Images in Cardiovascular Medicine Cardiac Amyloidosis Mimicking Hypertrophic Cardiomyopathy With Obstruction: Treatment With Disopyramide

71-year old-man presented with 4 posturally relatedsyncopal episodes. He carried a diagnosis of asymptom-atic hypertrophic cardiomyopathy (HCM) without obstruc-tion based on an echocardiogram 7 years earlier. Echocardi-ography at the time of syncope evaluation demonstrated ahyperdynamic left ventricle with a septal thickness of 20 mm (an increase of 4 mm from an earlier echocardio-gram), newly present systolic anterior motion of the mitralvalve, and a peak left ventricular (LV) outflow tract gradientof 42 mm Hg at rest and 120 mm Hg with Valsalva maneuver(Figure 1). He was referred for septal myectomy, and cardiaccatheterization demonstrated nonobstructive coronary arterydisease. An ECG showed low-voltage limb leads, unusual inHCM (Figure 2), and cardiac magnetic resonance imaging(MRI) revealed delayed gadolinium enhancement in the papil-lary muscles, transmural enhancement involving the basal lat-eral walls, and subendocardial enhancement of the basal, mid,and distal anterior walls. There was also extensive gadolin-ium uptake in the atrial walls (Figure 3). Because the cardiacMRI suggested an infiltrative process, a cardiac biopsy wasperformed. This demonstrated extensive amyloid infiltration(Figure 4). Immunohistochemistry was positive for transthy-retin, but negative for amyloid A and / light chains.Genetic testing for common mutations associated with HCMwas negative, and no transthyretin mutations were detected.A diagnosis of wild-type transthyretin cardiac amyloidosis(senile systemic amyloidosis) mimicking HCM with obstruc-tion was made.