Cardiac amyloidosis is a manifestation of one of several systemic diseases known as the amyloidoses.1,2 This uncommon disease is probably underdiagnosed, and even when a diagnosis of amyloidosis of the heart is made, the fact that there are several types of amyloid, each with its unique features and treatment, is often unrecognized. This can lead to errors in management and in the information conveyed to the patient. The purpose of this review is to familiarize the reader with the clinical features of amyloidosis and to address the approach to the patient with this disease, focusing on the various types of amyloidosis, their prognosis and treatment.

The common feature of this group of diseases is the extracellular deposition of a proteinaceous material that, when stained with Congo red, demonstrates apple-green birefringence under polarized light and that has a distinct color when stained with sulfated Alcian blue (Figure 1). Viewed with electron microscopy, the amyloid deposits are seen to be composed of a β-sheet fibrillar material (Figure 2). These nonbranching fibrils have a diameter3 of 7.5 to 10 nm and are the result of protein misfolding.4,5 Cardiac involvement in amyloidosis may be the predominant feature or may be found on investigation of a patient presenting with another major organ involvement. The presence of cardiac amyloidosis and its relative predominance varies with the type of amyloidosis. Thus, senile systemic amyloidosis and some forms of transthyretin amyloidosis invariably affect the heart, whereas cardiac involvement ranges from absent to severe in amyloidosis derived from a light-chain precursor (AL amyloidosis). Secondary amyloidosis almost never affects the heart in any clinically significant manner.6 The specific composition of the fibrils differs in the different types of amyloid7 and are outlined in the Table. Both on the basis of common usage and for …

Diagnosis and Management of the Cardiac Amyloidoses

Background— Most studies of amyloidotic cardiomyopathy consider as a single entity the 3 main systemic cardiac amyloidoses: acquired monoclonal immunoglobulin light-chain (AL); hereditary, mutated transthyretin-related (ATTRm); and wild-type transthyretin-related (ATTRwt). In this study, we compared the diagnostic/clinical profiles of these 3 types of systemic cardiac amyloidosis. Methods and Results— We conducted a longitudinal study of 233 patients with clear-cut diagnosis by type of cardiac amyloidosis (AL, n=157; ATTRm, n=61; ATTRwt, n=15) at 2 large Italian centers providing coordinated amyloidosis diagnosis/management facilities since 1990. Average age at diagnosis was higher in AL than in ATTRm patients; all ATTRwt patients except 1 were elderly men. At diagnosis, mean left ventricular wall thickness was higher in ATTRwt than in ATTRm and AL. Left ventricular ejection fraction was moderately depressed in ATTRwt but not in AL or ATTRm. ATTRm patients less often displayed low QRS voltage (25% versus ...

Systemic Cardiac Amyloidoses Disease Profiles and Clinical Courses of the 3 Main Types

The transthyretin amyloidoses (ATTR) are invariably fatal diseases characterized by progressive neuropathy and/or cardiomyopathy. ATTR are caused by aggregation of transthyretin (TTR), a natively tetrameric protein involved in the transport of thyroxine and the vitamin A–retinol-binding protein complex. Mutations within TTR that cause autosomal dominant forms of disease facilitate tetramer dissociation, monomer misfolding, and aggregation, although wild-type TTR can also form amyloid fibrils in elderly patients. Because tetramer dissociation is the rate-limiting step in TTR amyloidogenesis, targeted therapies have focused on small molecules that kinetically stabilize the tetramer, inhibiting TTR amyloid fibril formation. One such compound, tafamidis meglumine (Fx-1006A), has recently completed Phase II/III trials for the treatment of Transthyretin Type Familial Amyloid Polyneuropathy (TTR-FAP) and demonstrated a slowing of disease progression in patients heterozygous for the V30M TTR mutation. Herein we describe the molecular and structural basis of TTR tetramer stabilization by tafamidis. Tafamidis binds selectively and with negative cooperativity (Kds ∼2 nM and ∼200 nM) to the two normally unoccupied thyroxine-binding sites of the tetramer, and kinetically stabilizes TTR. Patient-derived amyloidogenic variants of TTR, including kinetically and thermodynamically less stable mutants, are also stabilized by tafamidis binding. The crystal structure of tafamidis-bound TTR suggests that binding stabilizes the weaker dimer-dimer interface against dissociation, the rate-limiting step of amyloidogenesis.

https://www.pnas.org/content/pnas/109/24/9629.full.pdf

Tafamidis, a potent and selective transthyretin kinetic stabilizer that inhibits the amyloid cascade

The intent of this American Heart Association (AHA) scientific statement is to summarize our current understanding of dilated cardiomyopathies. There is special emphasis on recent developments in diagnostic approaches and therapies for specific cardiomyopathies. Recommendations in this document are based on published studies, published practice guidelines from the American College of Cardiology (ACC)/AHA1 and other organizations,2,3 and the multidisciplinary expertise of the writing group. Existing evidence in epidemiology, classification, diagnosis, and management of specific cardiomyopathies is usually derived from nonrandomized observational studies, registries, case reports, or expert opinion based on clinical experience, not large-scale randomized clinical trials or systematic reviews. Therefore, in this document, rather than using the standard ACC/AHA classification schema of recommendations and level of evidence,4 we have included key management strategies at the end of each section and categorized our recommendations according to the level of consensus. Although the format of our recommendations might resemble the ACC/AHA classification of recommendations used in the ACC/AHA practice guidelines, because of the preponderance of expert opinion or level of evidence C evidence in our document, we elected to use different terminology to provide a distinction from the practice guidelines, in which stronger levels and quality of evidence with randomized clinical trials or meta-analyses are usually present.4 The levels of evidence follow the AHA and ACC methods of classifying the level of certainty of the treatment effect.4

The term dilated cardiomyopathy (DCM) refers to a spectrum of heterogeneous myocardial disorders that are characterized by ventricular dilation and depressed myocardial performance in the absence of hypertension, valvular, congenital, or ischemic heart disease.5

In clinical practice, the pathogenesis of heart failure (HF) has often been placed into 2 categories: ischemic and nonischemic cardiomyopathy. The term nonischemic cardiomyopathy has been interchangeably used with DCM. Although this …

Current Diagnostic and Treatment Strategies for Specific Dilated Cardiomyopathies: A Scientific Statement From the American Heart Association.

The systemic amyloidoses are a family of diseases induced by misfolded or misassembled proteins. Extracellular deposition of these proteins as soluble or insoluble cross β-sheets disrupts vital organ function.1 More than 27 different precursor proteins have the propensity to form amyloid fibrils.2 The particular precursor protein that misfolds to form amyloid fibrils defines the amyloid type and predicts the patient's clinical course. Several types of amyloid can infiltrate the heart, resulting in progressive diastolic and systolic dysfunction, congestive heart failure, and death. Treatment of cardiac amyloidosis is dictated by the amyloid type and degree of involvement. Consequently, early recognition and accurate classification are essential.3

The diagnosis of amyloidosis requires histological identification of amyloid deposits. Congo Red staining renders amyloid deposits salmon pink by light microscopy, with a characteristic apple green birefringence under polarized light conditions (Figure 1). Additional immunohistochemical staining for precursor proteins identifies the type of amyloidosis (Figure 2).4 Ultimately, immunogold electron microscopy and mass spectrometry confer the greatest sensitivity and specificity for amyloid typing.5,6



Figure 1. 
Congo Red staining of myocardial tissue from a patient with amyloid cardiomyopathy. A , Light microscopy; B , polarized light microscopy, 400× magnification.





Figure 2. 
Transthyretin amyloid cardiomyopathy by immunohistochemical staining. Endomyocardial biopsy samples were stained with antibodies to ( A ) kappa light chain, ( B ) lambda light-chain, ( C ) serum amyloid A, and ( D ) transthyretin amyloid. Bright-light micrographs at 400× magnification.



Two types of amyloid commonly infiltrate the heart: (1) Immunoglobulin light-chain (AL or primary systemic) amyloid and (2) transthyretin (TTR) amyloid. Transthyretin-related amyloidoses, in turn, encompass 2 forms of disease: Familial disease arising from misfolding of a mutated or variant TTR (familial amyloid cardiomyopathy or familial amyloidotic polyneuropathy [FAP]) and a sporadic, nongenetic disease caused by misaggregation of wild-type transthyretin (senile systemic amyloidosis [SSA]). Cardiac amyloidosis can also be …

/pdf/transthyretin-ttr-cardiac-amyloidosis-2d6v126inv.pdf

Transthyretin (TTR) Cardiac Amyloidosis

Background:Small deposits of amyloid are often found intheheartsofelderlypatients.However,extensivedepositionoftransthyretin-derivedamyloidfibrilsintheheart (senile systemic amyloidosis [SSA]) can cause heart failure. The clinical features of SSA that involve the heart are ill defined, and the condition may be overlooked as a cause of heart failure. We sought to better define the clinical,echocardiographic,andelectrocardiographicfeaturesofcardiacinvolvementinSSAandtocomparethem with the findings in patients with light chain–associated (AL) amyloidosis that affects the heart. Methods: Eighteen consecutive patients with SSA and heart failure evaluated at a tertiary referral center for the diagnosis and treatment of amyloidosis were compared with 18 randomly selected patients with AL amyloidosisthatinvolvedtheheart.Allpatientsunderwentacomplete clinical and biochemical evaluation. Echocardiogramsandelectrocardiogramswereinterpretedbyblinded investigators. Results:PatientswithSSAwereolderthanthosewithAL amyloidosis and were all male. Proteinuria (protein outputof1gper24hours)wascommoninALamyloidosis butwasnotpresentinSSA.Leftventricularwallthickness was greater in patients with SSA than those with AL amyloidosis,butdespitethickerwallsandolderage,theseverity of heart failure was less in the SSA group and the mediansurvivalwasmuchlonger(75vs11months;P=.003). Conclusions: Senile systemic amyloidosis is a disorder of elderly men and is characterized by amyloidosis clinically limited to the heart. In contrast to the rapid progression of heart failure in AL amyloidosis, SSA results in slowly progressive heart failure. The difference in survival, despite evidence of more myocardial disease in the senile group, suggests that heart failure in AL amyloidosis may have a toxic component, possibly related to the circulating monoclonal light chain. Arch Intern Med. 2005;165:1425-1429

/pdf/senile-systemic-amyloidosis-presenting-with-heart-failure-a-4uzofdncng.pdf

Belinda Ng

Papers

Senile Systemic Amyloidosis Presenting With Heart Failure A Comparison With Light Chain-Associated Amyloidosis