Myocardial Extracellular Volume Quantification by Cardiovascular Magnetic Resonance and Computed Tomography

Abstract

Purpose of review: This review article discusses the evolution of extracellular volume (ECV) quantification using both cardiovascular magnetic resonance (CMR) and computed tomography (CT).

Recent findings: Visualizing diffuse myocardial fibrosis is challenging and until recently, was restricted to the domain of the pathologist. CMR and CT both use extravascular, extracellular contrast agents, permitting ECV measurement. The evidence base around ECV quantification by CMR is growing rapidly and just starting in CT. In conditions with high ECV (amyloid, oedema and fibrosis), this technique is already being used clinically and as a surrogate endpoint. Non-invasive diffuse fibrosis quantification is also generating new biological insights into key cardiac diseases. CMR and CT can estimate ECV and in turn diffuse myocardial fibrosis, obviating the need for invasive endomyocardial biopsy. CT is an attractive alternative to CMR particularly in those individuals with contraindications to the latter. Further studies are needed, particularly in CT.

Keywords: Cardiovascular magnetic resonance; Computed tomography; Extracellular volume; Tissue characterization.

Fig. 1

Extracellular volume fraction (ECV) variability and outcome at 1.5T by myocardial pathologies. Top panel depicts ECV and associated outcome across health and disease with increasing ECV on the y-axis and outcome on the x-axis. Bottom panel shows four exemplar ECV maps of a healthy volunteer with normal ECV of 24% (a), a patient with aortic stenosis with mild ECV elevation at 30% (b), a patient with an inferior myocardial infarct (c), and a patient with AL cardiac amyloidosis with an ECV of 50% and the poorest outcome (d). (Adapted from Ugander 2014) [86]