Emerging therapies in transthyretin amyloidosis – a new wave of hope after years of stagnancy?

Outcomes in Cardiac Transthyretin Amyloidosis and Association With New York Heart Association Class: Real-World Data

BACKGROUND

Results from ATTR-ACT (Safety and Efficacy of Tafamidis in Patients With Transthyretin Cardiomyopathy) indicate that tafamidis prolongs survival and reduces cardiovascular hospitalizations in cardiac transthyretin amyloidosis (ATTR-CA). However, real-world data supporting these findings are scarce. Thus, we sought to characterize the clinical outcome of patients with ATTR-CA treated with tafamidis in a real-world setting and assess the prognostic role of the New York Heart Association (NYHA) classification.

METHODS AND RESULTS

We conducted a retrospective observational study, enrolling a consecutive sample of patients with ATTR-CA (wild-type or variant) treated with tafamidis. Clinical outcome was tracked through follow-up visits or phone calls. Primary outcomes were death and major adverse cardiac events (MACE), a composite end point of death and hospitalizations for acute cardiac decompensation, myocardial infarction, severe arrythmias, or stroke. Kaplan-Meier analysis estimated overall and MACE-free survival including NYHA subgroups (NYHA I/II versus NYHA III). One hundred sixty-seven patients with ATTR-CA (94.6% wild-type) were enrolled and followed for a median of 539 [323-869] days. Median overall survival was not reached. Estimated 1-year, 2-year, and 5-year overall survival among the whole cohort was 93.5%, 85.9%, and 70.2%, respectively. Overall survival was higher in the NYHA I/II subgroup (P=0.002). Median MACE-free survival time was 1082 (95% CI, 962-1202) days. MACE-free survival was higher in the NYHA I/II subgroup (P<0.001). With respective hazard ratios of 5.85 (95% CI, 1.48-23.18; P=0.012) and 3.95 (95% CI, 1.99-7.84; P<0.001), NYHA III was an independent predictor of death and MACE.

CONCLUSIONS

Treatment of ATTR-CA with tafamidis led to substantial improvements of clinical outcome. NYHA classification at treatment initiation is a reliable tool to provide patients with individualized prognostic information.

Identification and management of gastrointestinal manifestations of hereditary transthyretin amyloidosis: Recommendations from an Italian group of experts

Gastrointestinal manifestations are common across all hereditary transthyretin amyloidosis (ATTRv) genotypes. However, they are poorly specific, and their recognition as part of ATTRv is difficult, resulting in misdiagnosis with more common conditions. Moreover, delays in diagnosis occur because of fragmented knowledge, a shortage of centers of excellence and specialists dedicated to ATTRv management, and the scarce involvement of gastroenterologists in multidisciplinary teams. A group of Italian gastroenterologists with experience in the management of ATTRv took part in a project aimed at assessing the awareness of ATTRv among the community of Italian gastroenterologists through an online survey and providing education about practical aspects of ATTRv management. Survey results reported low participation, and very few patients with ATTRv were cared for by gastroenterologists. This highlights the need for greater attention to rare diseases in gastroenterology and emphasizes increasing awareness of ATTRv and diagnostic suspicion. Based on the experts' recommendations, a diagnosis of ATTRv should be suspected when at least one of the 'red flags' is detected. Subsequently, it is suggested to promptly ask for genetic testing and exclude a serum and urinary monoclonal protein, even before the detection of amyloid in biopsy samples, particularly in non-endemic areas.

Exploring Transthyretin Amyloid Cardiomyopathy: A Comprehensive Review of the Disease and Upcoming Treatments

Transthyretin amyloid cardiomyopathy (ATTR-CM) is a mutation-based genetic disorder due to the accumulation of unstable transthyretin protein and presents with symptoms of congestive heart failure (CHF) and numerous extracardiac symptoms like carpal tunnel syndrome and neuropathy. Two subtypes of ATTR-CM are hereditary and wild-type, both of which have different risk factors, gender prevalence and major clinical symptoms. Timely usage of imaging modalities like echocardiography, cardiac magnetic imaging resonance, and cardiac scintigraphy has made it possible to suspect ATTR-CM in patients presenting with CHF. Management of ATTR-CM includes appropriate treatment for heart failure for symptomatic relief, prevention of arrhythmias and heart transplantation for nonresponders. With the recent approval of tafamidis in the successful management of ATTR-CM, numerous potential therapeutic points have been identified to stop or delay the progression of ATTR-CM. This article aims to provide a comprehensive review of ATTR-CM and insights into its novel therapeutics and upcoming treatments.

Variation of tafamidis plasma levels during the treatment of TTR amyloidosis patients with Glu89Gln mutation

PURPOSE

The transthyretin kinetic stabilizer tafamidis, used as a first-line therapy of amyloidosis patients, binds selectively to the transthyretin protein structure and thus prevents its dissociation. The limited information regarding tafamidis application in Glu89Gln amyloidosis patients imposed our research team to determine and evaluate its individual mean plasma levels and their biological variation.

METHODS

The present cohort study investigated Bulgarian amyloidosis patients, grouped by gender, age, and therapy duration. A total of sixty patients aged 40-75 years and therapy duration up to 9 years were included. A precise and accurate high-performance liquid chromatography method with ultraviolet detection was used for plasma concentration measurement.

RESULTS

Mean plasma concentrations were 5.13 ± 2.64 µmol/L and showed low intra-individual (18.50%) and high inter-individual variability (51.43%). No significant difference was observed between tafamidis plasma levels and therapy duration with p = 0.5941 (p < 0.05 considered significant), but a significant positive correlation was found between plasma concentration, gender, and age with obtained results about p-value 0.0001 and 0.0235, respectively.

CONCLUSION

The summary results of the study showed differences that may be based on some specific clinical features of the Glu89Gln mutation.

Current trends of clinical trials involving CRISPR/Cas systems

The CRISPR/Cas9 system is a powerful genome editing tool that has made enormous impacts on next-generation molecular diagnostics and therapeutics, especially for genetic disorders that traditional therapies cannot cure. Currently, CRISPR-based gene editing is widely applied in basic, preclinical, and clinical studies. In this review, we attempt to identify trends in clinical studies involving CRISPR techniques to gain insights into the improvement and contribution of CRISPR/Cas technologies compared to traditional modified modalities. The review of clinical trials is focused on the applications of the CRISPR/Cas systems in the treatment of cancer, hematological, endocrine, and immune system diseases, as well as in diagnostics. The scientific basis underlined is analyzed. In addition, the challenges of CRISPR application in disease therapies and recent advances that expand and improve CRISPR applications in precision medicine are discussed.

Case report: Magnetocardiography as a potential method of therapy monitoring in amyloidosis

Amyloidosis is characterized by a disorder of protein conformation and metabolism, resulting in deposits of insoluble fibrils in various organs causing functional disturbances. Amyloidosis can also affect the heart. Cardiac amyloidosis tends to have a poor prognostic outcome if diagnosed at a late stage. Therefore, early diagnosis and initiation of therapy as well as monitoring of treatment response are crucial to improve outcomes and to learn more about its pathophysiology and clinical course. We present an 83-year-old woman with cardiac transthyretin amyloidosis (ATTR) who was treated with tafamidis. The patient significantly improved 18 months after initiation of therapy with regards to exercise capacity and quality of life. In addition to standard diagnostic methods, we used magnetocardiography (MCG) to monitor potential treatment response by detecting changes in the magnetic field of the heart. MCG is a non-invasive method that detects the cardiac magnetic field generated by electrical currents in the heart with high sensitivity. We have recently shown that this magnetic field changes in various types of cardiomyopathies may be used as a non-invasive screening tool. We determined previously that an MCG vector ≥0.052 was the optimal threshold to detect cardiac amyloidosis. The patient's MCG was measured at various time points during therapy. At the time of diagnosis, the patient's MCG vector was 0.052. After starting therapy, the MCG vector increased to 0.090, but improved to 0.037 after 4 months of therapy. The MCG vector reached a value of 0.017 after 5 months of therapy with tafamidis, and then increased slightly after 27 months to a value of 0.027 (<0.052). Data from this case support our previous findings that MCG may be used to monitor treatment response non-invasively. Further research is needed to understand the unexpected changes in the MCG vector that were observed at the beginning of therapy and later in the course. Larger studies will be necessary to determine how these changes in the electromagnetic field of the heart are related to structural changes and how they affect clinical outcomes.

Binding of a Pyrene-Based Fluorescent Amyloid Ligand to Transthyretin: A Combined Crystallographic and Molecular Dynamics Study

Misfolding and aggregation of transthyretin (TTR) cause several amyloid diseases. Besides being an amyloidogenic protein, TTR has an affinity for bicyclic small-molecule ligands in its thyroxine (T4) binding site. One class of TTR ligands are trans-stilbenes. The trans-stilbene scaffold is also widely applied for amyloid fibril-specific ligands used as fluorescence probes and as positron emission tomography tracers for amyloid detection and diagnosis of amyloidosis. We have shown that native tetrameric TTR binds to amyloid ligands based on the trans-stilbene scaffold providing a platform for the determination of high-resolution structures of these important molecules bound to protein. In this study, we provide spectroscopic evidence of binding and X-ray crystallographic structure data on tetrameric TTR complex with the fluorescent salicylic acid-based pyrene amyloid ligand (Py1SA), an analogue of the Congo red analogue X-34. The ambiguous electron density from the X-ray diffraction, however, did not permit Py1SA placement with enough confidence likely due to partial ligand occupancy. Instead, the preferred orientation of the Py1SA ligand in the binding pocket was determined by molecular dynamics and umbrella sampling approaches. We find a distinct preference for the binding modes with the salicylic acid group pointing into the pocket and the pyrene moiety outward to the opening of the T4 binding site. Our work provides insight into TTR binding mode preference for trans-stilbene salicylic acid derivatives as well as a framework for determining structures of TTR-ligand complexes.

Wild-Type Transthyretin Amyloid Cardiomyopathy: The Gordian-Knot of Novel Therapeutic Regimens

Wild-type TTR amyloidosis (wtATTR) represents a disease difficult to diagnose with poor prognosis. Increased clinical suspicion is key, allowing for timely diagnosis. Until recently, only off-label therapies were available but recent introduction of disease specific therapy has shown potential to alter the natural history of the disease. Tafamidis, the only currently approved drug for the therapy of wtATTR, provided significantly better survival and quality of life. However, not all subgroups of patients derived equal benefit. This, along with the increased cost of treatment raised question on whether treatment should be invariably administered through the wtATTR population. This review aims to summarize current evidence on the natural history and staging systems for wtATTR, as well as available treatment options. Special consideration is given to the selection process of patients who would be expected to gain maximum benefit from tafamidis treatment, based on an ethical and cost-effective point of view.

Incidental cardiac uptake of 99mTc-diphosphonates is predictive of poor outcome: data from 9616 bone scintigraphies

BACKGROUND

Bone scintigraphy (BS) is highly diagnostic for amyloid transthyretin (ATTR) cardiomyopathy. Prevalence and prognostic value of BS cardiac uptake is not well established. Our aim was to assess the prevalence of subclinical cardiac ATTR amyloidosis in patients undergoing [99mTc]MDP/DPD scintigraphy and to define their phenotype and prognosis.

METHODS AND RESULTS

BS scans performed for any clinical indications from 2009 to 2020 were reviewed. Patients were stratified according to Perugini visual score of cardiac uptake. Follow-up data were collected. Among 9616 BS scans, 0.7% (n = 67) showed cardiac uptake. In 47 (70%) patients, Perugini score was 1 and in 20 (30%) patients uptake was ≥ 2, suggesting cardiac ATTR amyloidosis. Forty subjects (61%) died during the follow-up (mean 47 ± 30 months). Compared with patients with Perugini score 1, those Perugini score ≥ 2 showed increased death rate (P = .018). Two (2/67) subjects were investigated for TTR gene mutations resulting negative.

CONCLUSIONS

In patients undergoing BS for different clinical indications, cardiac uptake suggesting cardiac ATTR amyloidosis is a rare, but still neglected finding, thus preventing possible diagnosis of ATTR cardiomyopathy. Importantly, cardiac uptake negatively affects the survival. Physicians should be aware of this rare, but crucial finding for timely diagnosis and treatment.

A natural history analysis of asymptomatic TTR gene carriers as they develop symptomatic transthyretin amyloidosis in the Transthyretin Amyloidosis Outcomes Survey (THAOS)

BACKGROUND

Hereditary transthyretin amyloidosis (ATTRv amyloidosis) results from pathogenic mutations in the transthyretin (TTR) gene. This analysis aimed to better understand ATTRv amyloidosis development in asymptomatic TTR gene carriers.

METHODS

The Transthyretin Amyloidosis Outcomes Survey (THAOS) is an ongoing, global, longitudinal, observational survey of patients with transthyretin amyloidosis, including both inherited and wild-type disease, and asymptomatic TTR gene carriers. Asymptomatic TTR gene carriers were assessed longitudinally to identify those who developed ATTRv amyloidosis after enrolment in THAOS (data cut-off: 1 August 2021).

RESULTS

Of 740 asymptomatic TTR gene carriers, 268 (36.2%) (Val30Met, 212/613 [34.6%]; non-Val30Met, 48/111 [43.2%]) developed ATTRv amyloidosis within a median 2.2 years after enrolment. The most common first symptoms were sensory (49.5%) and autonomic (37.3%) neuropathy in Val30Met patients, and sensory neuropathy (45.8%) and cardiac disorder (22.9%) in non-Val30Met patients. Most patients first presented with a predominantly neurologic phenotype (Val30Met, 77.8%; non-Val30Met, 70.8%).

CONCLUSIONS

More than one-third of asymptomatic TTR gene carriers in THAOS developed ATTRv amyloidosis within a median 2 years of enrolment. Val30Met versus non-Val30Met patients had a lower transition rate. Given the importance of early treatment, these findings underscore the need for identification and careful monitoring of at-risk TTR gene carriers to enable prompt treatment.

TRIAL REGISTRATION

ClinicalTrials.gov: NCT00628745.

Heart failure: an update from the last years and a look at the near future

In the last years, major progress occurred in heart failure (HF) management. Quadruple therapy is now mandatory for all the patients with HF with reduced ejection fraction. Whilst verciguat is becoming available across several countries, omecamtiv mecarbil is waiting to be released for clinical use. Concurrent use of potassium-lowering agents may counteract hyperkalaemia and facilitate renin-angiotensin-aldosterone system inhibitor implementations. The results of the EMPagliflozin outcomE tRial in Patients With chrOnic heaRt Failure With Preserved Ejection Fraction (EMPEROR-Preserved) trial were confirmed by the Dapagliflozin in Heart Failure with Mildly Reduced or Preserved Ejection Fraction (DELIVER) trial, and we now have, for the first time, evidence for treatment of also patients with HF with preserved ejection fraction. In a pre-specified meta-analysis of major randomized controlled trials, sodium-glucose co-transporter-2 inhibitors reduced all-cause mortality, cardiovascular (CV) mortality, and HF hospitalization in the patients with HF regardless of left ventricular ejection fraction. Other steps forward have occurred in the treatment of decompensated HF. Acetazolamide in Acute Decompensated Heart Failure with Volume Overload (ADVOR) trial showed that the addition of intravenous acetazolamide to loop diuretics leads to greater decongestion vs. placebo. The addition of hydrochlorothiazide to loop diuretics was evaluated in the CLOROTIC trial. Torasemide did not change outcomes, compared with furosemide, in TRANSFORM-HF. Ferric derisomaltose had an effect on the primary outcome of CV mortality or HF rehospitalizations in IRONMAN (rate ratio 0.82; 95% confidence interval 0.66-1.02; P = 0.070). Further options for the treatment of HF, including device therapies, cardiac contractility modulation, and percutaneous treatment of valvulopathies, are summarized in this article.

Toxic Misfolded Transthyretin Oligomers with Different Molecular Conformations Formed through Distinct Oligomerization Pathways

Protein aggregation is initiated by structural changes from native polypeptides to cytotoxic oligomers, which form cross-β structured amyloid. Identification and characterization of oligomeric intermediates are critically important for understanding not only the molecular mechanism of aggregation but also the cytotoxic nature of amyloid oligomers. Preparation of misfolded oligomers for structural characterization is, however, challenging because of their transient, heterogeneous nature. Here, we report two distinct misfolded transthyretin (TTR) oligomers formed through different oligomerization pathways. A pathogenic TTR variant with a strong aggregation propensity (L55P) was used to prepare misfolded oligomers at physiological pH. Our mechanistic studies showed that the full-length TTR initially forms small oligomers, which self-assemble into short protofibrils at later stages. Enzymatic cleavage of the CD loop was also used to induce the formation of N-terminally truncated oligomers, which was detected in ex vivo cardiac TTR aggregates extracted from the tissues of patients. Structural characterization of the oligomers using solid-state nuclear magnetic resonance and circular dichroism revealed that the two TTR misfolded oligomers have distinct molecular conformations. In addition, the proteolytically cleaved TTR oligomers exhibit a higher surface hydrophobicity, suggesting the presence of distinct oligomerization pathways for TTR oligomer formation. Cytotoxicity assays also revealed that the cytotoxicity of cleaved oligomers is stronger than that of the full-length TTR oligomers, indicating that hydrophobicity might be an important property of toxic oligomers. These comparative biophysical analyses suggest that the toxic cleaved TTR oligomers formed through a different misfoling pathway may adopt distinct structural features that produce higher surface hydrophobicity, leading to the stronger cytotoxic activities.

Myocardial Scintigraphy in Diagnosing Cardiac Transthyretin Amyloidosis

Myocardial scintigraphy with technetium-99m pyrophosphate is a minimally invasive technique that can distinguish between transthyretin amyloidosis (ATTR) and light-chain amyloidosis. We present a case in which it helped determine the amyloidosis type in a 74-year-old man with cardiac amyloidosis and multiple previous admissions for acute decompensated heart failure. The patient presented with increasing abdominal girth and bilateral lower extremity edema. His medical history also included atrial fibrillation, liver cirrhosis, hypertension, stage 3 chronic kidney disease, and peripheral vascular disease. We prescribed guideline-directed medical therapy for his acute decompensated heart failure with cardiorenal syndrome and his decompensated cirrhosis. Two years previously, a presumptive diagnosis of ATTR cardiomyopathy had been made on the basis of the patient's age, predominantly cardiac involvement, an unremarkable serum protein electrophoresis result, and an abnormal free κ/λ light-chain ratio of 2.24. Over the next year, the patient's clinical condition had worsened with the development of liver cirrhosis and peripheral neuropathy, and his free κ/λ light-chain ratio had become even more abnormal. At the current presentation, a technetium-99m pyrophosphate nuclear scintigram revealed a free κ/λ light-chain ratio of 1.52. This, combined with the patient's age and slow progression of primarily cardiac disease, supported the diagnosis of ATTR, and we prescribed tafamadis. This case suggests that technetium-99m pyrophosphate scintigraphy is valuable in definitively diagnosing ATTR cardiomyopathy and selecting patients who may benefit from disease-modifying therapy.

Analysis of amyloidogenic transthyretin mutations using continuum solvent free energy calculations

Many proteins can undergo pathological conformational changes that result in the formation of amyloidogenic fibril structures. Various neurodegenerative diseases are associated with such pathological fibril formation of specific proteins. Transthyretin (TTR) is a tetrameric globular transport protein in the blood plasma that can dissociate, unfold, and form long and stable fibrils. Many TTR mutations are known that promote (TTR) amyloidosis and cause severe diseases. TTR amyloidosis has been studied extensively using biochemical methods and structures of various mutations in the globular form have been characterized. Recently, also the structure of a TTR fibril has been determined. In an effort to better understand why some mutations increase or decrease the tendency of amyloid formation, we have applied a combined molecular dynamics and continuum solvent approach to calculate the energetic influence of residue changes in the globular versus fibril form. For 29 out of 36 tested TTR single residue mutations, the approach correctly predicts the increased or decreased tendency for amyloidosis allowing us also to elucidate the origins of the tendency. We find that indeed the destabilization of the globular monomer or changes in dimer and tetramer stability due to mutation has a dominant influence on the amyloidogenic tendency. The continuum solvent model predicts a significantly more favorable mean energy per residue of the fibril form compared to the globular form. This effect is only slightly modulated by single-point mutations preserving the energetic preference for fibril formation upon protein unfolding. It explains why no correlation between experimental amyloidosis and calculated change in fibril stability was observed.

Factors Associated with Increased Health-Related Quality of Life Benefits in Patients with Hereditary Transthyretin Amyloidosis with Polyneuropathy (ATTRv-PN) Treated with Inotersen

INTRODUCTION/AIMS

Hereditary transthyretin amyloidosis with polyneuropathy (ATTRv-PN) is a genetic condition associated with significant morbidity and mortality. We aimed to identify patient subgroups exhibiting the greatest health-related quality of life [HRQL] benefit from inotersen treatment.

METHODS

We examined data from the inotersen phase 2/3 randomized controlled trial for ATTRv-PN, NEURO-TTR (NCT01737398, 66 weeks). LASSO regression models predicted changes in Norfolk QoL-DN total score (TQoL, range -4 to 136; higher scores indicate poorer HRQL) from baseline in the inotersen and placebo arm, respectively. Individualized efficacy scores (ES) were calculated as differences between predicted change-scores had patients received inotersen vs. placebo. Patients were ranked by ES to define the greatest-benefit subpopulation (top 50%). Characteristics of the top 50% and bottom 50% of patients were compared.

RESULTS

The overall mean ± standard deviation TQoL change was -0.20±19.13 for inotersen (indicating no change) and 10.77±21.13 for placebo (indicating deterioration). Within the highest-benefit patients, mean TQoL change was -11.03±17.06 (improvement) for inotersen and 11.24±22.97 (deterioration) for placebo (P<0.001). Compared with the overall population, patients in the greatest-benefit subpopulation were younger, more likely to have polyneuropathy disability (PND) scores 1 or 2, less likely to have received prior tafamidis or diflunisal treatment, and more likely to have Val30Met mutations and higher (worse) baseline TQoL.

CONCLUSION

Patients who were younger and/or at earlier polyneuropathy stages experienced greater HRQL benefits from inotersen over 66 weeks. These findings underscore the need for early diagnosis and treatment initiation, especially among more severely affected patients in early stages of ATTRv-PN. This article is protected by copyright. All rights reserved.

Correlation Between Cardiac Images, Biomarkers, and Amyloid Load in Wild-Type Transthyretin Amyloid Cardiomyopathy

Background Several imaging parameters and biomarkers provide diagnostic and prognostic information for wild-type transthyretin amyloid cardiomyopathy. However, the relevance of these parameters and their association with cardiac amyloid load requires further substantiation. We aimed to elucidate the association of imaging parameters obtained using ^99mTc-labeled pyrophosphate scintigraphy, cardiovascular magnetic resonance imaging, global longitudinal strain (GLS), and cardiac biomarkers with cardiac amyloid load in patients with wild-type transthyretin amyloid cardiomyopathy. Methods and Results Eighty-eight patients with wild-type transthyretin amyloid cardiomyopathy who underwent ^99mTc-labeled pyrophosphate scintigraphy and cardiovascular magnetic resonance were retrospectively evaluated. Quantitative cardiac amyloid load was obtained from 61 patients after myocardial biopsy. Correlations were assessed using Pearson's correlation coefficient applied to medical record data. The mean heart to contralateral ratio, native T1, extracellular volume, and GLS were 1.91±0.36, 1419.4±56.4 ms, 56.5±13.6%, and -9.4±2.5%, respectively. Median high-sensitivity cardiac troponin T (hs-cTnT) and BNP (B-type natriuretic peptide) levels were 0.0478 (0.0334-0.0691) ng/mL and 213.8 (125.8-392.7) pg/mL, respectively. The mean cardiac amyloid load was 22.9±15.0%. The heart to contralateral ratio correlated significantly with native T1 (r=0.397), extracellular volume (r=0.477), GLS (r=0.363), cardiac amyloid load (r=0.379), and Ln (hs-cTnT) (r=0.247). Further, cardiac amyloid load correlated significantly with native T1 (r=0.509), extracellular volume (r=0.310), GLS (r=0.446), and Ln (hs-cTnT) (r=0.354). Compared with BNP, hs-cTnT levels better correlated with several imaging parameters and cardiac amyloid load. Conclusions Increased cardiac amyloid load correlated with increased ^99mTc-labeled pyrophosphate positivity, native T1, extracellular volume, and hs-cTnT levels, and an impaired GLS, suggesting that imaging parameters and cardiac biomarkers may reflect histological and functional changes attributable to amyloid deposition in the myocardium.

Correlation of Quantitative 99mTc DPD Scintigraphy With Echocardiographic Alterations in Left Atrial Parameters in Transthyretin Amyloidosis

AIM

Cardiac transthyretin amyloidosis (ATTR) patients have high rates of atrial arrhythmias. We evaluated echocardiographic structural and functional left atrial (LA) parameters and correlated these with technetium-99m 3,3-diphosphono-1,2-propanodicarboxylic acid (^99mTc-DPD) bone scintigraphy tracer uptake within the LA in ATTR patients.

METHODS

ATTR patients (wild-type, hereditary and asymptomatic transthyretin [TTR] variant carriers) who had undergone ^99mTc-DPD and transthoracic echocardiogram (TTE) were selected. Quantitative ^99mTc-DPD uptake analysis and echocardiographic evaluation of LA structural and functional parameters was performed.

RESULTS

Forty (40) ATTR patients (wild-type n=17; hereditary ATTR and TTR variant carriers n=23; median age 68.8±22 years) were included. TTE parameters including indexed LA minimum (LAV_min) (r=0.66), and LA maximum volumes (LAV_max) (r=0.64), LA emptying fraction (LAEF) (r=-0.68), LA function index (LAFI) (r=-0.70) and reservoir strain (ƐR) (r=-0.70) (p<0.001 for all) demonstrated good correlation to LA tracer uptake. Normal LA volume (LAV_min and LAV_max) and function (LAEF, LAFI and ƐR) was observed in hereditary ATTR and TTR variant carriers without cardiac tracer uptake. The subgroup of ATTR patients with atrial fibrillation/flutter demonstrated increased LAV_min and LAV_max with further reduction in LA function (LAEF, LAFI and ƐR). Receiver operating characteristic curves demonstrated strong diagnostic accuracies for LA structural (LAV_min and LAV_max; area under the curve [AUC] of 0.83 and 0.84 respectively) and functional (LAEF, LAFI and ƐR; AUC 0.81, 0.88 and 0.85, respectively) parameters.

CONCLUSION

Left atrial structural and functional parameters demonstrated good correlations with quantitative ^99mTc-DPD tracer LA uptake. Echocardiography and ^99mTc-DPD scintigraphy may have significant roles in identification and surveillance of ATTR patients likely to develop atrial arrhythmias.

Healthcare resource use associated with the diagnosis of transthyretin amyloidosis cardiomyopathy

OBJECTIVES

Our primary aim was to evaluate the healthcare resource use associated with the diagnosis of transthyretin amyloidosis cardiomyopathy. Second, we aim to assess the effect of the number of diagnostic tests and clinical contact points on the total time and costs between symptom onset and diagnosis defining a quantitative hypothetical optimized diagnostic pathway.

SETTING

Clinical and cost data were collected from patients presenting between 2010 and 2018 in a tertiary referral institution in South London involving two participating hospitals.

PARTICIPANTS

Thirty-eight adult patients with a definite diagnosis of transthyretin amyloidosis cardiomyopathy were included, mostly male (n = 28, 74%) and of African-Caribbean descent (n = 23, 64%). We excluded patients without a confirmed transthyretin amyloidosis cardiomyopathy or those on inotersen, patisiran, or diflunisal at point of referral.

PRIMARY AND SECONDARY OUTCOME MEASURES

The average time between first presentation and final diagnosis, and the cost per patient per month. By comparing to a more optimal clinical pathway towards diagnosis, we considered what could be the theoretical gain in terms of time to diagnosis and financial savings.

RESULTS

The average time between first presentation and final diagnosis was 2.74 years. The average cost per patient per month was higher with progressive heart failure symptoms. A hypothetical optimal pathway reduces time to diagnosis of 1.65 to 1.74 years per patient. The potential financial savings are estimated within the range of £3000 to £4800 per patient.

CONCLUSIONS

Patients diagnosed with transthyretin amyloidosis cardiomyopathy have substantial healthcare resource utilization and costs starting from symptom onset. Higher costs were observed with progression in symptoms and appear linked to a delayed diagnosis. The number of additional diagnostic tests and clinical contact points may contribute to this and could represent a path to explore further for important health and cost savings, with more efficient pathways for these patients to be managed.

Hereditary transthyretin amyloidosis overview

Hereditary amyloidogenic transthyretin (ATTRv) amyloidosis is a rare autosomal dominantly inherited disorder caused by mutations in the transthyretin (TTR) gene. The pathogenetic model of ATTRv amyloidosis indicates that amyloidogenic, usually missense, mutations destabilize the native TTR favouring the dissociation of the tetramer into partially unfolded species that self-assemble into amyloid fibrils. Amyloid deposits and monomer-oligomer toxicity are the basis of multisystemic ATTRv clinical involvement. Peripheral nervous system (autonomic and somatic) and heart are the most affected sites. In the last decades, a better knowledge of pathomechanisms underlying the disease led to develop novel and promising drugs that are rapidly changing the natural history of ATTRv amyloidosis. Thus, clinicians face the challenge of timely diagnosis for addressing patients to appropriate treatment. As well, the progressive nature of ATTRv raises the issue of presymptomatic testing and risk management of carriers. The main aim of this review was to focus on what we know about ATTRv so far, from pathogenesis to clinical manifestations, diagnosis and hence patient's monitoring and treatment, and from presymptomatic testing to management of carriers.

Searching for the Best Transthyretin Aggregation Protocol to Study Amyloid Fibril Disruption

Several degenerative amyloid diseases, with no fully effective treatment, affect millions of people worldwide. These pathologies—amyloidoses—are known to be associated with the formation of ordered protein aggregates and highly stable and insoluble amyloid fibrils, which are deposited in multiple tissues and organs. The disruption of preformed amyloid aggregates and fibrils is one possible therapeutic strategy against amyloidosis; however, only a few compounds have been identified as possible fibril disruptors in vivo to date. To properly identify chemical compounds as potential fibril disruptors, a reliable, fast, and economic screening protocol must be developed. For this purpose, three amyloid fibril formation protocols using transthyretin (TTR), a plasma protein involved in several amyloidoses, were studied using thioflavin-T fluorescence assays, circular dichroism (CD), turbidity, dynamic light scattering (DLS), and transmission electron microscopy (TEM), in order to characterize and select the most appropriate fibril formation protocol. Saturation transfer difference nuclear magnetic resonance spectroscopy (STD NMR) was successfully used to study the interaction of doxycycline, a known amyloid fibril disruptor, with preformed wild-type TTR (TTRwt) aggregates and fibrils. DLS and TEM were also used to characterize the effect of doxycycline on TTRwt amyloid species disaggregation. A comparison of the TTR amyloid morphology formed in different experimental conditions is also presented.

A year in heart failure: an update of recent findings

Major changes have occurred in these last years in heart failure (HF) management. Landmark trials and the 2021 European Society of Cardiology guidelines for the diagnosis and treatment of HF have established four classes of drugs for treatment of HF with reduced ejection fraction: angiotensin-converting enzyme inhibitors or an angiotensin receptor-neprilysin inhibitor, beta-blockers, mineralocorticoid receptor antagonists, and sodium-glucose co-transporter 2 inhibitors, namely, dapagliflozin or empagliflozin. These drugs consistently showed benefits on mortality, HF hospitalizations, and quality of life. Correction of iron deficiency is indicated to improve symptoms and reduce HF hospitalizations. AFFIRM-AHF showed 26% reduction in total HF hospitalizations with ferric carboxymaltose vs. placebo in patients hospitalized for acute HF (P = 0.013). The guanylate cyclase activator vericiguat and the myosin activator omecamtiv mecarbil improved outcomes in randomized placebo-controlled trials, and vericiguat is now approved for clinical practice. Treatment of HF with preserved ejection fraction (HFpEF) was a major unmet clinical need until this year when the results of EMPEROR-Preserved (EMPagliflozin outcomE tRial in Patients With chrOnic HFpEF) were issued. Compared with placebo, empagliflozin reduced by 21% (hazard ratio, 0.79; 95% confidence interval, 0.69 to 0.90; P < 0.001), the primary outcome of cardiovascular death or HF hospitalization. Advances in the treatment of specific phenotypes of HF, including atrial fibrillation, valvular heart disease, cardiomyopathies, cardiac amyloidosis, and cancer-related HF, also occurred. Coronavirus disease 2019 (COVID-19) pandemic still plays a major role in HF epidemiology and management. All these aspects are highlighted in this review.

Correlation Between Quantitative Uptake of 99mTC-DPD and Echocardiographic Parameters in Cardiac ATTR: A Novel Follow-Up Strategy

Aims: There has been a paradigm shift in diagnosis of cardiac transthyretin amyloidosis (ATTR) with non-invasive techniques including technetium-99m 3,3-diphosphono-1,2-propanodicarboxylic acid (99mTc-DPD) bone scintigraphy. We evaluated structural and functional biventricular alterations by transthoracic echocardiography (TTE) and determined the correlation with 99mTc-DPD tracer uptake in ATTR. Materials and Methods: ATTR patients (wild-type, hereditary or asymptomatic transthyretin [TTR] variant carriers) with 99mTc-DPD and TTE were selected; 99mTc-DPD uptake was analyzed quantitatively. TTE assessment of left ventricle (LV) and right ventricle (RV) parameters was performed. Results: Forty ATTR patients (wild-type n = 17; hereditary ATTR and TTR variant carriers n = 23; median age 68.8 ± 22 years) were included. TTE parameters displaying good correlation with 99mTc-DPD tracer uptake included LV average wall thickness (r = 0.837), LV indexed mass (LVMI; r = 0.802), RV wall thickness (r = 0.610), average e' (r = -0.830), E/e' ratio (r = 0.786), LV global longitudinal strain (GLS; r = 0.714) and RV GLS (r = 0.632; p < 0.001 for all). Hereditary ATTR and TTR variant carriers without cardiac tracer uptake had normal echocardiographic parameters. Receiver operating characteristic curves demonstrated strong diagnostic accuracies for structural (LV wall thickness, LVMI and RV wall thickness; area under the curve (AUC) of 0.96 for all) and functional (LV and RV GLS; AUC of 0.86 and 0.88, respectively) parameters. Conclusion: Good correlations between TTE biventricular structural and functional parameters were demonstrated with quantitative 99mTc-DPD uptake. Echocardiography may potentially assume a significant role in longitudinal follow-up for monitoring disease progression and for evaluating treatment response.

The discovery and development of transthyretin amyloidogenesis inhibitors: what are the lessons?

Transthyretin (TTR) is associated with several human amyloid diseases. Various kinetic stabilizers have been developed to inhibit the dissociation of TTR tetramer and the formation of amyloid fibrils. Most of them are bisaryl derivatives, natural flavonoids, crown ethers and carborans. In this review article, we focus on TTR tetramer stabilizers, genetic therapeutic approaches and fibril remodelers. The binding modes of typical bisaryl derivatives, natural flavonoids, crown ethers and carborans are discussed. Based on knowledge of the binding of thyroxine to TTR tetramer, many stabilizers have been screened to dock into the thyroxine binding sites, leading to TTR tetramer stabilization. Particularly, those stabilizers with unique binding profiles have shown great potential in developing the therapeutic management of TTR amyloidogenesis.

CRISPR-Cas9 In Vivo Gene Editing for Transthyretin Amyloidosis

BACKGROUND

Transthyretin amyloidosis, also called ATTR amyloidosis, is a life-threatening disease characterized by progressive accumulation of misfolded transthyretin (TTR) protein in tissues, predominantly the nerves and heart. NTLA-2001 is an in vivo gene-editing therapeutic agent that is designed to treat ATTR amyloidosis by reducing the concentration of TTR in serum. It is based on the clustered regularly interspaced short palindromic repeats and associated Cas9 endonuclease (CRISPR-Cas9) system and comprises a lipid nanoparticle encapsulating messenger RNA for Cas9 protein and a single guide RNA targeting TTR.

METHODS

After conducting preclinical in vitro and in vivo studies, we evaluated the safety and pharmacodynamic effects of single escalating doses of NTLA-2001 in six patients with hereditary ATTR amyloidosis with polyneuropathy, three in each of the two initial dose groups (0.1 mg per kilogram and 0.3 mg per kilogram), within an ongoing phase 1 clinical study.

RESULTS

Preclinical studies showed durable knockout of TTR after a single dose. Serial assessments of safety during the first 28 days after infusion in patients revealed few adverse events, and those that did occur were mild in grade. Dose-dependent pharmacodynamic effects were observed. At day 28, the mean reduction from baseline in serum TTR protein concentration was 52% (range, 47 to 56) in the group that received a dose of 0.1 mg per kilogram and was 87% (range, 80 to 96) in the group that received a dose of 0.3 mg per kilogram.

CONCLUSIONS

In a small group of patients with hereditary ATTR amyloidosis with polyneuropathy, administration of NTLA-2001 was associated with only mild adverse events and led to decreases in serum TTR protein concentrations through targeted knockout of TTR. (Funded by Intellia Therapeutics and Regeneron Pharmaceuticals; ClinicalTrials.gov number, NCT04601051.).

Association of the V122I Transthyretin Amyloidosis Genetic Variant With Cardiac Structure and Function in Middle-aged Black Adults: Coronary Artery Risk Development in Young Adults (CARDIA) Study

Importance

The variant V122I is commonly enriched in the transthyretin (TTR) gene in individuals of African ancestry and associated with greater risk of heart failure (HF) in older adulthood, after age 65 years. Prevention of HF may be most effective earlier in life, but whether screening with echocardiography can identify subclinical cardiac abnormalities during middle age to risk-stratify individuals appears to be unknown.

Objective

To examine the association between the V122I TTR variant and cardiac structure and function during middle age in those without prevalent HF.

Design, Setting, and Participants

This serial cross-sectional study of 875 Black participants in the Coronary Artery Risk Development in Young Adults (CARDIA) cohort was conducted at 4 urban sites across the US. Recruiting was completed in 1985-1986, and follow-up examinations occurred 25 and 30 years later. A subset of Black adults from the CARDIA cohort who underwent TTR genotyping was included. Data analysis was completed from January 2020 to October 2020.

Exposures

The V122I TTR genotype.

Main Outcomes and Measures

Echocardiographic left ventricular (LV) circumferential and longitudinal systolic strain and LV structure, measured at years 25 and 30 of follow-up. The analyses were adjusted for age, sex, echocardiography quality, genetic ancestry, and field center.

Results

Among the 875 Black adults (mean [SD] age, 49.4 [3.8] years at year 25; 543 women [62.1%]), there were 31 individuals who were heterozygous and 1 who was homozygous for the V122I TTR variant. Of the adults who had an echocardiogram at year 25, rates of hypertension (312 [46%]), diabetes (102 [15%]), and current smoking (128 [19%]) were not significantly different between those who did and did not carry V122I TTR. At year 25, there was no difference in LV circumferential strain, longitudinal strain, or LV structure between those who did vs did not carry V122I TTR. At year 30, those who carried V122I TTR had significantly lower absolute LV circumferential strain (mean [SD], 12.4 [4.2] percentage units) compared with those who did not carry the variant (mean [SD], 14.5 [3.7] percentage units). Those who carried V122I TTR also had significantly higher LV mass index values (mean [SD], 97.5 [34.1] g/m2) compared with those who did not (mean [SD], 83.7 [22.6] g/m2) at year 30.

Conclusions and Relevance

Carrier status for the V122I TTR variant is associated with subclinical cardiac abnormalities in middle age (worse LV systolic function and higher LV mass) that have been associated with increased risk of incident HF. Midlife screening of individuals who carry V122I TTR with echocardiography may prognosticate risk of symptomatic HF and inform prevention strategies.

Arrhythmic Sudden Cardiac Death and the Role of Implantable Cardioverter-Defibrillator in Patients with Cardiac Amyloidosis-A Narrative Literature Review

Cardiac amyloidosis (CA) is considered to be associated with an increased risk of sudden cardiac death (SCD) due to ventricular tachyarrhythmias and electromechanical dissociation. However, current arrhythmic risk stratification and the role of an implantable cardioverter-defibrillator (ICD) for primary prevention of SCD remains unclear. This article provides a narrative review of the literature on electrophysiological abnormalities in the context of ventricular arrhythmias in patients with CA and the role of ICD in terms of survival benefit in this group of patients.

Patisiran in hATTR Amyloidosis: Six-Month Latency Period before Efficacy

Hereditary amyloidosis associated with mutations in the transthyretin gene (hATTR) is a progressive devastating disease, with a fatal outcome occurring within 10years after onset. In recent years, TTR gene silencing therapy appeared as a promising therapeutic strategy, showing evidence that disease progression can be slowed and perhaps reversed. We report here 18 subjects affected by hATTR amyloidosis treated with patisiran, a small interfering RNA acting as TTR silencer, and evaluated with a PND score, the NIS and NIS-LL scale, and a Norfolk QOL-DN questionnaire at baseline and then every 6 months. A global clinical stabilizationwas observed for the majority of the patients, with mild-moderate improvements in some cases, even in advanced disease stage (PND score > 2). Analysis of NIS, NIS-LL and Norfolk QOL-DN results, and PND score variation suggest the possible presence of a 6-month latency period prior to benefit of treatment.

Emerging therapy in light-chain and acquired transthyretin-related amyloidosis: an Italian single-centre experience in heart transplantation

AIMS

The prognosis for patients affected by light-chain cardiac amyloidosis and acquired transthyretin-related (TTR) amyloidosis is poor. Heart transplantation (HTx) could improve prognosis also enabling autologous stem cell transplantation (ASCT) in the first group.

METHODS AND RESULTS

A total of 36 patients affected by systemic amyloidosis have been referred to our centre from 2009 to 2019. Of these, nine had cardiac involvement: seven by light-chain amyloidosis and two by acquired TTR amyloidosis. None died while waiting for HTx. A specific internal protocol useful to select candidates and to monitor the organ involvement after HTx was developed. Median age at diagnosis was 54 years and 66% were male. The most common short-term complication after HTx was renal failure (44%), followed by acute cardiac rejection more than 2R (22%). ASCT was performed in six out of seven light-chain cardiac amyloidosis patients, with a median time of 6 months after HTx. Two patients affected by light-chain cardiac amyloidosis died due to amyloidosis relapse: one before undergoing ASCT. After a median follow-up of 31 (7-124) months, 1- and 5-year survival was 88 and 66% in the cardiac light-chain amyloidosis group. Conversely, 1- and 5-year survival was 100% in the acquired TTR amyloidosis group.

CONCLUSION

HTx may represent a valuable option in carefully selected patients. ASCT after HTx is an effective treatment that could decrease amyloidosis relapse in light-chain cardiac amyloidosis patients. A multidisciplinary approach is mandatory to select the best candidates and to obtain the most effective results with a specific surveillance follow-up protocol.

Narrative review of pharmacotherapy for transthyretin cardiac amyloid

Treatment of cardiac amyloidosis is determined by the amyloid type and degree of involvement. Two types of amyloid commonly infiltrate the heart: immunoglobulin light-chain amyloid (AL), and transthyretin amyloid (ATTR), that encompasses other two forms, a hereditary form (hATTR), and a sporadic, age-related wild-type (wtATTR). The prevalence is expected to increase with aging population. The natural history of ATTR cardiomyopathy includes progressive heart failure (HF), complicated by arrhythmias and conduction system disease. New therapies options have been approved or are under investigation. We performed a narrative literature review, manually-searched the reference lists of included articles and relevant reviews. Treatment for cardiac ATTR should be directed towards alleviation of HF symptoms and to slow or stop progressive amyloid deposition. Conventional HF medications are poorly tolerated and may not alter the disease progression or symptoms, except perhaps with the administration of diuretics. There are three approaches of therapy for ATTR cardiomyopathy: tetramer stabilizers, inhibition of ATTR protein synthesis and clearance of deposited fibrils. Tafamidis diminishes the progression of cardiomyopathy, functional parameters, improves overall outcome in patients with early disease stages, irrespective of ATTR status and is well tolerated. Diflunisal has shown promising results in early studies, but at the expense of significant side effects. Two new agents, antisense oligonucleotides, patisiran and inotersen are under investigation in cardiac amyloidosis. Patisiran appears to be the most effective treatment for hATTR, although evidence is limited, with a relatively small cardiac subpopulation. Therapies considering clearance of amyloid fibrils from tissue remain experimental. In conclusion, tafamidis is the only approved agent for the treatment of ATTR cardiomyopathy although multiple other agents have shown promising early results and are undergoing clinical trials. Careful consideration of the type of ATTR, comorbidities and disease stage will be key in deciding the optimal therapy for ATTR patients.

Advances in Treatment of ATTRv Amyloidosis: State of the Art and Future Prospects

Hereditary amyloid transthyretin (ATTRv) amyloidosis with polyneuropathy is a progressive disease that is transmitted as an autosomal dominant trait and characterized by multiple organ failure, including axonal sensory-motor neuropathy, cardiac involvement, and autonomic dysfunction. Liver transplantation (LT) and combined heart-liver transplantation, introduced in the 1990s, have been the only therapies for almost two decades. In 2011, tafamidis meglumine became the first specific drug approved by regulatory agencies, since then the attention toward this disease has progressively increased and several drugs with different mechanisms of action are now available. This review describes the drugs already on the market, those that have shown interesting results although not yet approved, and those currently being tested.

Starting at the beginning: endoplasmic reticulum proteostasis and systemic amyloid disease

Systemic amyloid diseases are characterized by the deposition of an amyloidogenic protein as toxic oligomers and amyloid fibrils on tissues distal from the site of protein synthesis. Traditionally, these diseases have been viewed as disorders of peripheral target tissues where aggregates are deposited, and toxicity is observed. However, recent evidence highlights an important role for endoplasmic reticulum (ER) proteostasis pathways within tissues synthesizing and secreting amyloidogenic proteins, such as the liver, in the pathogenesis of these disorders. Here, we describe the pathologic implications of ER proteostasis and its regulation on the toxic extracellular aggregation of amyloidogenic proteins implicated in systemic amyloid disease pathogenesis. Furthermore, we discuss the therapeutic potential for targeting ER proteostasis to reduce the secretion and toxic aggregation of amyloidogenic proteins to mitigate peripheral amyloid-associated toxicity involved in the onset and progression of systemic amyloid diseases.

Targeting transthyretin - Mechanism-based treatment approaches and future perspectives in hereditary amyloidosis

The liver-derived, circulating transport protein transthyretin (TTR) is the cause of systemic hereditary (ATTRv) and wild-type (ATTRwt) amyloidosis. TTR stabilization and knockdown are approved therapies to mitigate the otherwise lethal disease course. To date, the variety in phenotypic penetrance is not fully understood. This systematic review summarizes the current literature on TTR pathophysiology with its therapeutic implications. Tetramer dissociation is the rate-limiting step of amyloidogenesis. Besides destabilizing TTR mutations, other genetic (RBP4, APCS, AR, ATX2, C1q, C3) and external (extracellular matrix, Schwann cell interaction) factors influence the type of onset and organ tropism. The approved small molecule tafamidis stabilizes the tetramer and significantly decelerates the clinical course. By sequence-specific mRNA knockdown, the approved small interfering RNA (siRNA) patisiran and antisense oligonucleotide (ASO) inotersen both significantly reduce plasma TTR levels and improve neuropathy and quality of life compared to placebo. With enhanced hepatic targeting capabilities, GalNac-conjugated siRNA and ASOs have recently entered phase III clinical trials. Bivalent TTR stabilizers occupy both binding groves in vitro, but have not been tested in trials so far. Tolcapone is another stabilizer with the potential to cross the blood-brain barrier, but its half-life is short and liver failure a potential side effect. Amyloid-directed antibodies and substances like doxycycline aim at reducing the amyloid load, however, none of the yet developed antibodies has successfully passed clinical trials. ATTR-amyloidosis has become a model disease for pathophysiology-based treatment. Further understanding of disease mechanisms will help to overcome the remaining limitations, including application burden, side effects, and blood-brain barrier permeability.

Prognostic value of cardiopulmonary exercise testing in cardiac amyloidosis

AIMS

In amyloid patients, cardiac involvement dramatically worsens functional capacity and prognosis. We sought to study how the cardiopulmonary exercise test (CPET) could help in functional assessment and risk stratification of patients with cardiac amyloidosis (CA).

METHODS AND RESULTS

We carried out a multicentre study including patients with light chain (AL) or transthyretin (TTR) CA. All patients underwent exhaustive examination including CPET and follow-up. The primary prognostic endpoint was the occurrence of death or heart failure hospitalization. Overall, 150 patients were included (91 AL and 59 TTR CA). Median age, systolic blood pressure, N-terminal pro B-type natriuretic peptide (NT-proBNP) and cardiac troponin T were 70 (64-78) years, 121 [interquartile range (IQR) 109-139] mmHg, 2806 (IQR 1218-4638) ng/L and 64 (IQR 33-120) ng/L, respectively. New York Heart Association classes were I-II in 64%. Median peak oxygen consumption (VO₂ ) and circulatory power were low at 13.0 (10.0-16.9) mL/kg/min and 1730 (1318-2614) mmHg/mL/min, respectively. The minute ventilation/carbon dioxide production slope was increased to 37 (IQR 33-45). A total of 77 patients (51%) had chronotropic insufficiency. After a median follow-up of 20 months, there were 37 deaths and 44 heart failure hospitalizations. At multivariate Cox analysis, peak VO₂  ≤13 mL/kg/min [hazard ratio (HR) 2.7, 95% confidence interval (CI) 1.6-4.8], circulatory power ≤1730 mmHg/mL/min (HR 2.4, 95% CI 1.2-4.6) and NT-proBNP ≥1800 ng/L (HR 2.2, 95% CI 1.1-4.3) were found to be associated with the primary outcome. No events occurred in patients with both peak VO₂  >13 mL/kg/min and NT-proBNP <1800 ng/L, while the association of VO₂  ≤13 mL/kg/min with NT-proBNP ≥1800 ng/L identified a very high-risk subgroup.

CONCLUSION

In CA, CPET is helpful in assessing functional capacity, circulatory and chronotropic responses as well as the prognosis of patients along with cardiac biomarkers.

Cardiac scintigraphy with 99mTc-diphosphonates in cardiac amyloidosis

Transthyretin cardiac amyloidosis (ATTR) has traditionally been considered a rare, difficult-to-diagnose and untreatable disease. However, its prevalence is known to be greater than what was previously thought, non-invasive diagnostic methods are available, and that effective treatments are emerging. In this context, cardiac scintigraphy (CS) with ^99mTc-labelled diphosphonates has aroused a noticeable surge in interest by demonstrating high sensitivity and specificity for the reliable, non-invasive diagnosis of ATTR. By way of a guide, this article aims to identify the critical components in the performance of CS that are useful in everyday clinical practice and, thus, help specialists use optimal radiopharmaceuticals, obtain the most appropriate images, interpret the results thereof, and acquaint themselves with those clinical scenarios in which it is convenient to perform CS.