MR imaging of myocardial infarction

Myocardial delayed enhancement on dual-energy computed tomography: The prevalence and related factors in patients with suspicion of coronary artery disease

BACKGROUND

We aimed to assess the prevalence of myocardial delayed enhancement (MDE) in patients with suspected obstructive coronary artery disease (CAD), and to investigate factors related to the presence or absence of MDE.

METHODS

We retrospectively evaluated 191 consecutive patients who underwent coronary computed tomography angiography (CCTA) with MDE imaging for clinical suspicion of CAD from December 2014 to December 2016. The presence of MDE on iodine-density images using dual-energy CT was assessed by two independent readers. Multivariable logistic regression analyses were used to determine factors associated with the presence of MDE.

RESULTS

MDE was detected in 58 (30%) patients. Male gender, hypertension, prior heart failure (HF) hospitalization, and CCTA-detected CAD were independent factors related to the presence of MDE. When CCTA-detected CAD was excluded to narrow down the analysis to factors obtainable before CCTA, interventricular septum thickness (IVST) ≥12 mm was added as another independent factor. The combination of the following four factors: female gender, no history of hypertension, no history of prior HF hospitalization, and IVST < 12 mm demonstrated high specificity (98.3%) and positive predictive value (96.2%) for predicting the absence of MDE.

CONCLUSIONS

Male gender, hypertension, prior HF hospitalization, and CAD were independently associated with the presence of MDE in patients with suspected CAD. The combination of female gender, no history of hypertension, no history of prior HF hospitalization, and IVST < 12 mm is likely to be a helpful predictor in discriminating patients without MDE before CCTA.

Assessment and Treatment of Patients With Type 2 Myocardial Infarction and Acute Nonischemic Myocardial Injury

Although coronary thrombus overlying a disrupted atherosclerotic plaque has long been considered the hallmark and the primary therapeutic target for acute myocardial infarction (MI), multiple other mechanisms are now known to cause or contribute to MI. It is further recognized that an MI is just one of many types of acute myocardial injury. The Fourth Universal Definition of Myocardial Infarction provides a taxonomy for acute myocardial injury, including 5 subtypes of MI and nonischemic myocardial injury. The diagnosis of MI is reserved for patients with myocardial ischemia as the cause of myocardial injury, whether attributable to acute atherothrombosis (type 1 MI) or supply/demand mismatch without acute atherothrombosis (type 2 MI). Myocardial injury in the absence of ischemia is categorized as acute or chronic nonischemic myocardial injury. However, optimal evaluation and treatment strategies for these etiologically distinct diagnoses have yet to be defined. Herein, we review the epidemiology, risk factor associations, and diagnostic tools that may assist in differentiating between nonischemic myocardial injury, type 1 MI, and type 2 MI. We identify limitations, review new research, and propose a framework for the diagnostic and therapeutic approach for patients who have suspected MI or other causes of myocardial injury.

Functional LGE Imaging: Cardiac Phase-Resolved Assessment of Focal Fibrosis

Cardiac Magnetic Resonance Imaging (CMR) is a central tool for diagnosis of various ischemic and non-ischemic cardiomyopathies. CMR protocols commonly comprise assessment of functional properties using cardiac phase-resolved CINE MRI and characterization of myocardial viability using late gadolinium enhancement (LGE) imaging. Conventional LGE imaging requires inversion recovery preparation with a specific inversion time to null the healthy myocardium, which restricts the acquisition to a single cardiac phase. In turn, this necessitates separate scans for cardiac function and viability. In this work, we develop a new method for functional LGE imaging in a single breath-hold using a three-step approach: 1) ECG-triggered multi-contrast data is acquired for each cardiac phase, 2) semi-quantitative relaxation maps are generated, 3) LGE imaging contrast is synthesized based on the semi-quantitative maps. The proposed functional LGE method is evaluated in four healthy subject and 20 patients at 1.5T and 3T. Thorough suppression of the healthy myocardium, as well as 40-80ms temporal resolution are achieved, with no visually apparent temporal blurring at tissue interfaces. Functional LGE in patients with focal scar demonstrates robust hyperenhancement in the scar area throughout all cardiac phases, allowing for visual assessment of scar motility. The proposed technique bears the potential to simplify and speedup common cardiac imaging protocols, while enabling improved data fusion of functional and viability information for improved evaluation of CMR.

Overview of complications of acute and chronic myocardial infarctions: revisiting pathogenesis and cross-sectional imaging

Myocardial infarction (MI) remains one of the leading contributors to overall mortality and morbidity in the modern world, even with recent advances in medicine. Various complications can arise following an MI, particularly with delayed or inadequate treatment. Even though many of these complications are uncommon, they can have a significant impact on patient outcomes. Some of these complications can be diagnosed based on clinical, laboratory and echocardiographic evaluation. Other times, however, cardiac MR and multidetector CT are necessary in their diagnosis and proper evaluation. Accurate detection of these complications is an important aspect of optimising prompt and effective patient care, leading to better clinical outcomes. It is the goal of this article to review the role of cross-sectional imaging in patients with post-MI as well as the characteristic imaging findings and differential diagnosis of common and uncommon complications of MI.

Development of the Troponin Detection System Based on the Nanostructure

During the last 30 years, the World Health Organization (WHO) reported a gradual increase in the number of patients with cardiovascular disease (CVD), not only in developed but also in developing countries. In particular, acute myocardial infarction (AMI) is one of the severe CVDs because of the high death rate, damage to the body, and various complications. During these harmful effects, rapid diagnosis of AMI is key for saving patients with CVD in an emergency. The prompt diagnosis and proper treatment of patients with AMI are important to increase the survival rate of these patients. To treat patients with AMI quickly, detection of a CVD biomarker at an ultra-low concentration is essential. Cardiac troponins (cTNs), cardiac myoglobin (cMB), and creatine kinase MB are typical biomarkers for AMI detection. An increase in the levels of those biomarkers in blood implies damage to cardiomyocytes and thus is related to AMI progression. In particular, cTNs are regarded as a gold standard biomarker for AMI diagnosis. The conventional TN detection system for detection of AMI requires long measurement time and is labor-intensive and tedious. Therefore, the demand for sensitive and selective TN detection techniques is increasing at present. To meet this demand, several approaches and methods have been applied to develop a TN detection system based on a nanostructure. In the present review, the authors reviewed recent advances in TN biosensors with a focus on four detection systems: (1) An electrochemical (EC) TN nanobiosensor, (2) field effect transistor (FET)-based TN nanobiosensor, (3) surface plasmon resonance (SPR)-based TN nanobiosensor and (4) surface enhanced Raman spectroscopy (SERS)-based TN nanobiosensor.

Role of Cardiac Magnetic Resonance Imaging in Patients with Idiopathic Ventricular Arrhythmias

Ventricular Arrhythmias (VAs) may present with a wide spectrum of clinical manifestations ranging from mildly symptomatic frequent premature ventricular contractions to lifethreatening events such as sustained ventricular tachycardia, ventricular fibrillation and sudden cardiac death. Myocardial scar plays a central role in the genesis and maintenance of re-entrant arrhythmias which are commonly associated with Structural Heart Diseases (SHD) such as ischemic heart disease, healed myocarditis and non-ischemic cardiomyopathies. However, the arrhythmogenic substrate may remain unclear in up to 50% of the cases after a routine diagnostic workup, comprehensive of 12-lead surface ECG, transthoracic echocardiography and coronary angiography/ computed tomography. Whenever any abnormality cannot be identified, VAs are referred as to "idiopathic". In the last decade, Cardiac Magnetic Resonance (CMR) imaging has acquired a growing role in the identification and characterization of myocardial arrhythmogenic substrate, not only being able to accurately and reproducibly quantify biventricular function, but, more importantly, providing information about the presence of myocardial structural abnormalities such as myocardial fatty replacement, myocardial oedema, and necrosis/ fibrosis, which may otherwise remain unrecognized. Moreover, CMR has recently demonstrated to be of great value in guiding interventional treatments, such as radiofrequency ablation, by reliably identifying VA sites of origin and improving long-term outcomes. In the present manuscript, we review the available data regarding the utility of CMR in the workup of apparently "idiopathic" VAs with a special focus on its prognostic relevance and its application in planning and guiding interventional treatments.

Role of Cardiac Computed Tomography in the Diagnosis of Left Ventricular Myocardial Diseases

Multimodality imaging is indicated for the evaluation of left ventricular (LV) myocardial diseases. Cardiac magnetic resonance (CMR) allows morphological and functional assessment of the LV along with soft tissue characterization. Technological advances in cardiac computed tomography (CT) have led to the development of techniques for diagnostic acquisition in LV myocardial disease. Cardiac CT facilitates the characterization of LV myocardial disease based on anatomy, function, and enhancement pattern. LV regional and global functional parameters are evaluated using multi-phasic cine CT images. CT myocardial perfusion facilitates the identification of hemodynamically significant coronary artery stenosis. Cardiac CT with delayed enhancement is used to detect myocardial scarring or fibrosis in myocardial infarction and non-ischemic cardiomyopathy, and for the measurement of extracellular volume fraction in non-ischemic cardiomyopathy. In this review, we review imaging techniques and key imaging features of cardiac CT used for the evaluation of myocardial diseases, along with CMR findings.

Myocardial Delayed Enhancement CT for the Evaluation of Heart Failure: Comparison to MRI

Purpose To assess the diagnostic performance of dual-energy CT with myocardial delayed enhancement (MDE) in the detection and classification of myocardial scar in patients with heart failure, with late gadolinium enhancement (LGE) MRI as the standard of reference. Materials and Methods MDE CT and LGE MRI were performed in 44 patients with heart failure (30 men; mean patient age, 66 years ± 14) between 2013 and 2016, and images were retrospectively analyzed. The presence and patterns of MDE on iodine-density and virtual monochromatic (VM) images were assessed by two independent readers. Contrast-to-noise ratio (CNR) and percentage signal intensity increase relative to normal myocardium were measured. Diagnostic performance and area under the receiver operating characteristic curve for MDE CT and kappa values for reader agreement were determined. Results Thirty-five of the 44 patients (80%) demonstrated a focal area of LGE, with a nonischemic pattern in 22 of the 44 patients (50%) and an ischemic pattern in 13 (30%). Iodine-density images demonstrated the highest CNR and percentage signal intensity increase on CT images (P < .05), resulting in the highest diagnostic performance in the detection of any MDE CT abnormality (92% sensitivity [195 of 213 segments] and 98% specificity [481 of 491 segments]). The areas under the receiver operating characteristic curve for iodine-density images and 40-keV VM images in the detection of MDE were 0.97 and 0.95, respectively (P < .001). Kappa values for reader agreement were 0.82 for iodine-density images and 0.72 for 40-keV VM images. Conclusion Myocardial delayed enhancement CT enables accurate detection and localization of scar in patients with heart failure when compared with late gadolinium enhancement MRI, the reference standard.

Noncongenital Ventricular Septal Defects: A Pictorial Review

The purpose of this article was to review the pathophysiology, imaging features, and imaging pitfalls of noncongenital ventricular septal defects (VSDs). Noncongenital VSDs can result from ischemic heart disease, trauma, infection, and iatrogenic causes. Ischemic VSDs typically involve the posterior descending or left anterior descending vascular territories and are commonly seen in the apical septum or basal-mid inferoseptum. VSDs can also occur in patients with infectious endocarditis or as a complication following cardiac surgery. Most of these involve the membranous portion of the interventricular septum. Traumatic VSDs are rare and commonly involve the mid to apical anteroseptum. Computed tomography and magnetic resonance imaging can accurately characterize the morphologic features of the defects and associated imaging findings.

Statistical shape modeling of the left ventricle: myocardial infarct classification challenge

Statistical shape modeling is a powerful tool for visualizing and quantifying geometric and functional patterns of the heart. After myocardial infarction (MI), the left ventricle typically remodels in response to physiological challenges. Several methods have been proposed in the literature to describe statistical shape changes. Which method best characterizes left ventricular remodeling after MI is an open research question. A better descriptor of remodeling is expected to provide a more accurate evaluation of disease status in MI patients. We therefore designed a challenge to test shape characterization in MI given a set of three-dimensional left ventricular surface points. The training set comprised 100 MI patients, and 100 asymptomatic volunteers (AV). The challenge was initiated in 2015 at the Statistical Atlases and Computational Models of the Heart workshop, in conjunction with the MICCAI conference. The training set with labels was provided to participants, who were asked to submit the likelihood of MI from a different (validation) set of 200 cases (100 AV and 100 MI). Sensitivity, specificity, accuracy and area under the receiver operating characteristic curve were used as the outcome measures. The goals of this challenge were to (1) establish a common dataset for evaluating statistical shape modeling algorithms in MI, and (2) test whether statistical shape modeling provides additional information characterizing MI patients over standard clinical measures. Eleven groups with a wide variety of classification and feature extraction approaches participated in this challenge. All methods achieved excellent classification results with accuracy ranges from 0.83 to 0.98. The areas under the receiver operating characteristic curves were all above 0.90. Four methods showed significantly higher performance than standard clinical measures. The dataset and software for evaluation are available from the Cardiac Atlas Project website1.

Imaging of isoproterenol-induced myocardial injury with 18F labeled fluoroglucaric acid in a rat model

Positron emission tomography (PET) of myocardial infarction (MI) by infarct avid imaging has the potential to reduce the time to diagnosis and improve diagnostic accuracy. The objective of this work was to synthesize ¹⁸F-labeled glucaric acid (FGA) for PET imaging of isoproterenol-induced cardiomyopathy in a rat model.

METHODS

We synthesized ¹⁸F-FGA by controlled oxidation of ¹⁸F-fluorodeoxy glucose (FDG), mediated by 4-acetamido-2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO) in presence of NaBr and NaOCl in highly-buffered reaction conditions. After ascertaining preferential uptake of ¹⁸F-FGA in necrotic as compared to normal H9c2 myoblasts, the biodistribution and circulation kinetics of ¹⁸F-FGA was assessed in mice. Moreover, the potential of ¹⁸F-FGA to image myocardial damage was investigated in a rat model of isoproterenol-induced cardiomyopathy. Isoproterenol-induced myocardial injury was verified at necropsy by tissue staining and plasma cardiac troponin levels.

RESULTS

Synthesis of radiochemically pure ¹⁸F-FGA was accomplished by a 5 min, one step oxidation of ¹⁸F-FDG. Reaction yield was quantitative and no side-products were detected. Biodistribution studies showed rapid elimination from the body (k_e = 0.83 h^-1); the major organ of ¹⁸F-FGA accumulation was kidney. In the rat model, isoproterenol-treatment resulted in significant increase in cardiac troponin. PET images showed that the hearts of isoproterenol-treated rats accumulated significant amounts of ¹⁸F-FGA, whereas healthy hearts showed negligible uptake of ¹⁸F-FGA. Target-to-nontarget contrast for ¹⁸F-FGA accumulation became significantly more pronounced in 4 h images as compared to images acquired 1 h post-injection.

CONCLUSION

¹⁸F-FGA can be easily and quantitatively synthesized from ubiquitously available ¹⁸F-FDG as a precursor. The resultant ¹⁸F-FGA has a potential to serve as an infarct-avid agent for PET imaging of MI. ADVANCES IN KNOWLEDGE AND IMPLICATIONS FOR PATIENT CARE: ¹⁸F-FGA/PET will complement existing perfusion imaging protocols in therapeutic decision making, determination of revascularization candidacy and success, differentiation of ischemia from necrosis in MI, discrimination of myocarditis from infarction, and surveillance of heart transplant rejection.

Complications of Intravenous Substance Use Disorders (SUDs): A Multimodality Pictorial Essay for Cardiothoracic Radiologists

With the growing substance use disorders epidemic in the United States, a wide range of complications may be seen in both the acute and chronic clinical setting. This article will use a multimodality approach to review complications of intravenous substance use that cardiothoracic radiologists are likely to encounter. Radiologists should be aware of these multisystem complications that can affect the cardiovascular, respiratory, and musculoskeletal systems in order to make an accurate and timely diagnosis, which can drastically alter the management of these patients.

Subacute and Chronic Left Ventricular Myocardial Scar: Accuracy of Texture Analysis on Nonenhanced Cine MR Images

Purpose To test whether texture analysis (TA) allows for the diagnosis of subacute and chronic myocardial infarction (MI) on noncontrast material-enhanced cine cardiac magnetic resonance (MR) images. Materials and Methods In this retrospective, institutional review board-approved study, 120 patients who underwent cardiac MR imaging and showed large transmural (volume of enhancement on late gadolinium enhancement [LGE] images >20%, n = 72) or small (enhanced volume ≤20%, n = 48) subacute or chronic ischemic scars were included. Sixty patients with normal cardiac MR imaging findings served as control subjects. Regions of interest for TA encompassing the left ventricle were drawn by two blinded, independent readers on cine images in end systole by using a freely available software package. Stepwise dimension reduction and texture feature selection based on reproducibility, machine learning, and correlation analyses were performed for selecting features, enabling the diagnosis of MI on nonenhanced cine MR images by using LGE imaging as the standard of reference. Results Five independent texture features allowed for differentiation between ischemic scar and normal myocardium on cine MR images in both subgroups: Teta1, Perc.01, Variance, WavEnHH.s-3, and S(5,5)SumEntrp (in patients with large MI: all P values < .001; in patients with small MI: Teta1 and Perc.01, P < .001; Variance, P = .026; WavEnHH.s-3, P = .007; S[5,5]SumEntrp, P = .045). Multiple logistic regression models revealed that combining the features Teta1 and Perc.01 resulted in the highest accuracy for diagnosing large and small MI on cine MR images, with an area under the curve of 0.93 and 0.92, respectively. Conclusion This proof-of-concept study indicates that TA of nonenhanced cine MR images allows for the diagnosis of subacute and chronic MI with high accuracy. ^© RSNA, 2017 Online supplemental material is available for this article.

Infarct characterization using CT

Myocardial infarction (MI) is a major cause of death and disability worldwide. The incidence is not expected to diminish, despite better prevention, diagnosis and treatment, because of the ageing population in industrialized countries and unhealthy lifestyles in developing countries. Nowadays it is highly requested an imaging tool able to evaluate MI and viability. Technology improvements determined an expansion of clinical indications from coronary plaque evaluation to functional applications (perfusion, ischemia and viability after MI) integrating additional phases and information in the mainstream examination. Cardiac computed tomography (CCT) and cardiac MR (CMR) employ different contrast media, but may characterize MI with overlapping imaging findings due to the similar kinetics and tissue distribution of gadolinium and iodinated contrast media. CCT may detect first-pass perfusion defects, dynamic perfusion after pharmacological stress, and delayed enhancement (DE) of non-viable territories.

Role of cardiovascular magnetic resonance in acute and chronic ischemic heart disease

Cardiovascular magnetic resonance (CMR) is a multi-parametric, multi-planar, non-invasive imaging technique, which allows accurate determination of biventricular function and precise myocardial tissue characterization in a one-stop-shop technique, free from the use of ionizing radiations. Though CMR has been increasingly applied over the last two decades in every-day clinical practice, its widest application has been in the assessment of ischemic cardiomyopathy.

Myocardial T1 and T2 Mapping: Techniques and Clinical Applications

Cardiac magnetic resonance (CMR) imaging is widely used in various medical fields related to cardiovascular diseases. Rapid technological innovations in magnetic resonance imaging in recent times have resulted in the development of new techniques for CMR imaging. T1 and T2 image mapping sequences enable the direct quantification of T1, T2, and extracellular volume fraction (ECV) values of the myocardium, leading to the progressive integration of these sequences into routine CMR settings. Currently, T1, T2, and ECV values are being recognized as not only robust biomarkers for diagnosis of cardiomyopathies, but also predictive factors for treatment monitoring and prognosis. In this study, we have reviewed various T1 and T2 mapping sequence techniques and their clinical applications.

Utility of late gadolinium enhancement in pediatric cardiac MRI

Late gadolinium enhancement (LGE) cardiac magnetic resonance (MR) imaging sequence is increasingly used in the evaluation of pediatric cardiovascular disorders, and although LGE might be a normal feature at the sites of previous surgeries, it is pathologically seen as a result of extracellular space expansion, either from acute cell damage or chronic scarring or fibrosis. LGE is broadly divided into ischemic and non-ischemic patterns. LGE caused by myocardial infarction occurs in a vascular distribution and always involves the subendocardial portion, progressively involving the outer regions in a waveform pattern. Non-ischemic cardiomyopathies can have a mid-myocardial (either linear or patchy), subepicardial or diffuse subendocardial distribution. Idiopathic dilated cardiomyopathy can have a linear mid-myocardial pattern, while hypertrophic cardiomyopathy can have fine, patchy enhancement in hypertrophied and non-hypertrophied segments as well as right ventricular insertion points. Myocarditis and sarcoidosis have a mid-myocardial or subepicardial pattern of LGE. Fabry disease typically affects the basal inferolateral segment while Danon disease typically spares the septum. Pericarditis is characterized by diffuse or focal pericardial thickening and enhancement. Thrombus, the most common non-neoplastic cardiac mass, is characterized by absence of enhancement in all sequences, while neoplastic masses show at least some contrast enhancement, depending on the pathology. Regardless of the etiology, presence of LGE is associated with a poor prognosis. In this review, we describe the technical modifications required for performing LGE cardiac MR sequence in children, review and illustrate the patterns of LGE in children, and discuss their clinical significance.

Incremental value of PET and MRI in the evaluation of cardiovascular abnormalities

Abstract

The cardiovascular system is affected by a wide range of pathological processes, including neoplastic, inflammatory, ischemic, and congenital aetiology. Magnetic resonance imaging (MRI) and positron emission tomography (PET) are state-of-the-art imaging modalities used in the evaluation of these cardiovascular disorders. MRI has good spatial and temporal resolutions, tissue characterization and multi-planar imaging/reconstruction capabilities, which makes it useful in the evaluation of cardiac morphology, ventricular and valvar function, disease characterization, and evaluation of myocardial viability. FDG-PET provides valuable information on the metabolic activity of the cardiovascular diseases, including ischemia, inflammation, and neoplasm. MRI and FDG-PET can provide complementary information on the evaluation of several cardiovascular disorders. For example, in cardiac masses, FDG-PET provides the metabolic information for indeterminate cardiac masses. MRI can be used for localizing and characterizing abnormal hypermetabolic foci identified incidentally on PET scan and also for local staging. A recent advance in imaging technology has been the development of integrated PET/MRI systems that utilize the advantages of PET and MRI in a single examination. The goal of this manuscript is to provide a comprehensive review on the incremental value of PET and MRI in the evaluation of cardiovascular diseases.

Main Messages

• MRI has good spatial and temporal resolutions, tissue characterization, and multi-planar reconstruction

• FDG-PET provides valuable information on the metabolic activity of cardiovascular disorders

• PET and MRI provide complementary information on the evaluation of cardiovascular disorders

Electronic supplementary material

The online version of this article (doi:10.1007/s13244-016-0494-5) contains supplementary material, which is available to authorized users.

Cardiac magnetic resonance imaging and computed tomography in ischemic cardiomyopathy: an update

Ischemic cardiomyopathy is one of the major health problems worldwide, representing a significant part of mortality in the general population nowadays. Cardiac magnetic resonance imaging (CMRI) and cardiac computed tomography (CCT) are noninvasive imaging methods that serve as useful tools in the diagnosis of coronary artery disease and may also help in screening individuals with risk factors for developing this illness. Technological developments of CMRI and CCT have contributed to the rise of several clinical indications of these imaging methods complementarily to other investigation methods, particularly in cases where they are inconclusive. In terms of accuracy, CMRI and CCT are similar to the other imaging methods, with few absolute contraindications and minimal risks of adverse side-effects. This fact strengthens these methods as powerful and safe tools in the management of patients. The present study is aimed at describing the role played by CMRI and CCT in the diagnosis of ischemic cardiomyopathies.

Cardiovascular imaging in children and adults following Kawasaki disease

Kawasaki disease (KD) is a paediatric vasculitis with coronary artery aneurysms (CAA) as its main complication. Two guidelines exist regarding the follow-up of patients after KD, by the American Heart Association and the Japanese Circulation Society. After the acute phase, CAA-negative patients are checked for cardiovascular risk assessment or with ECG and echocardiography until 5 years after the disease. In CAA-positive patients, monitoring includes myocardial perfusion imaging, conventional angiography and CT-angiography. However, the invasive nature and high radiation exposure do not reflect technical advances in cardiovascular imaging. Newer techniques, such as cardiac MRI, are mentioned but not directly implemented in the follow-up. Cardiac MRI can be performed to identify CAA, but also evaluate functional abnormalities, ischemia and previous myocardial infarction including adenosine stress-testing. Low-dose CT angiography can be implemented at a young age when MRI without anaesthesia is not feasible. CT calcium scoring with a very low radiation dose can be useful in risk stratification years after the disease. By incorporating newer imaging techniques, detection of CAA will be improved while reducing radiation burden and potential complications of invasive imaging modalities. Based on the current knowledge, a possible pathway to follow-up patients after KD is introduced. Key Points • Kawasaki disease is a paediatric vasculitis with coronary aneurysms as major complication. • Current guidelines include invasive, high-radiation modalities not reflecting new technical advances. • Cardiac MRI can provide information on coronary anatomy as well as cardiac function. • (Low-dose) CT-angiography and CT calcium score can also provide important information. • Current guidelines for follow-up of patients with KD need to be revised.

Appropriateness and diagnostic yield of cardiac magnetic resonance imaging from a tertiary referral center in the Middle East

PURPOSE

Cardiac magnetic resonance imaging (CMRI) is a novel non-invasive modality with many potential indications, and was recently introduced in Lebanon. We sought to assess the appropriateness and diagnostic yield of CMR studies performed at a tertiary referral center from the Middle East since the inception of the program.

METHODS

All patients who underwent CMR studies between January 1(st) 2013 and June 18(th) 2014 were enrolled in this study. CMR reports were retrospectively reviewed. The study indication, clinical history, and findings were extracted and analyzed. The appropriateness of the study was judged according to the 2010 updated Asian Society of Cardiac Imaging guidelines.

RESULTS

There were a total of 142 patients [mean age 42.1 (SD: 18) years, 24.6% females] that underwent CMR study. Two-thirds of studies were performed on an outpatient basis, and outside referrals constituted 16.2% of the entire cohort. The cardiologists referred 122 cases (86%) with main contribution from electrophysiology and imaging specialists. Of the 142 cases, 12 (8.4%) were not indicated and added little value. Of the remaining 130 appropriate studies (appropriateness level A8-A9), one-third had an incorrect diagnosis prior to CMR, and 8% had relevant findings that were missed on other studies but captured by CMR. Furthermore, CMR confirmed the diagnosis in 28% of the cases, provided relevant information on scar burden, shunt quantification, and ruled out infiltrative disease in the remaining patients. Also, CMR demonstrated the presence of scar in 45 of patients, among whom 20 (44%) had significant scar volume quantification (>5% of left ventricular myocardium). Finally, 9% of patients had a relevant extra-cardiac finding that needed further investigation.

CONCLUSIONS

Despite the recent launch of the CMR program at our institution, the majority of studies were appropriately indicated, provided relevant data and were clinically useful. Inappropriate or uncertain studies did not provide relevant data, and should be further minimized to avoid unnecessary costs and downstream testing. Large prospective CMR database with clinical follow-up is needed to provide more insight about cardiovascular disease and outcomes in our population.

Imaging of reperfused intramyocardial hemorrhage with cardiovascular magnetic resonance susceptibility weighted imaging (SWI)

Purpose

To report initial experience with TE-averaged susceptibility weighted imaging (SWI) in normal subjects and acute myocardial infarction (AMI) patients for the detection of intramyocardial hemorrhage (IMH).

Materials and Methods

15 healthy control and 11 AMI subjects were studied at 1.5T before contrast agent administration with a dark blood double inversion recovery multiple spoiled gradient-echo sequence. Magnitude, susceptibility weighted and TE-averaged images were reconstructed from raw data. Contrast and signal-difference-to-noise were measured and compared between methods for IMH detection.

Results

There were six patients with microvascular obstruction (MVO) and four patients with IMH detected by TE-averaged SWI imaging. All patients with IMH on SWI scans had MVO on late gadolinium-enhanced (LGE) imaging. There was a three-fold increase in IMH contrast with SWI compared to magnitude images. IMH contrast decreased and signal-to-noise increased with increased TE averages.

Conclusions

TE-averaged SWI imaging is a promising method for myocardial tissue characterization in the setting of AMI for the detection of IMH. Along with gray-scale colormap inversion, it combines not only magnitude and phase information, but also images across TEs to provide a single image sensitive to IMH with characteristics similar to LGE imaging.

Cardiac MR assessment of microvascular obstruction

Microvascular obstruction (MVO) is usually seen in a proportion of patients with acute myocardial infarction following reperfusion therapy of an occluded coronary artery. It is characterized by damage and dysfunction of the myocardial microvasculature with a no-reflow phenomenon within the infarct zone. While MVO may be demonstrated via a number of different imaging modalities, cardiac MR (CMR) enables accurate identification of MVO and also permits assessment of infarct extent and overall left ventricular function during the same imaging examination. We present a pictorial review of the characteristic appearances of MVO on CMR and highlight the importance of this imaging diagnosis for patient outcome following acute myocardial infarction.

Correlation of electrocardiogram and regional cardiac magnetic resonance imaging findings in ST-elevation myocardial infarction: a literature review

BACKGROUND

Patients with acute ST-elevation myocardial infarction (STEMI) benefit substantially from emergent coronary reperfusion. The principal mechanism is to open the occluded coronary artery to minimize myocardial injury. Thus the size of the area at risk is a critical determinant of the patient outcome, although other factors, such as reperfusion injury, have major impact on the final infarct size. Acute coronary occlusion almost immediately induces metabolic changes within the myocardium, which can be assessed with both the electrocardiogram (ECG) and cardiac magnetic resonance (CMR) imaging.

METHODS

The 12-lead ECG is the principal diagnostic method to detect and risk-stratify acute STEMI. However, to achieve a correct diagnosis, it is paramount to compare different ECG parameters with golden standards in imaging, such as CMR. In this review, we discuss aspects of ECG and CMR in the assessment of acute regional ischemic changes in the myocardium using the 17 segment model of the left ventricle presented by American Heart Association (AHA), and their relation to coronary artery anatomy.

RESULTS

Using the 17 segment model of AHA, the segments 12 and 16 remain controversial. There is an important overlap in myocardial blood supply at the antero-lateral region between LAD and LCx territories concerning these two segments.

CONCLUSION

No all-encompassing correlation can be found between ECG and CMR findings in acute ischemia with respect to coronary anatomy.

Myocardial viability and microvascular obstruction: role of cardiac magnetic resonance imaging

Established coronary artery disease has a prevalence of 7% in adult Americans, accounting for 16 million people. As morbidity and mortality rates have risen, research efforts to identify the pathophysiologic mechanisms of systolic dysfunction have risen in parallel. The current goal is to develop new therapeutic strategies with the potential to reverse systolic dysfunction in patients with established coronary artery disease. Cardiac magnetic resonance imaging has gained a key role in cardio vascular medicine. We will comment on the potential pivotal role of cardiac magnetic resonance imaging for the assessment of myocardial viability, including hibernating and stunned myocardium and microvascular obstruction.