Normal and diffusely abnormal myocardium in humans: functional and metabolic characterization with P-31 MR spectroscopy and cine MR imaging

The current study tested the concept that cine magnetic resonance (MR) imaging and phosphorus-31 MR spectroscopy might be used to provide a comprehensive evaluation of the functional and metabolic status of the myocardium in humans. Thirteen patients with congestive cardiomyopathy and eight healthy volunteers were imaged at 1.5 T with the one-dimensional chemical shift imaging technique for localization of P-31 MR spectroscopy and an electrocardiographically referenced gradient refocused sequence for imaging of the heart. Prominent peaks in the PDE and PME regions were observed in cardiomyopathic patients, but only the former peak was measured. The PCr/beta-ATP peak ratio was not significantly lower in cardiomyopathic patients compared with healthy subjects (1.51 +/- 0.08 vs 1.54 +/- 0.04). The ratios of PDE/PCr (0.80 +/- 0.07 vs 0.54 +/- 0.10) (P less than or equal to .01) and PDE/beta-ATP (1.19 +/- 0.10 vs 0.84 +/- 0.08) (P less than or equal to .05) were significantly higher in patients with dilated cardiomyopathy compared with healthy volunteers. Left ventricular systolic wall thickening was significantly lower and left ventricular peak and end-systolic wall stress and mass were significantly higher in cardiomyopathic patients compared with healthy volunteers. Thus, localized, gated P-31 MR spectroscopy combined with cine MR imaging allowed identification of both abnormal myocardial phosphate metabolism and abnormal ventricular function. While this study suggests that increased myocardial PDEs may be a marker for abnormal myocardium, the sensitivity and specificity of this marker need to be further evaluated.     

Functional evaluation of the heart with magnetic resonance imaging

This review examines the capability of cine MRI for evaluation of cardiovascular function and shows early results in valvular, ischemic, and congenital heart disease. MR assessment of left and right ventricular volumes is independent of geometrical models; dimensional values have been defined for normal individuals. Noninvasive measurement of peak and end systolic pressure along with cine MR imaging can be used to calculate left ventricular meridional wall stress which can be used for monitoring of myocardial diseases and evaluation of therapeutic intervention. Cine MR may be more accurate than angiography for identifying regional LV dysfunction since it can measure wall thickening as well as inward wall motion. Regurgitant jets due to valvular lesions are readily seen and their characteristics may be used to define the severity of aortic or mitral regurgitation. Calculation of the regurgitant volume separates patients with mild, moderate, or severe disease. Likewise, the shunt flow across ventricular and atrial septal defects has been visualized in cine MR images and shunt flow calculated. Cine MRI serves as a three-dimensional imaging technique with high temporal resolution. It extends the capability of MRI in cardiac disease beyond the depiction of anatomy and renders a comprehensive cardiac imaging technique for quantitation of cardiac anatomy and function.     

Efficacy of cardiac MRI in the evaluation of ischemic heart disease.

With the development of fast scan techniques and technical advances in software, cardiac MRI can now be used for morphological and functional evaluation of the heart with good reliability and high spatial and temporal resolution. Cardiac MRI is employed at many institutions, mainly for assessing ischemic heart disease. Cardiac MRI can be used to identify coronary artery stenosis, evaluate myocardial viability, assess left ventricular wall motion and function, measure coronary blood flow and flow reserve, and obtain other useful information for the diagnosis of ischemic heart disease in a single examination, serving as a true comprehensive cardiac study. With regard to the evaluation of coronary artery stenosis, new techniques, such as whole-heart coronary MRA, permit visualization of the coronary arteries to their peripheral branches without contrast agent. Good results have been reported for whole-heart MRA as compared with X-ray coronary angiography (CAG). Attempts to evaluate plaque characteristics by visualizing the walls of the coronary arteries have also been reported recently. Technical improvements have been made in myocardial perfusion MRI to detect myocardial ischemia and in delayed contrast-enhanced MRI to assess myocardial viability, and some researchers have recently reported that the diagnostic capabilities of these techniques match or surpass those of cardiac nuclear medicine studies. We outline the features of the latest MR imaging techniques for the diagnosis of ischemic heart disease, discuss their practical applications, and compare them with other imaging modalities.     

Magnetic resonance imaging in coronary heart disease

Modern level of cardiac magnetic resonance imaging (MRI) development already allows its routine use (with proper indications) in coronary heart disease patients for studies of heart morphology and functions, performance of stress tests for evaluation of myocardial perfusion and contractile function. Coronary MRA and some other new MR techniques are close to its wide-scale clinical application. It has been shown that cardiac MRI is a valuable tool for detection of postinfarction scars, aneurysms, pseudoaneurysms, septal defects, mural thrombi and valvular regurgitations. Due to intrinsic advantages of the method it is of special value when these pathological conditions cannot be fully confirmed or excluded with echocardiography. MRI is recognized as the best imaging method for quantification of myocardial thickness, myocardial mass, systolic myocardial thickening, chamber volumes, ejection fraction and other parameters of global and regional systolic and diastolic function. MRI is used in studies of cardiac remodeling in postinfarction patients. The most attractive areas for cardiovascular applications of MRI are assessment of myocardial perfusion and non-invasive coronary angiography. Substantial progress has been achieved in these directions. There are some other new developments in studies of coronary artery disease with MRI. High-resolution MR is used for imaging and quantification of atherosclerotic plaque composition in vivo. Intravascular MR devices suitable for performing imaging-guided balloon angioplasty are created. But before MRI will be widely accepted by the medical community as a important cardiovascular imaging modality several important problems have to be solved. Further technical advances are necessary for clinical implementation of all major diagnostic capabilities of cardiac MRI. The subjective obstacles for growth of clinical applications of cardiac MRI are lack of understanding of its possibilities and benefits both by clinicians and radiologists themselves. So proper training of specialists and promotion of this promising modality among the medical community are necessary.     

The role of positron emission tomography in the evaluation of myocardial ischemia in women

Cardiovascular disease continues to be the number one cause of death in women, yet most women are unaware of their risk. Over the last decade, radionuclide myocardial perfusion imaging with positron emission tomography (PET) has become a powerful tool for the diagnosis and risk stratification of patients with known or suspected coronary artery disease (CAD). This editorial viewpoint will review the maturing role of PET imaging in women, particularly as applied to the evaluation of ischemic heart disease. Specifically, we focus on distinct advantages offered by PET imaging in the evaluation of myocardial ischemia in women: (1) improved diagnostic accuracy, including in the presence of breast or adipose tissue and small left ventricular cavity size, (2) decreased radiation exposure through the use of short-lived radiopharmaceuticals, and (3) the ability to quantify myocardial blood flow and coronary flow reserve to diagnose ischemia, even in the absence of obstructive CAD. As such, cardiac PET perfusion imaging stands to play a unique role in defining the diagnosis and prognosis of women with ischemic heart disease, while also guiding new treatment strategies for their more prevalent cardiovascular disease phenotypes.     

Magnetic resonance spectroscopy of the heart. Overview of studies in animals and man

Magnetic resonance spectroscopy (MRS) has been used effectively in the evaluation of cardiac physiology. Studies have been done at various levels of complexity extending from isolated hearts to man. Correlation of high-energy phosphate compounds with contractile function is achieved by simultaneous or immediate sequential measurement of ventricular contractile function and the phosphorus-31 MR spectra. Studies in isolated hearts have monitored the response to ischemia of normal and hypertrophic hearts and the preservation of myocardial function and high- energy phosphate stores by drugs administered prior to the ischemic event. Regional myocardial ischemia has been evaluated by simultaneous monitoring of myocardial regional segment length by sonomicrometry and regional myocardial 31P MRS in the intact heart of larger animal models. Function and metabolism have been assessed in man by the combined application of cine MRI and 31P MRS acquired with a surface coil.     

Magnetic resonance imaging of the heart: perfusion, function, and structure

The use of interventional therapy in acute myocardial infarction has intensified the desire to obtain accurate information on regional myocardial perfusion. MR imaging using ultrafast techniques and contrast agents may be useful to estimate myocardial perfusion in patients with coronary artery disease. In addition, MR imaging with contrast agents is capable of defining the infarcted region and the area at risk after coronary artery occlusion. Quantitative evaluation of regional myocardial contractile function with and without pharmacologic stress testing further improves the utility of MR imaging in defining the effects of reperfusion therapy on dysfunctional myocardium and in detecting myocardial ischemia. Furthermore, cine MR techniques are now used extensively to assess cardiac function and volumes and to obtain flow velocity maps. Cardiac MR applications are evolving rapidly and the clinical significance is expanding.     

Evaluation of patients with coronary insufficiency using single-photon gamma tomography and positron-emission tomography

In summary, PET and SPECT myocardial imaging both have important roles to play in evaluation of patients with suspected coronary artery and myocardial disease. Tl-201 remains the predominant tracer in clinical use, and even when technetium-labeled myocardial perfusion agents are widely available, Tl-201 will undoubtedly continue to be used for the next few years. PET imaging remains the mode of choice for research evaluation of coronary artery and cardiovascular disease, as well as the preferred method for investigating difficult cases which are equivocal on SPECT perfusion imaging. Wider availability of both PET cameras and central radiopharmacies providing cyclotron produced PET radiopharmaceuticals should provide the impetus for expansion of PET myocardial imaging applications. Even at the price of $1,000-1,500 per scan, study results which permit better informed decisions regarding performance of $5,000-50,000 interventional procedures such as PTCA and CABG make the economics of PET justified. Even with the progress of competing modalities such as echocardiography, MR flow imaging, and MR spectroscopy with tissue characterization, nuclear medicine methods for myocardial evaluation should remain of major importance for the foreseeable future.     

Optimal use of contrast medium in contrast enhanced MR imaging of the heart

With the recent development of fast MR imaging techniques, the diagnostic value of contrast enhanced MR imaging of the heart has been substantially improved. Since no tissue-specific contrast medium is available for clinical cardiac MR imaging at this point, both the early and late dynamics of extracellular MR contrast medium should be carefully evaluated for assessing the multiple aspects of cardiac function, including myocardial blood flow, myocardial, viability, and left ventricular function. Myocardial blood flow can be assessed by monitoring the first-pass passage of MR contrast medium. Quantitative assessments of arterial input function and output function in the regional myocardium can provide more accurate detection of altered myocardial blood flow in patients with coronary artery disease. Excellent contrast between infarcted myocardium and normal tissue can be obtained with delayed contrast enhanced MR imaging. Myocardial infarction, including small subendocardial infarction and chronic scar, is demonstrated as an area of "hyperenhancement" on delayed enhanced MR images, while the signal from normal myocardium is nearly null. This review paper describes the optimal dose and injection rate of MR contrast material for functional cardiac MR imaging studies. In addition, practical suggestions for obtaining good cardiac MR images and interpreting contrast enhanced MR images are given and are explained in detail.     

Dynamic cardiac MR imaging. Techniques and applications

Current state-of-the-art dynamic or cine cardiac MR imaging is a time-effective study that offers a comprehensive evaluation of cardiac structure and function at rest. The major limitation at present is its inability to screen for coronary artery disease and evaluate ventricular function under stress. The future promises routine quantification of aortic, pulmonic, and other vascular flow rates, ultrafast (seconds) to real-time imaging, and paramagnetic or magnetic susceptibility perfusion markers. With the combination of real-time imaging and magnetic perfusion agents, imaging to detect coronary artery disease should also be possible. The use of pharmacologic stress or possibly physical stress with real-time imaging may also make this a reality in the not-too-distant future. MR coronary angiography remains a theoretical possibility but requires significant technologic advances, and is thus more remote. Existing and developing technology, however, seems to indicate that in the near-to-intermediate term, dynamic MR imaging will be an effective tool for evaluating almost all major types of cardiovascular disease.     

MRI in nonischemic acquired heart disease

Cardiac MRI applications for diagnosis and follow-up of patients with acquired heart disease are constantly expanding. This review article presents an overview of the use of cardiac MRI in nonischemic acquired heart disease. The role of MRI in nonischemic acquired heart disease continues to be influenced by perceived capabilities of echocardiography. The applications discussed in this review are: myocardial diseases including cardiomyopathies, arrhythmogenic right ventricular dysplasia and myocarditis; pericardial diseases, especially constrictive pericarditis; cardiac and paracardiac masses; and valvular heart disease. Cine MR is now regarded as the preferred method for evaluation and quantification of right ventricular function.     

Quantitation in echocardiography

Imaging of the heart is the predominant approach to cardiovascular diagnosis in current practice. Of the wide variety of cardiac imaging techniques available, echocardiography is one of the most widely used. Standard methods of quantitation of M-mode and two-dimensional echocardiograms yield reproducible, accurate measurements of cardiac chamber, wall, and great vessel dimensions. Qualitative analysis of valvular appearance and motion permits the diagnosis of a wide variety of valvular disorders. Doppler echocardiography yields information on blood flow velocity and pattern in the heart and great vessels. Evolving methods of quantitation in echocardiography include computerized image enhancement, computer-assisted border detection, analysis of regional left ventricular contraction, three-dimensional reconstruction, contrast-enhanced echocardiography, ultrasound myocardial tissue characterization, and intraoperative echocardiography. Echocardiography is a dynamic, evolving discipline with the potential of defining cardiac structure, function, blood flow dynamics, myocardial perfusion, and tissue characteristics. Thus, ultrasonography will continue to be of major importance in the diagnosis of cardiac disease.     

Feasibility of rapid-sequence 31P magnetic resonance spectroscopy in cardiac patients

PURPOSE: To determine the clinical feasibility of rapid-sequence phosphorus-31 magnetic resonance spectroscopy (31P-MRS) of the heart with cardiac patients using a 1.5T clinical MR system. MATERIAL AND METHODS: Twenty cardiac patients, i.e. dilated cardiomyopathy (DCM) 13 cases, hypertrophic cardiomyopathy (HCM) 3 cases, hypertensive heart diseases (HHD) 3 cases, and aortic regurgitation (AR) 1 case were examined using rapid cardiac 31P-MRS. Complete three-dimensional localization was performed using a two-dimensional phosphorus chemical-shift imaging sequence in combination with 30-mm axial slice-selective excitation. The rapid-sequence 31P-MRS procedure was phase encoded in arrays of 8 x 8 steps with an average of 4 acquisitions. The total examination time, including proton imaging and shimming, for the rapid cardiac 31P-MRS procedure, ranged from 10 to 15 min, depending on the heart rate. Student's t test was used to compare creatine phosphate (PCr)/adenosine triphosphate (ATP) ratios from the cardiac patients with those of the control subjects (n = 13). RESULTS: The myocardial PCr/ATP ratio obtained by rapid 31P-MRS was significantly lower (P < 0.001) in DCM patients (1.82 +/- 0.33, mean +/- SD), and in patients with global myocardial dysfunction (combined data for 20 patients: 1.89 +/- 0.32) than in normal volunteers (2.96 +/- 0.59). These results are similar to previous studies. CONCLUSION: Rapid-sequence 31P-MRS may be a valid diagnostic tool for patients with cardiac disease.     

MR spectroscopy of the heart

The present review outlines the clinical potential of magnetic resonance (MR) spectroscopy of the heart. The main acquisition and postprocessing techniques of myocardial phosphorous (31P) and proton (1H) MR spectroscopy are illustrated, along with the possibilities these techniques offer for assessing the myocardial metabolism of phosphates and the presence of lipids. Particular attention is paid to the significance of the main peaks of the myocardial spectrum of 31P: phosphomonoesters (PME), inorganic phosphate (Pi), phosphodiesters (PDE), phosphocreatine (PCr), and gamma-, alpha- and beta-adenosine triphosphate (ATP). The main findings of clinical research are presented with regard to myocardial hypertrophy and hypertrophic and dilated cardiomyopathy, ischaemic cardiomyopathy and myocardial involvement in multisystem disease such as muscular dystrophy and diabetes mellitus. Lastly, the recent prospects offered by technological innovations that increase the signal-to-noise ratio and reduce acquisition times are assessed with reference to the radiologist dedicated to cardiac imaging.     

MR-Tomographie des Herzens

The introduction of magnetic resonance (MR) tomography has fundamentally changed radiological diagnosis for many diseases. Invasive digital subtraction angiography has already been widely replaced by noninvasive MR angiography for most of the vascular diseases. The rapid technical development of MR imaging in recent years has opened new functional imaging techniques. MR imaging of the heart allows simultaneous measurement of morphological and functional parameters in a single noninvasive examination without any radiation exposure. Because of the high spatial resolution and the reproducibility cine MR imaging is now the gold standard for functional analysis. With the improvement of myocardial perfusion and viability studies many diseases of the heart can be diagnosed in a single examination. MR spectroscopy is the only method which allows a view of the metabolism of the heart. New examinations for vascular imaging and flow quantification complete the goal of "one-stop-shop" imaging of the heart. MR imaging is the only diagnostic modality which allows a complete evaluation of many diseases of the heart with one technique, basic examination as well as follow-up studies. The very rapid improvement in MRI will overcome most of the limitations in the near future, especially concerning MR coronary angiography.     

Fast magnetic resonance imaging of the heart.

Fast MR imaging techniques have multiple applications for evaluation of cardiac disease. Cine MRI and MR tagging have been shown to be highly accurate and reproducible in evaluating regional and global myocardial function. Segmented k-space cine MRI and echo-planar imaging (EPI) can considerably improve time efficiency and thereby the clinical utility of these techniques. Double IR fast spin-echo sequences enable breath-hold acquisition of T2 weighted MRI with good suppression of the blood signal. Myocardial perfusion can be assessed with fast dynamic MRI after administration of contrast media. Multi-shot EPI improves temporal resolution and also provides full coverage of the left ventricle. Substantial progress has been made in respiratory gated 3D coronary artery MR angiography with navigator echoes. The newer approaches for coronary arterial imaging including breath-hold three-dimensional segmented EPI and high resolution spiral MRI may further improve clinical usefulness of coronary MR angiography. Assessment of coronary blood flow and flow reserve with phase contrast MRI has the potential for the non-invasive evaluating of the presence and significance of stenosis in the native coronary artery and bypass grafts. Fast cardiac MRI may emerge as a cost effective modality for comprehensive assessments of both cardiac morphology, function, blood flow and perfusion.     

Diagnostic imaging techniques for analyzing heart function: indications and limitations

Cardiac function analysis is critical in the management of patients with cardiovascular diseases. The two most common non-invasive techniques used nowadays to evaluate cardiac function are ultrasonography and magnetic resonance imaging (MR). The parameters to be determined with both techniques include the systolic volume of the left ventricle, the cardiac mass, myocardial thickness and ejection fraction. Ultrasound images have high resolution and they do not need any cardiac or respiratory gating. It has limitations in obese patients, patients with pulmonary obstructive disease or patients after thoracic surgery. MR has a high spatial and temporal resolution. There are different sequences we can use to determine cardiac function parameters, Gradient Echo sequences are used to analyze the ventricular volume and the ejection fraction. Myocardial tagging sequences are used to quantify the myocardial wall motion. Computed Tomography constitutes other alternative that can be used in patients with claustrophobia or pace markers to evaluate cardiac function.     

Clinical applications of radionuclide imaging in the evaluation and management of patients with congenital heart disease

Non-invasive testing of children with congenital heart disease (CHD) began in the 1950s with the introduction of radionuclide studies to assess shunt fractions, pulmonary blood flow, and ventricular contractile function. Echocardiography and cardiac magnetic resonance imaging have since replaced radionuclide imaging in many of these roles. Concurrently, percutaneous and surgical repairs of complex CHD evolved, creating new roles for radionuclide imaging. In this paper on applications of radionuclide imaging in CHD, we review the multiple mechanisms for myocardial ischemia in CHD. We critically compare optimal radionuclide imaging techniques to other imaging modalities for assessing ischemia in CHD. We present the current role of nuclear imaging for assessing viability and pulmonary blood flow. We highlight the value added by advances in dedicated cardiac SPECT scanners, novel reconstruction software, and cardiac PET in performing low-dose radionuclide imaging in CHD. Finally, we discuss the emerging clinical indications for radionuclide imaging in CHD including coronary flow reserve assessment and evaluation of cardiovascular prosthesis and device infections.     

Magnetic resonance imaging of the heart: a review of the experience in 172 subjects

Gated magnetic resonance (MR) imaging was used to evaluate central cardiovascular anatomy in 172 subjects, 31 of whom were healthy volunteers. Using the spin-echo technique, images of diagnostic quality were obtained in 93% of cases with TE = 28 msec and in 65% of cases with TE = 56 msec. Transverse multisection sequences encompassing most of the left ventricle required approximately 6-8 minutes. Corroborative studies were available in 134 of 141 patients who had cardiovascular disease; two dimensional echocardiograms and angiography in 133 and 100 patients, respectively. Gated MR demonstrated the wall thinning and complications caused by prior myocardial infarctions and high signal intensity of the myocardium at the site of acute myocardial infarctions. MR accurately demonstrated anatomic abnormalities owing to hypertrophic and congestive cardiomyopathies, congenital abnormalities of the heart and great vessels, rheumatic heart disease, pulmonary hypertension, and cardiac and paracardiac masses. Depiction of cardiovascular anatomy and pathoanatomy was attained without the use of any contrast media. Consequently, gated MR is an effective technique for cardiac diagnosis. The short time required for tomographic examination of the entire heart using the multisection technique renders this a practical cardiac imaging modality.     

核心脏病学在心力衰竭中的临床应用

核心脏病学的显像技术是一种常用的无创的诊断心力衰竭的重要手段,在评估心力衰竭程度和指导心力衰竭治疗方面发挥了重要作用。定量门控SPECT心肌灌注显像借助其定量分析软件,可以定量评价心脏容积、左心室射血分数、每搏输出量、心脏舒张功能。静息和（或）负荷心肌灌注显像不仅能鉴别非缺血性心力衰竭和缺血性心力衰竭,而且能判别心肌是否存在活性。核心脏病显像技术能轻易地鉴别出舒张性心力衰竭（也称为射血分数正常的心力衰竭）,它通过高峰充盈率和高峰充盈率时间可以准确地评估舒张性心力衰竭的程度。借助三维成像等新技术定量门控SPECT能有效评估左室运动情况,评估室壁厚度对其是一个很好的补充。心肌灌注显像还常用于判别患者是否适合植入心脏除颤器及是否适合进行心脏再同步化治疗。123I-间碘苄胍神经递质显像能为心力衰竭患者提供预后信息。心肌代谢活动与其功能密切相关,能量代谢底物是评价药物治疗是否有助于提高心力衰竭患者心功能的一个指标,123I-15-(p-碘苯基)3-R,S-甲基十五烷酸是一种临床研究中常用的心肌代谢显像示踪剂。借助新示踪剂的应用,包括神经递质显像和心肌代谢显像在内的核心脏病学显像技术常用来完善心力衰竭的诊断。核心脏病学显像技术在诊断心力衰竭及指导临床治疗方面做出了巨大贡献。