Is cardiac magnetic resonance imaging assessment of myocardial viability useful for predicting which patients with impaired ventricles might benefit from revascularization?

A best evidence topic in cardiac magnetic resonance imaging (MRI) was written according to a structured protocol. The question addressed was: what is the role of cardiac magnetic resonance (CMR) imaging in viability assessment of ischaemic cardiomyopathy? Altogether more than 164 papers were found using the reported search; of which, 6 represented the best available evidence to answer the clinical question and an additional 4 were found by crosschecking the reference lists for further 'best available evidence' papers. The authors, journal, date and country of publication, patient group studied, study type, relevant outcomes and results of these papers are tabulated. Using late-gadolinium enhancement-cardiac magnetic resonance (LGE-CMR) imaging, infarcted myocardium can be identified by the presence of hyperenhanced signal. The extent of myocardial hyperenhancement correlates inversely with improved myocardial contractility following surgical or percutaneous revascularization. Furthermore, CMR is able to assess not only viability, but also make gold-standard assessment of ventricular function and volume as well as identify stress perfusion deficits, each of which is relevant to estimating patient prognosis. National bodies have also begun to formally recommend CMR imaging for cardiac viability assessment. For example, the Canadian Cardiovascular Society (CCS) has stated that 'assessment of myocardial viability in patients with left ventricle dysfunction or akinetic segments for predicting recovery of ventricular function following revascularization is a class I indication for the use of LGE-CMR'. We conclude that cardiac MRI is an excellent tool for predicting myocardial viability, in the context of acute and chronic ischaemic heart disease whether subsequent revascularization is achieved by surgical or percutaneous means. In addition, the versatility of CMR imaging makes it an increasingly attractive tool for the complete assessment of the patient with ischaemic cardiomyopathy.