When amyloid chooses sides: septal affection pattern as an atypical presentation of transthyretin amyloid cardiomyopathy.

In the last decades, significant advancement in diagnosing transthyretin amyloid cardiomyopathy (ATTR-CM) has been achieved by using multimodality imaging. Early diagnosis is essential in these patients since early initiation of disease-specific treatment may improve prognosis. ATTR-CM is a progressive disease marked by the misfolding of transthyretin proteins synthesized mainly in the liver, which subsequently deposit as amyloid fibrils within the heart's extracellular matrix. Classically, amyloid fibril accumulation starts in the basal and midventricular segments of the left ventricle (LV) in a symmetrical fashion, resulting in the typical "apical sparing" pattern on transthoracic echocardiographic (TTE) strain analysis. However, the presented case illustrates that amyloid distribution may vary in its pattern, leading to unusual findings on cardiac imaging. In our 73 years old male patient, wild-type ATTR-CM resulted in Technetium-99 m-labeled 3,3-diphosphono-1,2-propanodicarboxylic acid (99mTc-DPD) uptake almost exclusively confined to the ventricular septum on scintigraphy. This atypical distribution was mirrored by cardiovascular magnetic resonance imaging (CMR), which displayed diffuse late gadolinium enhancement (LGE) and elevated extracellular volume (ECV) predominantly in the ventricular septum, and by an unusual strain pattern on transthoracic echocardiography with markedly impaired longitudinal strain values in septal LV segments.