Scripties UMCG - Rijksuniversiteit Groningen
English | Nederlands

Imaging cardiac sympathetic innervation in hereditary transthyretin amyloidosis: a marker for neuropathy or cardiomyopathy? A retrospective correlation with bone scintigraphy, biomarkers and autonomic function tests

(2018) Jonker, D.L.

Objective – Nuclear imaging modalities using 123I-metaiodobenzylguanidine (123I-MIBG) and bone seeking tracers identify early cardiac involvement in hereditary amyloidosis (ATTRm) patients. However, little is known whether the results reflect cardiomyopathy or cardiac autonomic neuropathy. Therefore, the aim of this study was to gain insight whether both nuclear modalities reflect cardiomyopathy or cardiac neuropathy, and to gain insight whether cardiomyopathy may precede neuropathy or vice versa.
Methods – All genetically proven ATTRm patients who underwent both 123I-MIBG and 99mTc-hydroxymethylene diphosphonate (99mTc-HDP) scintigraphy, were included. From the patient chart additional findings concerning clinical examinations, neurological function tests, echocardiography, ECG and laboratory tests, were retrieved. Cardiomyopathy was defined as NT-proBNP >365 ng/l, and cardiac autonomic neuropathy as abnormal cardiovascular reflexes at autonomic function tests. Late heart-to-mediastinum ratio (HMR) <2.0 or wash-out >20% were considered as abnormal 123I-MIBG parameters. Any cardiac 99mTc-HDP uptake was considered as abnormal.
Results – 39 patients were included in this study (21 men and 18 women, mean ± standard deviation age was 51 ± 14 years). Patients with cardiomyopathy, with or without cardiac autonomic neuropathy, had lower late HMR than patients without cardiomyopathy, irrespective of cardiac autonomic neuropathy (respectively median 1.1 (range 1.0−1.5) and 1.5 (1.2−2.6) versus 2.4 (1.4−3.8) and 2.4 ± 0.67, p<0.001). Late HMR and wash-out were correlated with NT-proBNP, respectively r = -0.652 (p <0.001) and r = 0.756 (p <0.001), indicating that 123I-MIBG scintigraphy reflects cardiomyopathy instead of cardiac autonomic neuropathy. Furthermore, late HMR and wash-out correlated with cardiac 99mTc-HDP uptake, respectively r = -0.663 (p <0.001) and r = 0.617 (p <0.001).
Conclusion – 123I-MIBG scintigraphy seems to reflect cardiomyopathy instead of cardiac autonomic neuropathy in ATTRm patients. Furthermore, 123I-MIBG scintigraphy seems to be positive even before cardiac bone tracer accumulation is visible.

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