123I-Labelled metaiodobenzylguanidine for the evaluation of cardiac sympathetic denervation in early stage amyloidosis

Abstract

PurposeCardiac amyloidosis is a rare disorder, but it may lead to potentially life-threatening restrictive cardiomyopathy. Cardiac manifestations frequently occur in primary amyloidosis (AL) and familial amyloidosis (ATTR), but are uncommon in secondary amyloidosis (AA). Echocardiography is the method of choice for assessing cardiac amyloidosis. Amyloid deposits impair the function of sympathetic nerve endings. Disturbance of myocardial sympathetic innervations may play an important role in the remodelling process. 123I-MIBG can detect these innervation changes.MethodsPatients with biopsy-proven amyloidosis underwent general work-up, echocardiography and 123I-MIBG scintigraphy. Left ventricular internal dimensions and wall thickness were measured, and highly refractile cardiac echoes (sparkling) were analysed. Early (15 min) and late (4 h) heart-to-mediastinum ratio (HMR) and wash-out rate were determined after administration of MIBG.ResultsIncluded in the study were 61 patients (30 women and 31 men; mean age 62 years; 39 AL, 11 AA, 11 ATTR). Echocardiographic parameters were not significantly different between the groups. Sparkling was present in 72 % of ATTR patients, in 54 % of AL patients and in 45 % of AA patients. Mean late HMR in all patients was 2.3 ± 0.75, and the mean wash-out rate was 8.6 ± 14 % (the latter not significantly different between the patient groups). Late HMR was significantly lower in patients with echocardiographic signs of amyloidosis than in patients without (2.0 ± 0.70 versus 2.8 ± 0.58, p < 0.001). Wash-out rates were significantly higher in these patients (−3.3 ± 9.9 % vs. 17 ± 10 %, p < 0.001). In ATTR patients without echocardiographic signs of amyloidosis, HMR was lower than in patients with the other types (2.0 ± 0.59 vs. 2.9 ± 0.50, p = 0.007).ConclusionMIBG HMR is lower and wash-out rate is higher in patients with echocardiographic signs of amyloidosis. Also, 123I-MIBG scintigraphy can detect cardiac denervation in ATTR patients before signs of amyloidosis are evident on echocardiography.

Nuclear imaging modalities for cardiac amyloidosis

“…The author concluded that 123 I-MIBG scintigraphy can detect cardiac denervation in ATTRm patients before signs of amyloidosis on echocardiogram. 37 The early detection of cardiac denervation with 123 I-MIBG in ATTRm FAP is important as sympathetic denervation occurs early in the disease and all current therapies under investigation, including liver transplantation, 38 are aimed at preventing disease progression and not removing pre-existing amyloid.…”

Nuclear imaging of cardiac amyloidosis. ‘We’ve only just begun’

“…1 123 I mIBG has been shown to identify cardiac sympathetic denervation that is known to occur in the early stages of ATTR-type amyloidosis. 16 For PET imaging, the most commonly used cardiac tracers include 11 C-PIB and 18 F-florbetapir. A pilot study by Antoni and colleagues showed obvious 11 C-PIB uptake in the LV wall of all 10 patients with cardiac amyloidosis (7 AL and 3 ATTR subtypes), whereas no LV uptake was seen in any of the 5 healthy controls.…”

Late onset cardiomyopathy as presenting sign of ATTR A45G amyloidosis caused by a novel TTR mutation (p.A65G)

“…2) [9]. 123 I-metaiodobenzylguanidine ( 123 I-MIBG) scintigraphy showed an increased washout (34%) and low heart-mediastinum ratio (late uptake 1.16) indicative of cardiac denervation [10]. A fine needle subcutaneous abdominal fat aspirate yielded a TTR concentration of amyloid in fat of 658-ng/mg fat tissue (Nb7.5 ng/mg) [6,7].…”