Cardiac amyloidosis is a challenging diagnosis that often goes unrecognized for many years. The disease causes concentric hypertrophy of the ventricles and results in restrictive cardiomyopathy and heart failure, as in this case. The most common types of cardiac amyloidosis are systemic light chain (AL) and wild-type transthyretin (ATTRwt). Diagnosis of the correct cardiac amyloidosis type is important for management and treatment. The gold standard in diagnosis is endocardial biopsy, which is invasive. Increasingly, imaging is being used to non-invasively diagnose cardiac amyloidosis.
99mTc-pyrophosphate (PYP) is a radiotracer that commonly localizes to areas of hydroxyapatite deposition in bone-forming tissues. PYP also localizes to ATTRwt amyloidosis in the heart. Cardiac uptake greater than bone uptake in a ratio greater than or equal to 1.5 has been demonstrated in patients with ATTRwt amyloidosis. Ratios less than 1.5 are considered equivocal for ATTRwt and may represent AL amyloidosis. Combining PYP studies with cardiac imaging and laboratory work can result in a non-invasive diagnosis of amyloidosis, as well as the type of amyloidosis.
In this case, the patient was experiencing an acute exacerbation of heart failure resulting from ATTRwt amyloidosis.