Abstract
Background: The cardiac Magnetic Resonance Imaging (MRI) characteristics of rare diseases with the hypertrophic cardiomyopathy (HCM) phenotype are not well defined. Methods: Seventy-three sequential patients and 34 of their relatives, who have the HCM phenotype, were included. All subjects underwent cardiac MRI and genetic testing. Results: Of these 107 patients with phenotypic HCM, seven rare diseases were identified: four cases with LAMP2, one case with PRKAG2, one case with TTR mutation, and one case with senile systemic amyloidosis. Subjects with rare diseases had diffuse LGE, and the percentage of those with LGE was significantly higher than that of other HCM (median: 18.9%, interquartile range (IQR): 14.05 to 28.2% versus 7.8%, IQR: 4.41 to 14.56%; p = 0.003). Additionally, global T1 and ECV were significantly higher in subjects with rare diseases (global T1: 1423.1 ± 93.3 ms versus 1296.2 ± 66.6 ms; global ECV: 44.3 ± 11.5% versus 29.9 ± 4.5%; all p < 0.001). Conclusions: Cardiac MRI suggests the existence of distinct imaging characteristics, including via LGE and T1 mapping, among rare diseases that mimic HCM and HCM itself.
Highlights
Hypertrophic cardiomyopathy (HCM) is the most common primary cardiomyopathy and manifests as unexplained myocardial hypertrophy
The hypertrophic cardiomyopathy (HCM) phenotype was based on the presence of LV wall thickness ≥ 15 mm in one or more myocardial segments measured by any imaging criteria, including echocardiography, computerized tomography (CT) scan, and cardiac Magnetic Resonance Imaging (MRI) in the absence of secondary causes of hypertrophy [21]
The patients with rare diseases including patients with amyloidosis had a significantly higher extent of late gadolinium enhancement (LGE) than HCM patients (median: 18.9%, interquartile range (IQR): 14.05 to 28.2% versus 7.8%, IQR: 4.41 to 14.56%; p = 0.003, Figure 4), where LGE extent is quantified as %LGE
Summary
Hypertrophic cardiomyopathy (HCM) is the most common primary cardiomyopathy and manifests as unexplained myocardial hypertrophy. HCM is an autosomal dominant genetic disease with 40–60% of patients identified as having mutations of sarcomere-related genes. It remains a challenge to accurately identify these rare diseases among patients with phenotypic HCM. Difficulties remain in choosing which patients to refer for whole genome genetic testing and myocardial biopsy among patients with phenotypic HCM due to the low prevalence of such rare diseases. The cardiac Magnetic Resonance Imaging (MRI) characteristics of rare diseases with the hypertrophic cardiomyopathy (HCM) phenotype are not well defined. Results: Of these 107 patients with phenotypic HCM, seven rare diseases were identified: four cases with LAMP2, one case with PRKAG2, one case with TTR mutation, and one case with senile systemic amyloidosis. Conclusions: Cardiac MRI suggests the existence of distinct imaging characteristics, including via LGE and T1 mapping, among rare diseases that mimic HCM and HCM itself
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