Current Cardiovascular Imaging Reports

Chiribiri, Amedeo; Bettencourt, Nuno; Nagel, Eike

doi: 10.1007/s12410-009-0011-zpmid: N/A

Sosnovik, David; Caravan, Peter

doi: 10.1007/s12410-009-0012-ypmid: 20019886

Molecular MRI of atherosclerosis involves the use of novel contrast agents to image cellular and molecular processes within atherosclerotic plaque. Agents to image plaque lipid content, inflammation, angiogenesis, and thrombosis have been developed and studied extensively in animal models of atherosclerosis and vascular injury. Selected agents have also been studied in humans, with highly promising initial results. In this brief review, recent advances as well as opportunities and challenges in the field are discussed.

Jansen, Christian; Makowski, Marcus; Wiethoff, Andrea; Botnar, René

doi: 10.1007/s12410-009-0013-xpmid: N/A

Coronary artery disease (CAD) is the leading cause of morbidity and mortality in the Western world. Whereas atherosclerosis alone is rarely fatal, sudden luminal thrombosis precipitates life-threatening clinical events such as acute coronary syndromes and stroke. Plaques assumed to cause luminal thrombosis are referred to as vulnerable plaques, which tend to preserve a normal vessel lumen. Today’s clinical assessment of CAD is based on the severity of luminal narrowing or flow restriction and functional indices of cardiac ischemia, thus making a priori detection of vulnerable plaques ambiguous. MRI is an emerging noninvasive imaging modality and is unique in its ability to offer morphologic, functional, and biologic information, including several approaches to detect, quantify, and characterize atherosclerotic plaque burden and composition. These methods, which include noncontrast and contrast-enhanced vessel wall imaging, have shown great promise to assess morphological and biological characteristics of vulnerable plaques, such as inflammatory activity, neovasculature, or positive vessel wall remodeling. Current research that focuses on the development of novel contrast agents for the identification of biologic processes associated with plaque progression and plaque rupture ultimately may facilitate the detection of subclinical disease, enable earlier treatment, and allow imaging-based therapy control.

Kolandaivelu, Aravindan; Halperin, Henry

doi: 10.1007/s12410-009-0014-9pmid: N/A

Catheter ablation is a first-line treatment for many cardiac arrhythmias and is generally performed under x-ray fluoroscopy guidance. However, current techniques for ablating complex arrhythmias such as atrial fibrillation and ventricular tachycardia are associated with suboptimal success rates and prolonged radiation exposure. Pre-procedure three-dimensional (3-D) MRI has improved understanding of the anatomic basis of complex arrhythmias and is being used for planning and guidance of ablation procedures. A particular strength of MRI compared to other imaging modalities is the ability to visualize ablation lesions. Post-procedure MRI is now being applied to assess ablation lesion location and permanence, with the goal of indentifying factors leading to procedure success and failure. In the future, real-time MRI, together with the ability to image complex 3-D arrhythmogenic anatomy and target additional ablation to regions of incomplete lesion formation, may allow for more successful treatment of even complex arrhythmias without exposure to ionizing radiation.

Wu, Katherine

doi: 10.1007/s12410-009-0015-8pmid: N/A

Despite considerable progress in reducing sudden cardiac death (SCD), mortality remains high and risk stratification algorithms are limited. Many approaches to identifying at-risk patients target the electrophysiologic triggers or modulators of ventricular arrhythmias. Other than global left ventricular function, there has been minimal emphasis on evaluating the anatomic substrate that supports arrhythmia circuits, namely myocardial scarring. Myocardial scarring and fibrosis occurs in both ischemic and nonischemic cardiomyopathies and is detected noninvasively by cardiac MRI with late gadolinium enhancement (CMR-LGE). There is growing literature relating CMR-LGE to arrhythmic surrogates and clinical outcomes in vulnerable cohorts. Additionally, knowledge of the presence and extent of CMR-LGE is potentially valuable for guiding catheter ablative therapies. The incremental value of CMR-LGE in predicting SCD, above current risk factors, remains unknown, but its unique ability to provide anatomic and tissue characterization contributes to its appeal as a promising noninvasive tool for identifying susceptible patients.

Neizel, Mirja; Kaestner, Wiebke; Kelm, Malte; Kühl, Harald

doi: 10.1007/s12410-009-0016-7pmid: N/A

Identification of the functional severity of intermediate coronary artery lesions is challenging for the interventional cardiologist. Functional severity can be measured invasively using the fractional flow reserve (FFR). However, FFR has the disadvantage of being invasive and associated with radiation exposure. Cardiac MRI (CMR) offers the opportunity to assess myocardial perfusion noninvasively. A semiquantitative index of myocardial perfusion (perfusion reserve index or PRI) can be obtained from the first-pass of a bolus of gadolinium through the myocardium. Studies comparing the invasive FFR to CMR perfusion imaging in patients with coronary artery stenosis of undefined significance have demonstrated that CMR first-pass perfusion imaging may be useful for the assessment of their functional significance. However, in patients with a high prevalence of microvascular dysfunction, the value of this method may be limited because the PRI may be influenced by both the epicardial conductance vessel function as well as microvascular function.

Jesuthasan, Lalith; Selvanayagam, Joseph

doi: 10.1007/s12410-009-0017-6pmid: N/A

Cardiac magnetic resonance (CMR) perfusion imaging enables precise quantitation of myocardial blood flow and has been validated in animal models. Myocardial perfusion imaging using a T1-sensitive imaging sequence during the first pass bolus injection of a gadolinium-based contrast agent remains the most robust and extensively studied to date. Myocardial blood flow could be calculated from signal intensity curves utilizing a tracer kinetic model or a model-independent deconvolution method. Quantitative CMR perfusion imaging has provided pathophysiologic insights in epicardial coronary artery disease, microvascular disease, and cardiomyopathy. Imaging at higher field strength, for both CMR first-pass perfusion and myocardial blood oxygen level-dependent imaging, is likely to advance quantitative myocardial perfusion in the future.

Rolf, Andreas; Dill, Thorsten

doi: 10.1007/s12410-009-0018-5pmid: N/A

Despite optimized reperfusion strategies and adjunct pharmacotherapy, ischemic heart failure after myocardial infarction remains a major challenge. Early reports of the use of progenitor cells and their ability to transdifferentiate into myocytes from experimental studies have raised great expectations for new regenerative therapy strategies. However, the results of recent clinical studies have tempered the enthusiasm, and many questions are left unanswered. To better understand the efficacy of stem cell therapy, imaging techniques will help by providing techniques of cell tracking and a comprehensive evaluation of surrogate parameters such as left ventricular function, volumes, and wall motion. The ability of infarct characterization, including infarct size, transmurality, edema, and microvascular obstruction, is unique for MRI. Therefore, MRI has turned out to be the method of choice for cell tracking in experimental settings, as well as the assessment of the clinical effect of stem cell therapy in patients.

Meadows, Judith; Carballo, David; Kwong, Raymond

doi: 10.1007/s12410-009-0019-4pmid: N/A

Although cardiac MRI (CMR) provides accurate quantitative assessment of myocardial function, structure, and tissue characterization, there is growing evidence of the prognostic significance of CMR in the clinical setting. This article aims to not only review the diagnostic utility of CMR but all the prognostic implications in different cardiac conditions. First, CMR can distinguish ischemic from nonischemic cardiomyopathies and is establishing an increasing role in risk stratifying patients with heart failure. Second, CMR perfusion with vasodilator and inotropic stress has high sensitivity and specificity for prediction of cardiovascular events. Third, in addition to being an accurate tool for assessing myocardial viability and predicting the benefits of coronary revascularization, scar characterization by CMR late gadolinium enhancement imaging provides prognostic information beyond traditional markers of left ventricular function and volume. This article aims to explore the current evidence of each of these clinical settings.

Plein, Sven

doi: 10.1007/s12410-009-0020-ypmid: N/A

Cardiovascular magnetic resonance (CMR) imaging provides morphological and functional data relevant to the assessment of coronary artery disease (CAD). A wide range of such data can be acquired in a single multiparametric imaging session. In stable CAD, a combined CMR examination comprising assessment of cardiac function, perfusion, and myocardial viability can be used to detect the presence of CAD and to determine the appropriateness of coronary revascularization. In acute coronary syndromes, a combined CMR examination can be used for the differential diagnosis of myocarditis and other acute cardiac disease, for risk-stratification of patients after myocardial infarction and for the targeted assessment of complications of myocardial infarction. This article overviews the CMR methods that are available for assessment of CAD and describes situations when combined CMR examinations can play a role in its diagnosis and differential diagnosis.