Transthyretin (TTR) cardiac amyloidosis

After TOPCAT: What to do now in Heart Failure with Preserved Ejection Fraction

Although patients with heart failure and preserved ejection fraction (HF-PEF) represent nearly half of the population with chronic heart failure, few evidence-based medical therapies are available. The neutral overall results of the TOPCAT trial of spironolactone in HF-PEF leave clinicians who treat heart failure with an ongoing clinical dilemma. In this review, we outline an approach to the clinical management of the patient with HF-PEF synthesizing data from available clinical trials and expert consensus.

Comparison of the standard and speckle tracking echocardiographic features of wild-type and mutated transthyretin cardiac amyloidoses

AIMS

To compare cardiac function in patients with the two types of transthyretin (TTR)-related amyloidoses [wild-type (wt) and mutated (m) TTR amyloidoses (ATTR)] using standard and speckle tracking echocardiography (STE).

METHODS AND RESULTS

Twenty-one consecutive patients with biopsy-proved ATTRwt were compared with 21 patients with ATTRm from the database, matched by age and left ventricular (LV) wall thickness (n = 135, ATTRm). All patients were examined using 2D echocardiography. Apical four- and two-chamber, and long-axis views and basal, mid, and apical short-axis views were used to examine LV longitudinal, circumferential, and radial strains. LV ejection fraction (EF), LV basal circumferential/radial strain, and mid-radial strain were significantly lower in patients with ATTRwt compared with patients with ATTRm. There was no significant difference between the two groups in the other parameters. In the receiver-operating characteristic curve analysis, LVEF and LV basal mean radial strain were the best parameters for distinguishing between the two groups.

CONCLUSION

Patients with ATTRwt are characterized by lower LVEF, LV basal, and LV mid-radial strains compared with patients with ATTRm. LVEF and LV radial strain are useful in distinguishing between ATTRwt and ATTRm when TTR has been proved in biopsy specimens.

Carpal tunnel syndrome: a common initial symptom of systemic wild-type ATTR (ATTRwt) amyloidosis

BACKGROUND

Systemic wild-type ATTR (ATTRwt) amyloidosis is a prevalent aging-related disorder. However, a limited number of systemic ATTRwt amyloidosis patients have been diagnosed antemortem, and therefore, the prevalence of ATTRwt is underestimated. Here, we investigated clinical findings of a series of systemic ATTRwt amyloidosis patients with antemortem diagnosis.

METHODS

Thirty-one consecutive patients diagnosed with systemic ATTRwt amyloidosis at Shinshu University Hospital were included in this study. Systemic ATTRwt amyloidosis was diagnosed based on proven ATTR amyloid deposition in biopsy specimens and confirmation of wild-type TTR genotype.

RESULTS

The systemic ATTRwt amyloidosis patients consisted of 24 men and seven women, and mean age of onset was 69.8 ± 9.0 years. The most common initial symptom was carpal tunnel syndrome (CTS, 17 patients), followed by heart failure symptoms (14 patients). The mean age at diagnosis was 74.5 ± 8.3 years and the duration of illness from onset to diagnosis was 5.4 ± 4.4 years. Cardiogenic embolism and renal dysfunction are also frequently seen during the course of the disease.

CONCLUSIONS

CTS is the most common initial symptom of systemic ATTRwt amyloidosis. Our results suggest the possibility of systemic ATTRwt amyloidosis diagnosis at an early stage by carefully examining patients with CTS.

Evolving landscape in the management of transthyretin amyloidosis

Transthyretin (TTR) amyloidosis (ATTR amyloidosis) is a multisystemic, multigenotypic disease resulting from deposition of insoluble ATTR amyloid fibrils in various organs and tissues. Although considered rare, the prevalence of this serious disease is likely underestimated because symptoms can be non-specific and diagnosis largely relies on amyloid detection in tissue biopsies. Treatment is guided by which tissues/organs are involved, although therapeutic options are limited for patients with late-stage disease. Indeed, enthusiasm for liver transplantation for familial ATTR amyloidosis with polyneuropathy was dampened by poor outcomes among patients with significant neurological deficits or cardiac involvement. Hence, there remains an unmet medical need for new therapies. The TTR stabilizers tafamidis and diflunisal slow disease progression in some patients with ATTR amyloidosis with polyneuropathy, and the postulated synergistic effect of doxycycline and tauroursodeoxycholic acid on dissolution of amyloid is under investigation. Another therapeutic approach is to reduce production of the amyloidogenic protein, TTR. Plasma TTR concentration can be significantly reduced with ISIS-TTR(Rx), an investigational antisense oligonucleotide-based drug, or with patisiran and revusiran, which are investigational RNA interference-based therapeutics that target the liver. The evolving treatment landscape for ATTR amyloidosis brings hope for further improvements in clinical outcomes for patients with this debilitating disease.

Amyloid Cardiomyopathy in Hereditary Transthyretin V30M Amyloidosis - Impact of Sex and Amyloid Fibril Composition

Purpose

Transthyretin V30M (ATTR V30M) amyloidosis is a phenotypically diverse disease with symptoms ranging from predominant neuropathy to exclusive cardiac manifestations. The aims of this study were to determine the dispersion of the two types of fibrils found in Swedish ATTR V30M patients -Type A consisting of a mixture of truncated and full length ATTR fibrils and type B fibrils consisting of full length fibrils, and to estimate the severity of cardiac dysfunction in relation to fibril composition and sex.

Material and Methods

Echocardiographic data were analysed in 107 Swedish ATTR V30M patients with their fibril composition determined as either type A or type B. Measurements of left ventricular (LV) dimensions and evaluation of systolic and diastolic function including speckle tracking derived strain were performed. Patients were grouped according to fibril type and sex. Multivariate linear regression was utilised to determine factors of significant impact on LV thickness.

Results

There was no significant difference in proportions of the two types of fibrils between men and women. In patients with type A fibrils, women had significantly lower median septal (p = 0.007) and posterior wall thicknesses (p = 0.010), lower median LV mass indexed to height (p = 0.008), and higher septal strain (p = 0.037), as compared to males. These differences were not apparent in patients with type B fibrils. Multiple linear regression analysis revealed that fibril type, sex and age all had significant impact on LV septal thickness.

Conclusion

This study demonstrates a clear difference between sexes in the severity of amyloid heart disease in ATTR V30M amyloidosis patients. Even though type A fibrils were associated with more advanced amyloid heart disease compared to type B, women with type A fibrils generally developed less cardiac infiltration than men. The differences may explain the better outcome for liver transplanted late-onset female patients compared to males.

18F-Florbetapir Binds Specifically to Myocardial Light Chain and Transthyretin Amyloid Deposits: Autoradiography Study

BACKGROUND

(18)F-florbetapir is a promising imaging biomarker for cardiac light chain amyloidosis (AL) and transthyretin amyloidosis (ATTR). Our aim, using human autopsy myocardial specimens, was to test the hypothesis that (18)F-florbetapir binds specifically to myocardial AL and ATTR amyloid deposits.

METHODS AND RESULTS

We studied myocardial sections from 30 subjects with autopsy-documented AL (n=10), ATTR (n=10), and nonamyloid controls (n=10) using (18)F-florbetapir and cold florbetapir compound and digital autoradiography. Total and nonspecific binding of (18)F-florbetapir was determined using the maximum signal intensity values. Specific binding of (18)F-florbetapir was calculated by subtracting nonspecific from total binding measurements (in decays per minute/mm(2), DPM mm(2)) and was compared with cardiac structure and function on echocardiography and the histological extent of amyloid deposits. Diffuse or focally increased (18)F-florbetapir uptake was noted in all AL and ATTR samples and in none of the control samples. Compared with control samples, mean (18)F-florbetapir-specific uptake was significantly higher in the amyloid samples (0.94±0.43 versus 2.00±0.58 DPM/mm(2); P<0.001), and in the AL compared with the ATTR samples (2.48±0.40 versus 1.52±0.22 DPM/mm(2); P<0.001). The samples from subjects with atypical echocardiographic features of amyloidosis showed quantitatively more intense (18)F-florbetapir-specific uptake compared with control samples (1.50±0.17 versus 0.94±0.43 DPM/mm(2); P=0.004), despite smaller amyloid extent than in subjects with typical echocardiograms.

CONCLUSIONS

(18)F-florbetapir specifically binds to myocardial AL and ATTR deposits in humans and offers the potential to screen for the 2 most common types of myocardial amyloid.

Therapeutic Oligonucleotides Targeting Liver Disease: TTR Amyloidosis

The liver has become an increasingly interesting target for oligonucleotide therapy. Mutations of the gene encoding transthyretin (TTR), expressed in vast amounts by the liver, result in a complex degenerative disease, termed familial amyloid polyneuropathy (FAP). Misfolded variants of TTR are linked to the establishment of extracellular protein deposition in various tissues, including the heart and the peripheral nervous system. Recent progress in the chemistry and formulation of antisense (ASO) and small interfering RNA (siRNA) designed for a knockdown of TTR mRNA in the liver has allowed to address the issue of gene-specific molecular therapy in a clinical setting of FAP. The two therapeutic oligonucleotides bind to RNA in a sequence specific manner but exploit different mechanisms. Here we describe major developments that have led to the advent of therapeutic oligonucleotides for treatment of TTR-related disease.

European Cardiomyopathy Pilot Registry: EURObservational Research Programme of the European Society of Cardiology

AIMS

Cardiomyopathies are a heterogeneous group of disorders associated with premature death due to ventricular arrhythmia or heart failure. The purpose of this study was to examine the characteristics of patients enrolled in the pilot phase of the EURObservational Research Programme (EORP) cardiomyopathy registry.

METHODS AND RESULTS

Between 1 December 2012 and 30 November 2013, four cardiomyopathy phenotypes were studied: hypertrophic cardiomyopathy (HCM), dilated cardiomyopathy (DCM), arrhythmogenic right ventricular cardiomyopathy (ARVC), and restrictive cardiomyopathy (RCM). Twenty-seven centres in 12 countries participated; 1115 patients were enrolled. The commonest cardiomyopathy was HCM (n = 681), followed by DCM (n = 346), ARVC (n = 59), and RCM (n = 29); 423 patients (46.4% of those reported) had familial disease; and 56 (5.0%) had rare disease phenocopies. Median age at enrolment and diagnosis was 54 [interquartile range (IQR), 42-64] and 46 years (IQR, 32-58), respectively; fewer patients with ARVC and more with RCM were diagnosed in the upper age quartile (P < 0.0001). There was a male predominance for all cardiomyopathies except RCM (P = 0.0023). Most patients were in New York Heart Association functional class I (n = 813) at enrolment; 139 (12.5%) reported syncope, most frequently in ARVC (P = 0.0009). Five hundred and seven (45.5%) patients underwent cardiac magnetic resonance imaging, 117 (10.6%) endomyocardial biopsy, and 462 (41.4%) genetic testing with a causative mutation reported in 236 individuals (51.1%). 1026 patients (92.0%) were receiving drug therapy; 316 (28.3%) had received an implantable cardioverter defibrillator (highest proportion in ARVC, P < 0.0001).

CONCLUSION

This pilot study shows that services for patients with cardiomyopathy are complex, requiring access to a large range of invasive and non-invasive investigations and involvement of multidisciplinary teams. Treatment regimens are equally multifaceted and show that patients are likely to need long-term follow-up in close liaison with expert centres.

IgG Conformer's Binding to Amyloidogenic Aggregates

Amyloid-reactive IgGs isolated from pooled blood of normal individuals (pAbs) have demonstrated clinical utility for amyloid diseases by in vivo targeting and clearing amyloidogenic proteins and peptides. We now report the following three novel findings on pAb conformer's binding to amyloidogenic aggregates: 1) pAb aggregates have greater activity than monomers (HMW species > dimers > monomers), 2) pAbs interactions with amyloidogenic aggregates at least partially involves unconventional (non-CDR) interactions of F(ab) regions, and 3) pAb's activity can be easily modulated by trace aggregates generated during sample processing. Specifically, we show that HMW aggregates and dimeric pAbs present in commercial preparations of pAbs, intravenous immunoglobulin (IVIg), had up to ~200- and ~7-fold stronger binding to aggregates of Aβ and transthyretin (TTR) than the monomeric antibody. Notably, HMW aggregates were primarily responsible for the enhanced anti-amyloid activities of Aβ- and Cibacron blue-isolated IVIg IgGs. Human pAb conformer's binding to amyloidogenic aggregates was retained in normal human sera, and mimicked by murine pAbs isolated from normal pooled plasmas. An unconventional (non-CDR) component to pAb's activity was indicated from control human mAbs, generated against non-amyloid targets, binding to aggregated Aβ and TTR. Similar to pAbs, HMW and dimeric mAb conformers bound stronger than their monomeric forms to amyloidogenic aggregates. However, mAbs had lower maximum binding signals, indicating that pAbs were required to saturate a diverse collection of binding sites. Taken together, our findings strongly support further investigations on the physiological function and clinical utility of the inherent anti-amyloid activities of monomeric but not aggregated IgGs.

Enthalpic Forces Correlate with the Selectivity of Transthyretin-Stabilizing Ligands in Human Plasma

The plasma protein transthyretin (TTR) is linked to human amyloidosis. Dissociation of its native tetrameric assembly is a rate-limiting step in the conversion from a native structure into a pathological amyloidogenic fold. Binding of small molecule ligands within the thyroxine binding site of TTR can stabilize the tetrameric integrity and is a potential therapeutic approach. However, through the characterization of nine different tetramer-stabilizing ligands we found that unspecific binding to plasma components might significantly compromise ligand efficacy. Surprisingly the binding strength between a particular ligand and TTR does not correlate well with its selectivity in plasma. However, through analysis of the thermodynamic signature using isothermal titration calorimetry we discovered a better correlation between selectivity and the enthalpic component of the interaction. This is of specific interest in the quest for more efficient TTR stabilizers, but a high selectivity is an almost universally desired feature within drug design and the finding might have wide-ranging implications for drug design.

Left ventricular deformation and torsion assessed by speckle-tracking echocardiography in patients with mutated transthyretin-associated cardiac amyloidosis and the effect of diflunisal on myocardial function

Background

Mutated transthyretin-associated (ATTRm) amyloidosis with heart failure is associated with decreased longitudinal left ventricular (LV) myocardial contraction, as measured by strain Doppler echocardiography. We sought to clarify whether speckle-tracking echocardiography (STE) would provide useful information in patients with ATTRm cardiac amyloidosis.

Methods

One hundred twenty-three consecutive patients with ATTRm amyloidosis were divided into 3 groups. Group 1 had no evidence of cardiac involvement (n = 47), group 2 had heart involvement but no congestive heart failure (CHF) and/or serum brain natriuretic peptide (BNP) levels < 100 pg/mL (n = 35), and group 3 had heart involvement and CHF and/or serum BNP levels ≥ 100 pg/mL (n = 41). All patients underwent standard 2-dimensional (2D), Doppler echo, and STE.

Results

By standard 2D and Doppler echo, differences in parameters were only apparent between group 3 and groups 1 and 2. Global circumferential strains by STE at each LV level and LV torsion were different between group 1 and groups 2 and 3, but not between group 2 and group 3. In contrast, global longitudinal LV strain showed significant intergroup differences (− 17.3 ± 2.3%, − 13.3 ± 2.3%, − 9.9 ± 3.3% for groups 1 to 3, respectively, P < 0.0001). Radial strain also showed significant intergroup differences for each basal LV segment. Among 41 patients who could have been followed up after 1 year, 34 patients with diflunisal treatment had shown improvement in apical rotation and torsion without deterioration in multidirectional strains.

Conclusion

ATTRm cardiac amyloidosis is characterized by progressive impairment in longitudinal and basal LV radial function when global circumferential shortening and torsion remain unchanged.

Wild-type transthyretin amyloidosis as a cause of heart failure with preserved ejection fraction

AIMS

Heart failure with preserved ejection fraction (HFpEF) is a heterogeneous clinical syndrome with multiple underlying causes. Wild-type transthyretin (TTR) amyloidosis (ATTRwt) is an underdiagnosed cause of HFpEF that might benefit from new specific treatments. ATTRwt can be diagnosed non-invasively by (99m)Tc-3,3-diphosphono-1,2-propanodicarboxylic acid ((99m)Tc-DPD) scintigraphy. We sought to determine the prevalence of ATTRwt among elderly patients admitted due to HFpEF.

METHODS AND RESULTS

We prospectively screened all consecutive patients ≥60 years old admitted due to HFpEF [left ventricular (LV) ejection fraction ≥50%] with LV hypertrophy (≥12 mm). All eligible patients were offered a (99m)Tc-DPD scintigraphy. The study included 120 HFpEF patients (59% women, 82 ± 8 years). A total of 16 patients (13.3%; 95% confidence interval: 7.2-19.5) showed a moderate-to-severe uptake on the (99m)Tc-DPD scintigraphy. All patients with a positive scan underwent genetic testing of the TTR gene, and no mutations were found. An endomyocardial biopsy was performed in four patients, confirming ATTRwt in all cases. There were no differences in age, gender, hypertension, diabetes, coronary artery disease, or atrial fibrillation between ATTRwt patients and patients with other HFpEF forms. Although patients with ATTRwt exhibited higher median N-terminal pro-brain natriuretic peptide (6467 vs. 3173 pg/L; P = 0.019), median troponin I (0.135 vs. 0.025 µg/L; P < 0.001), mean LV maximal wall thickness (17 ± 3.4 vs. 14 ± 2.5 mm; P = 0.001), rate of pericardial effusion (44 vs. 19%; P = 0.047), and rate of pacemakers (44 vs. 12%; P = 0.004), clinical overlap between ATTRwt and other HFpEF forms was high.

CONCLUSION

ATTRwt is an underdiagnosed disease that accounts for a significant number (13%) of HFpEF cases. The effect of emerging TTR-modifying drugs should be evaluated in these patients.

Neuropathologic analysis of Tyr69His TTR variant meningovascular amyloidosis with dementia

Transthyretin/TTR gene mutations usually cause systemic amyloidotic diseases. Few TTR variants preferentially affect the central nervous system, manifesting as oculoleptomeningeal amyloidosis. Patients with TTR meningovascular amyloidosis often show dementia, however the neuropathologic features of dementia in these cases have not been elucidated. We report the neuropathologic findings from a brain autopsy of a 72-year-old man with the rare Tyr69His (Y69H) TTR gene variant, dementia and ataxia. Severe amyloid deposits were observed in the leptomeninges and in a subpial and subependymal distribution. Mass spectrometry analysis demonstrated that the amyloid deposits were comprised of over 80 % of the variant TTR. TTR was undetectable by mass spectrometry in the neocortex subjacent to the subpial amyloid deposits. Subpial TTR amyloid deposits were associated with brisk superficial reactive gliosis and siderosis in the neocortex and cerebellar cortex. Subependymal TTR amyloid deposits were associated with subjacent myelin pallor in the hippocampal outflow tract structures including the alveus, fimbria and fornix. Phospho-tau immunostains demonstrated transentorhinal-stage neurofibrillary degeneration (Braak stage II) which, in the absence of neocortical amyloid-beta and neuritic plaques, was indicative of primary age-related tauopathy (PART). However, distinctive phospho-tau aggregates were observed subjacent to the subpial TTR amyloid deposits in all regions of the neocortex, including the primary motor and striate cortices, suggesting a potential link between TTR amyloid and neocortical tauopathy. Our report reveals novel insights into the potential neuropathologic substrates of dementia in variant TTR amyloidosis that need to be investigated in larger autopsy series.

Infiltrative Cardiomyopathies

Infiltrative cardiomyopathies can result from a wide spectrum of both inherited and acquired conditions with varying systemic manifestations. They portend an adverse prognosis, with only a few exceptions (ie, glycogen storage disease), where early diagnosis can result in potentially curative treatment. The extent of cardiac abnormalities varies based on the degree of infiltration and results in increased ventricular wall thickness, chamber dilatation, and disruption of the conduction system. These changes often lead to the development of heart failure, atrioventricular (AV) block, and ventricular arrhythmia. Because these diseases are relatively rare, a high degree of clinical suspicion is important for diagnosis. Electrocardiography and echocardiography are helpful, but advanced techniques including cardiac magnetic resonance (CMR) and nuclear imaging are increasingly preferred. Treatment is dependent on the etiology and extent of the disease and involves medications, device therapy, and, in some cases, organ transplantation. Cardiac amyloid is the archetype of the infiltrative cardiomyopathies and is discussed in great detail in this review.

Syncope due to Autonomic Dysfunction: Diagnosis and Management

Syncope is one of several disorders that cause transient loss of consciousness. Cerebral hypoperfusion is the proximate cause of syncope. Transient or fixed autonomic nervous system dysfunction is a major contributor in many causes. A structured approach to the evaluation of syncope allows for more effective therapy.

The transthyretin amyloidoses: advances in therapy

There are two forms of transthyretin (TTR) amyloidosis: non-hereditary and hereditary. The non-hereditary form (ATTRwt) is caused by native or wild-type TTR and was previously referred to as senile systemic amyloidosis. The hereditary form (ATTRm) is caused by variant TTR which results from a genetic mutation of TTR. The predominant effect of ATTRwt amyloidosis is on the heart, with patients having a greater left ventricular wall thickness at presentation than the devastating form which is light chain (AL) amyloidosis. ATTRm amyloidosis is broadly split into two categories: a type that predominantly affects the nervous system (often called familial amyloid polyneuropathy (FAP)) and one with a predilection for the heart (often called familial amyloid cardiomyopathy (FAC)). Approximately half of all TTR mutations known to express a clinical phenotype cause a cardiomyopathy. Since the introduction of orthotopic liver transplantation for ATTRm amyloidosis in 1991, several additional therapies have been developed. These therapies aim to provide a reduction or elimination of TTR from the plasma (through genetic approaches), stabilisation of the TTR molecule (to prevent deposition) and dissolution of the amyloid matrix. We describe the latest developments in these approaches to management, many of which are also applicable to wild-type amyloidosis.

Case report: isolated cardiac amyloidosis: an enigma unravelled

Amyloidosis is a rare, multisystem disease characterized by deposition of fibrils in extracellular tissue involving kidney, liver, heart, autonomic nervous system, and several other organs. This report discusses a 75-year-old male who presented with worsening dyspnea on exertion, orthopnea, and lower-extremity edema. On physical exam, he had elevated jugular venous pressure and lower-extremity edema. Electrocardiogram depicted low voltage in limb leads and a prolonged PR interval. Echocardiogram revealed left ventricular hypertrophy, severe biatrial dilatation, and restrictive filling physiology. Coronary angiography showed absence of significant epicardial coronary artery disease. On right heart catheterization, a "dip-and-plateau sign" was noted on right ventricular pressure tracings. A diagnosis of cardiac amyloidosis was considered, but a complete hematology work-up for systemic amyloidosis was negative. Cardiac magnetic resonance imaging was pursued, showing delayed gadolinium enhancement, and this ultimately led to the myocardial biopsy confirming the diagnosis of isolated cardiac amyloidosis. Further genetic analyses confirmed isolated cardiac amyloid caused by mutant transthyretin protein (Val-122-Ile). Isolated cardiac amyloidosis is an extremely rare entity, and diagnosis may be difficult despite the use of multimodality imaging. If the index of suspicion is high, then myocardial biopsy should be considered.

Echocardiographic assessment of the cardiac amyloidoses

Cardiac amyloidosis is a cardiomyopathy characterized by increased left ventricular (LV) wall thickness and normal or decreased LV cavity size. Congestive heart failure in cardiac amyloidosis is generally considered a predominantly diastolic phenomenon, with systolic dysfunction only occurring in late-stage disease. Echocardiography is a noninvasive, reproducible method of assessing cardiac features and function in cardiac amyloidosis, and some echocardiographic indices are prognostic for the amyloidoses, with M-mode and 2-dimensional echocardiography able to detect increased LV wall thickness. Moreover, Doppler flow measurements can incrementally assess diastolic LV dysfunction, which is characteristic of cardiac amyloidosis, and provide important prognostic information. Additionally, tissue Doppler imaging can detect subtle changes in both systolic and diastolic LV function, which cannot be detected by Doppler flow measurements, and LV longitudinal strain assessed by color tissue Doppler and speckle tracking echocardiography can provide more accurate LV functional and prognostic information than tissue Doppler imaging. This review describes the advances in echocardiography and its crucial role in the diagnosis and management of cardiac amyloidosis.

Liver transplantation in transthyretin amyloidosis: issues and challenges

Hereditary transthyretin amyloidosis (ATTR) is a rare worldwide autosomal dominant disease caused by the systemic deposition of an amyloidogenic variant of transthyretin (TTR), which is usually derived from a single amino acid substitution in the TTR gene. More than 100 mutations have been described, with V30M being the most prevalent. Each variant has a different involvement, although peripheral neuropathy and cardiomyopathy are the most common. Orthotopic liver transplantation (OLT) was implemented as the inaugural disease-modifying therapy because the liver produces the circulating unstable TTR. In this review, we focus on the results and long-term outcomes of OLT for ATTR after more than 2063 procedures and 23 years of experience. After successful OLT, neuropathy and organ impairment are not usually reversed, and in some cases, the disease progresses. The overall 5-year survival rate is approximately 100% for V30M patients and 59% for non-ATTR V30M patients. Cardiac-related death and septicemia are the main causes of mortality. Lower survival is related to malnutrition, a longer duration of disease, cardiomyopathy, and a later onset (particularly for males). Deposits, which are composed of a mixture of truncated and full-length TTR (type A) fibrils, have been associated with posttransplant myocardial dysfunction. A higher incidence of early hepatic artery thrombosis of the graft has also been documented for these patients. Liver-kidney/heart transplantation is an alternative for patients with advanced renal disease or heart failure. The sequential procedure, in which ATTR livers are reused in patients with liver disease, reveals that neuropathy in the recipient may appear as soon as 6 years after OLT, and ATTR deposits may appear even earlier. Long-term results of trials with amyloid protein stabilizers or disrupters, silencing RNA, and antisense oligonucleotides will highlight the value and limitations of liver transplantation.

Cardiac amyloidosis in a heart transplant patient - A case report and retrospective analysis of amyloidosis evolution

Cardiac amyloidosis is a very rare cause of heart failure in heart transplant recipients but an important differential diagnosis in cases of progressive cardiac failure. We report a 72-year-old male patient with the diagnosis of senile systemic amyloidosis (SSA) in a transplanted heart 15 years after transplantation by the initial diagnosis of the dilated cardiomyopathy. Additionally performed immunohistochemical analysis with anti-transthyretin antibody of the cardiac biopsies of the last 15 years enabled the possibility to show the evolution of this disease with characteristic biphasic pattern.

Amyloid PET imaging: applications beyond Alzheimer's disease

As a biomarker of beta-amyloid, positron emission tomography (PET) amyloid imaging offers a unique opportunity to detect the presence of this protein in the human body during life. Besides Alzheimer's disease (AD), deposits of beta-amyloid in the brain are also present in other neurodegenerative diseases associated to dementia, such as Parkinson's disease and dementia with Lewy bodies, as well as in other processes affecting brain function, such as cerebral amyloid angiopathy, brain trauma, Down's syndrome and meningiomas, as shown by post-mortem pathology studies. Furthermore, in systemic amyloidosis other organs besides the brain are affected, and amyloid PET imaging may be suitable for the identification of these extra-cerebral amyloid depositions. Finally, the potential use of amyloid PET tracer accumulation in cerebral white matter (WM) as a marker of myelin is being investigated, leading to some promising results in patients with WM lesions and multiple sclerosis. In this article, a review of the ongoing research pointing to a broader application of amyloid PET imaging in clinical practice beyond AD is provided.

Tuning transthyretin amyloidosis inhibition properties of iododiflunisal by combinatorial engineering of the nonsalicylic ring substitutions

Two series of iododiflunisal and diflunisal analogues have been obtained by using a two step sequential reaction solution-phase parallel synthesis. The synthesis combined an aqueous Suzuki-Miyaura cross-coupling and a mild electrophilic aromatic iodination step using a new polymer-supported iodonium version of Barluenga's reagent. From a selected set of 77 noniodinated and 77 iodinated diflunisal analogues, a subset of good transthyretin amyloid inhibitors has been obtained with improved turbidimetry inhibition constants, high binding affinity to transthyretin, and good selectivity for TTR compared to other thyroxine binding proteins.

Transthyretin cardiac amyloidosis: pathogenesis, treatments, and emerging role in heart failure with preserved ejection fraction

Transthyretin (TTR) amyloidosis causes heart failure from cardiac deposition of TTR amyloid fibrils, the by-product of TTR homotetramer disassembly. Wild-type (WT) TTR deposition leads to senile amyloidosis, predominantly manifesting with cardiomyopathy. Missense mutations in the TTR gene result in familial TTR amyloidosis. Certain mutations are more likely to affect the heart, while others cause more neurologic involvement. Extracellular fibril deposition triggers intracellular stress response, upregulation of the inflammatory cascades, apoptosis, and organ dysfunction. Recent studies suggest that TTR cardiac amyloid may be a significant contributor to the pathogenesis of heart failure with preserved ejection fraction (HFpEF). Summarized in this review are the molecular pathways underlying the cellular toxicity of TTR amyloid fibrils and the emerging therapies aimed at TTR tetramer stabilization, abrogation of TTR synthesis in the liver, or inhibition of amyloidogenesis.

Cooperative stabilization of transthyretin by clusterin and diflunisal

The circulating protein transthyretin (TTR) can unfold, oligomerize, and form highly structured amyloid fibrils that are deposited in tissues, causing organ damage and disease. This pathogenic process is caused by a heritable TTR point mutation in cases of familial TTR-related amyloidosis or wild-type TTR in cases of age-associated amyloidosis (previously called senile systemic amyloidosis). The TTR amyloid cascade is hypothesized to begin with the dissociation of the TTR native tetrameric structure into folded but unstable monomeric TTR subunits. Unfolding of monomeric TTR initiates an oligomerization process leading to aggregation and fibril formation. Numerous proteostatic mechanisms for regulating the TTR amyloid cascade exist. Extracellular chaperones provide an innate defense against misfolded proteins. Clusterin (CLU), a plasma protein, has the capacity to recognize exposed hydrophobic regions of misfolded proteins, shielding them from aggregation. We have previously demonstrated that CLU is associated with the amyloid fibrils in cardiac tissues from patients with TTR amyloidosis. In this study, we have used tetrameric and monomeric TTR structural variants to determine the ability of CLU to inhibit TTR amyloid fibril formation. Using circular dichroism spectroscopy, we determined that CLU preferentially stabilizes monomeric TTR and generates increasingly stable conformations under acid stress. Moreover, studies using surface plasmon resonance showed a direct interaction of CLU with high-molecular weight TTR oligomers. The interactions of CLU with monomeric and aggregated TTR proceed in a cooperative manner in the presence of diflunisal, a small molecule drug used to stabilize TTR tetramers.

Transthyretin cardiac amyloidosis: an under-diagnosed cause of heart failure

INTRODUCTION

Cardiac amyloidosis is the most common cause of infiltrative cardiomyopathy and is associated with a poor prognosis. Transthyretin cardiac amyloidosis, particularly the type caused by the mutation that replaces the amino acid valine with the amino acid isoleucine at position 122 (Val122Ile), is most common among African- Americans above 65 years of age. Evidence suggests that this mutation is an important, though under-diagnosed, cause of heart failure in this population.

CASE PRESENTATION

A 74-year-old African American male with a diagnosis of non-ischemic cardiomyopathy for several years, presented with gradually worsening dyspnea on exertion and lower extremity edema. There is no known cardiac disease in his family. An echocardiogram was done showing a decrease in ejection fraction to 30% from 45% in the span of a year. An endomyocardial biopsy analysis identified transthyretin amyloid with the Val122Ile mutation, confirming the diagnosis of familial transthyretin cardiomyopathy.

DISCUSSION

Systemic amyloidosis is a group of diseases caused by the deposition of an abnormally folded, insoluble protein that can accumulate in multiple organs causing progressive and irreversible dysfunction. The mutations that most commonly induce variant transthyretin cardiac amyloidosis are Val122Ile, Val30Met and Thr60Ala. The Val122Ile mutation has been found to be present in 3-4% of the African American/Caribbean population.

CONCLUSIONS

Familial amyloid cardiomyopathy is an uncommonly recognized cause of heart failure in the population, and patients may wait several years before accurate diagnosis, risking additional significant irreversible deterioration. Patients that meet the high-risk profile criteria - male gender, age 65 years and older, heart failure symptoms, symmetric left ventricular (LV) hypertrophy, and moderately depressed LV function - should likely undergo additional testing for cardiac amyloidosis.

Novel drugs targeting transthyretin amyloidosis

Transthyretin amyloidosis (ATTR) is either a hereditary disease related to a mutation in the transthyretin gene that leads to neuropathy and/or cardiomyopathy or an acquired disease of the elderly that leads to restrictive cardiomyopathy. The prevalence of this disease is higher than once thought and awareness is likely to increase amongst physicians and in particular cardiologists. Until recently there have been no treatment options for this disease except to treat the heart failure with diuretics and the neuropathy symptomatically. However, there are several emerging pharmacologic therapies designed to slow or stop the progression of ATTR. This article reviews novel therapeutic drugs that work at different points in the pathogenesis of this disease attempting to change its natural history and improve outcomes.

Cardiac amyloidosis: a challenging diagnosis

Cardiovascular involvement of amyloidosis is present in 90% of cases, which is frequently associated with the primary form of the disease (AL amyloidosis). Clinical manifestations are represented by heart failure due to restrictive myocardiopathy and electrical impulse conduction abnormalities, which are clinically remarkable in up to 50% of the cases. The prognosis of patients with systemic amyloidosis is directly associated with the presence of cardiac involvement, such that survival does not usually exceed 4 months after the onset of heart failure signs and symptoms. The authors report a case of primary systemic amyloidosis, diagnosed only at autopsy, with severe cardiac involvement.

Expression of Transthyretin during bovine myogenic satellite cell differentiation

Adult myogenesis responsible for the maintenance and repair of muscle tissue is mainly under the control of myogenic regulatory factors (MRFs) and a few other genes. Transthyretin gene (TTR), codes for a carrier protein for thyroxin (T4) and retinol binding protein bound with retinol in blood plasma, plays a critical role during the early stages of myogenesis. Herein, we investigated the relationship of TTR with other muscle-specific genes and report their expression in muscle satellite cells (MSCs), and increased messenger RNA (mRNA) and protein expression of TTR during MSCs differentiation. Silencing of TTR resulted in decreased myotube formation and decreased expression of myosin light chain (MYL2), myosin heavy chain 3 (MYH3), matrix gla protein (MGP), and voltage-dependent L type calcium channel (Cav1.1) genes. Increased mRNA expression observed in TTR and other myogenic genes with the addition of T4 decreased significantly following TTR knockdown, indicating the critical role of TTR in T4 transportation. Similarly, decreased expression of MGP and Cav1.1 following TTR knockdown signifies the dual role of TTR in controlling muscle myogenesis via regulation of T4 and calcium channel. Our computational and experimental evidences indicate that TTR has a relationship with MRFs and may act on calcium channel and related genes.

Isolated heart transplantation for familial transthyretin (TTR) V122I cardiac amyloidosis

Transthyretin (TTR) cardiac amyloidosis is characterized by deposition of either mutant or wild type TTR amyloid protein in the myocardium ultimately leading to progressive cardiomyopathy and heart failure. The most common TTR gene mutation that leads to TTR cardiac amyloidosis is the valine-to-isoleucine substitution at position 122 (V122I or Ile122). Currently, the only definitive treatment suggested for mutant TTR cardiac amyloidosis is the combined or sequential liver-heart transplantation in eligible patients, since liver is the source of TTR production. Here, we report a case of heterozygous Val122L mutated TTR-related cardiac amyloidosis treated with isolated heart transplantation with no recurrence of amyloid in the cardiac allograft and no systemic abnormalities 5 years after heart transplantation. Abbreviations MMF mycophenolate mofetil NYHA New York Heart Association TTR transthyretin VE minute ventilation.

Imaging cardiac amyloidosis: a pilot study using ¹⁸F-florbetapir positron emission tomography

PURPOSE

Cardiac amyloidosis, a restrictive heart disease with high mortality and morbidity, is underdiagnosed due to limited targeted diagnostic imaging. The primary aim of this study was to evaluate the utility of (18)F-florbetapir for imaging cardiac amyloidosis.

METHODS

We performed a pilot study of cardiac (18)F-florbetapir PET in 14 subjects: 5 control subjects without amyloidosis and 9 subjects with documented cardiac amyloidosis. Standardized uptake values (SUV) of (18)F-florbetapir in the left ventricular (LV) myocardium, blood pool, liver, and vertebral bone were determined. A (18)F-florbetapir retention index (RI) was computed. Mean LV myocardial SUVs, target-to-background ratio (TBR, myocardial/blood pool SUV ratio) and myocardial-to-liver SUV ratio between 0 and 30 min were calculated.

RESULTS

Left and right ventricular myocardial uptake of (18)F-florbetapir were noted in all the amyloid subjects and in none of the control subjects. The RI, TBR, LV myocardial SUV and LV myocardial to liver SUV ratio were all significantly higher in the amyloidosis subjects than in the control subjects (RI median 0.043 min(-1), IQR 0.034 - 0.051 min(-1), vs. 0.023 min(-1), IQR 0.015 - 0.025 min(-1), P = 0.002; TBR 1.84, 1.64 - 2.50, vs. 1.26, IQR 0.91 - 1.36, P = 0.001; LV myocardial SUV 3.84, IQR 1.87 - 5.65, vs. 1.35, IQR 1.17 - 2.28, P = 0.029; ratio of LV myocardial to liver SUV 0.67, IQR 0.44 - 1.64, vs. 0.18, IQR 0.15 - 0.35, P = 0.004). The myocardial RI, TBR and myocardial to liver SUV ratio also distinguished the control subjects from subjects with transthyretin and those with light chain amyloid.

CONCLUSION

(18)F-Florbetapir PET may be a promising technique to image light chain and transthyretin cardiac amyloidosis. Its role in diagnosing amyloid in other organ systems and in assessing response to therapy needs to be further studied.

Yield of noncardiac biopsy for the diagnosis of transthyretin cardiac amyloidosis

Transthyretin (ATTR) cardiac amyloidosis may be because of mutant transthyretin causing familial amyloid cardiomyopathy (FAC) or wild-type transthyretin causing systemic senile amyloidosis (SSA). Histologic confirmation is often challenging and may require endomyocardial biopsy (EMB). The purpose of this study was to determine the frequency of amyloid protein deposition in positive noncardiac organ biopsy or fat aspiration in patients with ATTR cardiac amyloidosis. The medical records of 286 patients (mean age 66 ± 11, 85% men) with a diagnosis of ATTR cardiac amyloidosis at our institution who underwent noncardiac biopsy or subcutaneous fat aspiration were reviewed, including 186 patients (65%) with FAC and 100 patients (35%) with SSA. One hundred and thirty-one patients (46%) had EMB, all of which were positive. There were 210 patients (73%) with positive noncardiac tissue sampling, including 175 patients (94%) with FAC and 35 patients (35%) with SSA (p <0.001). There were 141 patients (76%) with FAC and 84 patients (84%) with SSA who underwent fat aspiration, and 67% and 14% were positive, respectively, whereas 100 (54%) and 64 (64%) underwent bone marrow biopsy, and 41% and 30% were positive, respectively. Rectal and sural nerve biopsies were performed in 52 (28%) and 54 (29%) patients with FAC and were positive in 81% and 83%, respectively. Biopsy of other noncardiac sites was performed with relatively lower frequency. In conclusion, although EMB is more commonly required to establish the diagnosis of SSA than FAC, noncardiac biopsy or fat aspiration could be considered as initial testing in patients evaluated for ATTR cardiac amyloidosis with characteristic echocardiography findings.

Noninvasive risk stratification of patients with transthyretin amyloidosis

OBJECTIVES

We sought to evaluate noninvasive parameters by electrocardiography, echocardiography, technetium-99m-3,3-diphosphono-1,2-propanodicarboxylic acid ((99m)Tc-DPD) scintigraphy, and cardiac magnetic resonance for the prediction of all-cause mortality in patients with cardiac transthyretin amyloidosis (ATTR).

BACKGROUND

ATTR may present with highly variable symptoms, including polyneuropathy and cardiomyopathy, the latter being associated with a poor outcome. However, data on noninvasive risk stratification of ATTR are limited.

METHODS

A total of 70 patients with ATTR were evaluated by echocardiography, cardiac biomarkers, and (99m)Tc-DPD scintigraphy. Cardiac magnetic resonance was performed in 30 patients. Echocardiographic findings and plasma levels of biomarkers were correlated with results of quantitative analysis of scintigraphy using a region-of-interest technique (whole-body as well as heart tracer retention). Receiver-operating characteristic (ROC) analysis was performed to calculate a cutoff value of (99m)Tc-DPD scintigraphy for heart retention for the diagnosis of cardiac amyloid involvement with the highest sensitivity and specificity. Univariate and multivariate analyses were performed in patients with cardiac involvement (n = 60) to determine noninvasive predictors of all-cause mortality.

RESULTS

Scintigraphy findings correlated with morphological (interventricular septum thickness, left ventricular hypertrophy index) as well as functional (mitral annular systolic velocity, mitral/tricuspid annular plane systolic excursion) findings, cardiac biomarkers, renal function, and late gadolinium enhancement. The ROC-derived cutoff for the detection of cardiac amyloidosis by scintigraphic heart tracer retention was 4.8%. Univariate Cox regression revealed N-terminal pro-B-type natriuretic peptide, troponin T, mitral annular plane systolic excursion, and left ventricular hypertrophy index as predictors of all-cause mortality. However, on multivariate analysis, troponin T remained the only independent predictor of survival. The ROC-derived cutoff value of troponin T predicting all-cause mortality with the highest sensitivity (80.0%) and specificity (68.7%) was 0.0375 ng/l.

CONCLUSIONS

Quantitative analysis of tracer retention is capable of characterizing the severity of cardiac involvement in ATTR. By multivariate analysis, troponin T remained the only independent predictor of survival.

Native T1 mapping in transthyretin amyloidosis

OBJECTIVES

The aims of the study were to explore the ability of native myocardial T1 mapping by cardiac magnetic resonance to: 1) detect cardiac involvement in patients with transthyretin amyloidosis (ATTR amyloidosis); 2) track the cardiac amyloid burden; and 3) detect early disease.

BACKGROUND

ATTR amyloidosis is an underdiagnosed cause of heart failure, with no truly quantitative test. In cardiac immunoglobulin light-chain amyloidosis (AL amyloidosis), T1 has high diagnostic accuracy and tracks disease. Here, the diagnostic role of native T1 mapping in the other key type of cardiac amyloid, ATTR amyloidosis, is assessed.

METHODS

A total of 3 groups were studied: ATTR amyloid patients (n = 85; 70 males, age 73 ± 10 years); healthy individuals with transthyretin mutations in whom standard cardiac investigations were normal (n = 8; 3 males, age 47 ± 6 years); and AL amyloid patients (n = 79; 55 males, age 62 ± 10 years). These were compared with 52 healthy volunteers and 46 patients with hypertrophic cardiomyopathy (HCM). All underwent T1 mapping (shortened modified look-locker inversion recovery); ATTR patients and mutation carriers also underwent cardiac 3,3-diphosphono-1,2-propanodicarboxylicacid (DPD) scintigraphy.

RESULTS

T1 was elevated in ATTR patients compared with HCM and normal subjects (1,097 ± 43 ms vs. 1,026 ± 64 ms vs. 967 ± 34 ms, respectively; both p < 0.0001). In established cardiac ATTR amyloidosis, T1 elevation was not as high as in AL amyloidosis (AL 1,130 ± 68 ms; p = 0.01). Diagnostic performance was similar for AL and ATTR amyloid (vs. HCM: AL area under the curve 0.84 [95% confidence interval: 0.76 to 0.92]; ATTR area under the curve 0.85 [95% confidence interval: 0.77 to 0.92]; p < 0.0001). T1 tracked cardiac amyloid burden as determined semiquantitatively by DPD scintigraphy (p < 0.0001). T1 was not elevated in mutation carriers (952 ± 35 ms) but was in isolated DPD grade 1 (n = 9, 1,037 ± 60 ms; p = 0.001).

CONCLUSIONS

Native myocardial T1 mapping detects cardiac ATTR amyloid with similar diagnostic performance and disease tracking to AL amyloid, but with lower maximal T1 elevation, and appears to be an early disease marker.