Utility and limitations of 3,3-diphosphono-1,2-propanodicarboxylic acid scintigraphy in systemic amyloidosis

"Loss of Bone Signal" on 99m Tc-Labeled Pyrophosphate Scintigraphy in a Patient With Wild-Type Transthyretin Amyloidosis

ABSTRACT

99m Tc-3,3-diphosphono-1,2-propanedicarboxylic acid (DPD) scintigraphy and 99m Tc-pyrophosphate (PYP) scintigraphy are highly sensitive modalities for imaging both myocardial and extracardiac amyloid transthyretin in patients with wild-type transthyretin (ATTRwt) amyloidosis. "Loss of bone signal" on planar imaging of 99m Tc-DPD scintigraphy, in which the tracer uptake in bone is obscured by marked tracer uptake in the overlying skeletal muscles, is reported. However, this phenomenon has not yet been documented on 99m Tc-PYP scintigraphy. We describe an 89-year-old woman with ATTRwt amyloidosis in whom "loss of bone signal" together with marked tracer uptake into the skeletal muscles was clearly demonstrated on 99m Tc-PYP scan.

Deep Learning-Enabled Quantification of 99mTc-Pyrophosphate SPECT/CT for Cardiac Amyloidosis

Transthyretin cardiac amyloidosis (ATTR CA) is increasingly recognized as a cause of heart failure in older patients, with 99mTc-pyrophosphate imaging frequently used to establish the diagnosis. Visual interpretation of SPECT images is the gold standard for interpretation but is inherently subjective. Manual quantitation of SPECT myocardial 99mTc-pyrophosphate activity is time-consuming and not performed clinically. We evaluated a deep learning approach for fully automated volumetric quantitation of 99mTc-pyrophosphate using segmentation of coregistered anatomic structures from CT attenuation maps. Methods: Patients who underwent SPECT/CT 99mTc-pyrophosphate imaging for suspected ATTR CA were included. Diagnosis of ATTR CA was determined using standard criteria. Cardiac chambers and myocardium were segmented from CT attenuation maps using a foundational deep learning model and then applied to attenuation-corrected SPECT images to quantify radiotracer activity. We evaluated the diagnostic accuracy of target-to-background ratio (TBR), cardiac pyrophosphate activity (CPA), and volume of involvement (VOI) using the area under the receiver operating characteristic curve (AUC). We then evaluated associations with the composite outcome of cardiovascular death or heart failure hospitalization. Results: In total, 299 patients were included (median age, 76 y), with ATTR CA diagnosed in 83 (27.8%) patients. CPA (AUC, 0.989; 95% CI, 0.974-1.00) and VOI (AUC, 0.988; 95% CI, 0.973-1.00) had the highest prediction performance for ATTR CA. The next highest AUC was for TBR (AUC, 0.979; 95% CI, 0.964-0.995). The AUC for CPA was significantly higher than that for heart-to-contralateral ratio (AUC, 0.975; 95% CI, 0.952-0.998; P = 0.046). Twenty-three patients with ATTR CA experienced cardiovascular death or heart failure hospitalization. All methods for establishing TBR, CPA, and VOI were associated with an increased risk of events after adjustment for age, with hazard ratios ranging from 1.41 to 1.84 per SD increase. Conclusion: Deep learning segmentation of coregistered CT attenuation maps is not affected by the pattern of radiotracer uptake and allows for fully automatic quantification of hot-spot SPECT imaging such as 99mTc-pyrophosphate. This approach can be used to accurately identify patients with ATTR CA and may play a role in risk prediction.

Breakthrough advances enhancing care in ATTR amyloid cardiomyopathy

Transthyretin amyloid cardiomyopathy (ATTR-CM) has been traditionally considered a rare and inexorably fatal condition. ATTR-CM now is an increasingly recognized cause of heart failure (HF) and mortality worldwide with effective pharmacological treatments. Advances in non-invasive diagnosis, coupled with the development of effective treatments, have transformed the diagnosis of ATTR-CM, which is now possible without recourse to endomyocardial biopsy in ≈70 % of cases. Many patients are now diagnosed at an earlier stage. Echocardiography and cardiac magnetic resonance have enabled identification of patients with possible ATTR-CM and more accurate prognostic stratification. Although radionuclide scintigraphy with 'bone' tracers has an established diagnostic value, the diagnostic performance of the bone tracers validated for non-invasive confirmation of ATTR-CM may not be equal. Characterising the wider clinical phenotype of patients with ATTR-CM has enabled identification of features with potential for earlier diagnosis such as carpal tunnel syndrome. Therapies able to slow or halt ATTR-CM progression and increase survival are now available and there is also evidence that patients may benefit from specific conventional HF medications. Cutting-edge research in the field of antibody-mediated removal of ATTR deposits compellingly suggest that ATTR-CM is a truly reversible disorder, bringing hope for patients even with advanced disease. A wide horizon of possibilities is unfolding and awaits discovery.

How Artificial Intelligence Can Enhance the Diagnosis of Cardiac Amyloidosis: A Review of Recent Advances and Challenges

Cardiac amyloidosis (CA) is an underdiagnosed form of infiltrative cardiomyopathy caused by abnormal amyloid fibrils deposited extracellularly in the myocardium and cardiac structures. There can be high variability in its clinical manifestations, and diagnosing CA requires expertise and often thorough evaluation; as such, the diagnosis of CA can be challenging and is often delayed. The application of artificial intelligence (AI) to different diagnostic modalities is rapidly expanding and transforming cardiovascular medicine. Advanced AI methods such as deep-learning convolutional neural networks (CNNs) may enhance the diagnostic process for CA by identifying patients at higher risk and potentially expediting the diagnosis of CA. In this review, we summarize the current state of AI applications to different diagnostic modalities used for the evaluation of CA, including their diagnostic and prognostic potential, and current challenges and limitations.

Clinical and Prognostic Implications of Right Ventricular Uptake on Bone Scintigraphy in Transthyretin Amyloid Cardiomyopathy

BACKGROUND

The extent of myocardial bone tracer uptake with technetium pyrophosphate, hydroxymethylene diphosphonate, and 3,3-diphosphono-1,2-propanodicarboxylate in transthyretin amyloid cardiomyopathy (ATTR-CM) might reflect cardiac amyloid burden and be associated with outcome.

METHODS

Consecutive patients with ATTR-CM who underwent diagnostic bone tracer scintigraphy with acquisition of whole-body planar and cardiac single-photon emission computed tomography (SPECT) images from the National Amyloidosis Centre and 4 Italian centers were included. Cardiac uptake was defined according to the Perugini classification: 0=absent cardiac uptake; 1=mild uptake less than bone; 2=moderate uptake equal to bone; and 3=high uptake greater than bone. Extent of right ventricular (RV) uptake was defined as focal (basal segment of the RV free wall only) or diffuse (extending beyond basal segment) on the basis of SPECT imaging. The primary outcome was all-cause mortality.

RESULTS

Among 1422 patients with ATTR-CM, RV uptake accompanying left ventricular uptake was identified by SPECT imaging in 100% of cases at diagnosis. Median follow-up in the whole cohort was 34 months (interquartile range, 21 to 50 months), and 494 patients died. By Kaplan-Meier analysis, diffuse RV uptake on SPECT imaging (n=936) was associated with higher all-cause mortality compared with focal (n=486) RV uptake (77.9% versus 22.1%; P<0.001), whereas Perugini grade was not associated with survival (P=0.27 in grade 2 versus grade 3). On multivariable analysis, after adjustment for age at diagnosis (hazard ratio [HR], 1.03 [95% CI, 1.02-1.04]; P<0.001), presence of the p.(V142I) TTR variant (HR, 1.42 [95% CI, 1.20-1.81]; P=0.004), National Amyloidosis Centre stage (each category, P<0.001), stroke volume index (HR, 0.99 [95% CI, 0.97-0.99]; P=0.043), E/e' (HR, 1.02 [95% CI, 1.007-1.03]; P=0.004), right atrial area index (HR, 1.05 [95% CI, 1.02-1.08]; P=0.001), and left ventricular global longitudinal strain (HR, 1.06 [95% CI, 1.03-1.09]; P<0.001), diffuse RV uptake on SPECT imaging (HR, 1.60 [95% CI, 1.26-2.04]; P<0.001) remained an independent predictor of all-cause mortality. The prognostic value of diffuse RV uptake was maintained across each National Amyloidosis Centre stage and in both wild-type and hereditary ATTR-CM (P<0.001 and P=0.02, respectively).

CONCLUSIONS

Diffuse RV uptake of bone tracer on SPECT imaging is associated with poor outcomes in patients with ATTR-CM and is an independent prognostic marker at diagnosis.

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.

Technetium-99m-pyrophosphate imaging-based computed tomography-guided core-needle biopsy of internal oblique muscle in wild-type transthyretin cardiac amyloidosis

BACKGROUND

Technetium-99m-pyrophosphate (99mTc-PYP) uptake in the internal oblique muscle (IOM), which is often observed in patients with wild-type transthyretin cardiac amyloidosis (ATTR-CA), indicates amyloid transthyretin (ATTR) deposition.

OBJECTIVE

This study aimed to assess the safety and efficacy of 99mTc-PYP imaging-based computed tomography (CT)-guided core-needle biopsy of the IOM as a new extracardiac screening biopsy for confirming the presence of ATTR deposits.

METHODS

Patients with suspected ATTR-CA in whom myocardial tracer uptake was detected on chest- and abdomen-centered images of 99mTc-PYP scintigraphy underwent CT-guided core-needle biopsy at the site with the highest tracer uptake in the IOM between September 2021 and November 2022.

RESULTS

All 18 consecutive patients (mean age, 86.3 years ± 6.5; 61.1% male) enrolled in the study showed 99mTc-PYP uptake into the IOM. Adequate tissue samples were obtained from all patients except one without serious complications. Immunohistochemical analysis confirmed ATTR deposits in 16/18 (88.9%) patients. In the remaining two patients, ATTR deposits were observed via endomyocardial biopsy. All patients were diagnosed with wild-type ATTR-CA based on transthyretin gene sequence testing results.

CONCLUSION

In wild-type ATTR-CA, 99mTc-PYP imaging-based CT-guided core-needle biopsy of the IOM could be used as an extracardiac screening biopsy to confirm the presence of ATTR deposits.

Deep phenotyping of p.(V142I)-associated variant transthyretin amyloid cardiomyopathy: Distinct from wild-type transthyretin amyloidosis?

AIMS

Transthyretin amyloid cardiomyopathy (ATTR-CM) is an increasingly recognized cause of heart failure. A total of 3-4% of individuals of African descent carry a TTR gene mutation encoding the p.(V142I) variant, a powerful risk factor for development of variant ATTR-CM (ATTRv-CM); this equates to 1.6 million carriers in the United States. We undertook deep phenotyping of p.(V142I)-ATTRv-CM and comparison with wild-type ATTR-CM (ATTRwt-CM).

METHODS AND RESULTS

A retrospective study of 413 patients with p.(V142I) ATTRv-CM who attended the UK National Amyloidosis Centre (NAC) was conducted. Patients underwent evaluation at time of diagnosis, including clinical, echocardiography, and biomarker analysis; a subgroup had cardiac magnetic resonance (CMR) imaging. A total of 413 patients with ATTRwt-CM, matched for independent predictors of prognosis (age, NAC Stage, decade of first presentation), were used as a comparator group. At time of diagnosis, patients with ATTRv-CM had significant functional impairment by New York Heart Association classification (NHYA class ≥ III; 38%) and 6-min walk test distance (median 276 m). Median 5-year survival in ATTRv-CM patients was 31 versus 59 months in matched patients with ATTRwt-CM (p < 0.001). Patients with ATTRv-CM had significant impairment of functional parameters by echocardiography including biventricular impairment, high burden of regurgitant valvular disease and low cardiac output. Multivariable analysis revealed the prognostic importance of right ventricular dysfunction. CMR and histological analysis revealed myocyte atrophy and widespread myocardial infiltration in ATTRv-CM.

CONCLUSION

p.(V142I)-ATTRv-CM has an aggressive phenotype characterized by myocyte loss and widespread myocardial infiltration which may account for frequent biventricular failure and poor prognosis in this ATTR-CM genotypic subgroup.

Optimizing cardiac amyloidosis assessment: utility of 1-h and 3-h 99mTc-PYP imaging

BACKGROUND

Transthyretin amyloid cardiomyopathy (ATTR-CM), characterized by the extracellular deposition of an insoluble amyloid protein in the heart, is one of the main causes of heart failure in elderly patients. In this study, our primary objective was to explore the diverse applications and temporal significance of 1-h and 3-h imaging using 99mTc-PYP in the context of ATTR-CM. Additionally, we compared tracer kinetics in the heart and bone to comprehensively assess the diagnostic advantages and time-related considerations associated with these two incubation periods.

METHODS

Twenty-seven patients at Nagasaki University Hospital who underwent 99mTc-PYP planar, and SPECT cardiac imaging were classified into two groups (ATTR-CM-positive and -negative groups) based on the American Heart Association statement. Cardiac retention was assessed with both a semiquantitative visual score and a quantitative analysis. To assess bone accumulation, a ROI with an equal volume was drawn on the sternum and calculated as the bone-to-contralateral ratio (B/CL). We also evaluated correlation between heart-to-contralateral lung (H/CL) ratio and left ventricular wall thickness.

RESULTS

Among patients who underwent 99mTc-PYP imaging, the H/CL ratio was significantly higher at 1 h than at 3 h regardless of the group (from 2.20 ± 0.36 to 1.99 ± 0.35, p < 0.01 in the positive group and from 1.35 ± 0.12 to 1.19 ± 0.21, p = 0.01 in the negative group). The gap of H/CL between highest H/CL of negative case and lowest H/CL of positive case was narrower in 3 h. On the other hand, correlation between H/CL and left ventricular posterior wall thickness tends to be clearer in 3 h (p = 0.12, r = 0.30 for 1 h, p = 0.04, r = 0.39 at 3 h).

CONCLUSION

Our study suggests that both 1-h and 3-h incubation times for 99mTc-PYP imaging have different benefits for ATTR cardiac amyloidosis. A one-hour incubation may be preferable for differential diagnostic purposes, while a three-hour incubation may provide greater utility in evaluating disease severity.

Monitoring cardiac amyloidosis with multimodality imaging

Cardiac amyloidosis (CA) refers to an infiltrative process involving amyloid fibril deposition in the myocardium causing restrictive cardiomyopathy. While various types can affect the heart, the predominant forms are immunoglobulin light-chain (AL) amyloidosis and transthyretin (ATTR) amyloidosis. This review article explores the expanding field of imaging techniques used to diagnose AL-CA and ATTR-CA, highlighting their usefulness in prognostication and disease surveillance. Echocardiography is often the initial imaging modality to suspect CA and, since the incorporation of nonbiopsy criteria using bone scintigraphy, diagnosing ATTR-CA has become more attainable following exclusion of plasma cell dyscrasia. Cardiac magnetic resonance is progressively emerging as a vital tool for imaging CA, and is used in diagnosis, prognostication, and disease surveillance. The use of cardiac magnetic resonance in AL-CA is discussed, as it has been shown to accurately evaluate organ response to chemotherapy. As novel drug treatments emerge in the realm of ATTR-CA, the use of cardiovascular imaging surveillance to monitor disease progression is discussed, as it is gaining prominence as a critical consideration. The ongoing phase III trials investigating treatments for patients with ATTR-CA, will undoubtedly enhance our understanding of cardiac imaging surveillance.

Emerging Role of Scintigraphy Using Bone-Seeking Tracers for Diagnosis of Cardiac Amyloidosis: AJR Expert Panel Narrative Review

Amyloidoses are a complex group of clinical diseases that result from progressive organ dysfunction due to extracellular protein misfolding and deposition. The two most common types of cardiac amyloidosis are transthyretin amyloidosis (ATTR) and light-chain (AL) amyloidosis. Diagnosis of ATTR cardiomyopathy (ATTR-CM) is challenging owing to its phenotypic similarity to other more common cardiac conditions, the perceived rarity of the disease, and unfamiliarity with its diagnostic algorithms; endomyocardial biopsy was historically required for diagnosis. However, myocardial scintigraphy using bone-seeking tracers has shown high accuracy for detection of ATTR-CM and has become a key noninvasive diagnostic test for the condition, receiving support from professional society guidelines and transforming prior diagnostic paradigms. This AJR Expert Panel Narrative Review describes the role of myocardial scintigraphy using bone-seeking tracers in the diagnosis of ATTR-CM. The article summarizes available tracers, acquisition techniques, interpretation and reporting considerations, diagnostic pitfalls, and gaps in the current literature. The critical need for monoclonal testing of patients with positive scintigraphy results to differentiate ATTR-CM from AL cardiac amyloidosis is highlighted. Recent updates in guideline recommendations that emphasize the importance of a qualitative visual assessment are also discussed.

Lights and Shadows of Clinical Applications of Cardiac Scintigraphy with Bone Tracers in Suspected Amyloidosis

Radionuclide bone scintigraphy is the cornerstone of an imaging-based algorithm for accurate non-invasive diagnosis of transthyretin cardiac amyloidosis (ATTR-CA). In patients with heart failure and suggestive echocardiographic and/or cardiac magnetic resonance imaging findings, the positive predictive value of Perugini grade 2 or 3 myocardial uptake on a radionuclide bone scan approaches 100% for the diagnosis of ATTR-CA as long as there is no biochemical evidence of a clonal dyscrasia. The technetium-labelled tracers that are currently validated for non-invasive diagnosis of ATTR-CA include pyrophosphate (99mTc-PYP); hydroxymethylene diphosphonate (99mTc-HMDP); and 3,3-diphosphono-1,2-propanodicarboxylate (99mTc-DPD). Although nuclear scintigraphy has transformed the contemporary diagnostic approach to ATTR-CA, a number of grey areas remains, including the mechanism for binding tracers to the infiltrated heart, differences in the kinetics and distribution of these radiotracers, differences in protocols of image acquisition worldwide, the clinical significance of extra-cardiac uptake, and the use of this technique for prognostic stratification, monitoring disease progression and assessing the response to disease-modifying treatments. This review will deal with the most relevant unmet needs and clinical questions concerning scintigraphy with bone tracers in ATTR-CA, providing expert opinions on possible future developments in the clinical application of these radiotracers in order to offer practical information for the interpretation of nuclear images by physicians involved in the care of patients with this ATTR-CA.

Prevalence and significance of extracardiac uptake on pyrophosphate imaging in the SCAN-MP study: the first 379 cases

INTRODUCTION

Technetium-labeled bone-avid radiotracers can be used to diagnose transthyretin cardiac amyloidosis (ATTR-CA). Extracardiac uptake of technetium pyrophosphate (Tc-99m PYP) in this context has not been extensively explored and its significance is not well characterized. We assessed extracardiac Tc-99m PYP uptake in individuals undergoing nuclear scintigraphy and the extent of clinically actionable findings.

METHODS

The Screening for Cardiac Amyloidosis with Nuclear Imaging in Minority Populations (SCAN-MP) study utilizes Tc-99m PYP imaging to identify ATTR-CA in self-identified Black and Caribbean Hispanic participants ≥ 60 years old with heart failure. We characterized the distribution of extracardiac uptake, including stratification of findings by timing of scan (1 hour vs 3 hours after Tc-99m PYP administration) and noted any additional testing in these subjects.

RESULTS

Of 379 participants, 195 (51%) were male, 306 (81%) Black race, and 120 (32%) Hispanic ethnicity; mean age was 73 years. Extracardiac Tc-99m PYP uptake was found in 42 subjects (11.1%): 21 with renal uptake only, 14 with bone uptake only, 4 with both renal and bone uptake, 2 with breast uptake, and 1 with thyroid uptake. Extracardiac uptake was more common in subjects with Tc-99m PYP scans at 1 hour (23.8%) than at 3 hours (6.2%). Overall, four individuals (1.1%) had clinically actionable findings.

CONCLUSION

Extracardiac Tc-99m PYP uptake manifested in about 1 in 9 SCAN-MP subjects but was clinically actionable in only 1.1% of cases.

Diagnostic accuracy of bone scintigraphy imaging for transthyretin cardiac amyloidosis: systematic review and meta-analysis

BACKGROUND

Bone scintigraphy imaging is frequently used to investigate patients with suspected transthyretin cardiac amyloidosis (ATTR-CM). However, the reported accuracy for interpretation approaches has changed over time. We performed a systematic review and meta-analysis to determine the diagnostic accuracy of visual planar grading, heart-to-contralateral (HCL) ratio, and quantitative analysis of SPECT imaging and evaluate reasons for shifts in reported accuracy.

METHODS

We performed a systematic review to identify studies of the diagnostic accuracy of bone scintigraphy for ATTR-CM from 1990 until February 2023 using PUBMED and EMBASE. Studies were reviewed separately by two authors for inclusion and for risk of bias assessment. Summary receiver operating characteristic curves and operating points were determined with hierarchical modeling.

RESULTS

Out of a total of 428 identified studies, 119 were reviewed in detail and 23 were included in the final analysis. The studies included a total of 3954 patients, with ATTR-CM diagnosed in 1337 (39.6%) patients and prevalence ranging from 21 to 73%. Visual planar grading and quantitative analysis had higher diagnostic accuracy (.99) than HCL ratio (.96). Quantitative analysis of SPECT imaging had the highest specificity (97%) followed by planar visual grade (96%) and HCL ratio (93%). ATTR-CM prevalence accounted for some of the observed between study heterogeneity.

CONCLUSIONS

Bone scintigraphy imaging is highly accurate for identifying patients with ATTR-CM, with between study heterogeneity in part explained by differences in disease prevalence. We identified small differences in specificity, which may have important clinical implications when applied to low-risk screening populations.

Randall-Type Monoclonal Immunoglobulin Deposition Disease in Bone Scintigraphy

ABSTRACT

Bone scintigraphy is recognized as a noninvasive alternative to endomyocardial biopsy for the diagnostic of wild-type (wATTR) and hereditary ATTR amyloidosis (hATTR). Light chain amyloidosis (AL), Randall-type monoclonal immunoglobulin deposition disease , sarcoidosis, hemochromatosis, Fabry disease, and mucopolysaccharidoses are differential diagnosis of ATTR amyloidosis. Bone scintigraphy allows visualization of extracardiac involvements of AL amyloidosis: pleural, retroperitoneal, liver, spleen, and soft tissue. We report the case of a patient who underwent bone scintigraphy for suspected ATTR amyloidosis. Bone scan showed cardiac (Perugini score 2), hepatic, and renal hyperfixation. A cardiac biopsy demonstrated a Randall-type deposit, without amyloid deposit.

Cardiac amyloidosis and aortic stenosis: a state-of-the-art review

Cardiac amyloidosis is caused by the extracellular deposition of amyloid fibrils in the heart, involving not only the myocardium but also any cardiovascular structure. Indeed, this progressive infiltrative disease also involves the cardiac valves and, specifically, shows a high prevalence with aortic stenosis. Misfolded protein infiltration in the aortic valve leads to tissue damage resulting in the onset or worsening of valve stenosis. Transthyretin cardiac amyloidosis and aortic stenosis coexist in patients > 65 years in about 4-16% of cases, especially in those undergoing transcatheter aortic valve replacement. Diagnostic workup for cardiac amyloidosis in patients with aortic stenosis is based on a multi-parametric approach considering clinical assessment, electrocardiogram, haematologic tests, basic and advanced echocardiography, cardiac magnetic resonance, and technetium labelled cardiac scintigraphy like technetium-99 m (99mTc)-pyrophosphate, 99mTc-3,3-diphosphono-1,2-propanodicarboxylic acid, and 99mTc-hydroxymethylene diphosphonate. However, a biopsy is the traditional gold standard for diagnosis. The prognosis of patients with coexisting cardiac amyloidosis and aortic stenosis is still under evaluation. The combination of these two pathologies worsens the prognosis. Regarding treatment, mortality is reduced in patients with cardiac amyloidosis and severe aortic stenosis after undergoing transcatheter aortic valve replacement. Further studies are needed to confirm these findings and to understand whether the diagnosis of cardiac amyloidosis could affect therapeutic strategies. The aim of this review is to critically expose the current state-of-art regarding the association of cardiac amyloidosis with aortic stenosis, from pathophysiology to treatment.

Amyloid Transthyretin Cardiomyopathy in Elderly Patients With Aortic Stenosis Undergoing Transcatheter Aortic Valve Implantation

Background The prevalence of calcific aortic stenosis and amyloid transthyretin cardiomyopathy (ATTR-CM) increase with age, and they often coexist. The objective was to determine the prevalence of ATTR-CM in patients with severe aortic stenosis and evaluate differences in presentations and outcomes of patients with concomitant ATTR-CM undergoing transcatheter aortic valve implantation. Methods and Results Prospective screening for ATTR-CM with Technetium99-3,3-diphosphono-1,2-propanodicarboxylic acid bone scintigraphy was performed in 315 patients referred with severe aortic stenosis between August 2019 and August 2021. Myocardial Technetium99-3,3-diphosphono-1,2-propanodicarboxylic acid tracer uptake was detected in 34 patients (10.8%), leading to a diagnosis of ATTR-CM in 30 patients (Perugini ≥2: 9.5%). Age (85.7±4.9 versus 82.8±4.5; P=0.001), male sex (82.4% versus 57.7%; P=0.005), and prior carpal tunnel surgery (17.6% versus 4.3%; P=0.007) were associated with coexisting ATTR-CM, as were ECG (discordant QRS voltage to left ventricular wall thickness [42% versus 12%; P<0.001]), echocardiographic (left ventricular ejection fraction 48.8±12.8 versus 58.4±10.8; P<0.001; left ventricular mass index, 144.4±45.8 versus 117.2±34.4g/m2; P<0.001), and hemodynamic parameters (mean aortic valve gradient, 23.4±12.6 versus 35.5±16.6; P<0.001; mean pulmonary artery pressure, 29.5±9.7 versus 25.8±9.5; P=0.037). Periprocedural (cardiovascular death: hazard ratio [HR], 0.71 [95% CI, 0.04-12.53]; stroke: HR, 0.46 [95% CI, 0.03-7.77]; pacemaker implantation: HR, 1.54 [95% CI, 0.69-3.43]) and 1-year clinical outcomes (cardiovascular death: HR, 1.04 [95% CI, 0.37-2.96]; stroke: HR, 0.34 [95% CI, 0.02-5.63]; pacemaker implantation: HR, 1.50 [95% CI, 0.67-3.34]) were similar between groups. Conclusions Coexisting ATTR-CM was observed in every 10th elderly patient with severe aortic stenosis referred for therapy. While patients with coexisting pathologies differ in clinical presentation and echocardiographic and hemodynamic parameters, peri-interventional risk and early clinical outcomes were comparable up to 1 year after transcatheter aortic valve implantation. REGISTRATION URL: https://www.clinicaltrials.gov. Unique identifier: NCT04061213.

Amyloid myopathy: expanding the clinical spectrum of transthyretin amyloidosis-case report and literature review

We identified two patients with transthyretin (ATTR) amyloid myopathy (one ATTR variant amyloidosis, ATTRv; one wild-type ATTR amyloidosis, ATTRwt). Myopathy was the initial manifestation in ATTRwt, whereas it followed neuropathy and cardiomyopathy in ATTRv. The ATTRwt patient showed muscular tracer uptake on 99mTc-DPD planar scintigraphy at the time of initial diagnosis, consistent with ATTR amyloid myopathy. The ATTRv patient underwent heart transplantation because of progressive heart failure. Within the next two years, progressive myopathic symptoms and extracardiac tracer uptake on 99mTc-DPD planar scintigraphy were documented, attributable to ATTR amyloid myopathy. Interstitial amyloid deposits were confirmed by muscle biopsy in both patients, with a particularly high amyloid burden in the adipose tissue. This case report highlights the frequent concomitant presence of cardiac ATTR amyloidosis and ATTR amyloid myopathy. ATTR amyloid myopathy may precede cardiac manifestation in ATTRwt or occur after heart transplantation in ATTRv. Due to the high diagnostic accuracy of 99mTc-DPD scintigraphy for detecting ATTR amyloid myopathy and the emergence of novel therapeutics, it is important to increase the awareness of its presence.

Cardiac DPD-uptake time dependency in ATTR patients verified by quantitative SPECT/CT and semiquantitative planar parameters

BACKGROUND

Bone scintigraphy plays an important role in the diagnosis of cardiac Transthyretin-Related Amyloidosis (ATTR). The mechanism of myocardial tracer accumulation and its dependence over time are not fully understood. Recently, a scintigraphic quantification of the cardiac amyloid deposition has been discussed. Nevertheless, little is known regarding the right time of quantitative imaging.

METHODS

The geometrical mean of decay corrected total counts over the heart and the heart/whole-body ratio (H/WB) were evaluated in 23 patients undergoing DPD-bone scan with planar whole-body images 1 and 3 hours post injection (p.i.). Myocardial standard uptake values (SUV)peak were assessed in another 15 patients with quantitative SPECT/CT imaging 1 hours and 3 hours p.i..

RESULTS

Total counts over the heart (1 hours p.i.: 81,676 cts, range 69,887 to 93,091 cts and 3 hours p.i.: 64,819 cts, range 52,048 to 86,123 cts, P = .0005) and H/WB ratio (1 hours p.i.:0.076 ± 0.020 and 3 hours p.i. 0.070 ± 0.022; P = .0003) were significantly increased 1 hours p.i.. Furthermore median myocardial SUVpeak (1 hours p.i.:12.2, range 9.6 to 18.9 and 3 hours p.i.: 9.6, range 8.2 to 15.0, P = 0.0012) was also significantly higher after 1 hours p.i. compared to 3 hours p.i..

CONCLUSION

Cardiac DPD activity and myocardial SUVpeak are time-dependent, which should be considered when using quantitative bone scintigraphy in ATTR patients.

Alternative Isotope Options for Amyloidosis Imaging: A Technologist's Perspective

The recent pyrophosphate shortages can limit the availability of ^99mTc-pyrophosphate scans for cardiac amyloidosis. However, another radiotracer is available: ^99mTc-hydroxymethylene diphosphonate (HMDP). ^99mTc-HMDP, widely available in the United States for bone scanning, has effectively been used in Europe to diagnose transthyretin amyloidosis. ^99mTc-HMDP and ^99mTc-pyrophosphate have comparable blood clearance and sensitivity. The imaging protocols for ^99mTc-HMDP and ^99mTc-pyrophosphate are similar, except ^99mTc-HMDP is imaged 2-3 h after injection and whole-body imaging is optional. The interpretation is also essentially the same; however, caution is needed because of the high soft-tissue uptake with ^99mTc-HMDP, which can affect heart-to-contralateral-lung ratios.

Semi-Quantification of Myocardial Uptake of Bone-Seeking Agents in Suspected Cardiac Amyloidosis

INTRODUCTION

Bone scintigraphy has emerged as a key tool for non-invasive etiologic diagnosis of transthyretin (ATTR) cardiac amyloidosis (CA). We focused on a new semi-quantification method (on planar imaging) that could complement the qualitative/visual Perugini scoring system, especially when SPET/CT is not available.

MATERIAL AND METHODS

We retrospectively/qualitatively evaluated 8674 consecutive, planar 99mTc-biphosphonate scintigraphies (performed for non-cardiac reasons), identifying 68 (0.78%) individuals (mean age 79 ± 7 years, range 62-100 years; female/male ratio 16/52) presenting myocardial uptake. Due to the retrospective nature of the study, no SPET/CT, pathologic or genetic confirmation was obtained. The Perugini scoring system was determined (in patients presenting cardiac uptake) and compared with three newly proposed semi-quantitative indices. We took 349 consecutive bone scintigraphies, qualitatively absent of any cardiac/pulmonary uptake, as "healthy controls" (HC).

RESULTS

The heart-to-thigh ratio (RHT) and lung-to-thigh ratio (RLT) indices were significantly higher in patients than in HCs (p ≤ 0.0001). There were statistically significant differences for RHT in HCs vs. patients with qualitative Perugini scores of 1 or >1 (with p ranging from ≤0.001 to ≤0.0001). ROC curves showed that RHT outperformed the other indices and was more accurate in both male and female groups. Furthermore, in the male population, RHT accurately distinguished HCs and patients with scores of 1 (less likely affected by ATTR) from patients with qualitative scores >1 (more likely affected by ATTR) with an AUC of 99% (sensitivity: 95%; specificity: 97%).

CONCLUSION

The proposed semi-quantitative RHT index can accurately/semi-quantitatively distinguish between HCs and subjects probably affected by CA (Perugini scores from 1 to 3), and could be particularly useful when no SPET/CT data are available (such as in retrospective studies and data mining). Furthermore, RHT can semi-quantitatively predict, with very high accuracy, subjects in the male population more likely to be affected by ATTR. The present study, although using a very large sample, is however retrospective, monocentric, and therefore the generalizability of the results should be proved by an accurate external validation.

ADVANCES IN KNOWLEDGE

The proposed heart-to-thigh ratio (RHT) can distinguish healthy controls and subjects that are probably affected by cardiac amyloidosis in a simple and more reproducible way, as compared to standard qualitative/visual evaluation.

99m Technetium-pyrophosphate bone scan: A potential biomarker for the burden of transthyretin amyloidosis in skeletal muscle: A preliminary study

INTRODUCTION/AIMS

Transthyretin amyloidosis (ATTR) proteins can infiltrate skeletal muscle and infrequently cause a myopathy. ^99m Technetium-pyrophosphate (^99m Tc-PYP) is a validated biomarker for cardiac involvement in variant and wild-type ATTR (ATTRv and ATTRwt, respectively). The aim of this study was to test the hypothesis that ^99m Tc-PYP is a biomarker for muscle burden of ATTR.

METHODS

Radioisotope uptake in the deltoid muscles of patients with ATTR was compared to uptake in control subjects without amyloidosis in a retrospective study. ^99m Tc-PYP scans were evaluated in 11 patients with ATTR (7 ATTRv, 4 ATTRwt) and 14 control subjects. Mean count (MC) values were measured in circular regions of interest (ROIs) 2.5-3.8 cm² in area. Tracer uptake was quantified in the heart, contralateral chest (CC), and deltoid muscles.

RESULTS

Tracer uptake was significantly higher over the deltoids and heart but not the CC, in patients with ATTR than in control subjects. MC values were 120.1 ± 43.7 (mean ± SD) in ATTR patients and 78.9 ± 20.4 in control subjects over the heart (p = 0.005), 73.3± 21.0 and 63.5 ± 14.4 over CC (p = 0.09), and 37.0 ± 11.7 and 26.0 ± 7.1 averaged over both deltoid muscles (p = 0.014).

DISCUSSION

^99m Tc-PYP is a potential biomarker for ATTR amyloid burden in skeletal muscle.

99mTc Bone-Avid Tracer Cardiac Scintigraphy: Role in Noninvasive Diagnosis of Transthyretin Cardiac Amyloidosis

Transthyretin cardiac amyloidosis (ATTR-CA) is an overlooked cause of heart failure, with substantial morbidity and mortality. The emergence of several novel therapies has fueled the interest in early and accurate diagnosis of ATTR-CA so that potentially life-saving pharmacologic therapy can be administered in a timely manner. The most promising imaging modality and biomarker is SPECT imaging with technetium 99m (99mTc)-radiolabeled bone-seeking tracers, which have high specificity in the diagnosis of ATTR-CA, potentially obviating biopsy. In this article, the authors provide a focused review on the use of 99mTc pyrophosphate (PYP), 3,3-diphosphono-1,2-propanodicarboxylic acid (DPD), and hydroxymethylene diphosphonate (HMDP) for diagnosis of ATTR-CA, present a systematic approach to interpretation of the scans, and highlight several common pitfalls to illustrate important diagnostic principles for accurate interpretation of these images. The authors indicate when to use endomyocardial biopsy for the diagnosis of cardiac amyloidosis and conclude with a section on quantitation of 99mTc-PYP/DPD/HMDP imaging.

Does [99mTc]-3,3-diphosphono-1,2-propanodicarboxylic acid (DPD) soft tissue uptake allow the identification of patients with the diagnosis of cardiac transthyretin-related (ATTR) amyloidosis with higher risk for polyneuropathy?

BACKGROUND

With the introduction of several drugs for the therapy of transthyretin-related amyloidosis (ATTR) which slow down the disease, early detection of polyneuropathy (PNP) is becoming increasingly of interest. [99mTc]-3,3-Diphosphono-1,2-Propanodicarboxylic Acid (DPD) bone scintigraphy, which is used for the diagnosis of cardiac (c)ATTR, can possibly make an important contribution in the identification of patients at risk for PNP.

METHODS

Fifty patients with cATTR, who underwent both planar whole-body DPD scintigraphy and nerve conduction studies (NCS) were retrospectively evaluated. A subgroup of 22 patients also underwent quantitative SPECT/CT of the thorax from which Standardized Uptake Values (SUVpeak) in the subcutaneous fat tissue of the left axillar region were evaluated.

RESULTS

The Perugini score was significantly increased in patients with cATTR and additional diagnosis of PNP compared to patients without (2.51 ± 0.51 vs 2.13 ± 0.52; P = 0.03). Quantitative SPECT/CT revealed that DPD uptake in the subcutaneous fat of the left axillar region was significantly increased in cATTR patients with compared to patients without (1.36 ± 0.60 vs 0.74 ± 0.52; P = 0.04).

CONCLUSION

This study suggests that DPD bone scintigraphy is a useful tool for identification of patients with cATTR and a risk for PNP due to increased DPD soft tissue uptake.

Comparison of 1-h with 3-h planar 99mTc-pyrophosphate scintigraphy in patients with suspected transthyretin cardiac amyloidosis using SPECT as a reference standard

OBJECTIVES

The purpose of this study was to examine the diagnostic value of planar ^99mTc-pyrophosphate (PYP) imaging at 1 and 3 h after tracer administration in patients with suspected transthyretin cardiac amyloidosis (ATTR-CA) using SPECT as a reference standard. We also tested whether blood pool activity of PYP is associated with renal dysfunction.

METHODS

PYP images of 109 consecutive patients with suspected ATTR-CA were retrospectively reviewed. The myocardial PYP uptake was visually graded on a scale of 0 to 3 and quantified with the heart-to-contralateral (H/CL) ratio in accordance with the current expert consensus recommendations. The diagnostic value of planar images for identifying positive PYP SPECT was assessed by a receiver-operating characteristic curve analysis with the area under the curve (AUC). The uptake ratios of the ascending and descending aorta, left atrium, and trapezius muscle divided by the liver uptake were measured on SPECT images and compared to the renal function.

RESULTS

A total of 41 patients (38%) had myocardial PYP uptake on SPECT images. In comparison with the visual scores on 1-h anterior planar images, those on 3-h anterior planar images had lower sensitivity (80.5% vs. 97.6%) and higher specificity (86.8% vs. 55.9%) for identifying positive PYP SPECT. The ROC analysis showed that the combination of visual scores on both 1-h and 3-h anterior planar images had significantly higher AUC values in comparison with 1-h anterior planar images alone (0.90 [95% CI 0.83-0.94] vs. 0.83 [95% CI 0.75-0.88]; P < 0.001), which was comparable to the AUC values on 3-h anterior planar images alone (0.88 [95% CI 0.80-0.92]; P = 0.071). In comparison with visual scores on 1-h or 3-h anterior planar images alone, the combination of visual scores and H/CL ratio did not significantly improve the diagnostic value for identifying positive PYP SPECT (P = 0.73 and P = 0.50, respectively). The uptake ratios of ascending aorta/liver, descending aorta/liver, left atrium/liver, and trapezius muscle/liver were not significantly associated with the serum creatinine level or estimated glomerular filtration rate (P > 0.05 for all).

CONCLUSIONS

In the assessment of ATTR-CA using PYP imaging, visual scores on 3-h anterior planar images for identifying positive PYP SPECT had lower sensitivity and higher specificity in comparison with those on 1-h anterior planar images. The diagnostic value of the visual scores on 1-h and 3-h anterior planar images was not improved by adding the H/CL ratio. Blood pool activity of PYP was not significantly associated with renal dysfunction.

99mTc-Pyrophosphate Scintigraphy Can Image Tracer Uptake in Skeletal Trunk Muscles of Transthyretin Cardiac Amyloidosis

PURPOSE

99mTc-pyrophosphate (99mTc-PYP) uptake in the skeletal muscles is minimal in patients with transthyretin cardiac amyloidosis (ATTR-CA) when assessed qualitatively and quantitatively. We previously demonstrated moderate- to high-grade 99mTc-PYP uptake in the subcutaneous abdominal fat of some patients with ATTR-CA and showed that this abnormal finding could reflect the regional amyloid burden of this tissue. We aimed to investigate the frequency of 99mTc-PYP uptake in skeletal trunk muscles of patients with ATTR-CA.

METHODS

Chest- and abdomen-centered 99mTc-PYP scintigraphy images were obtained 2 hours after IV injections of the tracer (20 mCi) in 36 patients with ATTR-CA. The frequency of 99mTc-PYP uptake in the following 11 skeletal trunk muscles was investigated: pectoralis major, deltoid, subscapularis, infraspinatus, trapezius, latissimus dorsi, erector spinae, psoas major, abdominal oblique, rectus abdominis, and the gluteus muscles.

RESULTS

Ten of the 11 muscles were involved in patients with the highest number of 99mTc-PYP uptake in the skeletal trunk muscles examined, whereas no muscle was involved in a patient with the least uptake. The muscle with the highest rate of 99mTc-PYP uptake, observed in 34 of 36 patients (94.4%), was the abdominal oblique. No tracer uptake was observed in the psoas major. The frequency of radiotracer uptake in the remaining examined muscles was between those of abdominal oblique and psoas major muscles.

CONCLUSIONS

Radiotracer uptake was often detectable in some skeletal trunk muscles of ATTR-CA, although the muscles of patients examined and the skeletal trunk muscles of 1 patient showed heterogeneity in the uptake of 99mTc-PYP.

Amyloid deposit corresponds to technetium-99m-pyrophosphate accumulation in abdominal fat of patients with transthyretin cardiac amyloidosis

BACKGROUND

Radionuclide imaging using bone-avid tracers plays a critical role in diagnosing transthyretin cardiac amyloidosis (ATTR-CA), but technetium-99m-pyrophosphate (PYP) rarely allows the detection of extracardiac amyloid infiltration. We retrospectively investigated the frequency of PYP uptake in the subcutaneous abdominal fat of patients with ATTR-CA and its relevance to the results of fine-needle aspiration biopsy (FNAB) of this tissue.

METHODS

Chest-centered images of PYP scintigraphy were obtained 2 h after the intravenous injection of the tracer (20 mCi), and the frequency of PYP uptake in the subcutaneous abdominal fat was evaluated. Amyloid deposits of fat smears taken by subcutaneous abdominal fat FNAB were assessed by Congo red staining.

RESULTS

Twenty-four patients with ATTR-CA were included. Ten (41.7%) patients showed some PYP uptake in the subcutaneous abdominal fat (positive PYP group), and 14 patients did not (negative PYP group). Amyloid deposits were detected by subcutaneous abdominal fat FNAB in 7/10 patients (70.0%) of the positive PYP group versus 0/14 patients (0%) of the negative PYP group, and the difference was significant.

CONCLUSIONS

In patients with ATTR-CA, abnormal PYP uptake in the subcutaneous abdominal fat could reflect the regional amyloid deposition confirmed by FNAB of this tissue.

Prevalence and Outcomes of Cardiac Amyloidosis in All-Comer Referrals for Bone Scintigraphy

The prevalence of cardiac amyloidosis (CA) in the general population and associated prognostic implications remain poorly understood. We aimed to identify CA prevalence and outcomes in bone scintigraphy referrals. Methods: Consecutive all-comers undergoing ^99mTc-3,3-diphosphono-1,2-propanodicarboxylic-acid (^99mTc-DPD) bone scintigraphy between 2010 and 2020 were included. Perugini grade 1 was defined as low-grade uptake and grade 2 or 3 as confirmed CA. All-cause mortality, cardiovascular death, and heart failure hospitalization (HHF) served as endpoints. Results: In total, 17,387 scans from 11,527 subjects (age, 61 ± 16 y; 63.0% women, 73.6% cancer) were analyzed. Prevalence of ^99mTc-DPD positivity was 3.3% (n = 376/11,527; grade 1: 1.8%, grade 2 or 3: 1.5%), and was higher among cardiac than noncardiac referrals (18.2% vs. 1.7%). In individuals with more than 1 scan, progression from grade 1 to grade 2 or 3 was observed. Among patients with biopsy-proven CA, the portion of light-chain (AL)-CA was significantly higher in grade 1 than grade 2 or 3 (73.3% vs. 15.4%). After a median of 6 y, clinical event rates were: 29.4% mortality, 2.6% cardiovascular death, and 1.5% HHF, all independently predicted by positive ^99mTc-DPD. Overall, adverse outcomes were driven by confirmed CA (vs. grade 0, mortality: adjusted hazard ratio [AHR] 1.46 [95% CI 1.12-1.90]; cardiovascular death: AHR 2.34 [95% CI 1.49-3.68]; HHF: AHR 2.25 [95% CI 1.51-3.37]). One-year mortality was substantially higher in cancer than noncancer patients. Among noncancer patients, also grade 1 had worse outcomes than grade 0 (HHF/death: AHR 1.45 [95% CI 1.01-2.09]), presumably because of longer observation and higher prognostic impact of early infiltration. Conclusion: Positive ^99mTc-DPD was identified in a substantial number of consecutive ^99mTc-DPD referrals and associated with adverse outcomes.

New quantitative indices of cardiac amyloidosis with 99mTc-pyrophosphate scintigraphy

PURPOSE

Amyloid light chain (AL) and transthyretin (ATTR) are the major subtypes of cardiac amyloidosis (CA). ^99mTc-pyrophosphate (PYP) scintigraphy is used to differentiate ATTR from other CA subtypes. We adapted the standardized uptake value (SUV) for ^99mTc-PYP and proposed two quantitative indices, amyloid deposition volume (AmyDV) and total amyloid uptake (TAU). This study aimed to evaluate the utility of these quantitative indices in differentiating ATTR from non-ATTRs.

MATERIALS AND METHODS

Before the SUV measurement, the Becquerel calibration factor (BCF) of ^99mTc was obtained by a phantom experiment. Thirty-two patients who had undergone hybrid SPECT/CT imaging 3 h after injection of ^99mTc-PYP (370 MBq) were studied. CT attenuation correction for image reconstruction was applied in all. We calculated SUV, AmyDV, and TAU using a quantitative analysis software program for bone SPECT (GI-BONE) and analyzed AmyDV using two methods: threshold method (set 40%); and constant value method (average SUV_max of ribs). We assessed the diagnostic ability of heart-to-contralateral lung (H/CL) ratio, SUV, AmyDV, and TAU to differentiate ATTR from non-ATTR using receiver operating characteristic (ROC) analysis.

RESULTS

Statistically significant differences in all quantitative indices were observed between ATTR and non-ATTR. The area under the curve of each quantitative index for discriminating between ATTR and non-ATTR were as follows: H/CL, 0.997; SUV_max, 0.953; SUV_mean (M1), 0.964; SUV_mean (M2), 0.969; AmyDV (M1), 0.875; AmyDV (M2), 0.974; and TAU, 0.974. The AmyDV (M2) had higher diagnostic ability than AmyDV (M1). Thus, TAU was calculated as AmyDV (M2) × SUV_mean (M2). In the ROC curve, SUV, AmyDV, and TAU had almost the same diagnostic ability as H/CL in distinguishing ATTR from non-ATTRs.

CONCLUSIONS

We propose two novel 3D-based quantitative parameters (AmyDV and TAU) that have almost equal ability to discriminate ATTR from non-ATTR.

Prevalence and Risk Factors of Cardiac Amyloidosis in Heart Failure: A Systematic Review and Meta-Analysis

AIMS

Heart failure (HF) is one of the leading causes of mortality worldwide. Heart failure is also one of the most common presentations of cardiac amyloidosis (CA). Contemporary epidemiological data of CA in HF patients is lacking. Hence, this systematic review and meta-analysis was conducted to determine the prevalence of amyloidosis in HF patients, and to clarify the risk factors of concomitant CA and HF.

METHODS

A systematic review and meta-analysis was performed. Studies were retrieved from Medline, EMBASE, Scopus and Cochrane library. The search was not restricted in time, type or language of publication. The prevalence of CA in HF grouped according to diagnostic techniques and risk factors of CA with HF was analysed.

RESULTS

Eleven (11) studies were included, involving 3,303 patients. The pooled prevalence of CA in HF was 13.7%. The overall prevalence of CA in HF with preserved ejection fraction was 15.1%, and that of HF with reduced ejection fraction was 11.3%. The main factors associated with the diagnosis of CA in HF included older age, males, raised NT pro-BNP, increased interventricular septal thickness in diastole, apical sparing, and reduced left ventricular systolic function.

CONCLUSION

A high index of clinical suspicion is required to identify HF patients with CA. Supportive investigations may be helpful when clinically correlated. A considerable proportion of HF patients have CA and certain risk factors may be helpful in increasing suspicions of CA in HF.

Unveiling Cardiac Amyloidosis, its Characteristics, and Outcomes Among Patients With MR Undergoing Transcatheter Edge-to-Edge MV Repair

BACKGROUND

Mitral regurgitation (MR) and cardiac amyloidosis (CA) both primarily affect older patients. Data on coexistence and prognostic implications of MR and CA are currently lacking.

OBJECTIVES

This study sought to identify the prevalence, clinical characteristics, and outcomes of MR CA compared with lone MR.

METHODS

Consecutive patients undergoing transcatheter edge-to-edge repair (TEER) for MR at 2 sites were screened for concomitant CA using a multiparametric approach including core laboratory 99mTc-3,3-diphosphono-1,2-propanodicarboxylic acid bone scintigraphy and echocardiography and immunoglobulin light chain assessment. Transthyretin CA (ATTR) was diagnosed by 99mTc-3,3-diphosphono-1,2-propanodicarboxylic acid (Perugini grade 1: early infiltration; grades 2/3: clinical CA) and the absence of monoclonal protein, and light chain (AL) CA via tissue biopsy. All-cause mortality and hospitalization for heart failure (HHF) served as the endpoints.

RESULTS

A total of 120 patients (age 76.9 ± 8.1 years, 55.8% male) were recruited. Clinical CA was diagnosed in 14 patients (11.7%; 12 ATTR, 1 AL, and 1 combined ATTR/AL) and early amyloid infiltration in 9 patients (7.5%). Independent predictors of MR CA were increased posterior wall thickness and the presence of a left anterior fascicular block on electrocardiography. Procedural success and periprocedural complications of TEER were similar in MR CA and lone MR (P for all = NS). After a median of 1.7 years, 25.8% had experienced death and/or HHF. MR CA had worse outcomes compared with lone MR (HR: 2.2; 95% CI: 1.0-4.7; P = 0.034), driven by a 2.5-fold higher risk for HHF (HR: 2.5; 95% CI: 1.1-5.9), but comparable mortality (HR: 1.6; 95% CI: 0.4-6.1).

CONCLUSIONS

Dual pathology of MR CA is common in elderly patients with MR undergoing TEER and has worse postinterventional outcomes compared with lone MR.

Multimodality Imaging in the Diagnosis and Assessment of Cardiac Amyloidosis

Amyloidosis is a rare disorder where abnormal protein aggregates are deposited in tissues forming amyloid fibrils, leading to progressive organ failure. Although any organ can be affected, cardiac involvement is the main cause of morbidity and mortality associated with amyloidosis as diagnosis is often delayed due to the indolent nature of the disease in some forms. An early diagnosis of disease and knowledge of the type/subtype of cardiac amyloidosis (CA) are essential for appropriate management and better outcome. Echocardiography is often the first line of investigation for patients suspected of CA and offers superior hemodynamic assessment. Although cardiovascular magnetic resonance (CMR) imaging is not diagnostic of CA, it provides vital clues to diagnosis and has a role in disease quantification and prognostication. Radiolabeled bone seeking tracers are the mainstay of diagnosis of CA and when combined with screening of monoclonal light chains, bone scintigraphy offers high sensitivity in diagnosing transthyretin type of CA. This review aims to describe the noninvasive imaging assessment and approach to diagnosis of patients with suspected CA. Imaging features of echocardiography, nuclear scintigraphy, and CMR are described with a brief mention on computed tomography.

Transthyretin cardiac amyloidosis

Transthyretin cardiac amyloidosis (ATTR-CA) is an increasingly recognized cause of heart failure (HF) and mortality worldwide. Advances in non-invasive diagnosis, coupled with the development of effective treatments, have shifted ATTR-CA from a rare and untreatable disease to a relatively prevalent condition that clinicians should consider on a daily basis. Amyloid fibril formation results from age-related failure of homoeostatic mechanisms in wild-type ATTR (ATTRwt) amyloidosis (non-hereditary form) or destabilizing mutations in variant ATTR (ATTRv) amyloidosis (hereditary form). Longitudinal large-scale studies in the United States suggest an incidence of cardiac amyloidosis in the contemporary era of 17 per 100 000, which has increased from a previous estimate of 0.5 per 100 000, which was almost certainly due to misdiagnosis and underestimated. The presence and degree of cardiac involvement is the leading cause of mortality both in ATTRwt and ATTRv amyloidosis, and can be identified in up to 15% of patients hospitalized for HF with preserved ejection fraction. Associated features, such as carpal tunnel syndrome, can preceed by several years the development of symptomatic HF and may serve as early disease markers. Echocardiography and cardiac magnetic resonance raise suspicion of disease and might offer markers of treatment response at a myocardial level, such as extracellular volume quantification. Radionuclide scintigraphy with 'bone' tracers coupled with biochemical tests may differentiate ATTR from light chain amyloidosis. Therapies able to slow or halt ATTR-CA progression and increase survival are now available. In this evolving scenario, early disease recognition is paramount to derive the greatest benefit from treatment.

Suspicion, screening, and diagnosis of wild-type transthyretin amyloid cardiomyopathy: a systematic literature review

Wild-type transthyretin amyloid cardiomyopathy (ATTRwt CM) is a more common disease than previously thought. Awareness of ATTRwt CM and its diagnosis has been challenged by its unspecific and widely distributed clinical manifestations and traditionally invasive diagnostic tools. Recent advances in echocardiography and cardiac magnetic resonance (CMR), non-invasive diagnosis by bone scintigraphy, and the development of disease-modifying treatments have resulted in an increased interest, reflected in multiple publications especially during the last decade. To get an overview of the scientific knowledge and gaps related to patient entry, suspicion, diagnosis, and systematic screening of ATTRwt CM, we developed a framework to systematically map the available evidence of (i) when to suspect ATTRwt CM in a patient, (ii) how to diagnose the disease, and (iii) which at-risk populations to screen for ATTRwt CM. Articles published between 2010 and August 2021 containing part of or a full diagnostic pathway for ATTRwt CM were included. From these articles, data for patient entry, suspicion, diagnosis, and screening were extracted, as were key study design and results from the original studies referred to. A total of 50 articles met the inclusion criteria. Of these, five were position statements from academic societies, while one was a clinical guideline. Three articles discussed the importance of primary care providers in terms of patient entry, while the remaining articles had the cardiovascular setting as point of departure. The most frequently mentioned suspicion criteria were ventricular wall thickening (44/50), carpal tunnel syndrome (42/50), and late gadolinium enhancement on CMR (43/50). Diagnostic pathways varied slightly, but most included bone scintigraphy, exclusion of light-chain amyloidosis, and the possibility of doing a biopsy. Systematic screening was mentioned in 16 articles, 10 of which suggested specific at-risk populations for screening. The European Society of Cardiology recommends to screen patients with a wall thickness ≥12 mm and heart failure, aortic stenosis, or red flag symptoms, especially if they are >65 years. The underlying evidence was generally good for diagnosis, while significant gaps were identified for the relevance and mutual ranking of the different suspicion criteria and for systematic screening. Conclusively, patient entry was neglected in the reviewed literature. While multiple red flags were described, high-quality prospective studies designed to evaluate their suitability as suspicion criteria were lacking. An upcoming task lies in defining and evaluating at-risk populations for screening. All are steps needed to promote early detection and diagnosis of ATTRwt CM, a prerequisite for timely treatment.

Bradycardia, Renal Failure, Atrioventricular Nodal Blockade, Shock, and Hyperkalemia Syndrome as a Clinical Profile Leading to the Diagnosis of Transthyretin Amyloidosis: A Report of Two Cases

We describe two cases in which the onset of bradycardia, renal failure, atrioventricular (AV) nodal blockade, shock, and hyperkalemia (BRASH) syndrome led to the diagnosis of transthyretin cardiac amyloidosis. In Case 1, BRASH syndrome developed shortly after a therapeutic dose of AV nodal blockers was prescribed for new-onset atrial flutter. BRASH syndrome improved with intravenous dopamine infusion and temporary cardiac pacing. In Case 2, BRASH syndrome developed immediately after bronchopneumonia followed by worsening heart failure, despite no change in medications such as AV nodal blockers. Intravenous injection of calcium dramatically improved BRASH syndrome.

Practical guidelines for the diagnosis and treatment of transthyretin amyloid cardiomyopathy (ATTR-CM or transthyretin cardiac amyloidosis)

This paper summarizes the data from updated international protocols and guidelines for diagnosis of transthyretin amyloid cardiomyopathy (ATTR-CM). The invasive and non-invasive diagnosis techniques and their combinations are briefly reviewed; the evidentiary foundations for each diagnostic option and tool are analyzed. The paper describes a customized algorithm for sequential diagnosis and differential diagnosis of patients with suspected ATTR-CM with allowance for the combination of clinical signs and diagnostic findings. Along with the awareness of primary care providers about the red flags of the disease and visualization criteria, as well as providing information to the patients about the possibility of performing therapy of ATTR amyloidosis and the risks of delayed diagnosis, the proposed algorithm enables timely patient routing and prescribing specific treatment.

New Advanced Imaging Parameters and Biomarkers-A Step Forward in the Diagnosis and Prognosis of TTR Cardiomyopathy

Transthyretin amyloid cardiomyopathy (ATTR-CM) is an infiltrative disorder characterized by extracellular myocardial deposits of amyloid fibrils, with poor outcome, leading to heart failure and death, with significant treatment expenditure. In the era of a novel therapeutic arsenal of disease-modifying agents that target a myriad of pathophysiological mechanisms, timely and accurate diagnosis of ATTR-CM is crucial. Recent advances in therapeutic strategies shown to be most beneficial in the early stages of the disease have determined a paradigm shift in the screening, diagnostic algorithm, and risk classification of patients with ATTR-CM. The aim of this review is to explore the utility of novel specific non-invasive imaging parameters and biomarkers from screening to diagnosis, prognosis, risk stratification, and monitoring of the response to therapy. We will summarize the knowledge of the most recent advances in diagnostic, prognostic, and treatment tailoring parameters for early recognition, prediction of outcome, and better selection of therapeutic candidates in ATTR-CM. Moreover, we will provide input from different potential pathways involved in the pathophysiology of ATTR-CM, on top of the amyloid deposition, such as inflammation, endothelial dysfunction, reduced nitric oxide bioavailability, oxidative stress, and myocardial fibrosis, and their diagnostic, prognostic, and therapeutic implications.

Pulmonary 99mTc-HMDP uptake correlates with restrictive ventilatory defects and abnormal lung reactance in transthyretin cardiac amyloidosis patients

BACKGROUND

Pulmonary involvement in individuals with transthyretin cardiac amyloidosis is unclear. The aim of this study was to quantify 99mTc-hydroxy methylene diphosphonate (HMDP) lung retention in hereditary transthyretin (ATTRv) cardiac amyloidosis patients and to relate tracer uptake intensity to pulmonary function and aerobic capacity.

METHODS

We prospectively enrolled 20 patients with biopsy-proven ATTRv cardiac amyloidosis and 20 control subjects. Cardiac involvement was confirmed by echocardiography and nuclear imaging using 99mTc-HMDP. Semi-quantitative analysis of the heart, rib and lung retention was assessed using a simple region of interest technique. Pulmonary function was evaluation by the means of whole-body plethysmography, diffusing capacity of the lung for carbon monoxide, forced oscillation technique and cardiopulmonary exercise testing.

RESULTS

Pulmonary tracer uptake estimated by lung to rib retention ratio was higher in ATTRv amyloidosis patients compared with control subjects: median 0.62 (0.55-0.69) vs 0.51 (0.46-0.60); p = 0.014. Analysis of relation between lung 99mTc-HMDP retention and pulmonary function parameters shown statistically significant correlations with total lung volume (% predicted), lung reactance (Xrs 5 Hz) and peak VO2, suggesting total lung capacity restriction impaired elastic properties of the lung and poor aerobic capacity.

CONCLUSION

Our study suggests that some grade of pulmonary retention of 99mTc-HMDP may occur in patients with cardiac ATTRv amyloidosis, which can elicit deleterious effects on patient's lung function and aerobic capacity.

Multimodality Imaging in the Evaluation and Prognostication of Cardiac Amyloidosis

Cardiac amyloidosis (CA) is an infiltrative cardiomyopathy resulting from deposition of misfolded immunoglobulin light chains (AL-CA) or transthyretin (ATTR-CA) proteins in the myocardium. Survival varies between the different subtypes of amyloidosis and degree of cardiac involvement, but accurate diagnosis is essential to ensure initiation of therapeutic interventions that may slow or potentially prevent morbidity and mortality in these patients. As there are now effective treatment options for CA, identifying underlying disease pathogenesis is crucial and can be guided by multimodality imaging techniques such as echocardiography, magnetic resonance imaging, and nuclear scanning modalities. However, as use of cardiac imaging is becoming more widespread, understanding optimal applications and potential shortcomings is increasingly important. Additionally, certain imaging modalities can provide prognostic information and may affect treatment planning. In patients whom imaging remains non-diagnostic, tissue biopsy, specifically endomyocardial biopsy, continues to play an essential role and can facilitate accurate and timely diagnosis such that appropriate treatment can be started. In this review, we examine the multimodality imaging approach to the diagnosis of CA with particular emphasis on the prognostic utility and limitations of each imaging modality. We also discuss how imaging can guide the decision to pursue tissue biopsy for timely diagnosis of CA.

The role of serial 99mTc-DPD scintigraphy in monitoring cardiac transthyretin amyloidosis

PURPOSE

Cardiac transthyretin amyloidosis is a usually fatal form of restrictive cardiomyopathy for which clinical trials of treatments are ongoing. It is anticipated that quantitative nuclear medicine scintigraphy, which is experiencing growing interest, will soon be used to evaluate treatment efficacy. We investigated its utility for monitoring changes in disease load over a significant time period.

METHODS

Sixty-two treatment-naive patients underwent ^99mTc-labelled 3,3-diphosphono-1,2propanodicarboxylic acid (^99mTc-DPD) scintigraphy two to four times each over a five-year period. Quantitation of cardiac ^99mTc-DPD retention was performed according to two established methods: measurement of heart-to-contralateral ratio (H/CL) in the anterior view (planar) and percentage of administered activity in the myocardium (SPECT).

RESULTS

In total 170 datasets were analysed. Increased myocardial retention of ^99mTc-DPD was demonstrable as early as 12 months from baseline. Year-on-year progression across the cohort was observed using SPECT-based quantitation, though on 30 occasions (27.8%) the change in our estimate was negative.

CONCLUSIONS

The spread of our results was notably high compared to the year-on-year increases. If left unaccounted for, variance may draw fallacious conclusions about changes in disease load. We therefore urge caution in drawing conclusions solely from nuclear medicine scintigraphy on a patient-by-patient basis, particularly across a short time period.

[Cardiac imaging in infiltrative cardiomyopathies. What cardiovascular imaging modalities to propose in hypertrophic cardiomyopathies ?]

Infiltrative cardiomyopathies are abnormal accumulations or depositions of different substances in cardiac tissue leading to its dysfunction, first diastolic, then systolic. The different infiltrative cardiomyopathies are amyloidosis (both light chain amyloidosis and transthyretin amyloidosis variants), lysosomal and glycogen storage disorders (Fabry-Anderson disease), and iron overload (hemochromatosis and thalassemia associated with blood transfusions), as well as inflammatory diseases such as sarcoidosis. We also evoke hypereosinophilic syndrome associated with endomyocardial fibrosis. Echocardiography is the first essential step after interrogatory and clinical examination and may help the cardiologist as a screening tool. Cardiac MRI is the second fundamental step towards the diagnosis especially due to the late gadolinium enhancement and to the T1-mapping. Cardiac amyloidosis diagnosis also requires the use of nuclear imaging. Cardiac CT-Scan may be useful for estimating the amyloid load, identify potential cardiac thrombus and rule out associated coronaropathy.