Reversible myocardial oedema due to acute myocardial infarction as differential diagnosis of cardiac transthyretin amyloidosis

Using bone-avid radiotracers, cardiac transthyretin (TTR) amyloidosis can be diagnosed by scintigraphy, thus obviating endomyocardial biopsy. Radiotracer accumulation, however, may also be due to other causes. A 68-year-old male with acute myocardial infarction underwent recanalization of the left anterior descending coronary artery (LAD). Postinterventionally, transthoracic echocardiography showed hypokinesia of the septum and anterior wall and a thickened myocardium with granular sparkling appearance. Cardiac amyloidosis was suspected. A 99mTc-3,3-diphosphono-1,2-propanodicarboxylic acid whole-body scan 4 days after LAD recanalization showed Perugini 2 myocardial tracer uptake. Monoclonal gammopathy was excluded, and cardiac TTR amyloidosis was diagnosed. Three months later, 99m-Tc-hydroxydiphosphate scan showed no myocardial tracer uptake. Cardiac magnetic resonance imaging revealed late gadolinium enhancement within the LAD supply area. No mutation of the TTR gene was found. Suspicion of amyloidosis should consider not only echocardiography but also history and clinical findings. Myocardial oedema due to reperfusion should be acknowledged as a differential diagnosis for cardiac uptake of bone-avid radiotracers.

Keywords: Bone scintigraphy; Cardiac magnetic resonance imaging; Echocardiography; Myocardial infarction; Transthyretin amyloidosis.