Redefining cardiomyopathies: the role of cardiovascular magnetic resonance imaging

We read with great interest the article by Monserrat et al.1 published in a recent issue of European Heart Journal. The authors report on the E101K mutation in the alpha-cardiac actin gene that has previously been reported as a cause of apical hypertrophic cardiomyopathy (HCM) by the same group.2 They now hypothesize that this mutation may be present with the same or a different phenotype. Having screened 247 families with HCM, left ventricular non-compaction (LVNC), and dilated cardiomyopathy, the authors identified five index patients: one with LVNC and four with apical HCM. A total of 46 mutation carriers with an abnormal LV phenotype were identified; they were associated mainly with LVNC but also with apical HCM and septal defects. Inevitably, the question arises as to whether this represents an overlapping phenotype between apical HCM and LVNC. Monserrat et al.1 admit the choice of imaging modality as one of their limitations, but we would like to elaborate on this point. In their study, they used transthoracic echocardiography without contrast to perform family screening and to characterize ventricular morphology. Conventional transthoracic echocardiography has inherent limitations, particularly in the visualization of the apex where hypertrophy or trabeculations may be seen associated with the E101K mutation. Cardiovascular magnetic resonance (CMR) is a powerful non-invasive imaging modality capable of assessing global and regional functions and performing tissue characterization with and without contrast administration.3 CMR can image in any plane, and the introduction of steady-state free precession sequences has resulted in a substantial improvement in the endocardial border definition, which is ideal for consistent and accurate imaging of the apex.4 Moon et al.5 reported the usefulness of CMR in assessing the apex in a group of subjects with ECG abnormalities suggestive of apical HCM but normal echocardiograms. Increasing numbers of case reports indicate that echocardiography without contrast may misdiagnose LVNC as apical HCM.6,7 Contrast-enhanced CMR, namely, perfusion and delayed enhancement CMR, provides diagnostic and potentially prognostic information in various types of cardiomyopathies.8–10 With reference to LVNC particularly, we believe that CMR can make a difference in discriminating between apical HCM, mild-normal trabeculations, and grossly trabeculated LV myocardium with intertrabecular recesses.11 The interesting study by Monserrat et al.1 illustrates the importance of correctly phenotyping patients with pathologies in the ventricular apex. We believe that the time has come to apply multi-parametric CMR imaging in patients with cardiomyopathy and to redefine these conditions with seemingly overlapping features.