Andrew J. Taylor, Ph.D., Alfred Hospital and Baker IDI Heart and Diabetes Institute, Melbourne, Australia
Myocardial fibrosis is a fundamental event in the development of cardiac failure, and is a common feature in all patients with advanced cardiac failure regardless of the aetiology of cardiomyopathy. Increasing myocardial fibrosis results in progressive deterioration of myocardial function, with more extensive myocardial fibrosis identified histologically in the hearts of patients with advanced heart failure. Regional myocardial fibrosis, whilst most commonly observed in ischaemic cardiomyopathy, is present in a broad range of non-ischaemic cardiomyopathies. With the advent of cardiac magnetic resonance (CMR) imaging, identification and quantification of regional fibrosis with late gadolinium enhancement (LGE) has stimulated research into the diagnostic and pathological role of regional cardiac fibrosis in cardiomyopathy. Whilst initially focused on its role in the identification of myocardial scar in ischaemic heart disease, the presence and distribution of LGE has improved diagnosis across a range of cardiomyopathies, including sarcoidosis and amyloidosis. Regional fibrosis is also now thought to play a significant role as a substrate for malignant ventricular arrhythmia, and its presence has been linked to pathological cardiac remodelling and adverse prognosis. Diffuse myocardial fibrosis is observed in all forms of advanced cardiomyopathy, and can now be assessed semi-quantitatively with CMR T1 mapping. Prior studies using either contrast-enhanced or non-contrast T1 mapping have demonstrated strong correlations with myocardial T1 time and the extent of diffuse fibrosis histologically. Using CMR T1 mapping, a relationship between interstitial fibrosis and cardiac stiffness has been demonstrated, where it is likely to play a significant mechanistic role in heart failure with preserved ejection fraction (HFPEF). Additional studies have demonstrated the utility of CMR T1 mapping in the differentiation of cardiomyopathy, and the extent of diffuse fibrosis identified by CMR has been shown to be a strong, independent predictor of adverse outcome in heart failure.