Phenotyping heart failure by cardiac magnetic resonance imaging of cardiac macro- and microscopic structure: state of the art review.

Heart failure demographics have evolved in past decades with the development of improved diagnostics, therapies and prevention. Cardiac magnetic resonance (CMR) has developed in a similar timeframe to become the gold-standard non-invasive imaging modality for characterising diseases causing heart failure. CMR techniques to assess cardiac morphology and function have progressed since their first use in the 1980s. Increasingly efficient acquisition protocols generate high spatial and temporal resolution images in shorter time frames. This has enabled new methods of characterising cardiac systolic and diastolic function such as strain analysis, exercise real-time (RT) cine imaging and four-dimensional (4D) flow. A key strength of CMR is its ability to non-invasively interrogate the myocardial tissue composition. Gadolinium contrast agents revolutionised non-invasive cardiac imaging with the late gadolinium enhancement (LGE) technique. Further advances enabled quantitative parametric mapping to increase sensitivity at detecting diffuse pathology. Novel methods such as diffusion tensor imaging (DTI) and artificial intelligence-enhanced image generation are on the horizon. MRS provides a window into the molecular environment of the myocardium. Specifically, phosphorus (31P) spectroscopy can inform the status of cardiac energetics in health and disease. Proton (1H) spectroscopy can complement this by measuring creatine and intramyocardial lipids. Hyperpolarised carbon (13C) spectroscopy is a novel method that could further our understanding of dynamic cardiac metabolism. CMR of other organs such as the lungs may add further depth into phenotypes of heart failure. The vast capabilities of CMR need to be deployed and interpreted in context of current heart failure challenges.