Background: Limb-girdle muscular dystrophy (LGMD) is a genetically and clinically heterogeneous group of rare muscular dystrophies. Subtype 2A (LGMD2A) also known as "calpainopathy" is an inherited autosomal recessive gene defect. Cardiac dysfunction is common in several forms of LGMD. Cardiac involvement in LGMD2A, however, is not clear. The aim of this study was to perform cardiac magnetic resonance (CMR)-based strain analysis in LGMD2A patients, as this is a diagnostic parameter of subclinical cardiac involvement and a powerful independent predictor of mortality. We conducted the largest prospective cardiac magnetic resonance study to date, including 11 genetically verified LGMD2A patients and 11 age- and sex-matched control subjects and performed CMR-based strain analysis of the left and right ventricles.
Results: Left and right global longitudinal strain (GLS) were not significantly different between the two groups and within normal reference ranges (left ventricle: control - 21.8 (5.1) % vs. patients - 22.3 (3.2) %, p = 0.38; right ventricle: control - 26.3 (7.2) % vs. patients - 26.8 (5.8) %, p = 0.85). Also, global circumferential and radial strains did not significantly differ between the two groups (p = 0.95 and p = 0.86, respectively). LGMD2A patients did not show relevant amounts of late gadolinium enhancement (LGE) or malignant ventricular arrhythmias.
Conclusions: No evidence of even subtle cardiac dysfunction is evident form CMR-based strain analysis in LGMD2A patients. Malignant ventricular arrhythmias were not detected. Thus, in case of non-pathological initial echocardiographic and electrocardiographic examination, a less frequent or even no cardiac follow-up may be acceptable in these patients. However, if there are signs and symptoms that suggest an underlying cardiac condition (e.g. palpitations, angina, shortness of breath), this approach needs to be individualized to account for the unknown.
Keywords: Calpainopathy; Cardiac magnetic resonance imaging; Feature-tracking; Global longitudinal strain; LGMD2A; Limb-girdle muscular dystrophy; Strain analysis.