Unveiling nonischemic cardiomyopathies with cardiac magnetic resonance

Abstract

Cardiomyopathy is defined as a heterogeneous group of myocardial disorders with mechanical or electrical dysfunction. Identification of the etiology is important for accurate diagnosis, treatment and prognosis, but continues to be challenging. The ability of cardiac MRI to non-invasively obtain 3D-images of unparalleled resolution without radiation exposure and to provide tissue characterization gives it a distinct advantage over any other diagnostic tool used for evaluation of cardiomyopathies. Cardiac MRI can accurately visualize cardiac morphology and function and also help identify myocardial edema, infiltration and fibrosis. It has emerged as an important diagnostic and prognostic tool in tertiary care centers for work up of patients with non-ischemic cardiomyopathies. This review covers the role of cardiac MRI in evaluation of nonischemic cardiomyopathies, particularly in the context of other diagnostic and prognostic imaging modalities.

Keywords::

• cardiac magnetic resonance
• cardiovascular imaging
• dilated cardiomyopathy
• hypertrophic cardiomyopathy
• infiltrative cardiomyopathy
• late gadolinium enhancement
• non-ischemic cardiomyopathy

Financial & competing interests disclosure

The authors have no relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending or royalties.

No writing assistance was utilized in the production of this manuscript.

Key issues

• Cardiac MRI plays a pivotal role in detection, characterization and differentiation of non-ischemic cardiomyopathies. It also has an emerging role in monitoring response to therapy and prognosis.

• Cardiac MRI in patients with hypertrophic cardiomyopathy not only improves the diagnostic sensitivity, but also adds valuable prognostic information, and helps with procedural planning. Mild patchy myocardial late gadolinium enhancement (LGE) is often present.

• In patients with arrhythmogenic right ventricular cardiomyopathy, cardiac MRI provides highly reliable assessment of the right ventricular size, presence of regional akinesis or dyskinesis and global ejection fraction.

• Morphologic features of noncompaction cardiomyopathy include a spongy myocardium, prominent ventricular trabeculations, deep intertrabecular recesses and a noncompacted to compacted myocardial ratio >2.3 in end-diastole. Subendocardial LGE, reflective of fibrosis, may also be present that correlates with the clinical severity of the disease.

• Cardiac MRI features of cardiac amyloidosis include diffuse biventricular wall thickening, atrial wall thickening, atrial enlargement due to diastolic dysfunction, multivalvular leaflet thickening and pericardial and pleural effusions. Diffuse global subendocardial LGE and difficulty adequately nulling the myocardium are highly suggestive of amyloidosis and associated with poor prognosis.

• Use of cardiac MRI plays a pivotal role in management of patients with iron overload cardiomyopathy. The paramagnetic effects of iron cause the myocardium to have decreased signal intensity and appear darker than the normal myocardium.

• Patients with cardiac sarcoidosis often demonstrate patchy LGE in the subepicardium or mid-myocardium region that does not correspond to any vascular distribution. Although this pattern is non-specific, it is associated with adverse prognosis.

• Cardiac MRI is currently the preferred imaging modality for patients with eosinophilic myocarditis as not only can it aid in diagnosis, but can also delineate the different stages of the disease. Advanced stages of the disease may demonstrate a tri-layered appearance, starting from the outside with diffusely thickened myocardium, an enhancing subendocardial layer of fibrosis in the middle and a non-enhancing layer of thrombus.

• Cardiac MRI plays a pivotal role in patients with myocarditis for identification of edema, hyperemia and fibrosis. While not recommended in all patients, endomyocardial biopsy may occasionally be indispensable in certain patients particularly those with cardiomyopathy of unexplained etiology, and with refractory arrhythmias and heart failure.

• With the advent of dedicated cardiac scanners, steady improvement in MRI technology and faster imaging sequences, cardiac MRI is being increasingly used, and provides valuable information to guide with diagnosis, prognosis and follow-up of patients with non-ischemic cardiomyopathies.

Notes