Significance of 11C-PIB PET/CT in cardiac amyloidosis compared with 99mTc-aprotinin scintigraphy: A pilot study

The flutemetamol analogue cyano-flutemetamol detects myocardial AL and ATTR amyloid deposits: a post-mortem histofluorescence analysis

BACKGROUND

[18F]flutemetamol is a PET radioligand used to image brain amyloid, but its detection of myocardial amyloid is not well-characterized. This histological study characterized binding of fluorescently labeled flutemetamol (cyano-flutemetamol) to amyloid deposits in myocardium.

METHODS

Myocardial tissue was obtained post-mortem from 29 subjects with cardiac amyloidosis including transthyretin wild-type (ATTRwt), hereditary/variant transthyretin (ATTRv) and immunoglobulin light-chain (AL) types, and from 10 cardiac amyloid-free controls. Most subjects had antemortem electrocardiography, echocardiography, SPECT and cardiac MRI. Cyano-flutemetamol labeling patterns and integrated density values were evaluated relative to fluorescent derivatives of Congo red (X-34) and Pittsburgh compound-B (cyano-PiB).

RESULTS

Cyano-flutemetamol labeling was not detectable in control subjects. In subjects with cardiac amyloidosis, cyano-flutemetamol labeling matched X-34- and cyano-PiB-labeled, and transthyretin- or lambda light chain-immunoreactive, amyloid deposits and was prevented by formic acid pre-treatment of myocardial sections. Cyano-flutemetamol mean fluorescence intensity, when adjusted for X-34 signal, was higher in the ATTRwt than the AL group. Cyano-flutemetamol integrated density correlated strongly with echocardiography measures of ventricular septal thickness and posterior wall thickness, and with heart mass.

CONCLUSION

The high selectivity of cyano-flutemetamol binding to myocardial amyloid supports the diagnostic utility of [18F]flutemetamol PET imaging in patients with ATTR and AL types of cardiac amyloidosis.

Independent Prognostic Utility of 11C-Pittsburgh Compound B PET in Patients with Light-Chain Cardiac Amyloidosis

¹¹C-Pittsburgh compound B (PiB) PET/CT visualizes the amount of myocardial amyloid deposit and can be used to prognosticate patients with amyloid light-chain (AL) cardiac amyloidosis (CA). However, whether ¹¹C-PiB PET/CT has any independent additional prognostic value beyond the commonly used biomarkers remains unknown. Methods: This prospective study was on a cohort of 58 consecutive patients with AL CA who underwent ¹¹C-PiB PET/CT. The patients were stratified into 2 groups on the basis of a visual assessment of whether there was myocardial ¹¹C-PiB uptake on PET/CT. The primary endpoint was 1-y overall mortality. The independent prognostic utility of ¹¹C-PiB PET/CT was analyzed using net reclassification improvement and integrated discrimination improvement. Results: Among the 58 patients enrolled, 35 were positive for myocardial ¹¹C-PiB uptake on PET/CT. Patients with myocardial ¹¹C-PiB PET uptake had a worse 1-y overall survival rate than those without (81.8% vs. 45.5%, P = 0.003 by log-rank test). In the multivariate analysis, positivity for myocardial ¹¹C-PiB uptake on PET/CT was an independent predictor of 1-y mortality (adjusted hazard ratio, 3.382; 95% CI, 1.011-11.316; P = 0.048). In analysis of 3 subgroups of patients-those with a troponin I level of at least 0.1 ng/mL, those with an N-terminal pro-B-type natriuretic peptide (NT-proBNP) level of at least 1,800 pg/mL, and those with a difference of at least 180 mg/L between free light chains (the 3 commonly used biomarkers and their thresholds for staging in AL amyloidosis)-Kaplan-Meier curves showed for all 3 subgroups that patients positive for myocardial ¹¹C-PiB uptake on PET/CT had a worse prognosis than those who were negative. Additionally, when the results of ¹¹C-PiB PET/CT were added to these 3 biomarkers, the performance of 1-y mortality prediction significantly improved by net reclassification improvement (troponin I, 0.861; NT-proBNP, 0.914; difference between free light chains, 0.987) and by integrated discrimination improvement (0.200, 0.156, and 0.108, respectively). Conclusion:¹¹C-PiB PET/CT is a strong independent predictor of 1-y overall mortality and provides incremental prognostic benefits beyond the 3 commonly used biomarkers of AL amyloidosis staging. Considering the recent development of numerous amyloid-targeting molecular imaging agents, further investigations are warranted on whether PET/CT should be included in risk stratification for patients with AL CA.

A Narrative Review of 99mTc-Aprotinin in the Diagnosis of Cardiac Amyloidosis and a New Life for an Unfairly Abandoned Drug

Several studies investigated the use of 99mTc-labelled Aprotinin as an amyloid seeker some years ago. In vitro tests showed high binding affinity for several types of amyloid fibrils accompanied by an excellent specificity. Initial human studies demonstrated good accuracy in detecting cardiac involvement. Scintigraphy results were confirmed in a group of 28 endomyocardial biopsies. Unfortunately, clinical studies were halted because of a temporary suspension of the vector protein (Trasylol) and public health concerns over prion contamination of the bovine origin compound. To obviate these limitations, efforts have been made to label a recombinant Aprotinin with 99mTc, which exhibits the same affinity for h-insulin fibrils. With the aim of developing a PET tracer, the same recombinant protein was labeled with Gallium. The introduction of a bifunctional chelator did not affect fibril affinity. Finally, a synthetic peptidic fragment, the cyclic 30-51 SS, was synthetized. After direct technetium labeling, an impressive increase in affinity was demonstrated. This peptide appears to be a potential candidate for Gallium labeling through a bifunctional chelator for PET imaging.

Diagnostic performance of CMR, SPECT, and PET imaging for the detection of cardiac amyloidosis: a meta-analysis

Background

Noninvasive myocardial imaging modalities, such as cardiac magnetic resonance (CMR), single photon emission computed tomography (SPECT), and Positron emission tomography (PET), are well-established and extensively used to detect cardiac amyloid (CA). The purpose of this study is to directly compare CMR, SPECT, and PET scans in the diagnosis of CA, and to provide evidence for further scientific research and clinical decision-making.

Methods

PubMed, Embase, and Cochrane Library were searched. Studies used CMR, SPECT and/or PET for the diagnosis of CA were included. Pooled sensitivity, specificity, positive and negative likelihood ratio (LR), diagnostic odds ratio (DOR), their respective 95% confidence intervals (CIs) and the area under the summary receiver operating characteristic (SROC) curve (AUC) were calculated. Quality assessment of included studies was conducted.

Results

A total of 31 articles were identified for inclusion in this meta-analysis. The pooled sensitivities of CMR, SPECT and PET were 0.84, 0.98 and 0.78, respectively. Their respective overall specificities were 0.87, 0.92 and 0.95. Subgroup analysis demonstrated that ^99mTc-HMDP manifested the highest sensitivity (0.99). ^99mTc-PYP had the highest specificity (0.95). The AUC values of ^99mTc-DPD, ^99mTc-PYP, ^99mTc-HMDP were 0.89, 0.99, and 0.99, respectively. PET scan with ¹¹C-PIB demonstrated a pooled sensitivity of 0.91 and specificity of 0.97 with an AUC value of 0.98.

Conclusion

Our meta-analysis reveals that SEPCT scans present better diagnostic performance for the identification of CA as compared with other two modalities.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12872-021-02292-z.

Review of cardiovascular imaging in the Journal of Nuclear Cardiology 2020: positron emission tomography, computed tomography, and magnetic resonance

Although the year 2020 was different from other years in many respects, the Journal of Nuclear Cardiology published excellent articles pertaining to imaging in patients with cardiovascular disease due to the dedication of the investigators in our field all over the world. In this review, we will summarize a selection of these articles to provide a concise review of the main advancements that have recently occurred in the field and provide the reader with an opportunity to review a wide selection of articles. We will focus on publications dealing with positron emission tomography, computed tomography, and magnetic resonance and hope that you will find this review helpful.

Procedural recommendations of cardiac PET/CT imaging: standardization in inflammatory-, infective-, infiltrative-, and innervation (4Is)-related cardiovascular diseases: a joint collaboration of the EACVI and the EANM

With this document, we provide a standard for PET/(diagnostic) CT imaging procedures in cardiovascular diseases that are inflammatory, infective, infiltrative, or associated with dysfunctional innervation (4Is). This standard should be applied in clinical practice and integrated in clinical (multicenter) trials for optimal procedural standardization. A major focus is put on procedures using [¹⁸F]FDG, but 4Is PET radiopharmaceuticals beyond [¹⁸F]FDG are also described in this document. Whilst these novel tracers are currently mainly applied in early clinical trials, some multicenter trials are underway and we foresee in the near future their use in clinical care and inclusion in the clinical guidelines. Finally, PET/MR applications in 4Is cardiovascular diseases are also briefly described. Diagnosis and management of 4Is-related cardiovascular diseases are generally complex and often require a multidisciplinary approach by a team of experts. The new standards described herein should be applied when using PET/CT and PET/MR, within a multimodality imaging framework both in clinical practice and in clinical trials for 4Is cardiovascular indications.

Diagnostic performance of PET for detection of cardiac amyloidosis: A systematic review and meta-analysis

OBJECTIVES

The purpose of the current investigation was to evaluate the diagnostic accuracy of amyloid and F-18 sodium fluoride (NaF) positron emission tomography/computed tomography (PET/CT) for the detection of cardiac amyloidosis (CA) using diagnostic accuracy test.

MATERIALS AND METHODS

The PubMed, Cochrane, and EMBASE database, from the earliest available date of indexing through February 29, 2020, were searched for results investigating the diagnostic accuracy of amyloid and F-18 NaF PET for the diagnosis of CA. We calculated the pooled sensitivities and specificities of included studies, calculated positive and negative likelihood ratios (LR+ and LR-), and obtained summary receiver operating characteristic (SROC) curves.

RESULTS

Across 13 studies with 14 results (90 patients), the pooled sensitivity of amyloid PET was 0.97 and a pooled specificity was 0.98. The pooled sensitivity of F-18 NaF PET was 0.63 and a pooled specificity was 1.00. The pooled sensitivity of combined amyloid and F-18 NaF PET was 0.88 and a pooled specificity was 0.98.

CONCLUSION

Amyloid PET has a high sensitivity and specificity for the detection of CA. However, F-18 NaF PET showed relatively low sensitivity with high specificity. At present, the literature regarding the use of amyloid and F-18 NaF PET for diagnosis of CA is still limited; thus, further large multicenter studies would be necessary to substantiate the diagnostic accuracy of amyloid and F-18 NaF PET for detection of CA.