Download Role of nuclear imaging in cardiac amyloidosis

Role of nuclear imaging in cardiac amyloidosis - case report
Štalc M1, Dolenc Novak M1, Latifić Jasnič D2, Gužič Salobir B1
1
Department for nuclear medicine, 2Cardiology department
University Medical Centre, Ljubljana, Slovenia
Background: Amyloidosis refers to large group of disorders caused by extracellular
deposition of insoluble abnormal fibrils of misfolded proteins, which can alter tissue structure
and impair function of multiple organs, including the heart. Cardiac amyloidosis is often
misdiagnosed. Histological analysis of endomyocardial tissue is still the gold standard for the
diagnosis of cardiac amyloidosis, but has its limitations. Accordingly, there is a need for noninvasive modalities to diagnose cardiac amyloidosis. Echocardiography and magnetic
resonance imaging can detect thickened ventricular walls and systolic/diastolic dysfunction,
characteristics that are not very specific for cardiac amyloid. Among nuclear medicine
techniques, scintigraphy with bone-seeking tracers (diphosphonates) is very useful in the
evaluation of transthyretin (TTR) (both hereditary and wild type) related cardiac amyloidosis.
However, the diagnosis of the type of cardiac amyloidosis is not always straightforward. We
present a case of a cardiac amyloidosis that highlights the potential difficulties in determining
the diagnosis and the role of nuclear imaging.
Results: A 53-year old Caucasian male was admitted to the hospital for the first time after an
episode of syncope. Electrocardiogram revealed paroxysmal atrial fibrillation and left bundle
branch block. Transthoracic echocardiogram showed severe left ventricular hypertrophy,
bilateral atrial dilation and decreased ejection fraction. Since infiltrative cardiomyopathy was
suspected, the subcutaneous fat pad biopsy was performed with negative result. Few months
later he complained of marked dyspnea on exertion and palpitations. Coronary angiography
was performed and no abnormalities were found. In the next two years his status was stable.
Three years after the first hospitalization his condition deteriorated. He was admitted to the
hospital several times with chest pain and paroxysmal atrial fibrillation. Another coronary
angiography with stenting of 70% stenosis of right coronary artery was performed. Two years
later, he presented with severe right sided cardiac decompensation. At that time, thickened
rectal mucosa on computer tomography of abdomen was observed. Rectal biopsy was
performed and light chain (AL) amyloidosis was confirmed histologically. Serum protein
electrophoresis and bone marrow biopsy did not show any abnormalities. In the meantime,
our nuclear medicine department was asked if we could offer any additional diagnostic
method to elucidate his condition. We decided for 99mTc-aprotinin scintigraphy which showed
accumulation in the heart as well as in the liver, kidneys, bladder and right lobe of lung.
Additionally, we performed a 99mTcDPD (99mTc-3,3 diphosphono-1,2-propanodicarboxylic
acid) bone scintigraphy. We confirmed an intense myocardial uptake of the tracer. As intense
99m
TcDPD retention is characteristic for TTR and not AL amyloidosis, we proposed to revise
histopathological specimen. With immunohistochemistry study, TTR amyloid deposition was
found. Finally, genetic testing confirmed c.425C>T TTR gene mutation.
Conclusion: Once the diagnosis of amyloidosis is made, specific type of amyloidosis should
be determined because the prognosis and the treatment plan depends on it. Our case supports
the important role of 99mTc-aprotinin scintigraphy for the evaluation of the extent of disease
and 99mTcDPD bone scintigraphy as a non-invasive method in the diagnosis of TTR-related
amyloidotic cardiomyopathy.