This session was on the value of multimodality imaging in restrictive cardiomyopathies.
From the 2014 guidelines of cardiomyopathies classification, it is important to realize that restrictive cardiomyopathies is the only category of cardiomyopathies that it is not an anatomic but rather a functional entity. This implies that there may potentially be a significant overlap among the various anatomic classifications from the hypertrophics to dilated and arrhythmogenic cardiomyopathies. Multimodality imaging is therefore important to help characterize the marked phenotypic variations.
Echocardiography is clearly the first line imaging modality that may identify the correct etiology in 80% of patients with amyloid, carcinoid, Anderson-Fabry’s or endomyocardial fibroelastosis types of restrictive cardiomyopathies in expert departments, but also differentiate restrictive cardiomyopathy from constrictive pericarditis. Nuclear/CT can aid by detecting involvement in other organs using 99mTc-PYP, 99mTc-DPD as for hereditary TTR amyloidosis, or 99mTc-HMDP tracers. Bone scintigraphy has a 99% sensitivity for systemic amyloidosis. The greatest complementary contribution however is perhaps the 18F-FDG-PET/CT, which has low ionizing radiation and can detect active sarcoid lesions, but also the systemic localization or mediastinal lymph nodes of active inflammatory tissues.
Cardiac MRI by its non-ionizing radiation nature can contribute in characterizing tissues using late gadolinium enhancement. It can detect oedema and extracellular myocardial fibrosis in different myocardial localisations, many of which are quite pathognomonic for specific phenotypes. While sensitivity of the various localisations is high, specificity is low for specific disease as there is a wide overlap of patterns with few exceptions, like in cardiac amyloidosis. T1 mapping is a promising new modality in tissue characterization depicting diffuse interstitial fibrosis but lacks universal standardization.
In summary, while echocardiography remains the main problem-solving imaging modality in 80% of clinical presentations with good haemodynamic assessment, the supplementary information of targeted radiolabeled compounds by nuclear techniques or myocardial tissue characterization using CMR may unveil the etiology of the vast majority of restrictive types of cardiomyopathies.