Cardiac amyloidosis masquerading as hypertrophic cardiomyopathy: the importance of multimodality imaging
Chawla D, Cheema O, Tajik AJ. Cardiac Amyloidosis Masquerading As Hypertrophic Cardiomyopathy: The Importance Of Multimodality Imaging. Journal of the American College of Cardiology. 2017;69(11):2127. doi:10.1016/s0735-1097(17)35516-x.
BACKGROUND: Hypertrophic cardiomyopathy (HCM) and cardiac amyloidosis are pathologically distinct disorders. In older patients, clinical differentiation between these disorders is challenging as both lead to a homologous phenotype of thickened left ventricle (LV) walls.
CASE: A 75-year-old African-American female with a diagnosis of HCM was referred to our HCM clinic for diastolic heart failure. She noted worsening dyspnea and intermittent chest pain with a baseline troponin elevation of 0.2 ng/mL. Transthoracic echocardiogram supported a diagnosis of HCM with thickened LV walls (23 mm in the anterior basal septum and 30 mm in the posterior septum) but no obstructive gradient. Ejection fraction was 50% with grade 1 diastolic dysfunction, right ventricular systolic pressure of 34 mmHg, and reduced LV global longitudinal strain of -13% in a pattern of relative apical sparing. Cardiac catheterization revealed normal coronary arteries and LV end diastolic pressure of 27 mmHg. Cardiac MRI demonstrated thickened LV walls (27 mm in the mid inferior septum) and patchy delayed enhancement consistent with suspected HCM.
DECISION-MAKING: Given the patient's symptoms and sub-optimal response to therapy, we considered cardiac amyloidosis since infiltrative diseases may present as either a restrictive or unexplained hypertrophic cardiomyopathy. Consequently, we performed a 99m Tc-pyrophosphate scan with findings of biventricular uptake suggesting a diagnosis of transthyretin amyloidosis (ATTR). Endomyocardial biopsy and Congo red staining confirmed cardiac amyloidosis, and mass spectroscopy-proteomic analysis further identified an ATTR subtype. Subsequent genetic analysis revealed a Val122Ile mutation. Given the heritable nature of mutant ATTR, we recommended genetic screening for the patient's family members, including her 5 children and 3 siblings.
CONCLUSIONS: We report a challenging case of mutant ATTR in a 75-year-old African-American female masquerading as HCM. Our case highlights the importance of multimodality imaging in differentiating between the disorders and also illustrates the clinical implications of accurate diagnosis for both the patient and family members.