The Role of Scintigraphy with Bone Radiotracers in Cardiac Amyloidosis.

Cardiac amyloidosis (CA) is caused by the myocardial deposition of misfolded proteins, either amyloid transthyretin (ATTR) or immunoglobulin light chains (AL). The paradigm of this condition has transformed, since CA is increasingly recognized as a relatively prevalent cause of heart failure. Cardiac scintigraphy with bone tracers is the unique noninvasive technique able to confirm CA without performing tissue biopsy or advanced imaging tests. A moderate-to-intense myocardial uptake (Perugini grade ≥2) associated with the absence of a monoclonal component is greater than 99% specific for ATTR-CA, while AL-CA confirmation requires tissue biopsy.

The Role of Echocardiography for the Clinical Diagnosis, Risk Stratification, and Management of Cardiac Amyloidosis.

Amyloidosis is a rare, heterogeneous group of diseases characterized by extracellular infiltration and deposition of misfolded fibrils in different organs and tissues. A timely diagnosis is important as it can improve outcome. Echocardiography has emerged as a powerful tool to prompt suspicion and refer patients to second-level evaluation to reach a definitive diagnosis. In this scenario, new echo techniques offer new insight into the cardiac amyloidosis (CA) pathophysiology and clinical course. The present review aims to describe the developments in echocardiographic assessment of patients with suspected CA and it summarizes new available echocardiographic scores able to guide a definite diagnosis.

Cardiovascular Magnetic Resonance in the Management of Cardiac Amyloidosis: Current and Future Clinical Applications.

Cardiac magnetic resonance represents the gold standard imaging technique to assess cardiac volumes, wall thickness, mass, and systolic function but also to provide noninvasive myocardial tissue characterization across almost all cardiac diseases. In patients with cardiac amyloidosis, increased wall thickness of all heart chambers, a mildly reduced ejection fraction and occasionally pleural and pericardial effusion are the characteristic morphologic anomalies. The typical pattern after contrast injection is represented by diffuse areas of late gadolinium enhancement, which can be focal and patchy in very early stages, circumferential, and subendocardial in intermediate stages or even diffuse transmural in more advanced stages.

The Most Predictive Red Flags for Suspecting Cardiac Amyloidosis in Patients with Heart Failure with Preserved Ejection Fraction.

OBJECTIVE: Cardiac amyloidosis (CA) is a cardiomyopathy characterized by amyloid infiltration in the myocardium. Transthyretin cardiac amyloidosis (TTR-CA), commonly presenting as heart failure with preserved ejection fraction (HFpEF), was the focus of our study, which aimed to identify red flags that heighten suspicion of CA in HFpEF patients. METHODS: We prospectively included patients diagnosed with HFpEF. All patients were assessed for TTR-CA red flag features, cardiac and extra-cardiac, as outlined in the 'Diagnosis and Treatment of Cardiac Amyloidosis: A Position Statement of the European Society of Cardiology.' Technetium-99m pyrophosphate (99mTc-PYP) cardiac scintigraphy was performed in 167 HFpEF patients suspected of having TTR-CA. Patients testing positive and negative for TTR-CA were compared based on these red flag features. RESULTS: Out of 167 HFpEF patients, 19 (11.3%) were diagnosed with TTR-CA. In the TTR-CA group, 17 (89.5%) patients were 65 years or older. The presence of three or more red flags differentiated the TTR-CA positive and negative groups (P = 0.040). Features such as low voltage and pseudo infarct patterns were more prevalent in the TTR-CA group (P < 0.001 and P < 0.048, respectively). Left ventricular global longitudinal strain (LV-GLS) was lower in the TTR-CA positive group (P < 0.001). Multivariate analysis identified four variables-older age, pseudo infarct pattern, low/decreased QRS voltage, and LV-GLS-as strong, independent predictors of TTR-CA, with significant odds ratios (ORs) of 7.8, 6.8, 16.9, and 1.2, respectively. CONCLUSION: In this study, TTR-CA etiology occurs in approximately one in every ten HFpEF patients. The presence of three or more red flags increases the likelihood of TTR-CA. Older age, pseudo infarct pattern, low/decreased QRS voltage, and reduced LV-GLS are the most significant red flags indicating TTR-CA in HFpEF patients.

A Novel Approach to Cardiac Magnetic Resonance Scar Characterization in Patients Affected by Cardiac Amyloidosis: A Pilot Study.

Background and Objectives: Cardiac magnetic resonance (CMR) imaging has become an essential instrument in the study of cardiomyopathies; it has recently been integrated into the diagnostic workflow for cardiac amyloidosis (CA) with remarkable results. An additional emerging role is the stratification of the arrhythmogenic risk by scar analysis and the possibility of merging these data with electro-anatomical maps. This is made possible by using a software (ADAS 3D, Galgo Medical, Barcelona, Spain) able to provide 3D heart models by detecting fibrosis along the whole thickness of the myocardial walls. Little is known regarding the applications of this software in the wide spectrum of cardiomyopathies and the potential benefits have yet to be discovered. In this study, we tried to apply the ADAS 3D in the context of CA. Materials and Methods: This study was a retrospectively analysis of consecutive CMR imaging of patients affected by CA that were treated in our center (Marche University Hospital). Wherever possible, the data were processed with the ADAS 3D software and analyzed for a correlation between the morphometric parameters and follow-up events. The outcome was a composite of all-cause mortality, unplanned cardiovascular hospitalizations, sustained ventricular arrhythmias (VAs), permanent reduction in left ventricular ejection fraction, and pacemaker implantation. The secondary outcomes were the need for a pacemaker implantation and sustained VAs. Results: A total of 14 patients were deemed eligible for the software analysis: 8 patients with wild type transthyretin CA, 5 with light chain CA, and 1 with transthyretin hereditary CA. The vast majority of imaging features was not related to the composite outcome, but atrial wall thickening displayed a significant association with both the primary (p = 0.003) and the secondary outcome of pacemaker implantation (p = 0.003). The software was able to differentiate between core zones and border zones of scars, with the latter being the most extensively represented in all patients. Interestingly, in a huge percentage of CMR images, the software identified the highest degree of core zone fibrosis among the epicardial layers and, in those patients, we found a higher incidence of the primary outcome, without reaching statistical significance (p = 0.18). Channels were found in the scar zones in a substantial percentage of patients without a clear correlation with follow-up events. Conclusions: CMR imaging plays a pivotal role in cardiovascular diagnostics. Our analysis shows the feasibility and applicability of such instrument for all types of CA. We could not only differentiate between different layers of scars, but we were also able to identify the presence of fibrosis channels among the different scar zones. None of the data derived from the ADAS 3D software seemed to be related to cardiac events in the follow-up, but this might be imputable to the restricted number of patients enrolled in the study.

Light-Chain Cardiac Amyloidosis: Cardiac Magnetic Resonance for Assessing Response to Chemotherapy.

OBJECTIVE: Cardiac magnetic resonance (CMR) is a diagnostic tool that provides precise and reproducible information about cardiac structure, function, and tissue characterization, aiding in the monitoring of chemotherapy response in patients with light-chain cardiac amyloidosis (AL-CA). This study aimed to evaluate the feasibility of CMR in monitoring responses to chemotherapy in patients with AL-CA. MATERIALS AND METHODS: In this prospective study, we enrolled 111 patients with AL-CA (50.5% male; median age, 54 [interquartile range, 49-63] years). Patients underwent longitudinal monitoring using biomarkers and CMR imaging. At follow-up after chemotherapy, patients were categorized into superior and inferior response groups based on their hematological and cardiac laboratory responses to chemotherapy. Changes in CMR findings across therapies and differences between response groups were analyzed. RESULTS: Following chemotherapy (before vs. after), there were significant increases in myocardial T2 (43.6 ± 3.5 ms vs. 44.6 ± 4.1 ms; P = 0.008), recovery in right ventricular (RV) longitudinal strain (median of -9.6% vs. -11.7%; P = 0.031), and decrease in RV extracellular volume fraction (ECV) (median of 53.9% vs. 51.6%; P = 0.048). These changes were more pronounced in the superior-response group. Patients with superior cardiac laboratory response showed significantly greater reductions in RV ECV (-2.9% [interquartile range, -8.7%-1.1%] vs. 1.7% [-5.5%-7.1%]; P = 0.017) and left ventricular ECV (-2.0% [-6.0%-1.3%] vs. 2.0% [-3.0%-5.0%]; P = 0.01) compared with those with inferior response. CONCLUSION: Cardiac amyloid deposition can regress following chemotherapy in patients with AL-CA, particularly showing more prominent regression, possibly earlier, in the RV. CMR emerges as an effective tool for monitoring associated tissue characteristics and ventricular functional recovery in patients with AL-CA undergoing chemotherapy, thereby supporting its utility in treatment response assessment.

Bilateral Multiple Fractures Obstruct Quantitation of 99m Tc-Pyrophosphate Imaging for Cardiac Amyloidosis.

ABSTRACT: A 57-year-old woman who had persistent symptoms of transthyretin cardiac amyloidosis underwent 99m Tc-pyrophosphate ( 99m Tc-PYP) scintigraphy. The 99m Tc-PYP planar and SPECT/CT fusion image showed diffuse myocardial uptake and multiple fractures of the sternum and ribs. These fractures interfered with semiquantitative scores of 99m Tc-PYP uptake, leading to false positive in 99m Tc-PYP imaging.

Preclinical evaluation of Tc-99m p5+14 peptide for SPECT detection of cardiac amyloidosis.

INTRODUCTION: Amyloid deposition is a cause of restrictive cardiomyopathy. Patients who present with cardiac disease can be evaluated for transthyretin (TTR)-associated cardiac amyloidosis using nuclear imaging with 99mTc-labeled pyrophosphate (PYP); however, light chain-associated (AL) cardiac amyloid is generally not detected using this tracer. As an alternative, the amyloid-binding peptide p5+14 radiolabeled with iodine-124 has been shown to be an effective pan-amyloid radiotracer for PET/CT imaging. Here, a 99mTc-labeled form of p5+14 peptide has been prepared to facilitate SPECT/CT imaging of cardiac amyloidosis. METHOD: A synthesis method suitable for clinical applications has been used to prepare 99mTc-labeled p5+14 and tested for peptide purity, product bioactivity, radiochemical purity and stability. The product was compared with99mTc-PYP for cardiac SPECT/CT imaging in a mouse model of AA amyloidosis and for reactivity with human tissue sections from AL and TTR patients. RESULTS: The 99mTc p5+14 tracer was produced with >95% yields in radiopurity and bioactivity with no purification steps required and retained over 95% peptide purity and >90% bioactivity for >3 h. In mice, the tracer detected hepatosplenic AA amyloid as well as heart deposits with uptake ~5 fold higher than 99mTc-PYP. 99mTc p5+14 effectively bound human amyloid deposits in the liver, kidney and both AL- and ATTR cardiac amyloid in tissue sections in which 99mTc-PYP binding was not detectable. CONCLUSION: 99mTc-p5+14 was prepared in minutes in >20 mCi doses with good performance in preclinical studies making it suitable for clinical SPECT/CT imaging of cardiac amyloidosis.

Diagnosis and prognosis of abnormal cardiac scintigraphy uptake suggestive of cardiac amyloidosis using artificial intelligence: a retrospective, international, multicentre, cross-tracer development and validation study.

BACKGROUND: The diagnosis of cardiac amyloidosis can be established non-invasively by scintigraphy using bone-avid tracers, but visual assessment is subjective and can lead to misdiagnosis. We aimed to develop and validate an artificial intelligence (AI) system for standardised and reliable screening of cardiac amyloidosis-suggestive uptake and assess its prognostic value, using a multinational database of 99mTc-scintigraphy data across multiple tracers and scanners. METHODS: In this retrospective, international, multicentre, cross-tracer development and validation study, 16 241 patients with 19 401 scans were included from nine centres: one hospital in Austria (consecutive recruitment Jan 4, 2010, to Aug 19, 2020), five hospital sites in London, UK (consecutive recruitment Oct 1, 2014, to Sept 29, 2022), two centres in China (selected scans from Jan 1, 2021, to Oct 31, 2022), and one centre in Italy (selected scans from Jan 1, 2011, to May 23, 2023). The dataset included all patients referred to whole-body 99mTc-scintigraphy with an anterior view and all 99mTc-labelled tracers currently used to identify cardiac amyloidosis-suggestive uptake. Exclusion criteria were image acquisition at less than 2 h (99mTc-3,3-diphosphono-1,2-propanodicarboxylic acid, 99mTc-hydroxymethylene diphosphonate, and 99mTc-methylene diphosphonate) or less than 1 h (99mTc-pyrophosphate) after tracer injection and if patients' imaging and clinical data could not be linked. Ground truth annotation was derived from centralised core-lab consensus reading of at least three independent experts (CN, TT-W, and JN). An AI system for detection of cardiac amyloidosis-associated high-grade cardiac tracer uptake was developed using data from one centre (Austria) and independently validated in the remaining centres. A multicase, multireader study and a medical algorithmic audit were conducted to assess clinician performance compared with AI and to evaluate and correct failure modes. The system's prognostic value in predicting mortality was tested in the consecutively recruited cohorts using cox proportional hazards models for each cohort individually and for the combined cohorts. FINDINGS: The prevalence of cases positive for cardiac amyloidosis-suggestive uptake was 142 (2%) of 9176 patients in the Austrian, 125 (2%) of 6763 patients in the UK, 63 (62%) of 102 patients in the Chinese, and 103 (52%) of 200 patients in the Italian cohorts. In the Austrian cohort, cross-validation performance showed an area under the curve (AUC) of 1·000 (95% CI 1·000-1·000). Independent validation yielded AUCs of 0·997 (0·993-0·999) for the UK, 0·925 (0·871-0·971) for the Chinese, and 1·000 (0·999-1·000) for the Italian cohorts. In the multicase multireader study, five physicians disagreed in 22 (11%) of 200 cases (Fleiss' kappa 0·89), with a mean AUC of 0·946 (95% CI 0·924-0·967), which was inferior to AI (AUC 0·997 [0·991-1·000], p=0·0040). The medical algorithmic audit demonstrated the system's robustness across demographic factors, tracers, scanners, and centres. The AI's predictions were independently prognostic for overall mortality (adjusted hazard ratio 1·44 [95% CI 1·19-1·74], p<0·0001). INTERPRETATION: AI-based screening of cardiac amyloidosis-suggestive uptake in patients undergoing scintigraphy was reliable, eliminated inter-rater variability, and portended prognostic value, with potential implications for identification, referral, and management pathways. FUNDING: Pfizer.

18 F-Florbetapir PET/CT and 68 Ga-FAPI PET/CT in a Case of Light Chain Amyloidosis With Predominant Multiple Tumor-Like Deposits.

ABSTRACT: A 66-year-old man presented with multiple masses in different regions, including the left groin, back subcutaneous area, and lungs. Pathological examination confirmed localized amyloid deposits after 3 surgeries. Serum-free λ light chains were elevated. To evaluate systemic involvement, the patient underwent 18 F-Florbetapir PET/CT and 68 Ga-FAPI-04 PET/CT. Both scans showed increased uptake in multiple masses and nodules throughout the body. This report presents a rare case of light chain (AL) amyloidosis, primarily characterized by multiple localized tumor-like deposits with high activity on 18 F-Florbetapir PET/CT and 68 Ga-FAPI-04 PET/CT.

Cardiac MRI feature-tracking-derived torsion mechanics in systolic and diastolic dysfunction in systemic light-chain cardiac amyloidosis.

AIM: To describe the myocardial torsion mechanics in cardiac amyloidosis (CA), and evaluate the correlations between left ventricle (LV) torsion mechanics and conventional parameters using cardiac magnetic resonance imaging feature tracking (CMR-FT). MATERIALS AND METHODS: One hundred and thirty-nine patients with light-chain CA (AL-CA) were divided into three groups: group 1 with preserved systolic function (LV ejection fraction [LVEF] ≥50%, n=55), group 2 with mildly reduced systolic function (40% ≤ LVEF <50%, n=51), and group 3 with reduced systolic function (LVEF <40%, n=33), and compared with age- and gender-matched healthy controls (n=26). All patients underwent cine imaging and late gadolinium-enhancement (LGE). Cine images were analysed offline using CMR-FT to estimate torsion parameters. RESULTS: Global torsion, base-mid torsion, and peak diastolic torsion rate (diasTR) were significantly impaired in patients with preserved systolic function (p<0.05 for all), whereas mid-apex torsion and peak systolic torsion rate (sysTR) were preserved (p>0.05 for both) compared with healthy controls. In patients with mildly reduced systolic function, global torsion and base-mid torsion were lower compared to those with preserved systolic function (p<0.05 for both), while mid-apex torsion, sysTR, and diasTR were preserved (p>0.05 for all). In patients with reduced systolic function, only sysTR was significantly worse compared with mildly reduced systolic function (p<0.05). At multivariable analysis, right ventricle (RV) end-systolic volume RVESV index and NYHA class were independently related to global torsion, whereas LVEF was independently related to sysTR. RV ejection fraction (RVEF) was independently related to diasTR. LV global torsion performed well (AUC 0.71; 95% confidence interval [CI]: 0.61, 0.77) in discriminating transmural from non-transmural LGE in AL-CA patients. CONCLUSION: LV torsion mechanics derived by CMR-FT could help to monitor LV systolic and diastolic function in AL-CA patients and function as a new imaging marker for LV dysfunction and LGE transmurality.