Abstract
BackgroundLimb girdle muscular dystrophies (LGMD) are inclusive of 7 autosomal dominant and 14 autosomal recessive disorders featuring progressive muscle weakness and atrophy. Studies of cardiac function have not yet been well-defined in deficiencies of dysferlin (LGMD2B) and fukutin related protein (LGMD2I). In this study of patients with these two forms of limb girdle muscular dystrophy, cardiovascular magnetic resonance (CMR) was used to more specifically define markers of cardiomyopathy including systolic dysfunction, myocardial fibrosis, and diastolic dysfunction.MethodsConsecutive patients with genetically-proven LGMD types 2I (n = 7) and 2B (n = 9) and 8 control subjects were enrolled. All subjects underwent cardiac magnetic resonance (CMR) on a standard 1.5 Tesla clinical scanner with cine imaging for left ventricular (LV) volume and ejection fraction (EF) measurement, vector velocity analysis of cine data to calculate myocardial strain, and late post-gadolinium enhancement imaging (LGE) to assess for myocardial fibrosis.ResultsSixteen LGMD patients (7 LGMD2I, 9 LGMD2B), and 8 control subjects completed CMR. All but one patient had normal LV size and systolic function; one (type 2I) had severe dilated cardiomyopathy. Of 15 LGMD patients with normal systolic function, LGE imaging revealed focal myocardial fibrosis in 7 (47%). Peak systolic circumferential strain rates were similar in patients vs. controls: εendo was -23.8 ± 8.5vs. -23.9 ± 4.2%, εepi was -11.5 ± 1.7% vs. -10.1 ± 4.2% (p = NS for all). Five of 7 LGE-positive patients had grade I diastolic dysfunction [2I (n = 2), 2B (n = 3)]. that was not present in any LGE-negative patients or controls.ConclusionsLGMD2I and LGMD2B generally result in mild structural and functional cardiac abnormalities, though severe dilated cardiomyopathy may occur. Long-term studies are warranted to evaluate the prognostic significance of subclinical fibrosis detected by CMR in these patients.
Highlights
Limb girdle muscular dystrophies (LGMD) are inclusive of 7 autosomal dominant and 14 autosomal recessive disorders featuring progressive muscle weakness and atrophy
Cardiac involvement has not been systematically studied in dysferlin deficiency [15]
Transmitral flow measurements were obtained at the mitral leaflet tips in end-diastole using electrocardiographicallytriggered phase-contrast acquisition with a velocity sensitivity of 130 cm/s; myocardial tissue velocities were measured phase contrast MR prescribed at the basal third of the left ventricular (LV) in a short-axis plane with velocity encoding of 30 cm/s [25]
Summary
Limb girdle muscular dystrophies (LGMD) are inclusive of 7 autosomal dominant and 14 autosomal recessive disorders featuring progressive muscle weakness and atrophy. Studies of cardiac function have not yet been well-defined in deficiencies of dysferlin (LGMD2B) and fukutin related protein (LGMD2I). In this study of patients with these two forms of limb girdle muscular dystrophy, cardiovascular magnetic resonance (CMR) was used to define markers of cardiomyopathy including systolic dysfunction, myocardial fibrosis, and diastolic dysfunction. Limb-girdle muscular dystrophy (LGMD) comprises a group of genetically-heterogeneous disorders that present with variable skeletal and cardiac muscle involvement [1,2,3]. The degree of cardiac myopathy, presenting with distal lower limb weakness and atrophy affecting the posterior calf muscles [9,10]. Wenzel et al observed symptomatic dilated cardiomyopathy in 2 of 7 total subjects [16]
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