Cardiovascular magnetic resonance in adults with previous cardiovascular surgery

European Heart Journal – Cardiovascular Imaging (2014) 15, 235–248 doi:10.1093/ehjci/jet138 REVIEW Cardiovascular magnetic resonance in adults with previous cardiovascular surgery Florian von Knobelsdorff-Brenkenhoff 1,2*, Ralf Felix Trauzeddel 1,2, and Jeanette Schulz-Menger1,2 Received 8 May 2013; revised 23 June 2013; accepted after revision 27 June 2013; online publish-ahead-of-print 2 August 2013 Cardiovascular magnetic resonance (CMR) is a versatile non-invasive imaging modality that serves a broad spectrum of indications in clinical cardiology and has proven evidence. Most of the numerous applications are appropriate in patients with previous cardiovascular surgery in the same manner as in non-surgical subjects. However, some specifics have to be considered. This review article is intended to provide information about the application of CMR in adults with previous cardiovascular surgery. In particular, the two main scenarios, i.e. following coronary artery bypass surgery and following heart valve surgery, are highlighted. Furthermore, several pictorial descriptions of other potential indications for CMR after cardiovascular surgery are given. ----------------------------------------------------------------------------------------------------------------------------------------------------------Keywords magnetic resonance † cardiovascular surgery † coronary bypass † valve replacement † aorta Introduction Cardiovascular surgery is used in a wide variety of indications to treat cardiovascular diseases in adults. Thorough follow-up is mandatory to optimally guide these patients and appropriately discover potential complications. It is predominantly performed by clinical interrogation and transthoracic echocardiography (TTE), sometimes accompanied by exercise test, and if necessary extended by computed tomography, cardiovascular magnetic resonance (CMR), or invasive measures. CMR acquires images of the heart and the large vessels noninvasively and without ionizing radiation. Specific image contrasts and characteristics can be selected depending on the clinical question, often enhanced by intravenous administration of gadolinium-based contrast agents. Images can be acquired as a dynamic series or as a still image in any desired plane independent from the patient’s physique. CMR provides information about cardiac dimensions and function [e.g. steady-state free-precession (SSFP) cine imaging], myocardial perfusion (first pass of contrast), oedema (T2-weighted imaging), necrosis or fibrosis (late gadolinium enhancement), blood flow (phase-contrast imaging), as well as vessel geometry and morphology (e.g. contrast-enhanced angiography).1 Hence, a comprehensive assessment of both anatomy (e.g. myocardial scar in coronary artery disease or orifice area in valvular heart disease) and function (e.g. myocardial perfusion or regurgitant volume, respectively) is possible. Compared with TTE, which is the first-line imaging modality, CMR has the main advantage of unimpaired image quality independent from post-surgical adhesions, obesity, or pulmonary emphysema, which allows an accurate assessment of cardiovascular function and morphology (Table 1). The potential of CMR in adults with previous cardiovascular surgery is potentially under-represented in the current guidelines.2,3 This review is intended to give a summary regarding CMR after coronary artery bypass grafting (CABG) and after valvular surgery, and to provide a pictorial overview of various less-frequent indications for CMR in adults with previous cardiovascular surgery. Safety of CMR after cardiovascular surgery General contraindications and safety measures for CMR have to be regarded in patients with previous cardiovascular surgery in the same way as in every other patient. Additional aspects regarding implants have to be considered.4 The sternal wires do not raise safety concerns during CMR, and usually image interpretation is not impeded unless the region of interest is very close to the artefacts caused by the sternal wires.5 Vascular clips used to ligate side branches of a venous graft for coronary bypass, do in general not present an additional risk. The majority of mechanical and stented * Corresponding author. Tel: +49 30 450 540 654; Fax: +49 30 450 540915, Email Published on behalf of the European Society of Cardiology. All rights reserved. & The Author 2013. For permissions please email: 1 Working Group Cardiovascular Magnetic Resonance, Experimental and Clinical Research Center, A Joint Cooperation Between the Charité Medical Faculty and the Max-Delbrueck Center for Molecular Medicine, Lindenberger Weg 80, Berlin 13125, Germany; and 2Department of Cardiology and Nephrology, HELIOS Klinikum Berlin Buch, Berlin, Germany 236 Table 1 F. von Knobelsdorff-Brenkenhoff et al. Characteristics of cardiac imaging modalities after cardiac surgery Temporal resolution Spatial resolution Anatomical assessment Functional assessment Radiation Contrast agent Time need Costs Availability Echocardiography +++ ++ ++ +++ – + + + +++ Computed tomography + +++ +++ + +++ +++ ++ ++ ++ Magnetic resonance ++ ++ +++ +++ – ++ +++ +++ + ............................................................................................................................................................................... CMR after coronary artery bypass grafting Stress perfusion CMR after CABG Stress perfusion CMR analyses the first pass of an extracellular contrast agent bolus within the myocardium during intravenous administration of a vasodilator that causes hyperaemia. The hyperaemic flow is compromised in myocardial segments that are supplied by a significantly stenosed vessel because of the drop of coronary perfusion pressure downstream of the stenosis. Segments with a perfusion defect in relation with the hyperaemic myocardium will be identifiable by a lower signal intensity9 (Figure 1). There is fundamental evidence that stress perfusion CMR detects native coronary artery stenosis with high diagnostic accuracy, comprising a sensitivity and specificity around 91 and 81%, respectively.10 However, there have been concerns whether this method is also appropriate to assess myocardial perfusion in patients after CABG, who were often under-represented in previous stress perfusion trials. There might be altered myocardial contrast kinetics owing to more complex myocardial perfusion and different distances of the contrast bolus through different bypasses and native coronary vessels, thereby possibly imitating a perfusion defect. Kelle et al. applied semi-quantitative perfusion parameters in patients with CABG to assess possible differences in epicardial contrast kinetics in areas supplied by native coronaries without significant stenosis and by CABG without significant stenosis. They observed a short delay regarding the time to 50 and 100% maximal signal intensity between areas perfused by (...truncated)