Can computed tomography improve outcomes in acute coronary syndrome?

Each year, six million patients in the USA visit the emergency department for acute chest pain. Many patients are hospitalized because immediate discharge of those suspected of acute coronary syndrome could be disastrous. This review looks at whether patient outcomes could be improved by coronary computed tomography angiography.

Reformatted Four-Chamber and Short-Axis Views of the Heart Using Thin Section (

RATIONALE AND OBJECTIVES: In cardiovascular computed tomography (CT), thin collimation results in a large number of images per examination. Moreover, interpretation relies on multiplanar reformatted images. MATERIALS AND METHODS: Although many strategies for approaching cardiac reformations have been described, as CT use increases, so does the importance of simple and reproducible postprocessing algorithms. The clinical importance of reformations has recently extended beyond the left ventricle to include the right ventricular in patients with pulmonary embolism. RESULTS: This work illustrates an algorithm to reformat two of the most important views in cardiovascular CT: the four-chamber and short axis views. CONCLUSIONS: The illustration is performed in the context of two cardiovascular examinations: cardiac CT and CT pulmonary angiography.

CT for intracardiac thrombi and tumors.

Although cardiac tumors are rare, they nevertheless represent an important subgroup, the diagnosis of which is challenging for the primary care physician. Symptoms are not characteristic and serious complications including stroke, myocardial infarction and even sudden death from arrhythmia may be the first signs of tumor. The most common primary cardiac neoplasm is the benign myxoma and the most frequent primary malignant lesion is sarcoma. Cardiac metastases from distant primary carcinomas are now frequently encountered. Echocardiography until the past decade was the only consistently reliable and available non-invasive diagnostic tool. New non-invasive CT and MRI exams are changing the diagnostic approach. Echocardiography and angiocardiography with or without coronary arteriography remain routine methods for evaluating cardiac neoplasms. However, CT provides additional diagnostic information and is regarded as essential for adequate staging and treatment planning, particularly when surgical resection is being considered. This chapter reviews the wide spectrum of intracardiac thrombi and tumors including their incidence and imaging characteristics with particular reference to the CT findings and differential diagnosis.

How to approach cardiac diagnosis from the chest radiograph.

Direct visualization of pathologic changes in the heart has significantly influenced the diagnostic accuracy and management of patients with cardiovascular disease. This article presents an approach to plain film examination of the heart based on basic principles of radiologic evaluation. It emphasizes the relationship between the radiologic appearance of a structure and the technique used to obtain that image, and the relationship between the observation of a structural abnormality and the anatomic relationships that allow that observation to be made. This approach is simple, organized in a logical manner, and when applied rigorously results in not only accurate and insightful differential diagnosis, but also a deep understanding of cardiovascular disease processes.

CT and MR imaging of the thoracic aorta: current techniques and clinical applications.

Disease of the thoracic aorta can present with a broad clinical spectrum of symptoms and signs. The accepted diagnostic gold standard, selective digital subtraction angiography, is now being challenged by state-of-the-art CT angiography (CTA) and MR angiography(MRA). Currently, in many centers, cross-sectional imaging modalities are being used as the first line of diagnosis to evaluate the cardiovascular system, and conventional angiography is reserved for therapeutic intervention. Understanding the principles of CTA and MRA techniques is essential to acquire diagnostic images consistently. This article reviews current CTA and MRA methods used in the evaluation of thoracic aortic disease.

CT and MR imaging of pericardial disease.

The diagnosis and therapy of pericardial diseases are still a physician's challenge. Advanced CT and MR imaging technologies can display the complete morphology of the heart and the pericardium and of the adjacent thoracic structures with a spatial and contrast resolution below 1 mm. All the macromorphologic determinants of pericardial constriction and their functional sequels may be identified by these remarkable technologies. A careful systematic image analysis defines not only a precise diagnosis but also determines the optimal surgical or conservative therapy for the individual patient and minimizes the risk of perisurgical mortality.

New model for analysis of dynamic contrast-enhanced MRI data distinguishes metastatic from nonmetastatic transplanted rodent prostate tumors.

Dynamic contrast-enhanced MRI (DCEMRI) data were acquired from metastatic and nonmetastatic tumors in rodents to follow the uptake and washout of a low-molecular-weight contrast agent (Gd-DTPA) and a contrast agent with higher molecular weight (P792). The concentration vs. time curves calculated for the tumor rims and centers were analyzed using the two-compartment model (TCM) and a newly developed empirical mathematical model (EMM). The EMM provided improved fits to the experimental data compared to the TCM. Parameters derived from the empirical model showed that the contrast agent washout rate was significantly slower in metastatic tumors than in nonmetastatic tumors for both Gd-DTPA (P < 0.03) and P792 (P < 0.04). The effects of the tumor on blood flow in "normal" tissue immediately adjacent to the tumors were evident: Gd-DTPA uptake and washout rates were much lower in muscle near the tumor (P < 0.05) than normal muscle farther from the tumor. The results suggest that accurate fits of DCEMRI data provide kinetic parameters that distinguish between metastatic and relatively benign cancers. In addition, a comparison of the dynamics of Gd-DTPA and P792 provides information regarding the microenvironment of tumors.

From the RSNA refresher courses: MR imaging of aortic and peripheral vascular disease.

Acquired diseases of the aorta and peripheral arteries are common. Owing to technical advances, magnetic resonance (MR) angiography has become the primary imaging modality for assessment of aortic and peripheral arterial disease. Contrast material-enhanced MR angiography is a rapid and robust technique that has emerged as the principal MR angiographic technique for evaluation of vascular disease. Two-dimensional time-of-flight MR angiography still has some well-validated applications, especially in distal peripheral vascular disease. Phase-contrast flow imaging is an important technique for quantification of blood flow. Black-blood imaging is a valuable tool for evaluation of the vessel wall. Understanding the principles of the main MR angiographic techniques is essential for consistent acquisition of diagnostic images. In addition, tailoring the acquisition parameters and the imaging protocol to the vessel being imaged and the clinical question is mandatory for optimal results. Future technical developments that will lead to faster image acquisition and better contrast agents promise to further improve image quality.

MR Imaging of arrhythmogenic right ventricular cardiomyopathy: morphologic findings and interobserver reliability.

BACKGROUND: Magnetic resonance (MR) imaging is frequently used to diagnose arrhythmogenic right ventricular cardiomyopathy/dysplasia (ARVC/D). However, the reliability of various MR imaging features for diagnosing ARVC/D is unknown. The purpose of this study was to determine which morphologic MR imaging features have the greatest interobserver reliability for diagnosing ARVC/D. METHODS: Forty-five sets of films of cardiac MR images were sent to 8 radiologists and 5 cardiologists with experience in this field. There were 7 cases of definite ARVC/D as defined by the Task Force criteria. Six cases were controls. The remaining 32 cases had MR imaging because of clinical suspicion of ARVC/D. Readers evaluated the images for the presence of (a) right ventricle (RV) enlargement, (b) RV abnormal morphology, (c) left ventricle enlargement, (d) presence of high T(1) signal (fat) in the myocardium, and (e) location of high T(1) signal (fat) on a Likert scale with formatted responses. RESULTS: Readers indicated that the Task Force ARVC/D cases had significantly more (chi(2) = 119.93, d.f. = 10, p < 0.0001) RV chamber size enlargement (58%) than either the suspected ARVC/D (12%) or no ARVC/D (14%) cases. When readers reported the RV chamber size as enlarged they were significantly more likely to report the case as ARVC/D present (chi(2)(= )33.98, d.f. = 1, p < 0.0001). When readers reported the morphology as abnormal they were more likely to diagnose the case as ARVC/D present (chi(2) = 78.4, d.f. = 1, p < 0.0001), and the Task Force ARVC/D (47%) cases received significantly more abnormal reports than either suspected ARVC/D (20%) or non-ARVC/D (15%) cases. There was no significant difference between patient groups in the reported presence of high signal intensity (fat) in the RV (chi(2) = 0.9, d.f. = 2, p > 0.05). CONCLUSIONS: Reviewers found that the size and shape of abnormalities in the RV are key MR imaging discriminates of ARVD. Subsequent protocol development and multicenter trials need to address these parameters. Essential steps in improving accuracy and reducing variability include a standardized acquisition protocol and standardized analysis with dynamic cine review of regional RV function and quantification of RV and left ventricle volumes.

Computed tomography for assessment of cardiac chambers, valves, myocardium and pericardium.

The focus to date of MDCT has been primarily on CT applications for evaluating the coronary arteries, notably the measurement of coronary artery calcification, plaque characterization, and atherosclerotic lumen stenosis. This is because of the limited temporal resolution of CT, and the recent rapid improvements in MRI for cardiac applications. However, if the temporal resolution of MDCT can be improved, there will be a compelling argument for undertaking further CT validation studies. Feasibility of CT has already been established by EBT for general cardiac diagnosis. Modifications for MDCT include improved software methods for post processing ECG-gated scan data or higher speed CT hardware for faster image acquisition, both of which are being developed at this time. EBT is also evolving and continuously being refined so that the new generation of scanners have exposure times of 50 msec or less. There are many considerations in comparing the pros and cons of competing cardiac imaging modalities. Published diagnostic validations studies, convenience, procedure time, the comfort level (of patients and physicians), availability, and cost are all critical. The level of acceptance and the accuracy with which specific patient management questions can be appropriately answered are crucial issues in determining which diagnostic procedure to perform. However, the jury is still out regarding the ultimate role of CT in the diagnosis of heart disease; certainly the great potential of cardiac CT has not yet been fully realized.

Imaging of ischemic heart disease.

Despite advances in the understanding and treatment of ischemic cardiomyopathy, characterized by extensive coronary artery disease and left ventricular (LV) dysfunction, the prognosis remains poor with only a 50-60% 5-year survival rate. The composition of atherosclerotic lesions is currently regarded as being more important than the degree of stenosis in determining acute events. If imaging techniques could distinguish vulnerable from stable plaques, then high-risk patient subgroups could be identified. Another important concept is that LV dysfunction may be the result of either scarring due to necrosis or to the presence of myocardial hibernation, in which there is sufficient blood flow to sustain viable myocytes, but insufficient to maintain systolic contraction. This concept of myocardial viability is critical for making optimal clinical management decisions. This review describes how noninvasive imaging methods can be used to distinguish regions of irreversibly injured myocardium from viable but hibernating segments. Technical advances in CT and MR have made imaging of the beating heart possible. Considerable clinical progress has already been made and further cardiac applications are expected. Radiologists therefore have new opportunities for involvement in cardiac imaging but must recognize the political implications as well as the diagnostic potential of these modalities not only for the heart, but also for the whole vascular system. This review focuses on imaging myocardial injury. It compares state-of-the-art CT and MR with more established yet contemporary echocardiography and nuclear scintigraphy.