David F. Hutt

Nonbiopsy Diagnosis of Cardiac Transthyretin Amyloidosis

Background— Cardiac transthyretin (ATTR) amyloidosis is a progressive and fatal cardiomyopathy for which several promising therapies are in development. The diagnosis is frequently delayed or missed because of the limited specificity of echocardiography and the traditional requirement for histological confirmation. It has long been recognized that technetium-labeled bone scintigraphy tracers can localize to myocardial amyloid deposits, and use of this imaging modality for the diagnosis of cardiac ATTR amyloidosis has lately been revisited. We conducted a multicenter study to ascertain the diagnostic value of bone scintigraphy in this disease. Methods and Results— Results of bone scintigraphy and biochemical investigations were analyzed from 1217 patients with suspected cardiac amyloidosis referred for evaluation in specialist centers. Of 857 patients with histologically proven amyloid (374 with endomyocardial biopsies) and 360 patients subsequently confirmed to have nonamyloid cardiomyopathies, myocardial radiotracer uptake on bone scintigraphy was >99% sensitive and 86% specific for cardiac ATTR amyloid, with false positives almost exclusively from uptake in patients with cardiac AL amyloidosis. Importantly, the combined findings of grade 2 or 3 myocardial radiotracer uptake on bone scintigraphy and the absence of a monoclonal protein in serum or urine had a specificity and positive predictive value for cardiac ATTR amyloidosis of 100% (positive predictive value confidence interval, 98.0–100). Conclusions— Bone scintigraphy enables the diagnosis of cardiac ATTR amyloidosis to be made reliably without the need for histology in patients who do not have a monoclonal gammopathy. We propose noninvasive diagnostic criteria for cardiac ATTR amyloidosis that are applicable to the majority of patients with this disease.

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.

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

AIMS Technetium-99m-labelled 3,3-diphosphono-1,2-propanodicarboxylic acid ((99m)Tc-DPD) is a sensitive method for imaging cardiac transthyretin (ATTR) amyloid. We report utility and limitations of (99m)Tc-DPD scintigraphy in 321 patients with suspected cardiac amyloidosis. METHODS AND RESULTS The cohort included wild-type ATTR (ATTRwt) amyloidosis in 94 (29%), ATTR-Val122Ile amyloidosis in 38 (12%), hereditary ATTR (ATTRmt) amyloidosis in 46 (14%), primary light-chain (AL) amyloidosis in 44 (14%), secondary (AA) amyloidosis in three (1%), other hereditary amyloidosis types in nine (3%), undetermined types in two (0.5%), and 85 (26.5%) patients in whom systemic amyloidosis was ultimately excluded. All 158 patients with ATTR amyloidosis with clinical cardiac involvement had cardiac (99m)Tc-DPD uptake, with median Grade 2 intensity. Thirteen further ATTR amyloidosis patients without clinical evidence of cardiac involvement also demonstrated (99m)Tc-DPD cardiac uptake. Eighteen of 35 (51%) AL patients with cardiac involvement had (99m)Tc-DPD cardiac uptake (median Grade 1 intensity). SPECT imaging indicates that the apparent reciprocal reduction in bone uptake is due to masking of bone uptake by extensive soft-tissue uptake in ATTR amyloidosis, especially ATTRwt, and ATTR-Val122Ile types. CONCLUSION (99m)Tc-DPD scintigraphy is a highly sensitive technique for imaging cardiac ATTR amyloidosis and is an important investigation in the diagnostic pathway of patients with cardiac amyloidosis. It is not specific for ATTR in isolation but must be interpreted in a broad clinical context to avoid dangerous diagnostic errors. Diffuse skeletal muscle uptake identifies muscle as a hitherto unrecognized site that merits investigation as a target organ in ATTR amyloidosis.

Differential Myocyte Responses in Patients with Cardiac Transthyretin Amyloidosis and Light-Chain Amyloidosis: A Cardiac MR Imaging Study

PURPOSE To investigate cardiac magnetic resonance (MR) imaging measurements of extracellular volume (ECV) and total cell volume in immunoglobulin light-chain amyloidosis (AL) and transthyretin amyloidosis (ATTR) in order to evaluate the amyloid and myocyte volumes. MATERIALS AND METHODS All ethics were approved, and participants provided written informed consent. Of the 257 subjects who were recruited, 92 had AL (mean age, 62 years ± 10), 44 had mutant ATTR (mean age, 68 years ± 10), and 66 had wild-type ATTR (mean age, 75 years ± 7). In addition, eight healthy subjects with ATTR mutations (mean age, 47 years ± 6) and 47 healthy volunteers (mean age, 45 years ± 15) participated. All participants underwent equilibrium contrast material-enhanced cardiac MR imaging. ECV and total cell volume were measured in the heart. T test, χ(2), and one-way analysis of variance with posthoc Bonferroni correction were used. RESULTS Both the left ventricular indexed mass and ECV were elevated in patients with amyloidosis. For left ventricular indexed mass, mean AL was 107 g/m(2) ± 30; mean mutant ATTR was 137 g/m(2) ± 29; and mean wild-type ATTR was 133 g/m(2) ± 27 versus 65 g/m(2) ± 15 in healthy subjects (P < .0001 for all measures). For ECV, mean AL was 0.54 ± 0.07, mean mutant ATTR was 0.60 ± 0.07, and mean wild-type ATTR was 0.57 ± 0.06 versus 0.27 ± 0.03 in healthy subjects (P < .0001 for all measures). Patients with ATTR had a higher total cell volume than did healthy subjects (mean, 53 mL/m(2) ± 12 vs 45 mL/m(2) ± 11; P = .001), but in patients with AL, total cell volume was normal (mean, 47 mL/m(2) ± 17 vs 45 mL/m(2) ± 11; P > .99). The result is that, in patients with AL, all of the increase in left ventricular indexed mass is extracellular volume, whereas in patients with ATTR, the increase is extracellular, with an additional 18% increase in the intracellular space. CONCLUSION Quantification of ECV measures cardiac amyloid deposition in both types of amyloidosis and shows that amyloid deposition is more extensive in patients with ATTR than in those with AL; however, ATTR is associated with higher cell volume, which suggests concomitant cell hypertrophy.

Occult Transthyretin Cardiac Amyloid in Severe Calcific Aortic Stenosis Prevalence and Prognosis in Patients Undergoing Surgical Aortic Valve Replacement

Background—Calcific aortic stenosis (cAS) affects 3% of individuals aged >75 years, leading to heart failure and death unless the valve is replaced. Wild-type transthyretin cardiac amyloid is also a disorder of ageing individuals. Prevalence and clinical significance of dual pathology are unknown. This study explored the prevalence of wild-type transthyretin amyloid in cAS by myocardial biopsy, its imaging phenotype and prognostic significance. Methods and Results—A total of 146 patients with severe AS requiring surgical valve replacement underwent cardiovascular magnetic resonance and intraoperative biopsies; 112 had cAS (75±6 years; 57% men). Amyloid was sought histologically using Congo red staining and then typed using immunohistochemistry and mass spectrometry; patients with amyloid underwent clinical evaluation including genotyping and 99mTC-3,3-diphosphono-1,2-propanodicarboxylic-acid (DPD) bone scintigraphy. Amyloid was identified in 6 of 146 patients, all with cAS and >65 years (prevalence 5.6% in cAS >65). All 6 patients had wild-type transthyretin amyloid (mean age 75 years; range, 69–85; 4 men), not suspected on echocardiography. Cardiovascular magnetic resonance findings were of definite cardiac amyloidosis in 2, but could be explained solely by AS in the other 4. Postoperative DPD scans demonstrated cardiac localization in all 4 patients who had this investigation (2 died prior). At follow-up (median, 2.3 years), 50% with amyloid had died (versus 7.5% in cAS; 6.9% in age >65 years). In univariable analyses, the presence of transthyretin amyloidosis amyloid had the highest hazard ratio for death (9.5 [95% confidence interval, 2.5–35.8]; P=0.001). Conclusions—Occult wild-type transthyretin cardiac amyloid had a prevalence of 6% among patients with AS aged >65 years undergoing surgical aortic valve replacement and was associated with a poor outcome.Background— Calcific aortic stenosis (cAS) affects 3% of individuals aged >75 years, leading to heart failure and death unless the valve is replaced. Wild-type transthyretin cardiac amyloid is also a disorder of ageing individuals. Prevalence and clinical significance of dual pathology are unknown. This study explored the prevalence of wild-type transthyretin amyloid in cAS by myocardial biopsy, its imaging phenotype and prognostic significance. Methods and Results— A total of 146 patients with severe AS requiring surgical valve replacement underwent cardiovascular magnetic resonance and intraoperative biopsies; 112 had cAS (75±6 years; 57% men). Amyloid was sought histologically using Congo red staining and then typed using immunohistochemistry and mass spectrometry; patients with amyloid underwent clinical evaluation including genotyping and 99mTC-3,3-diphosphono-1,2-propanodicarboxylic-acid (DPD) bone scintigraphy. Amyloid was identified in 6 of 146 patients, all with cAS and >65 years (prevalence 5.6% in cAS >65). All 6 patients had wild-type transthyretin amyloid (mean age 75 years; range, 69–85; 4 men), not suspected on echocardiography. Cardiovascular magnetic resonance findings were of definite cardiac amyloidosis in 2, but could be explained solely by AS in the other 4. Postoperative DPD scans demonstrated cardiac localization in all 4 patients who had this investigation (2 died prior). At follow-up (median, 2.3 years), 50% with amyloid had died (versus 7.5% in cAS; 6.9% in age >65 years). In univariable analyses, the presence of transthyretin amyloidosis amyloid had the highest hazard ratio for death (9.5 [95% confidence interval, 2.5–35.8]; P =0.001). Conclusions— Occult wild-type transthyretin cardiac amyloid had a prevalence of 6% among patients with AS aged >65 years undergoing surgical aortic valve replacement and was associated with a poor outcome.

Prognostic utility of the Perugini grading of 99mTc-DPD scintigraphy in transthyretin (ATTR) amyloidosis and its relationship with skeletal muscle and soft tissue amyloid

Aims High-grade (Perugini grade 2 or 3) cardiac uptake on bone scintigraphy with 99mTechnetium labelled 3,3-diphosphono-1,2-propanodicarboxylic acid (99mTc-DPD) has lately been confirmed to have high diagnostic sensitivity and specificity for cardiac transthyretin (ATTR) amyloidosis. We sought to determine whether patient stratification by Perugini grade on 99mTc-DPD scintigraphy has prognostic significance in ATTR amyloidosis. Methods and results Patient survival from time of 99mTc-DPD scintigraphy was determined in 602 patients with ATTR amyloidosis, including 377 with wild-type ATTR (ATTRwt) and 225 with mutant ATTR (ATTRm) amyloidosis. Patients were stratified according to Perugini grade (0-3) on 99mTc-DPD scan. The prognostic significance of additional patient and disease-related factors at baseline were determined. In the whole cohort, the finding of a Perugini grade 0 99mTc-DPD scan (n = 28) was invariably associated with absence of cardiac amyloid according to consensus criteria as well as significantly better patient survival compared to a Perugini grade 1 (n = 28), 2 (n = 436) or 3 (n = 110) 99mTc-DPD scan (P < 0.005). There were no differences in survival between patients with a grade 1, grade 2 or grade 3 99mTc-DPD scan in ATTRwt (n = 369), V122I-associated ATTRm (n = 92) or T60A-associated ATTRm (n = 59) amyloidosis. Cardiac amyloid burden, determined by equilibrium contrast cardiac magnetic resonance imaging, was similar between patients with Perugini grade 2 and Perugini grade 3 99mTc-DPD scans but skeletal muscle/soft tissue to femur ratio was substantially higher in the latter group (P < 0.001). Conclusion 99mTc-DPD scintigraphy is exquisitely sensitive for identification of cardiac ATTR amyloid, but stratification by Perugini grade of positivity at diagnosis has no prognostic significance.

Repeat doses of antibody to serum amyloid P component clear amyloid deposits in patients with systemic amyloidosis

Repeat cycles of miridesap, to deplete circulating serum amyloid P component (SAP), followed by the anti-SAP antibody, dezamizumab, cleared visceral amyloid deposits in patients with systemic amyloidosis. Making amyloid vanish Fatal systemic amyloidosis is caused by extracellular amyloid deposition that disrupts tissue structure and function. The normal plasma protein, serum amyloid P component (SAP), is always present within amyloid deposits. Richards et al. now show that previous depletion of circulating SAP by the drug, miridesap, uniquely enables subsequent administration of the humanized anti-SAP antibody, dezamizumab, to patients with systemic amyloidosis. Dezamizumab bound to residual SAP in the amyloid deposits and triggered their removal. Repeat cycles of miridesap followed by dezamizumab progressively removed amyloid from the liver, spleen, and kidneys of the patients. Evidence of clinical benefit suggests that this new approach has potential to improve management and outcome for patients with systemic amyloidosis. Systemic amyloidosis is a fatal disorder caused by pathological extracellular deposits of amyloid fibrils that are always coated with the normal plasma protein, serum amyloid P component (SAP). The small-molecule drug, miridesap, [(R)-1-[6-[(R)-2-carboxy-pyrrolidin-1-yl]-6-oxo-hexanoyl]pyrrolidine-2-carboxylic acid (CPHPC)] depletes circulating SAP but leaves some SAP in amyloid deposits. This residual SAP is a specific target for dezamizumab, a fully humanized monoclonal IgG1 anti-SAP antibody that triggers immunotherapeutic clearance of amyloid. We report the safety, pharmacokinetics, and dose-response effects of up to three cycles of miridesap followed by dezamizumab in 23 adult subjects with systemic amyloidosis (ClinicalTrials.gov identifier: NCT01777243). Amyloid load was measured scintigraphically by amyloid-specific radioligand binding of 123I-labeled SAP or of 99mTc-3,3-diphosphono-1,2-propanodicarboxylic acid. Organ extracellular volume was measured by equilibrium magnetic resonance imaging and liver stiffness by transient elastography. The treatment was well tolerated with the main adverse event being self-limiting early onset rashes after higher antibody doses related to whole body amyloid load. Progressive dose-related clearance of hepatic amyloid was associated with improved liver function tests. 123I-SAP scintigraphy confirmed amyloid removal from the spleen and kidneys. No adverse cardiac events attributable to the intervention occurred in the six subjects with cardiac amyloidosis. Amyloid load reduction by miridesap treatment followed by dezamizumab has the potential to improve management and outcome in systemic amyloidosis.

Changing epidemiology of AA amyloidosis: clinical observations over 25 years at a single national referral centre

Abstract Objective: Systemic AA amyloidosis is a serious complication of chronic inflammation; however, there are relatively few published data on its incidence. We investigated the changing epidemiology of AA amyloidosis over a 25-year period at a single national referral centre. Methods: We conducted a retrospective study of all patients diagnosed with AA amyloidosis who had attended the centre between 1990 and 2014 inclusive. Six hundred and twenty-five patients were studied in three cohorts: C1: 1990–1997; C2: 1998–2006; C3: 2007–2014. Results: Mean age at presentation increased from 46 in C1 to 56 in C3 (p < .0001). The proportion of South Asian patients increased from 4% in C1 to 17% in C3 (p = .0006). Comparison of underlying diseases between C1 and C3 revealed a reduction in patients with juvenile idiopathic arthritis from 25% to 2% (p < .0001), but an increase in patients with chronic infection due to intravenous recreational drug use from 1% to 13% (p < .0001), and uncharacterized inflammatory disorders from 10% to 27% (p <.0001). More patients were in end-stage renal failure at presentation in C3 (29%) than C1 (15%) (p = .0028). Median age at death was later in C3 (62 years) than C1 (54 years) (p = .0012). Conclusion: These data suggest both falling incidence and better outcome in AA amyloidosis over a quarter of a century, reflecting advances in therapeutics and overall management of complex chronic disease in an ageing population. AA amyloidosis of uncertain aetiology presents an emerging major problem. Newer techniques such as next-generation sequencing may aid diagnosis and effective treatment, thereby improving overall survival.

Misdiagnosing renal amyloidosis as minimal change disease

BACKGROUND Minimal change disease (MCD) accounts for 10-15% of all adult nephrotic syndrome cases and requires normal renal histology by light microscopy and negative immunohistology. Foot process effacement on electron microscopy (EM) is typical. Renal amyloid deposits demonstrate pathognomonic green birefringence when viewed under cross-polarized light after staining tissue with Congo red (CR) and may reveal fibrils on EM. Late diagnosis and delayed treatment of renal amyloidosis negatively impact on renal and patient survival. METHODS A retrospective analysis was performed on 2116 patients referred to the National Amyloidosis Centre between 2001 and 2013, in whom renal amyloidosis was confirmed histologically. Twenty-seven of these patients had renal histology initially interpreted to be MCD. RESULTS Among 26 patients in whom biopsy specimens and/or reports were retrieved, the median age at MCD diagnosis was 62 years and presenting proteinuria averaged 7.8 g/24 h. The median time period between the two diagnoses was 241 days (range: 20-2632 days). MCD was diagnosed without CR in 17/26 (65%) biopsies, but all specimens contained amyloid on retrospective CR staining. MCD was diagnosed without EM in 17/26 (65%) cases and all of 10 such biopsies subsequently demonstrated fibrils. Sixteen patients were subjected to two or more renal biopsies when their proteinuria proved steroid refractory. CONCLUSION This study highlights the need to stain renal biopsies from proteinuric adults with CR, examine them under cross-polarized light and perform EM wherever possible. If the suspicion of renal amyloidosis remains high, despite apparent negative histology, specimens should be reviewed at specialist centres before undertaking a second kidney biopsy.

Clinical characteristics and SAP scintigraphic findings in 10 patients with AGel amyloidosis

Abstract The clinical features of hereditary gelsolin (AGel) amyloidosis include corneal lattice dystrophy, distal sensorimotor, cranial neuropathy and cutis laxa. To date, four mutations of the gelsolin (GSN) gene encoding the following variants have been identified as the cause of this malady; p.D214N, p.D214Y, p.G194R and p.N211K (this nomenclature includes the 27-residue signal peptide). Interestingly, the latter two variants are associated exclusively with a renal amyloidosis phenotype. Here we report the clinical features in 10 patients with AGel amyloidosis associated with the p.D214N mutation, all of whom underwent whole body 123I-SAP scintigraphy and were followed up in a single UK Centre for a prolonged period. Two patients, from the same kindred presented with proteinuria; eight subjects had a characteristic AGel amyloidosis phenotype including cranial neuropathy and/or corneal lattice dystrophy. 123I-SAP scintigraphy revealed substantial renal amyloid deposits in all 10 patients, including those with preserved renal function, and usually without tracer uptake into other visceral organs. 123I-SAP scintigraphy is a non-invasive technique that aids early diagnosis of patients with this rare disease, especially those who lack a family history and/or present with an unusual clinical phenotype.