Images in cardiovascular medicine: Right ventricular late enhancement as a magnetic resonance marker of glycogen storage disease

Cardiac Phenotype Characterization at MRI in Patients with Danon Disease: A Retrospective Multicenter Case Series

Danon disease (DD) is a rare X-chromosome-linked dominant lysosomal glycogen storage disease. Its features have seldom been reported by using cardiac MRI. This case series aimed to evaluate cardiac features of DD on the basis of MRI observations from five centers in China. From January 2010 to May 2019, 16 patients with DD (13 male patients [81%]; median age, 19 years; age range, 14-44 years) underwent MRI. The most frequent DD cardiomyopathy manifestation was symmetric hypertrophy cardiomyopathy (HCM) phenotype (nine of 16; 56%), followed by asymmetric HCM phenotype (six of 16; 38%) and dilated cardiomyopathy phenotype (one of 16; 6%). The characteristic late gadolinium enhancement features included midbasal septum sparing (14 of 16; 88%) and apex involvement (16 of 16; 100%) with a base-to-apex increasing tendency, free wall involvement (15 of 16; 94%), and extensive subendocardium involvement (14 of 16; 88%). Abnormal T2 signal (seven of 16; 44%) and resting perfusion defect (14 of 16; 88%) were not uncommon in patients with DD. Furthermore, the cardiac MRI features of DD cohort in this study were compared with those of DD in previous literature and with genetically confirmed sarcomeric HCM.

Cardiovascular magnetic resonance findings in patients with PRKAG2 gene mutations

BACKGROUND

Autosomal dominantly inherited PRKAG2 cardiac syndrome is due to a unique defect of the cardiac cell metabolism and has a distinctive histopathology with excess intracellular glycogen, and prognosis different from sarcomeric hypertrophic cardiomyopathy. We aimed to define the distinct characteristics of PRKAG2 using cardiovascular magnetic resonance (CMR).

METHODS

CMR (1.5 T) and genetic testing were performed in two families harboring PRKAG2 mutations. On CMR, segmental analysis of left ventricular (LV) hypertrophy (LVH), function, native T1 mapping, and late gadolinium enhancement (LGE) were performed.

RESULTS

Six individuals (median age 23 years, range 16-48; two females) had a PRKAG2 mutation: five with an R302Q mutation (family 1), and one with a novel H344P mutation (family 2). Three of six mutation carriers had LV mass above age and gender limits (203 g/m2, 157 g/m2 and 68 g/m2) and others (with R302Q mutation) normal LV masses. All mutation carriers had LVH in at least one segment, with the median maximal wall thickness of 13 mm (range 11-37 mm). Two R302Q mutation carriers with markedly increased LV mass (203 g/m2 and 157 g/m2) showed a diffuse pattern of hypertrophy but predominantly in the interventricular septum, while other mutation carriers exhibited a non-symmetric mid-infero-lateral pattern of hypertrophy. In family 1, the mutation negative male had a mean T1 value of 963 ms, three males with the R302Q mutation, LVH and no LGE a mean value of 918 ± 11 ms, and the oldest male with the R302Q mutation, extensive hypertrophy and LGE a mean value of 973 ms. Of six mutations carriers, two with advanced disease had LGE with 11 and 22 % enhancement of total LV volume.

CONCLUSIONS

PRKAG2 cardiac syndrome may present with eccentric distribution of LVH, involving focal mid-infero-lateral pattern in the early disease stage, and more diffuse pattern but focusing on interventricular septum in advanced cases. In patients at earlier stages of disease, without LGE, T1 values may be reduced, while in the advanced disease stage T1 mapping may result in higher values caused by fibrosis. CMR is a valuable tool in detecting diffuse and focal myocardial abnormalities in PRKAG2 cardiomyopathy.

Right Ventricular Dimensions and Function: Why do we Need a More Accurate and Quantitative Imaging?

The right ventricle plays an important role in the morbidity and mortality of patients presenting with symptoms and signs of cardiopulmonary disease. This cardiac chamber has a unique crescent shape, which adds complexity to the quantification of its size and function. Until recently, little uniformity in echocardiographic imaging of the right heart existed because of a lack of familiarity with various techniques, and the enormous attention directed towards left heart quantification. Three-dimensional (3D) echocardiography, a major technological breakthrough in the field of cardiovascular imaging, provides several advantages over two-dimensional (2D) imaging in the quantitative evaluations of right ventricle because of its independence from any geometrical assumption. In this review, we focus on the contribution of this new modality to the evaluation of right ventricle.

Imaging the right heart: the use of integrated multimodality imaging

During recent years, right ventricular (RV) structure and function have been found to be an important determinant of outcome in different cardiovascular and also pulmonary diseases. Currently, echocardiography and cardiac magnetic resonance (CMR) imaging are the two imaging modalities most commonly used to visualize the RV. Most structural abnormalities of the RV can be reliably described by echocardiography but due its complex geometrical shape, echocardiographic assessment of RV function is more challenging. Newer promising echocardiographic techniques are emerging but lack of validation and limited normal reference data influence their routine clinical application. Cardiac magnetic resonance is generally considered the clinical reference technique due to its unlimited imaging planes, superior image resolution, and three-dimensional volumetric rendering. The accuracy and reliability of CMR measurements make it the ideal tool for serial examinations of RV function. Multidetector computed tomography (MDCT) plays an important role in the diagnosis of pulmonary emboli but can also be used for assessing RV ischaemic disease or as an alternative for CMR if contra-indicated. Radionuclide techniques have become more obsolete in the current era. The different imaging modalities should be considered complimentary and each plays a role for different indications.