Amyloid heart disease: genetics translated into disease-modifying therapy

Advances in the screening, diagnosis, and treatment of transthyretin amyloid cardiomyopathy: New insights and future directions

Transthyretin amyloid cardiomyopathy (ATTR-CM) is a progressive form of heart failure caused by myocardial tissue infiltration with fibrillar amyloid deposits. ATTR-CM has been traditionally underrecognized and regarded by clinicians as a challenging condition to manage, owing to limited availability of effective screening methods, diagnostic testing, and therapeutic options. More recently, multiple clinical trials have emerged evaluating the efficacy of novel pharmacologic therapies which target amyloid generation and pre-existing amyloid deposits. Results reveal robust treatment benefits in function and survival, offering clinicians and patients new therapeutics which alter the clinical trajectory of ATTR-CM. Importantly, the benefits of treatment with these therapies appear to be more pronounced when initiated at an early stage of disease. As a result, a renewed interest in the early detection of ATTR-CM has developed, with efforts currently underway to promote increased disease awareness and enhance diagnosis through standardized screening algorithms and advanced imaging techniques. This review will provide an in-depth description of the advancements in ATTR-CM screening, diagnosis, and treatment that are currently available for implementation in routine care. Furthermore, we highlight several investigational modalities on the horizon for ATTR-CM with a particular focus on their potential roles in future clinical practice.

Contextualizing the results of HELIOS-B in the broader landscape of clinical trials for the treatment of transthyretin cardiac amyloidosis

This focused review will highlight the results of HELIOS-B, the first randomized outcomes trial evaluating a gene silencing treatment for transthyretin cardiac amyloidosis (ATTR-CM). In HELIOS-B, vutrisiran was tested against placebo and demonstrated a 28% reduction in the composite of all-cause mortality and recurrent cardiovascular events. Additionally, there were clinically significant benefits on the 6-min walk test, Kansas City Cardiomyopathy Questionnaire, and NYHA class. Discontinuation rates and adverse events were similar between treatment and control arms, suggesting that vutrisiran is well tolerated. In this review, these promising results are explored and compared with other treatment trials in ATTR-CM.

Clinical differential factors in patients with hereditary transthyretin amyloidosis with Val142Ile and Ser43Asn mutations

BACKGROUND

Hereditary transthyretin amyloidosis (hATTR) is a rare autosomal dominant disease with high clinical variability, influenced by both genotype and the geographic origins of carriers. There is a limited understanding of the Val142Ile and Ser43Asn recognised mutations in Ecuador and Colombia. Therefore, the objective of this study is to describe the neurological and functional characteristics of patients with hATTR associated with the Val142Ile and Ser43Asn mutations, as well as to identify possible differentiating factors between the two mutations.

METHODS

This cross-sectional, multicenter study included 35 hATTR patients from rehabilitation centers in Ecuador and Colombia. Patients had confirmed Val142Ile or Ser43Asn mutations. Neurological and functional assessments included the Neurological Impairment Scale, Norfolk Quality of Life-Diabetic Neuropathy (QOL-DN), Composite Autonomic Symptom Score-31, and various motor function tests as nine-hole peg test (NHP). Quantitative Sensory Testing (QST) evaluating small fiber function, while ultrasound measured the cross-sectional area (CSA) of peripheral nerves. Statistical analysis employed nonparametric tests and random forest classifiers, using SHAP values to identify differentiating variables.

RESULTS

Val142Ile carriers showed lower performance in the right NHP test and greater sensitivity to cold pain in hand and leg. Ultrasound revealed increased CSA of the median nerve at the elbow and arm and the ulnar nerve at the arm in Val142Ile carriers compared to Ser43Asn carriers. The final random forest model identified the NHP test, Norfolk QOL-DN score, and CSA of the median and ulnar nerves as key discriminating variables.

CONCLUSION

This study identified significant neurophysiological and ultrasound markers differentiating Val142Ile and Ser43Asn mutations in hATTR-PN patients. Increased nerve CSA and specific motor and sensory impairments highlight the need for comprehensive evaluations to guide diagnosis and treatment.

Cardiomyopathy: pathogenesis and therapeutic interventions

Cardiomyopathy is a group of disease characterized by structural and functional damage to the myocardium. The etiologies of cardiomyopathies are diverse, spanning from genetic mutations impacting fundamental myocardial functions to systemic disorders that result in widespread cardiac damage. Many specific gene mutations cause primary cardiomyopathy. Environmental factors and metabolic disorders may also lead to the occurrence of cardiomyopathy. This review provides an in-depth analysis of the current understanding of the pathogenesis of various cardiomyopathies, highlighting the molecular and cellular mechanisms that contribute to their development and progression. The current therapeutic interventions for cardiomyopathies range from pharmacological interventions to mechanical support and heart transplantation. Gene therapy and cell therapy, propelled by ongoing advancements in overarching strategies and methodologies, has also emerged as a pivotal clinical intervention for a variety of diseases. The increasing number of causal gene of cardiomyopathies have been identified in recent studies. Therefore, gene therapy targeting causal genes holds promise in offering therapeutic advantages to individuals diagnosed with cardiomyopathies. Acting as a more precise approach to gene therapy, they are gradually emerging as a substitute for traditional gene therapy. This article reviews pathogenesis and therapeutic interventions for different cardiomyopathies.

Characterization and natural history of different phenotypes in hereditary transthyretin amyloidosis: 40-year experience at a single Italian referral centre

AIMS

Hereditary transthyretin amyloidosis (ATTRv) is one of the leading aetiologies of systemic amyloidosis with more than 135 mutations described and a broad spectrum of clinical manifestations. We aimed to provide a systematic description of a population of individuals carrying pathogenic mutations of transthyretin (TTR) gene and to investigate the major clinical events during follow-up.

METHODS AND RESULTS

This was an observational, retrospective, cohort study including consecutive patients with mutations of TTR gene, admitted to a tertiary referral centre in Bologna, Italy, between 1984 and 2022. Three hundred twenty-five patients were included: 106 asymptomatic carriers, 49 cardiac phenotype, 49 neurological phenotype, and 121 mixed phenotype. Twenty-two different mutations were found, with Ile68Leu (41.8%), Val30Met (19%), and Glu89Gln (10%) being the most common. After a median follow-up of 51 months, 111 patients (38.3%) died and 9 (11.5%) of the 78 asymptomatic carriers developed ATTRv. Carriers had a prognosis comparable with healthy population, while no significant differences were seen among the three phenotypes adjusted by age. Age at diagnosis, New York Heart Association class III, left ventricular ejection fraction, modified polyneuropathy disability score IV, and disease-modifying therapy were independently associated with survival.

CONCLUSION

This study offers a wide and comprehensive overview of ATTRv from the point of view of a tertiary referral centre in Italy. Three main phenotypes can be identified (cardiac, neurological, and mixed) with specific clinical and instrumental features. Family screening programmes are essential to identify paucisymptomatic affected patients or unaffected carriers of the mutation, to be followed through the years. Lastly, disease-modifying therapy represents an evolving cornerstone of the management of ATTRv, with a great impact on mortality.

[Incidence and causes of hospitalization in patients with transthyretin (ATTR-CA) and light chain (AL-CA) cardiac amyloidosis]

INTRODUCTION AND OBJETIVES

Cardiac amyloidosis (CA) is a disorder associated with high number of hospital admissions. Given the scarce information available, we propose an analysis of the incidence and causes of hospitalization in this disease.

MATERIAL AND METHODS

One hundred and forty-three patients [128 by transthyretin (ATTR-CA) and 15 by light chains (AL-CA)] included in Registro de Amiloidosis Cardiaca de Galicia (AMIGAL) were evaluated, including all hospitalizations.

RESULTS

During a median follow-up of 959 days there were 179 unscheduled hospitalizations [incidence rate (IR) 512.6 admissions per 1000 patients-year], most common due to cardiovascular reasons (n=109, IR 312.2). Most frequent individual cause of hospitalization was heart failure (n=87, TI 249.2). AL-CA was associated with a higher IR of unscheduled hospitalizations than ATTR-CA (IR 781 vs. 483.2; HR 1.62; p=0,029) due to non-cardiovascular admissions (IR 376 vs. 181.2; HR 2.07; p=0.027). Unscheduled admission-free survival at 1 and 3 years in AL-CA was inferior than in ATTR-CA (46.7% and 20.0% vs. 73.4% and 35.2%, respectively; p=0.021).

CONCLUSIONS

CA was associated with high incidence of hospitalizations, being heart failure the most frequent individual cause; unscheduled admission-free survival in AL-CA was lower than in ATTR-CA due mostly to non-cardiovascular admissions.

Vasovagal Syncope and Pulseless Electrical Activity Cardiac Arrest in Patients With Immunoglobulin Light Chain Cardiac Amyloidosis: A Case Series

Immunoglobulin light chain (AL) amyloidosis may lead to amyloid fibril deposition into peripheral and autonomic nerves, resulting in resting and orthostatic hypotension. While most patients die from progressive heart failure, the most commonly proposed cardiac rhythm associated with sudden death is pulseless electrical activity (PEA). Herein, we describe four patients with severe AL cardiac amyloidosis who had witnessed cardiac arrest with pulseless electrical activity as a result of vasovagal syncope. Healthcare providers should be aware of severe autonomic dysfunction in cardiac amyloidosis and the potential for an abnormal vasovagal response leading to syncope or death.

Primer on the Differential Diagnosis and Workup for Transthyretin Cardiac Amyloidosis

Amyloidosis has often been referred to as a "great masquerader," mimicking other systemic and cardiac diseases. As diagnostic techniques such as echocardiography with longitudinal strain, cardiac magnetic resonance imaging, and nuclear scintigraphy have advanced, identification of cardiac amyloidosis has become less daunting. This review covers the differential diagnosis and workup of patients with transthyretin cardiac amyloidosis, with a specific focus on developing a clinical suspicion through demographic, clinical, and echocardiographic features of the disease. The most common mimics of cardiac amyloidosis, i.e., conditions that likewise cause heart failure with preserved or mildly reduced ejection fraction, are also explored with respect to differential diagnosis, both for patients with normal and increased ventricular wall thickness. Ultimately, this review aims to demystify the diagnostic process by offering an algorithmic approach to the identification of transthyretin cardiac amyloidosis.

Electrocardiogram Criteria to Diagnose Cardiac Amyloidosis in Men With a Bundle Branch Block

Diagnosing cardiac amyloidosis is challenging and requires a high index of suspicion in patients with an increased left ventricular wall thickness (LVWT). Low QRS voltage on electrocardiogram (ECG) has been regarded as the hallmark ECG finding in cardiac amyloidosis; however, the presence of low voltage can range from 20-74% and the voltage/mass ratio carries a greater diagnostic accuracy than QRS voltage alone. Patients with cardiac amyloidosis can have conduction system infiltration and this may result in a BBB. Therefore, the ECG or mass/voltage criteria established for patients with a narrow QRS in the diagnosis of cardiac amyloidosis may not be applicable in patients with a BBB. We sought to identify criteria to aid in the diagnosis of cardiac amyloidosis in patients with increased LVWT on echocardiogram and with a BBB on ECG. We calculated the total QRS score/LVWT, limb lead QRS score/LVWT, R in lead aVL/LVWT, R in lead I/LVWT, and Sokolow index/LVWT. In patients with an increase in LVWT and BBB, total QRS voltage that is indexed to wall thickness can help distinguish between patients with increased wall thickness who have cardiac amyloidosis from those who have LVH related to a pressure overload state. A unique index of Total QRS Score/LVWT is the best predictor of cardiac amyloidosis with a cutoff value of 92.5 mV/cm which is 100% sensitive and 83% specific for the diagnosis of cardiac amyloidosis. This may be a useful screening tool in patients with an increased wall thickness to raise diagnostic suspicion for cardiac amyloidosis.

Musculoskeletal pathology as an early warning sign of systemic amyloidosis: a systematic review of amyloid deposition and orthopedic surgery

BACKGROUND

Transthyretin and immunoglobulin light-chain amyloidoses cause amyloid deposition throughout various organ systems. Recent evidence suggests that soft tissue amyloid deposits may lead to orthopedic conditions before cardiac manifestations occur. Pharmacologic treatments reduce further amyloid deposits in these patients. Thus, early diagnosis improves long term survival.

QUESTIONS/PURPOSES

The primary purpose of this systematic review was to characterize the association between amyloid deposition and musculoskeletal pathology in patients with common orthopedic conditions. A secondary purpose was to determine the relationship between amyloid positive biopsy in musculoskeletal tissue and the eventual diagnosis of systemic amyloidosis.

METHODS

We performed a systematic review using PRISMA guidelines. Inclusion criteria were level I-IV evidence articles that analyzed light-chain or transthyretin amyloid deposits in common orthopedic surgeries. Study methodological quality, risk of bias, and recommendation strength were assessed using MINORS, ROBINS-I, and SORT.

RESULTS

This systematic review included 24 studies for final analysis (3606 subjects). Amyloid deposition was reported in five musculoskeletal pathologies, including carpal tunnel syndrome (transverse carpal ligament and flexor tenosynovium), hip and knee osteoarthritis (synovium and articular cartilage), lumbar spinal stenosis (ligamentum flavum), and rotator cuff tears (tendon). A majority of studies reported a mean age greater than 70 for patients with TTR or AL positive amyloid.

CONCLUSIONS

This systematic review has shown the presence of amyloid deposition detected at the time of common orthopedic surgeries, especially in patients ≥70 years old. Subtyping of the amyloid has been shown to enable diagnosis of systemic light-chain or transthyretin amyloidosis prior to cardiac manifestations.

LEVEL OF EVIDENCE

Level IV.

Real-Time 3D Imaging and Inhibition Analysis of Various Amyloid Aggregations Using Quantum Dots

Amyloidosis refers to aggregates of protein that accumulate and are deposited as amyloid fibrils into plaques. When these are detected in organs, they are the main hallmark of Alzheimer's disease, Parkinson's disease, and other related diseases. Recent medical advances have shown that many precursors and proteins can induce amyloidosis even though the mechanism of amyloid aggregation and the relationship of these proteins to amyloidosis remains mostly unclear. In this study, we report the real-time 3D-imaging and inhibition analysis of amyloid β (Aβ), tau, and α-synuclein aggregation utilizing the affinity between quantum dots (QD) and amyloid aggregates. We successfully visualized these amyloid aggregations in real-time using fluorescence microscopy and confocal microscopy simply by adding commercially available QD. The observation by transmission electron microscopy (TEM) showed that QD particles bound to all amyloid fibrils. The 3D-imaging with QD revealed differences between amyloid aggregates composed of different amyloid peptides that could not be detected by TEM. We were also able to quantify the inhibition activities of these proteins by rosmarinic acid, which has high activity for Aβ aggregation, from fluorescence micrographs as half-maximal effective concentrations. These imaging techniques with QD serve as quick, easy, and powerful tools to understand amyloidosis and to discover drugs for therapies.

Amyloid Cardiomyopathy

Amyloid cardiomyopathy is emerging as an important and under-recognised cause of heart failure and cardiac arrhythmias, especially in older adults. This disorder is characterised by extracellular deposition of amyloid fibrils that form due to misfolding of secreted light chains (AL) or transthyretin protein (ATTR). In ATTR, amyloid aggregates typically result from excessive accumulation of wild-type transthyretin (ATTRwt) or from protein structural defects caused by TTR gene variants (ATTRv). Amyloid fibril deposition may predominantly affect the heart or show multi-system involvement. Previously considered to be rare and inexorably progressive with no specific therapy, there has been enormous recent interest in ATTR cardiomyopathy due to upwardly-revised estimates of disease prevalence together with development of disease-modifying interventions. Because of this, there is a clinical imperative to have a high index of suspicion to identify potential cases and to be aware of contemporary diagnostic methods and treatment options. Genetic testing should be offered to all patients with proven ATTR to access the benefits of new therapies specific to ATTRv and allow predictive testing of family members. With heightened awareness of amyloid cardiomyopathy and expanded use of genetic testing, a substantial rise in the numbers of asymptomatic individuals who are carriers of pathogenic variants is expected, and optimal strategies for monitoring and treatment of these individuals at risk need to be determined. Pre-emptive administration of fibril-modifying therapies provides an unprecedented opportunity for disease prevention and promises to change amyloid cardiomyopathy from being a fatal to a treatable disorder.

Gut Microbiota and Their Neuroinflammatory Implications in Alzheimer's Disease

The bidirectional communication between the central nervous system (CNS) and the gut microbiota plays a pivotal role in human health. Increasing numbers of studies suggest that the gut microbiota can influence the brain and behavior of patients. Various metabolites secreted by the gut microbiota can affect the cognitive ability of patients diagnosed with neurodegenerative diseases. Nearly one in every ten Korean senior citizens suffers from Alzheimer’s disease (AD), the most common form of dementia. This review highlights the impact of metabolites from the gut microbiota on communication pathways between the brain and gut, as well as the neuroinflammatory roles they may have in AD patients. The objectives of this review are as follows: (1) to examine the role of the intestinal microbiota in homeostatic communication between the gut microbiota and the brain, termed the microbiota–gut–brain (MGB) axis; (2) to determine the underlying mechanisms of signal dysfunction; and (3) to assess the impact of signal dysfunction induced by the microbiota on AD. This review will aid in understanding the microbiota of elderly people and the neuroinflammatory roles they may have in AD.

Diflunisal tolerability in transthyretin cardiac amyloidosis: a single center's experience

OBJECTIVE

Transthyretin (ATTR) amyloidosis is an under-recognized, progressive disease manifesting as cardiomyopathy and/or polyneuropathy. Diflunisal, a nonsteroidal anti-inflammatory drug (NSAID), has demonstrated transthyretin stabilization in vitro and slowing of polyneuropathy progression in the hereditary ATTR subtype (ATTRm). However, the use of diflunisal has only been described in a small cohort of patients with ATTR cardiac amyloidosis (CA). We hypothesized that selected patients with ATTR-CA, both hereditary and wild-type (ATTRwt), would tolerate diflunisal with limited adverse events.

MATERIALS AND METHODS

This is a retrospective, longitudinal study of 23 patients with ATTR-CA (10 ATTRm and 13 ATTRwt) diagnosed at the Cleveland Clinic from May 2007 to August 2017 who were treated with diflunisal. Patients were prescribed diflunisal, fully informed of the risks of side effects. Patient characteristics and subsequent adverse events were recorded.

RESULTS

The duration of diflunisal therapy ranged from 1-89 months (median 15 months). Average eGFR at diflunisal initiation was 61.9 ± 15.4 mL/min/m². Only one patient had a transient rise in Cr of 0.31 mg/dL. There were no clinically significant bleeding events, despite most of the patients being on anticoagulants or antiplatelet agents. Three of 23 patients (13%) withdrew treatment due to drug side effects (erosive gastritis, epigastric pain and decreased appetite). No patients died or were hospitalized for heart failure.

CONCLUSION

Diflunisal was well-tolerated in both the ATTRm- and ATTRwt-CA populations. Withdrawal due to side effects was related to gastrointestinal complaints, but most patients had no adverse events. Diflunisal can be safely used in a selected group of ATTR-CA patients with appropriate clinical, renal and hematologic monitoring.

Exosomes: Outlook for Future Cell-Free Cardiovascular Disease Therapy

Cardiovascular diseases are the number one cause of death globally with an estimated 7.4 million people dying from coronary heart disease. Studies have been conducted to identify the therapeutic utility of exosomes in many diseases, including cardiovascular diseases. It has been demonstrated that exosomes are immune modulators, can be used to treat cardiac ischemic injury, pulmonary hypertension and many other diseases, including cancers. Exosomes can be used as a biomarker for disease and cell-free drug delivery system for targeting the cells. Many studies suggest that exosomes can be used as a cell-free vaccine for many diseases. In this chapter, we explore the possibility of future therapeutic potential of exosomes in various cardiovascular diseases.

Recent Advances in Understanding and Managing Cardiomyopathy

Cardiomyopathy is a disease of the heart muscle leading to abnormal structure or function in the absence of coronary artery disease, hypertension, or valvular or congenital heart disease. Currently, cardiomyopathy is the leading diagnosis of heart transplant patients worldwide. Incorporation of next-generation sequencing strategies will likely revolutionize genetic testing in cardiomyopathy. The use of patient-specific pluripotent stem cell-derived cardiomyocytes for disease modeling and therapeutic testing has opened a new avenue for precision medicine in cardiomyopathy. Stem cell therapy, gene therapy, interfering RNA, and small molecules are actively being evaluated in clinical trials.