Nuclear imaging modalities for cardiac amyloidosis

Abstract

Amyloidosis is a heterogeneous group of diseases characterized by localized or systemic deposition of insoluble extracellular fibrillary proteins in organs and tissues. Several types of amyloid can infiltrate the heart resulting in a restrictive cardiomyopathy, heart failure, and atrial and ventricular arrhythmias. Scintigraphy is a noninvasive method that may facilitate early diagnosis, distinguish various forms of cardiac amyloid, and may be useful in following disease burden. The amyloid-specific tracers presented in this article have been used with planar imaging and/or single-photon emission computed tomography. To date, there are no approved cardiac amyloid tracers although investigational tracers are currently under examination. This article serves to review the current nuclear imaging modalities available in the detection of cardiac amyloid.

Usefulness of99mTc-HDP scintigraphy in the diagnosis of suspected cardiac amyloidosis revealed by heart failure: A case report of an amyloidogenic transthyretin mutation and literature review

“…TTR is a transport protein primarily expressed by the liver and circulates as homotetramer; under genetic mutation or aging, tetramers dissociate to monomers leading to amyloid fibrils [2]. Aggregate autopsy data show presence of wild-type TTR in 25-30% of hearts, leading to cardiac dysfunction in a smaller but significant elderly population [2,4]. As for variant TTR more than 80 mutations have been described [1].…”

“…V122I TTR variant is one of the most widespread with a population prevalence of 4% in AfroCaribbeans [2,4]. Its diagnosis has to be confirmed by the immunohistochemical demonstration of amyloidogenic TTR-form on a biopsy specimen and by the presence of an ATTR mutation on protein/DNA analysis [2][3][4]. However myocardial biopsy is not often performed in practice because it is invasive, results are late with the possibility of false-negatives.…”

Improving strategies for the diagnosis of cardiac amyloidosis

“…Other phosphate derivatives tagged with 99mTc, including 99mTc pyrophosphate, 99mTc-methylene diphosphonate and 99mTc-aprotinin have been developed (reviewed in [115]) but their incremental diagnostic value is unknown since there has been no 'head-to-head' comparison of these agents. Other tracers studied more recently in amyloidosis include 123 I-metaiodobenzylguanidine, which is a norepinephrine analog used to identify early sympathetic denervation in patients with mt-ATTR while the myocardium is still viable and before clinical heart disease or echocardiographic changes set in [116,117].…”

Non-invasive imaging for cardiac amyloidosis — Delaying the obvious?

“…As worsening renal function precluded a cardiac magnetic resonance (CMR), a 99m technetium (Tc)-pyrophosphate scan was performed to differentiate between ATTR and AL amyloidosis. This showed increased uptake of the radiotracer in the heart compared to the chest at a ratio of 1.67, implying ATTR amyloidosis [1,2] (Fig. 1A).…”