Abstract
BackgroundNuclear imaging modalities using 123Iodine-metaiodobenzylguanidine (123I-MIBG) and bone seeking tracers identify early cardiac involvement in ATTRm amyloidosis patients. However, little is known whether results from 123I-MIBG scintigraphy actually correlate to markers for either cardiac autonomic neuropathy or cardiomyopathy. MethodsAll TTR mutation carriers and ATTRm patients who underwent both 123I-MIBG and 99mTechnetium-hydroxymethylene diphosphonate (99mTc-HDP) scintigraphy were included. Cardiomyopathy was defined as NT-proBNP > 365 ng/L, and cardiac autonomic neuropathy as abnormal cardiovascular reflexes at autonomic function tests. Late 123I-MIBG heart-to-mediastinum ratio (HMR) < 2.0 or wash-out > 20%, and any cardiac 99mTc-HDP uptake were considered as abnormal. Results39 patients (13 carriers and 26 ATTRm patients) were included in this study. Patients with cardiomyopathy, with or without cardiac autonomic neuropathy, had lower late HMR than similar patients without cardiomyopathy [median 1.1 (range 1.0-1.5) and 1.5(1.2-2.6) vs 2.4 (1.4-3.8) and 2.5 (1.5-3.7), respectively, P < 0.001]. Late HMR and wash-out (inversely) correlated with NT-proBNP r = − 0.652 (P < 0.001) and r = 0.756 (P < 0.001), respectively. Furthermore, late HMR and wash-out (inversely) correlated with cardiac 99mTc-HDP uptake r = − 0.663 (P < 0.001) and r = 0.617 (P < 0.001), respectively. ConclusionIn case of heart failure, 123I-MIBG scintigraphy reflects cardiomyopathy rather than cardiac autonomic neuropathy in ATTRm patients and TTR mutation carriers. 123I-MIBG scintigraphy may already be abnormal before any cardiac bone tracer uptake is visible.
Highlights
Amyloidosis comprises a group of diseases, all characterized by the deposition of insoluble amyloid fibrils derived from soluble misfolded proteins
Hereditary transthyretin (TTR)-derived amyloidosis and senile transthyretin-derived amyloidosis are the two types of systemic amyloidosis that originate from TTR1,3 and both are associated with cardiac involvement.[4,5]
While searching for noninvasive alternatives, Nterminal pro-B-type natriuretic peptide (NTproBNP)[10,11,12] and autonomic function tests became of value as markers of cardiomyopathy and cardiac autonomic neuropathy, respectively.[13,14]
Summary
Amyloidosis comprises a group of diseases, all characterized by the deposition of insoluble amyloid fibrils derived from soluble misfolded proteins These deposits change the structure of tissues resulting in dysfunction of several organs, including the heart.[1] Cardiac deposits cause symptoms of restrictive cardiomyopathy and cardiac autonomic neuropathy, when the myocardium and the cardiac conductive system, respectively, are infiltrated.[2] Hereditary transthyretin (TTR)-derived amyloidosis (mutant transthyretin, ATTRm) and senile transthyretin-derived amyloidosis (wild-type transthyretin, ATTRwt) are the two types of systemic amyloidosis that originate from TTR1,3 and both are associated with cardiac involvement.[4,5] Endomyocardial biopsy is currently the gold standard for diagnosing cardiac amyloidosis,[6,7,8] but this procedure is time consuming with an increased risk of complications, such as arrhythmias, puncture of central arteries, pneumothorax, and perforation with pericardial tamponade.[9]. Little is known whether results from 123I-MIBG scintigraphy correlate to markers for either cardiac autonomic neuropathy or cardiomyopathy
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