Ending the legacy of an incorrect diagnosis: cardiovascular MRI scanning of legacy cardiac implantable electronic devices

Le résumé fourni par la source

A 67-year-old male of African descent with a historical diagnosis of sarcomeric hypertrophic cardiomyopathy (HCM) and dual-chamber pacemaker for high-degree atrioventricular block presented with worsening dyspnoea. Echocardiography demonstrated significant left ventricular (LV) wall thickening without intra-cavity obstruction (see Supplementary data online, Videos S1 and S2). He was previously ineligible for cardiovascular magnetic resonance imaging (CMR) due to a non-conditional (‘legacy’) cardiovascular implantable electronic device (CIED). Development of our institutional ‘legacy-CIED CMR’ service enabled safe, high-quality scanning of such patients. Pre-contrast, SSFP cine imaging [SSFP (steady-state free-precession) cine imaging: A bright-blood (blood is of high signal intensity) sequence providing high spatial and temporal resolution, and high contrast (different signal intensities dependent on differences in tissue/fluid composition) and is the sequence typically used in cine imaging.] demonstrated severe asymmetrical neutral-septal LV hypertrophy, moderate systolic dysfunction and apically displaced, hypertrophied anterolateral papillary muscle, typical of sarcomeric HCM. However, a global pericardial effusion and interatrial septum thickening were noted (see Supplementary data online, Videos S3 and S4). Panel A illustrated globally, uniformly severely elevated native T1 values (∼1150 ms) and extracellular volume fraction (ECVF, 48%). T2 times were normal, indicating widespread abnormal tissue composition but absent active inflammation. Manual cardiac shim application facilitated high-quality parametric mapping {Parametric mapping: This allows uniquely powerful, high-resolution, non-invasive myocardial tissue characterization. Pre-contrast (‘native’) T1 mapping typically uses a Modified Look-Locker (MOLLI) sequence and allows quantification of myocardial T1 times (time taken for recovery of 63% of cellular magnetization lost in the longitudinal direction after application of a radiofrequency excitation pulse), which differ depending on myocardial tissue composition (normal at 1.5T field strength is ∼980 ms; increased in fibrosis, amyloidosis, infarct, inflammation, oedema; reduced with fat and iron). Adding post-contrast T1 mapping allows ECVF quantification, which is a highly sensitive marker of infiltration and fibrosis as such materials are deposited in myocardial extracellular matrix (normal ECVF is ∼28%). Pre-contrast T2 mapping allows quantification of myocardial T2 times [time taken for loss (decay) of 63% of cellular magnetization in the transverse direction after application of a radiofrequency excitation pulse], which differ depending on myocardial water content. This permits detection of myocardial oedema (normal T2 time at 1.5 T is <∼60 ms; increased in oedema), which is a marker of acute/sub-acute myocardial processes (e.g. inflammation, infarction). Elevated T2 times have recently been shown to be associated with the AL rather than ATTR cardiac amyloidosis subtype.} with no significant CIED-related artefact or quantitative accuracy reduction. Post-contrast Look-Locker TI scout demonstrated reversed nulling kinetics [Look-Locker and myocardial nulling kinetics: A Look-Locker sequence or ‘scout’ is performed to identify the optimal inversion time (TI) for LGE imaging. This consists of a series of LGE images produced at a range of increasing TI times (typically from ∼60 ms to >1000 ms). Typically, as the TI increases, the LV blood pool should null (turn black) before myocardium. Where myocardium nulls before blood pool, this is known as ‘reversed nulling kinetics’ and is associated with cardiac amyloidosis due to its extensive infiltration and resultant myocardial contrast uptake and binding to extracellular amyloid fibrils.] (Panel B), consistent with widespread infiltration. LGE imaging [LGE (late gadolinium enhancement) imaging: This inversion recovery sequence (protons are fully inverted by the radiofrequency pulse) allocates a greyscale value from black to white depending on myocardial T1 times, where gadolinium contrast binds to regions of myocardial pathology and reduces their T1 times resulting in high signal intensity (white). Magnitude LGE reconstructions rely on detecting only the magnitude of signal and its difference to a manually selected point known as the nulling inversion time (‘nulling TI’) where the signal intensity of normal myocardium is zero (black). This requires selection of the correct TI, and also importantly can in certain scenarios, where the extent of affected myocardium is severe result in inaccurate LGE reconstructions, as two areas of myocardium with magnetization at the selected TI of equal magnitude but in opposite directions (negative vs. positive) could be designated the same signal intensity and be indistinguishable (e.g. abnormal and normal myocardium could be given a signal intensity of zero and appear black and normal). Phase sensitive inversion recovery (PSIR) LGE reconstruction also assesses polarity of magnetization and thus is a more robust method of allocating signal intensity to pixels regardless of the magnitude of signal or type and extent of myocardial pathology. PSIR LGE reconstructions are crucial in assessing for infiltrative conditions where widespread myocardial involvement is possible (e.g. amyloidosis)] using magnitude and PSIR reconstructions with ipsilateral arm-raised, high-bandwidth acquisition demonstrated transmural interatrial and interventricular-septal hyper-enhancement, global ventricular and bi-atrial sub-endocardial enhancement (Panel C). Native parametric mapping and post-contrast imaging ended the legacy of an incorrect diagnosis of sarcomeric HCM, where typically moderately elevated native T1 times (∼1000–1100 ms) and ECVF (∼30–40%) occur due to myocardial fibrosis. In our case, severely elevated native T1 times (>1100 ms) and ECVF (≥45%) reflected extensive extracellular deposition of amyloid protein fibrils, with corroborative findings of interatrial thickening, pericardial effusion, reversed nulling kinetics and global sub-endocardial LGE in ventricular and atrial myocardium; typical of a unifying diagnosis of cardiac amyloidosis. Bone-marrow sampling with Congo red staining demonstrated transthyretin amyloidosis (Panel D), sub-typed as wild type after negative genetic testing. Author contributions: All authors contributed to the clinical case management and to the production of this manuscript. Consent: The authors confirm that written consent for submission and publication of this case report including images and associated text has been obtained from the patient in line with the journal and the Commitee on Publication Ethics guidance. Supplementary data are available at European Heart Journal—Cardiovascular Imaging online. Funding: None declared. Data availability: The data underlying this article are available in the article and in its Supplementary data online.

Ce résumé expose les affirmations des auteurs. BNTIC ne l’interprète pas comme une validation indépendante des résultats.