Assessment of myocardial ischemia and viability using cardiac magnetic resonance

In the past decade, cardiac magnetic resonance (CMR) has evolved dramatically. Its clinical applications are now a major tool in the diagnosis and prognostic assessment of patients with ischemic heart disease. CMR can be used for detection and quantification of ischemia and for viability assessment using different techniques that are now well validated. Scar can be easily detected using contrast enhancement (late gadolinium enhancement). Ischemia detection is usually achieved with stress CMR techniques, whereas prediction for the recovery of function (detection of dysfunctional but viable myocardial segments) can be deduced from scar and stress imaging. Although determination of which approach is better may depend on the population group, the major advantage of CMR is the ability to integrate different information about anatomy, wall motion, myocardial perfusion, and tissue characterization in a single comprehensive examination.     

心脏核磁共振成像技术在肥厚型心肌病中的应用现状及最新进展

Hypertrophic cardiomyopathy(HCM)is the most common genetic cardiomyopathy and the leading cause of sudden death in young people and a major cause of heart failure symptoms at any age.Due to its genetic etiology,there is substantial heterogeneity in the phenotypic expression and clinical course of patients with HCM.Traditionally,two-dimensional echocardiography has been the easiest and reliable technique for establishing a diagnosis of HCM.However,cardiovascular magnetic resonance(CMR)has emerged as a novel,3-dimensional tomographic imaging technique,which provides high spatial and temporal resolution images of the heart (not limited by thoracic or pulmonary parenchyma),in any plane and without ionizing radiation.As a result,CMR is particularly well suited to provide detailed characterization of the HCM phenotype,including a precise assessment of the location and distribution of LV wall thickening(as well as other myocardial structures such as the right ventricle and papillary muscles).In this regard,CMR has been demonstrated to provide a diagnosis of HCM in cases where the echocardiogam was non-diagnostic.Furthermore,CMR provides an accurate assessment of total LV mass which is a more robust marker of hypertrophy,with potential implications for risk stratification.In addition,with the intravenous administration of gadolinium,first-pass perfusion sequences can identify myocardial perfusion abnormalities,while late gadolinium enhancement sequences can identify areas of myocardial fibrosis/scarring.Although the clinical implications of late gadolinium enhancement in HCM are still uncertain this information may,in the near-future,have important implications with regard to identifying HCM patients at high risk of sudden death and progressive heart failure,including evolution into the end-stage phase of HCM.Therefore,at present,CMR provides important information impacting on diagnosis and clinical management strategies in patients with HCM and will likely have an expanding role in the evaluation of patients with this complex disease.     

The role of cardiovascular magnetic resonance in heart failure

Cardiovascular Magnetic Resonance (CMR) is an accepted gold standard for non-invasive, accurate, and reproducible assessment of cardiac mass and function. The interest in its use for viability, myocardial perfusion and coronary artery imaging is also widespread and growing rapidly as the hardware and expertise becomes available in more centres, and the scans themselves become more cost effective. In patients with heart failure, accurate and reproducible serial assessment of remodelling is of prognostic importance and the lack of exposure to ionizing radiation is helpful. The concept of an integrated approach to heart failure and its complications using CMR is fast becoming a reality, and this will be tested widely in the coming few years, with the new generation of dedicated CMR scanners.     

CMR of ventricular function

Cardiovascular magnetic resonance (CMR) is the reference standard for the assessment of ventricular dimensions, function, and mass in terms of accuracy and reproducibility. It has been thoroughly validated both ex vivo and against other imaging techniques. Measurements are highly accurate and no geometrical assumptions need to be made about the ventricle. A routine ventricular dataset of images can be acquired in less than 5 minutes and analyzed in about the same time. The field is rapidly advancing with increasing automation and simplification in both image acquisition and analysis. Using parallel and real time imaging techniques, good quality data can be obtained even in patients who are unable to hold their breath. While providing useful information in all patients with suspected heart failure, CMR should particularly be considered in those with poor echo windows, where it can also be combined with myocardial stress. Tagging techniques can provide highly detailed information about myocardial torsion and strain for individual myocardial segments. In a research environment, the very high degree of interscan reproducibility can dramatically reduce the number of patients needed to perform clinical trials.     

Cardiovascular Magnetic Resonance in Heart Failure

Imaging has a central role in the evaluation of patients with heart failure (HF). Cardiovascular magnetic resonance (CMR) is rapidly evolving as a versatile imaging modality that often provides additional information to echocardiography in patients with suspected or known HF. CMR is the only imaging modality that has the ability to assess, without exposure to ionizing radiation, cardiac function, structure (tissue characterization), perfusion, and viability. Moreover, magnetic resonance spectroscopy techniques can assess the pathophysiologic role of deranged cardiac energetics in HF. In this review we discuss the role of CMR in the evaluation of patients with HF giving particular emphasis to recent developments and the additional information that can be obtained with this imaging modality, over and above standard echocardiography.     

Emerging MRI Methods in Translational Cardiovascular Research

Cardiac magnetic resonance imaging (CMR) has become a reference standard modality for imaging of left ventricular (LV) structure and function and, using late gadolinium enhancement, for imaging myocardial infarction. Emerging CMR techniques enable a more comprehensive examination of the heart, making CMR an excellent tool for use in translational cardiovascular research. Specifically, emerging CMR methods have been developed to measure the extent of myocardial edema, changes in ventricular mechanics, changes in tissue composition as a result of fibrosis, and changes in myocardial perfusion as a function of both disease and infarct healing. New CMR techniques also enable the tracking of labeled cells, molecular imaging of biomarkers of disease, and changes in calcium flux in cardiomyocytes. In addition, MRI can quantify blood flow velocity and wall shear stress in large blood vessels. Almost all of these techniques can be applied in both pre-clinical and clinical settings, enabling both the techniques themselves and the knowledge gained using such techniques in pre-clinical research to be translated from the lab bench to the patient bedside.     

Gewebedifferenzierung mittels Kontrast-MRT („late enhancement“)

Cardiovascular MR (CMR) is a new diagnostic technique that not only provides morphologic and functional information about the entire cardiovascular system, but also allows non-invasive tissue characterization of the myocardium. Myocardial tissue characterization is mainly based on contrast-enhanced CMR. The main principle of contrast-enhanced CMR is the accumulation of gadolinium-based MR contrast agents in myocardial areas with enlarged extracellular space, such as regions of necrosis, fibrosis or deposits of abnormal proteins (e.g., amyloid), in the absence of contrast enhancement in normal myocardium. Based on the evidence presented in this review article, it is safe to conclude that contrast CMR can reliably detect acute and chronic myocardial infarcts in clinical routine, and that contrast CMR is capable of predicting recovery of wall motion after revascularization with a high degree of accuracy. In addition, contrast CMR is a valuable tool for the work up of new-onset heart failure, since the myocardial distribution of contrast enhancement often points to the underlying disease by providing insight into the myocardium in vivo that could previously only be obtained by postmortem examination. This information about the distribution of abnormal myocardial regions is also important for improving the sensitivity of endomyocardial biopsies that may be necessary in certain myocardial diseases, e.g., myocarditis.     

The role of cardiovascular magnetic resonance imaging in the diagnosis and prognosis of patients with heart failure

Cardiovascular magnetic resonance (CMR) imaging is a tomographic technique, which allows three-dimensional slice orientation without limitations from acoustic windows inherent to echocardiography. Further advantages of CMR are its high temporal and spatial resolution, its excellent soft tissue resolution and its high blood-to-tissue contrast. Cardiovascular magnetic resonance is currently the only imaging technique, which provides a comprehensive study of both structure and function of the heart as well as myocardial perfusion and viability. Moreover, post-processing of CMR images does not require any geometric assumptions as in echocardiography to determine ventricular dimensions. This is particularly important when evaluating ventricles of patients with chronic heart failure with severely altered morphology that may have regional variations in wall thickness and contractility at least in ischemic cardiomyopathy. The highly reproducible results of CMR imaging have turned this technique into a reference standard for the non-invasive assessment of ventricular dimensions, mass and function. In cases with indeterminate results of clinical, electrocardiographic and particularly echocardiographic findings CMR should be used early in the process of diagnosis of patients with heart failure. Not only can altered structure and degree of ventricular and valvular dysfunctions be accurately assessed but also regional perfusion deficits and/or myocardial scars are easily detected. For therapeutic and prognostic reasons a simple differentiation between ischemic and non-ischemic cardiomyopathy should be achieved as the first diagnostic step. In addition, the type and localization of the late gadolinium enhancement (LGE) phenomenon may aid in non-invasively differentiating the etiology of non-ischemic cardiomyopathy. CMR may also improve the assessment and extent of interventricular and intraventricular dyssynchrony in patients to be selected for cardiac resynchronization therapy (CRT). Lastly, the LGE phenomenon may provide independent prognostic information in patients with a CRT system implanted, as well as in patients with ischemic and non-ischemic cardiomyopathy. Thus, CMR imaging should be implemented early in the diagnostic process of patients with heart failure to significantly improve the speed and accuracy of diagnostic procedures, to control the effect of therapeutic measures, and to select patients with a limited prognosis by assessing the degree of ventricular dysfunction and the extent of myocardial scarring.     

Non-invasive methods in differentiating ischaemic from non-ischaemic cardiomyopathy. A review paper

Chronic heart failure is a common disorder associated with high mortality and morbidity. Patients' numbers and the burden placed on health care services increase as the average age of the population rises. Non-invasive imaging plays a central role in the correct diagnosis of heart failure, the determination of aetiology and prognosis, as well as the monitoring of ongoing therapy. In this review paper we critically summarize techniques that differentiate ischaemic from non-ischaemic cardiomyopathy. Coronary angiography has been used as the primary method for distinguishing ischaemic from non-ischaemic cardiomyopathy; while studies utilizing echocardiography, myocardial perfusion imaging or electron computed tomography and positron emission tomography, have played a substantial role. More recently, CMR and multislice computed tomography have demonstrated ability in initial functional assessment and in the determination of secondary causes of heart failure.     

Cardiac magnetic resonance imaging for stage B heart failure

Cardiac magnetic resonance imaging (CMR) can play a key role in the assessment and follow-up of patients with stage B heart failure. CMR currently serves as the reference standard for quantifying right and left ventricular size and ejection fraction. Technical advances have also enabled CMR to provide noninvasive tissue characterization and detailed assessments of myocardial performance. Thus, in addition to standard metrics of cardiac structure and function, CMR offers a variety of tools for determining cause, severity, and estimating the prognosis associated with an asymptomatic cardiomyopathy.     

Cardiac magnetic resonance imaging: A teaching atlas with emphasizing current clinical indications

Cardiovascular magnetic resonance (CMR) is an amazing technology that continues to provide new innovative approaches for evaluating the heart and blood vessels. It can assess cardiac morphology, function, perfusion, viability, coronary and peripheral arteries, and metabolism and tissue characterization. The basic pulse sequences of CMR include; Spin Echo, Gradient echo, and Steady stet free precision. Current clinical indications of CMR are multiple and continuously evolving. CMR often works in complementary fashions to other cardiac imaging techniques or to resolve residual diagnostic dilemma. The purpose of this illustrative review is to review current clinical applications of CMR and to provide physicians and technologists with simple, and regular CMR cases form daily practice. Each case discusses briefly the related clinical history, followed by CMR imaging findings, and simple discussion to highlight the role of CMR in a particular cardiovascular disorder.     

The Current and Emerging Role of Cardiovascular Magnetic Resonance Imaging in Hypertrophic Cardiomyopathy

Hypertrophic cardiomyopathy (HCM) is the most common genetic cardiomyopathy with substantial heterogeneity in phenotypic expression and clinical course. Traditionally, two-dimensional echocardiography has been the easiest and most reliable technique for establishing a diagnosis of HCM. However, cardiovascular magnetic resonance (CMR) has emerged as a novel, three-dimensional tomographic imaging technique, which provides high spatial and temporal resolution images of the heart in any plane and without ionizing radiation. As a result, CMR is particularly well suited to provide detailed characterization of the HCM phenotype, including precise assessment of the location and distribution of left ventricular (LV) wall thickening. In this regard, CMR can identify hypertrophy (particularly in the anterolateral free wall and apex), not well appreciated (or underestimated) by two-dimensional echocardiography, with important implications for diagnosis. CMR can also provide detailed characterization of other myocardial structures such as the papillary muscles, which may impact on preoperative management strategies for patients who are candidates for surgical myectomy. Furthermore, CMR enables an accurate assessment of total LV mass, a robust marker of the overall extent of hypertrophy, which may have implications for risk stratification. In addition, a subgroup of HCM patients have normal LV mass (with focal hypertrophy), suggesting that a limited extent of hypertrophy is consistent with a diagnosis of HCM. Finally, following the intravenous administration of gadolinium, first-pass perfusion sequences can identify myocardial perfusion abnormalities, while late gadolinium enhancement (LGE) sequences can characterize areas of myocardial fibrosis/scarring. LGE is associated with systolic dysfunction and likelihood for ventricular tachyarrhythmias on ambulatory Holter monitoring in patients with HCM. However, the precise clinical implications of myocardial perfusion abnormalities and LGE in HCM are still uncertain; this information may have important implications with regard to identifying HCM patients at risk of sudden death and adverse LV remodeling associated with systolic dysfunction. Therefore, at present, CMR provides important information impacting on diagnosis and clinical management strategies in patients with HCM and will likely have an expanding role in the evaluation of patients with this complex disease.     

Imaging Heart Failure: Current and Future Applications

A variety of cardiac imaging tests are used to help manage patients with heart failure (HF). This article reviews current and future HF applications for the major noninvasive imaging modalities: transthoracic echocardiography (TTE), single-photon emission computed tomography (SPECT), positron emission tomography (PET), cardiovascular magnetic resonance (CMR), and computed tomography (CT). TTE is the primary imaging test used in the evaluation of patients with HF, given its widespread availability and reliability in assessing cardiac structure and function. Recent developments in myocardial strain, 3-dimensional TTE, and echo contrast appear to offer superior diagnostic and prognostic information. SPECT imaging is a common method employed to detect ischemia and viability in patients with HF; however, PET offers higher diagnostic accuracy for both. Ongoing study of sympathetic and molecular imaging techniques may enable early disease detection, better risk stratification, and ultimately targeted treatment interventions. CMR provides high-quality information on cardiac structure and function and allows the characterization of myocardial tissue. Myocardial late gadolinium enhancement allows the determination of HF etiology and may predict patient outcomes and treatment response. Cardiac CT has become a reliable means for detecting coronary artery disease, and recent advances have enabled concurrent myocardial function, perfusion, and scar analyses. Overall, available imaging methods provide reliable measures of cardiac performance in HF, and recent advances will allow detection of subclinical disease. More data are needed demonstrating the specific clinical value of imaging methods and particularly subclinical disease detection in large-scale, clinical settings.     

Cardiac Imaging Integration in 2009 and Beyond: Cardiovascular magnetic resonance

Cardiovascular magnetic resonance (CMR) is currently well recognized in clinical practice for the diagnosis and management of cardiovascular diseases. CMR is helpful in the diagnosis and prognosis of patients with myocardial infarction. The high spatial resolution of CMR enables accurate assessment of tissue characterization in various types of cardiomyopathy. In addition, CMR may play a complementary role with echocardiography in clinical evaluation of patients with valvular and congenital heart disease.     

The role of nuclear imaging in the failing heart: myocardial blood flow,sympathetic innervation,and future applications

Heart failure represents a common disease affecting approximately 5 million patients in the United States. Several conditions play an important role in the development and progression of heart failure, including abnormalities in myocardial blood flow and sympathetic innervation. Nuclear imaging represents the only imaging modality with sufficient sensitivity to assess myocardial blood flow and sympathetic innervation of the failing heart. Although nuclear imaging with single-photon emission computed tomography (SPECT) is most commonly used for the evaluation of myocardial perfusion, positron emission tomography (PET) allows absolute quantification of myocardial blood flow beyond the assessment of relative myocardial perfusion. Both techniques can be used for evaluation of diagnosis, treatment options, and prognosis in heart failure patients. Besides myocardial blood flow, cardiac sympathetic innervation represents another important parameter in patients with heart failure. Currently, sympathetic nerve imaging with 123-iodine metaiodobenzylguanidine (123-I MIBG) is often used for the assessment of cardiac innervation. A large number of studies have shown that an abnormal myocardial sympathetic innervation, as assessed with 123-I MIBG imaging, is associated with increased mortality and morbidity rates in patients with heart failure. Also, cardiac 123-I MIBG imaging can be used to risk stratify patients for ventricular arrhythmias or sudden cardiac death. Furthermore, novel nuclear imaging techniques are being developed that may provide more detailed information for the detection of heart failure in an early phase as well as for monitoring the effects of new therapeutic interventions in patients with heart failure.     

Newer Applications of Nuclear Cardiology in Systolic Heart Failure: Detecting Coronary Artery Disease and Guiding Device Therapy

Radionuclide-based imaging techniques can be applied to the heart failure population to derive clinically useful information. This review discusses the specific role of myocardial perfusion imaging for determining heart failure etiology, and the potential application of radionuclide-based imaging techniques for the optimal selection of patients with heart failure for device therapy.     

Impact of Diabetes on Postinfarction Heart Failure and Left Ventricular Remodeling

Diabetes mellitus, the metabolic syndrome, and the underlying insulin resistance are increasingly associated with diastolic dysfunction and reduced stress tolerance. The poor prognosis associated with heart failure in patients with diabetes after myocardial infarction is likely attributable to many factors, important among which is the metabolic impact from insulin resistance and hyperglycemia on the regulation of microvascular perfusion and energy generation in the cardiac myocyte. This review summarizes epidemiologic, pathophysiologic, diagnostic, and therapeutic data related to diabetes and heart failure in acute myocardial infarction and discusses novel perceptions and strategies that hold promise for the future and deserve further investigation.     

Delayed enhancement cardiovascular magnetic resonance assessment of non-ischaemic cardiomyopathies.

Non-ischaemic cardiomyopathies (NICMs) are chronic, progressive myocardial diseases with distinct patterns of morphological, functional, and electrophysiological changes. In the setting of cardiomyopathy (CM), determining the exact aetiology is important because the aetiology is directly related to treatment and patient survival. Determining the exact aetiology, however, can be difficult using currently available imaging techniques, such as echocardiography, radionuclide imaging or X-ray coronary angiography, since overlap of features between CMs may be encountered. Cardiovascular magnetic resonance (CMR) imaging has recently emerged as a new non-invasive imaging modality capable of providing high-resolution images of the heart in any desired plane. Delayed contrast enhanced CMR (DE-CMR) can be used for non-invasive tissue characterization and may hold promise in differentiating ischaemic from NICMs, as the typical pattern of hyperenhancement can be classified as 'ischaemic-type' or 'non-ischaemic type' on the basis of pathophysiology of ischaemia. This article reviews the potential of DE-CMR to distinguish between ischaemic and NICM as well as to differentiate non-ischaemic aetiologies. Rather than simply describing various hyperenhancement patterns that may occur in different disease states, our goal will be (i) to provide an overall imaging approach for the diagnosis of CM and (ii) to demonstrate how this approach is based on the underlying relationships between contrast enhancement and myocardial pathophysiology.     

A clinical cardiovascular magnetic resonance service: operational considerations and the basic examination

Cardiovascular magnetic resonance (CMR) is now considered the "gold standard" for the assessment of regional and global systolic function, myocardial infarction and viability, and congenital heart disease. At specialized centers, CMR has become a clinical workhorse for the evaluation of ischemic heart disease and for heart failure and cardiomyopathies. Despite this versatility, general acceptance of CMR in cardiovascular medicine has progressed slowly. This article provides a basic understanding of important operational considerations when starting a CMR service and describes a conceptual framework of the components of a CMR examination.     

Myocardial Amyloidosis: The Exemplar Interstitial Disease

Cardiac involvement drives prognosis and treatment choices in cardiac amyloidosis. Echocardiography is the first-line examination for patients presenting with heart failure, and it is the imaging modality that most often raises the suspicion of cardiac amyloidosis. Echocardiography can provide an assessment of the likelihood of cardiac amyloid infiltration versus other hypertrophic phenocopies and can assess the severity of cardiac involvement. Visualizing myocardial amyloid infiltration is challenging and, until recently, was restricted to the domain of the pathologist. Two tests are transforming this: cardiac magnetic resonance (CMR) imaging and bone scintigraphy. After the administration of contrast, CMR is highly sensitive and specific for the 2 main types of ventricular myocardial amyloidosis, light chain amyloidosis (AL) and transthyretin amyloidosis (ATTR). CMR structural and functional assessment combined with tissue characterization can redefine cardiac involvement by tracking different disease processes, ranging from amyloid infiltration, to the myocardial response associated with amyloid deposition, through the visualization and quantification of myocardial edema and myocyte response. Bone scintigraphy (paired with exclusion of serum free light chains) is emerging as the technique of choice for distinguishing ATTR from light chain cardiac amyloidosis and other cardiomyopathies; it has transformed the diagnostic pathway for ATTR, allowing noninvasive diagnosis of ATTR without the need for a tissue biopsy in the majority of patients. CMR with tissue characterization and bone scintigraphy are rewriting disease understanding, classification, and definition, and leading to a change in patient care.