SCMR 22nd Annual Scientific Sessions
Description of Clinical Presentation:
A 62 year old man with worsening fatigue and a history of left ventricular hypertrophy (LVH) associated with paroxysmal atrial fibrillation was referred for a cardiac magnetic resonance (CMR) to evaluate for hypertrophic cardiomyopathy (HCM) and determine the burden of myocardial fibrosis.
Diagnostic Techniques and Their Most Important Findings:
The CMR (Philips Achieva 1.5 T) protocol included SSFP cine, T1 mapping, T2*, and late gadolinium enhancement (LGE) imaging. The left ventricular (LV) ejection fraction (EF) was 54%. There was severe, concentric LVH with a septal thickness of 24 mm (Fig 1). The right ventricle was mildly hypertrophied and had an EF of 46%. The native myocardial T1 relaxation time (Fig 2) was low (870 ms). The T2*decay time was normal (38 ms). There was no LGE. Further review of systems was positive for hypohidrosis and a brother who was told he had a thickened heart. His electrocardiogram had voltage criteria for LVH with prominent ST depression and deep T wave inversions (Fig 3). There was proteinuria on urinalysis. The differential for severe LVH includes, but is not limited to, hypertensive heart disease, cardiac amyloidosis, HCM, and Fabry’s disease (FD). Given his CMR findings, particularly the low T1 time, there was high suspicion for FD, an X-linked lysosomal storage disease due to a deficiency in alpha-galactosidase causing accumulation of glycosphingolipids. In the heart, there is an affinity for globotriaosylceramide accumulation in cardiomyocytes leading to LVH. To diagnose FD, an alpha-galactosidase activity level was checked and was low 1.2). Confirmatory genetic testing revealed a hemizygous alteration of amino acids p.I232T and a DNA change of c.695T>C. These mutations have been described in a later-onset variant of FD with men primarily presenting with cardiomyopathy in the fifth to eighth decade of life versus the classic phenotype that presents in childhood or adolescence. The patient was started on enzyme replacement therapy. Additionally, his family members were screening for FD, and two were also diagnosed with FD.
Learning Points from this Case:
Unexplained LVH is the hallmark of FD and CMR with tissue characterization is very helpful in differentiating FD from its mimickers. Small studies have suggested that FD accounts for 1-3% of patients with HCM. A low T1 time is suggestive of FD or hemochromatosis, but a normal T2* decay time is not indicative of iron overload cardiomyopathy. Conversely, moderate to severely increased T1 time is characteristic cardiac amyloidosis and HCM. Patients with FD often show a basal to mid anterolateral and inferolateral mid-wall LGE in contrast to the pattern of patchy LGE in the hypertrophied segments and RV insertion points seen in HCM. Although a common reason for performing CMR in patients with suspected HCM is to determine their risk for sudden cardiac death, CMR also helps identify mimickers of HCM such as FD, cardiac sarcoidosis, or cardiac amyloidosis which could significantly alter the treatment plan and prognosis.