cardiac magnetic resonance, computed tomography, and nuclear imaging. This review discusses currently available noninvasive imaging techniques, provides insights into their strengths and limitations, and examines novel developments that will affect the future of noninvasive imaging of myocardial fibrosis.     

Application of cardiac magnetic resonance imaging in cardiomyopathy

Cardiomyopathies account for a significant portion of morbidity and mortality in patients with heart disease. The diagnosis and identification of the underlying disorder are essential for directing appropriate life-saving therapy. Cardiac magnetic resonance imaging (CMR) is an ideal method for the noninvasive evaluation of cardiomyopathies of unknown etiology. In addition, there is increasing prognostic evidence to support the use of this technology in patient risk stratification. CMR is not limited by anatomic barriers and is able to characterize tissue abnormalities that previously could often be identified only through biopsy. This review discusses the utility of CMR in the assessment of cardiomyopathies, including specific imaging techniques and their application in ischemic and nonischemic settings.     

Imaging myocardial scar and arrhythmic risk prediction—a role for the electrocardiogram?

Risk stratification for sudden cardiac death (SCD) has become increasingly important to identify candidates for implantable cardioverter-defibrillators (ICDs). Existing clinical guidelines to identify patients for ICDs focus on reduced left ventricular ejection fraction (LVEF); however, the average annual rate of appropriate ICD shocks is only 5.1% in this select group (LVEF ≤35%), and these patients only represent a small fraction of the total number of patients who die of SCD. Magnetic resonance imaging (MRI) with late gadolinium enhancement has recently emerged as the in vivo gold standard for detecting and quantifying myocardial scar after infarction and in nonischemic cardiomyopathies. Myocardial scar, particularly in the scar border zone, interrupts electrical conduction providing regions that support reentrant ventricular arrhythmias. Recent studies have shown that increased MRI scar in both prior infarction and nonischemic cardiomyopathy patients is associated with arrhythmogenesis, worsening heart failure, and cardiac mortality. This review will focus on the emerging role of MRI to quantify scar and predict arrhythmogenesis in patients with prior infarction and with nonischemic cardiomyopathies—including idiopathic, hypertrophic, Fabry's disease, myocarditis, Chagas' disease, and sarcoidosis. Furthermore, this review will discuss the potential role of the 12-lead electrocardiographic Selvester QRS scoring system to quantify myocardial scar and predict arrhythmogenesis in prior infarct and nonischemic cardiomyopathy patients.     

Myocardial Scar in Sarcoidosis by 12‐lead ECG and Pathology

This case demonstrates the use of QRS scoring to quantify myocardial scar in a patient with cardiac sarcoidosis and left bundle branch block who progressively received an implantable defibrillator, cardiac resynchronization therapy (CRT), left ventricular assist device and cardiac transplantation. QRS scoring has been shown to correlate with magnetic resonance imaging measurements of scar, identify arrhythmogenic substrate and predict response to CRT, but had not previously been compared to pathology‐documented scar in nonischemic cardiomyopathies. Further study is warranted to assess the ability of QRS scoring to guide therapy for individual patients. Ann Noninvasive Electrocardiol 2011;16(2):219–222     

Ablation of ventricular tachycardia in patients with nonischemic cardiomyopathy

Nonischemic Cardiomyopathy. Mapping and ablation of ventricular tachycardia (VT) in patients with nonischemic cardiomyopathy can be challenging. In this article, we describe the approach to VT in patients with nonischemic cardiomyopathy that we use at the University of Michigan. Imaging, especially with delayed enhanced cardiac magnetic resonance imaging, plays a central role in planning a mapping and ablation procedure. During the mapping procedure, pace-mapping in conjunction with voltage maps focusing on areas with isolated potentials helps to identify scar areas that are critical for VT in these patients.     

Cardiac magnetic resonance imaging:Which information is useful for the arrhythmologist?

Cardiac magnetic resonance(CMR) is a non-invasive,nonionizing,diagnostic technique that uses magnetic fields,radio waves and field gradients to generate images with high spatial and temporal resolution.After administration of contrast media(e.g.,gadolinium chelate),it is also possible to acquire late images,which make possible the identification and quantification of myocardial areas with scar/fibrosis(late gadolinium enhancement,LGE).CMR is currently a useful instrument in clinical cardiovascular practice for the assessment of several pathological conditions,including ischemic and nonischemic cardiomyopathies and congenital heart disease.In recent years,its field of application has also extended to arrhythmology,both in diagnostic and prognostic evaluation of arrhythmic risk and in therapeutic decisionmaking.In this review,we discuss the possible useful applications of CMR for the arrhythmologist.It is possible to identify three main fields of application of CMR in this context:(1) arrhythmic and sudden cardiac death risk stratification in different heart diseases;(2) decisionmaking in cardiac resynchronization therapy device implantation,presence and extent of myocardial fibrosis for left ventricular lead placement and cardiac venous anatomy; and(3) substrate identification for guiding ablation of complex arrhythmias(atrial fibrillation and ventricular tachycardias).     

Assessment of myocardial fibrosis with cardiovascular magnetic resonance

Diffuse interstitial or replacement myocardial fibrosis is a common feature of a broad variety of cardiomyopathies. Myocardial fibrosis leads to impaired cardiac diastolic and systolic function and is related to adverse cardiovascular events. Cardiovascular magnetic resonance (CMR) may uniquely characterize the extent of replacement fibrosis and may have prognostic value in various cardiomyopathies. Myocardial longitudinal relaxation time mapping is an emerging technique that could improve CMR's diagnostic accuracy, especially for interstitial diffuse myocardial fibrosis. As such, CMR could be integrated in the monitoring and therapeutic management of a large number of patients. This review summarizes the advantages and limitations of CMR for the assessment of myocardial fibrosis.     

Cardiomyopathies:Evolution of pathogenesis concepts and potential for new therapies

Cardiomyopathies are defined as diseases of the myocardium with associated structural and functional abnormalities. Knowledge of these pathologies for a long period was not clear in clinical practice due to uncertainties regarding definition,classification and clinical diagnosis. In recent decades,major advances have been made in the understanding of the molecular and genetic issues,pathophysiology,and clinical and radiological assessment of the diseases. Progress has been made also in management of several types of cardiomyopathy. Advances in the understanding of these diseases show that cardiomyopathies represent complex entities. Here,special attention is given to evolution of classification of cardiomyopathies,with the aim of assisting clinicians to look beyond schematic diagnostic labels in order to achieve more specific diagnosis. Knowledge of the genotype of cardiomyopathies has changed the pathophysiological understanding of their etiology and clinical course,and has become more important in clinical practice for diagnosis and prevention of cardiomyopathies. New approaches for clinical and prognostic assessment are provided based on contemporary molecular mechanisms of contribution in the pathogenesis of cardiomyopathies. The genotype-phe-notype complex approach for assessment improves the clinical evaluation and management strategies of these pathologies. The review covers also the important role of imaging methods,particularly echocardiography,and cardiac magnetic resonance imaging in the evaluation of different types of cardiomyopathies. In summary,this review provides complex presentation of current state of cardiomyopathies from genetics to management aspects for cardiovascular specialists.     

The Prognostic Role of Late Gadolinium Enhancement Magnetic Resonance Imaging in Patients With Cardiomyopathy

Cardiovascular magnetic resonance imaging (CMRI) is currently considered part of standard care at many academic centres for the evaluation of patients with ischemic or nonischemic cardiomyopathy. While CMRI provides unparalleled diagnostic versatility for the assessment of myocardial function, perfusion, and tissue health, evidence supporting its prognostic value for the prediction of important cardiovascular events is now emerging. Given the low specificity of currently available clinical markers in patients with cardiomyopathy, more-robust biomarkers aimed at identifying those at high risk of sudden cardiac death and other relevant outcomes are desirable. Late gadolinium enhancement (LGE) CMRI offers the novel capacity to quantify the burden of myocardial fibrosis, a common pathophysiological end point of most cardiomyopathy states. As such, it has the potential to be a robust and ubiquitous marker of cardiovascular events related to the presence of advanced tissue disease. This review paper focuses on the evidence to date supporting LGE imaging as a tool for the prediction of future cardiovascular events in patients with ischemic and nonischemic cardiomyopathy.     

The right ventricle in “Left-sided” cardiomyopathies: The dark side of the moon

The right ventricle (RV) has long been regarded as the forgotten and neglected cardiac chamber and it has been overshadowed by the left ventricle (LV). However, in the last decades, important advances in non-invasive cardiac imaging, from myocardial deformation imaging to cardiovascular magnetic resonance (CMR), have overcome the challenges imposed by the complex anatomy of the right heart, leading to a deep understanding of cardiovascular physiology and pathophysiology. The importance of the RV in different cardiac disease is now unquestionable and the current evidence emphasizes the forgotten interdependent relationship between the right and the left heart and the pivotal role of RV dysfunction in determining functional performance and outcomes in many cardiac disorders and particularly in cardiomyopathies. The purpose of this review is to summarize the current evidence about the diagnostic and prognostic value of the right heart in the “left-sided” cardiomyopathies, highlighting the relevance to assess RV size and function by multimodality imaging techniques in order to obtain useful information for a proper diagnostic workup and for the prognosis.     

Integrated Biomarkers in Cardiomyopathies

In an integrated approach, the authors examine the most efficient combination of noninvasive and invasive biochemical, immunologic, functional, molecular, imaging and biopsy-derived biomarkers for their applicability in the diagnosis of cardiomyopathies in general and dilated cardiomyopathy (DCM) in particular. A careful selection out of the cascade of available biomarkers will allow, in individual patients, to diagnose certain conditions of cardiomyopathies without endomyocardial biopsy, e.g., borreliosis, rickettsiosis, HIV cardiomyopathy. Viral persistence in DCM associated with inflammation will need both noninvasive (echocardiography, cardiovascular magnetic resonance) and invasive biomarkers (polymerase chain reaction for viral persistence or their exclusion in case of autoreactive myocarditis and quantitative immunohistology, both from endomyocardial biopsy).     

The Role of Cardiac MR in New-Onset Heart Failure

In patients with heart failure, cardiovascular magnetic resonance imaging (CMR) allows a multifaceted approach to cardiac evaluation by enabling an assessment of morphology, function, perfusion, viability, tissue characterization, and blood flow during a single comprehensive examination. Given its accuracy and reproducibility, many believe CMR is the reference standard for the noninvasive assessment of ventricular volumes, mass, and function, and offers an ideal means for the serial assessment of disease progression or treatment response in individual patients. Delayed-enhancement (DE)-CMR provides a direct assessment of myopathic processes. This permits a fundamentally different approach than that traditionally taken to ascertaining the etiology of cardiomyopathy, which is vital in patients with nonischemic cardiomyopathy and incidental coronary artery disease and patients with mixed, ischemic and nonischemic cardiomyopathy. Precise tissue characterization with DE-CMR also improves the diagnosis of left ventricular thrombus, for which it is the emerging clinical reference standard. There is a growing body of literature on the utility of CMR for patient risk stratification, and its potential role in important management decisions such as for cardiac resynchronization therapy and defibrillator placement.     

Sudden Death Late After Doxorubicin Administration: Use of Electrophysiological Study and Treatment by Automatic Implantable Cardioverter Defibrillator

Two patients who survived cardiac arrest late after doxorubicin administration are described. Both patients had nonischemic, dilated cardiomyopathies and underwent electrophysiological studies during which no ventricular arrhythmias were induced. Their negative electrophysiological studies despite well documented cardiac arrests and subsequent clinical courses suggest that patients with cardiomyopathies after doxorubicin administra tion and dilated cardiomyopathies of other etiologies have similar natural histories. Treatment with an automatic implantable cardioverter defibrillator appears to be a reasonable therapeutic option for patients with anthracyline associated cardiac disease who have survived their malignancy but at the price of developing life-threatening arrhythmias.     

Significance of Late Gadolinium Enhancement in Cardiovascular Magnetic Resonance Imaging (CMR)

Cardiovascular magnetic resonance imaging (CMR) permits optimal differentiation between normal and diseased myocardium with the use of gadoliniumbased contrast agents and special magnetic resonance pulse sequences. Imaging is performed 10-20 min after contrast agent application to produce so-called late gadolinium enhancement (LGE) images which depict diseased myocardium with excellent reproducibility. Areas showing LGE correspond to zones of myocyte necrosis or myocardial fibrosis as shown by comparison with histopathology. Typical patterns of hyperenhancement exist in ischemic heart disease but also in dilated cardiomyopathy, hypertrophic cardiomyopathy and other inflammatory or infiltrative myocardial disease and are described in this article. LGE-CMR is helpful to distinguish advanced ischemic heart disease from nonischemic dilated cardiomyopathy. In ischemic heart disease LGE can also predict the functional recovery after revascularization procedures by directly showing the remaining viable myocardium. LGE may also become useful to predict malignant arrhythmias in patients with ischemic heart disease or nonischemic cardiomyopathy. This may lead in future to an increased role of LGE-CMR as a prognostic tool.     

Left Atrial Function Using Cardiovascular Magnetic Resonance Imaging Independently Predicts Life-Threatening Arrhythmias in Patients Referred to Receive a Primary Prevention Implantable Cardioverter Defibrillator

BackgroundIn this study we aimed to investigate left atrial (LA) function, measured from routine cine cardiovascular magnetic resonance imaging, to determine its value for the prediction of sudden cardiac death (SCD) or appropriate implantable cardioverter defibrillator (ICD) shock in patients who received primary prevention ICD implantation.MethodsWe studied 203 patients with ischemic or idiopathic nonischemic dilated cardiomyopathy who underwent cardiovascular magnetic resonance imaging before primary prevention ICD implantation. LA volumes were measured at end-diastole and end-systole from 4- and 2-chamber cine images, and LA emptying function (LAEF) calculated. Patients were followed for the primary composite end point of SCD or appropriate ICD shock.ResultsMean age was 61 ± 12 years with a mean left ventricular ejection fraction of 24 ± 7%. The mean LAEF was 27 ± 15% (range, 0.9%-73%). At a median follow-up of 1639 days, 35 patients (17%) experienced the primary composite outcome. LAEF was strongly associated with the primary outcome (P = 0.001); patients with an LAEF ≤ 30% experienced a cumulative event rate of 26.1% vs 5.7% (hazard ratio, 5.5; P < 0.001) in patients above this cutoff. This finding was maintained in multivariable analysis (hazard ratio, 4.7; P = 0.002) and was consistently shown in the ischemic and nonischemic dilated cardiomyopathy subgroups.ConclusionsLAEF is a simple, powerful, and independent predictor of SCD in patients being referred for primary prevention ICD implantation.     

Cardiac Magnetic Resonance Fingerprinting: Technical Overview and Initial Results

Cardiovascular magnetic resonance is a versatile tool that enables noninvasive characterization of cardiac tissue structure and function. Parametric mapping techniques have allowed unparalleled differentiation of pathophysiological differences in the myocardium such as the delineation of myocardial fibrosis, hemorrhage, and edema. These methods are increasingly used as part of a tool kit to characterize disease states such as cardiomyopathies and coronary artery disease more accurately. Currently conventional mapping techniques require separate acquisitions for T₁ and T₂ mapping, the values of which may depend on specifics of the magnetic resonance imaging system hardware, pulse sequence implementation, and physiological variables including blood pressure and heart rate. The cardiac magnetic resonance fingerprinting (cMRF) technique has recently been introduced for simultaneous and reproducible measurement of T₁ and T₂ maps in a single scan. The potential for this technique to provide consistent tissue property values independent of variables including scanner, pulse sequence, and physiology could allow an unbiased framework for the assessment of intrinsic properties of cardiac tissue including structure, perfusion, and parameters such as extracellular volume without the administration of exogenous contrast agents. This review seeks to introduce the basics of the cMRF technique, including pulse sequence design, dictionary generation, and pattern matching. The potential applications of cMRF in assessing diseases such as nonischemic cardiomyopathy are also briefly discussed, and ongoing areas of research are described.