Myocardial Scintigraphy in Diagnosing Cardiac Transthyretin Amyloidosis.

Myocardial scintigraphy with technetium-99m pyrophosphate is a minimally invasive technique that can distinguish between transthyretin amyloidosis (ATTR) and light-chain amyloidosis. We present a case in which it helped determine the amyloidosis type in a 74-year-old man with cardiac amyloidosis and multiple previous admissions for acute decompensated heart failure. The patient presented with increasing abdominal girth and bilateral lower extremity edema. His medical history also included atrial fibrillation, liver cirrhosis, hypertension, stage 3 chronic kidney disease, and peripheral vascular disease. We prescribed guideline-directed medical therapy for his acute decompensated heart failure with cardiorenal syndrome and his decompensated cirrhosis. Two years previously, a presumptive diagnosis of ATTR cardiomyopathy had been made on the basis of the patient's age, predominantly cardiac involvement, an unremarkable serum protein electrophoresis result, and an abnormal free κ/λ light-chain ratio of 2.24. Over the next year, the patient's clinical condition had worsened with the development of liver cirrhosis and peripheral neuropathy, and his free κ/λ light-chain ratio had become even more abnormal. At the current presentation, a technetium-99m pyrophosphate nuclear scintigram revealed a free κ/λ light-chain ratio of 1.52. This, combined with the patient's age and slow progression of primarily cardiac disease, supported the diagnosis of ATTR, and we prescribed tafamadis. This case suggests that technetium-99m pyrophosphate scintigraphy is valuable in definitively diagnosing ATTR cardiomyopathy and selecting patients who may benefit from disease-modifying therapy.