Cardiac Amyloidosis: Evolving Approach to Diagnosis and Management

Cardiac Amyloidosis: A Narrative Review of Diagnostic Advances and Emerging Therapies

Background/Objectives: Cardiac amyloidosis (CA) is an underdiagnosed and potentially life-threatening infiltrative cardiomyopathy characterized by the extracellular deposition of misfolded amyloid fibrils in cardiac tissue. It is most commonly associated with light-chain (AL) amyloidosis and transthyretin (ATTR) amyloidosis, either hereditary or wild-type. The disease often presents with non-specific symptoms, leading to delayed diagnosis and treatment. This study aims to provide a comprehensive overview of the pathophysiology, diagnostic strategies, and current therapeutic approaches for cardiac amyloidosis, with a focus on improving early detection and clinical outcomes. Methods: A narrative review was conducted using databases such as PubMed and Scopus, covering the period from September 2016 to March 2025. Keywords such as "cardiac amyloidosis", "cardiac amyloidosis from transthyretin", "cardiomyopathy", "transthyretin", "immunoglobulin light-chain amyloidosis", and "familial amyloidosis" were used. Relevant clinical trials and guideline-based management recommendations were also included. Results: This review highlights that non-invasive imaging modalities and serum biomarker analyses are key to reducing diagnostic delays. New therapeutic developments, including gene-editing technologies and RNA-based therapies, show promise in early trials. Multidisciplinary management and increased awareness are crucial for timely diagnosis and treatment optimization. Conclusions: The early recognition of cardiac amyloidosis remains a major clinical challenge. Advances in non-invasive diagnostics and emerging disease-modifying therapies are transforming the prognosis of affected patients. Continued research and heightened clinical suspicion are essential to improve outcomes in this complex and heterogeneous disease.

Cardiac amyloid presenting as cardiogenic shock: case series

Background

Amyloidosis is a systemic infiltrative disease that can affect nearly every organ in the human body. It is characterized by the deposition of misfolded protein within various tissues and organs. Once there is cardiac involvement this portends a worse prognosis.

Case summary

We describe a case series of two patients with cardiac amyloidosis presenting as a cardiogenic shock. There were several missed opportunities in diagnosing cardiac amyloid prior to their fatal presentations. In the first case, a 65-year-old African-American male patient presented with worsening shortness of breath and signs of heart failure. Echocardiography revealed preserved ejection fraction. He was diagnosed with light chain subtype of cardiac amyloidosis, and rapidly deteriorated during his admission. Patient in the second case is a 75-year-old African-American female who presented with worsening heart failure and hypotension. Echocardiography revealed reduced ejection fraction. She was diagnosed with transthyretin cardiac amyloid. Her clinical status worsened during admission and she went into cardiogenic shock requiring multiple vasopressors.

Discussion

This case series discusses two incidences of cardiac amyloidosis presenting as cardiogenic shock in African-American patients. This article postulates that cardiac amyloidosis may be misdiagnosed for more common causes of heart failure especially among this demographic group. Once patients with cardiac amyloid present with cardiogenic shock their clinical course is typically rapidly fatal despite aggressive measures. Earlier detection is imperative to prevent poor outcomes.

Cardiac Care of Patients with Cardiac Amyloidosis

Cardiac amyloidosis, the majority of cases of which are due to immunoglobulin light chain amyloidosis (AL) and transthyretin amyloidosis (ATTR), affects different aspects of the heart and cardiovascular system. Amyloid-induced cardiomyopathy, clinically manifesting with heart failure and electrophysiological abnormalities, has distinct characteristics compared to non-amyloid cardiomyopathies. Accordingly, specific management strategies are required. This paper will review the cardiovascular manifestations of patients with cardiac amyloidosis and their suggested treatment strategies, emphasizing the importance of multidisciplinary care.

Monoclonal gammopathy of undetermined significance in systemic transthyretin amyloidosis (ATTR)

OBJECTIVE

To identify the prevalence of monoclonal gammopathy of undetermined significance (MGUS) in patients with transthyretin (ATTR) amyloidosis.

PATIENTS AND METHODS

We performed a retrospective analysis of patients with biopsy-proven ATTRwt (wild-type transthyretin amyloid protein) and genopositive ATTR V122I (valine-to-isoleucine substitution at position 122 of the TTR gene) amyloidosis evaluated at the Amyloidosis Center at Boston University and Boston Medical Center between 1 January 2003 and 31 December 2016.

RESULTS

There were a total of 226 patients with ATTRwt and ATTR V122I amyloidosis evaluated during the specified time frame with 155 and 71 patients in each cohort, respectively. Those with complete medical records, 140 patients with ATTRwt and 57 V1221 ATTRm subjects, were included in the analyses. Fifty-five patients (39%) in the ATTRwt cohort and 28 patients (49%) in the ATTR V122I cohort had an MGUS, as indicated by an abnormality in the serum-free light-chain ratio and/or serum immunofixation electrophoresis.

CONCLUSION

These data confirm the high prevalence of coexistent MGUS with ATTR amyloidosis in this patient population, with an MGUS rate that is higher than the general population. These findings also highlight the importance of a thorough diagnostic evaluation in patients with amyloidosis to determine the precursor protein, as the clinical course and treatment of AL (light-chain amyloid protein) and ATTR amyloidosis are distinct.

ER Protein Quality Control and the Unfolded Protein Response in the Heart

Cardiac myocytes are the cells responsible for the robust ability of the heart to pump blood throughout the circulatory system. Cardiac myocytes grow in response to a variety of physiological and pathological conditions; this growth challenges endoplasmic reticulum-protein quality control (ER-PQC), a major feature of which includes the unfolded protein response (UPR). ER-PQC and the UPR in cardiac myocytes growing under physiological conditions, including normal development, exercise, and pregnancy, are sufficient to support hypertrophic growth of each cardiac myocyte. However, the ER-PQC and UPR are insufficient to respond to the challenge of cardiac myocyte growth under pathological conditions, including myocardial infarction and heart failure. In part, this insufficiency is due to a continual decline in the expression levels of important adaptive UPR components as a function of age and during myocardial pathology. This chapter will discuss the physiological and pathological conditions unique to the heart that involves ER-PQC, and whether the UPR is adaptive or maladaptive under these circumstances.

Cardiovascular magnetic resonance for amyloidosis

Cardiac involvement drives the prognosis and treatment in systemic amyloid. Echocardiography, the mainstay of current cardiac imaging, defines cardiac structure and function. Echocardiography, in conjunction with clinical phenotype, electrocardiogram and biomarkers (brain natriuretic peptide and troponin), provides an assessment of the likelihood and extent of cardiac involvement. Two tests are transforming our understanding of cardiac amyloidosis, bone tracer scanning and cardiovascular magnetic resonance (CMR). CMR provides a "second opinion" on the heart's structure and systolic function with better accuracy and more precision than echocardiography but is unable to assess diastolic function and is not as widely available. Where CMR adds unique advantages is in evaluating myocardial tissue characterisation. With administration of contrast, the latest type of late gadolinium enhancement imaging (phase-sensitive inversion recovery sequence) is highly sensitive and specific with images virtually pathognomonic for amyloidosis. CMR is also demonstrating that the range of structural and functional changes in cardiac amyloid is broader than traditionally thought. CMR with T1 mapping, a relatively new CMR technique, can measure the amyloid burden and the myocyte response to infiltration (hypertrophy/cell loss) with advantages for tracking change (e.g. the wall thickness can stay the same but the composition can change) over time or during therapy. Such techniques hold great promise for advancing drug development in this arena and providing new prognostic insights. CMR with tissue characterisation is rewriting our understanding of cardiac amyloidosis and may lead to the development of new classification, therapies and prognostic systems.

High dose melphalan and autologous peripheral blood stem cell transplantation in AL amyloidosis

AL amyloidosis is the most common form of systemic amyloidosis and is associated with an underlying plasma cell dyscrasia. It is often difficult to recognize because of its many manifestations. Recent diagnostic and prognostic advances include the serum-free light chain assay, cardiac MRI, and serologic cardiac biomarkers. Treatment strategies that have evolved during the past decade are prolonging survival and preserving organ function. This article outlines the role of high-dose melphalan and stem cell transplantation. This year marks the 20th anniversary for the first patient who underwent successful stem cell transplantation for this disease at Boston Medical Center.

Plerixafor-augmented peripheral blood stem cell mobilization in AL amyloidosis with cardiac involvement: a case series

Nearly half of AL amyloidosis patients have cardiac involvement, an independent predictor of poor prognosis. High-dose melphalan and autologous stem-cell transplantation (HDM/SCT) can induce complete hematologic responses and prolong survival in AL amyloidosis. Granulocyte colony-stimulating factor (G-CSF)-induced mobilization of peripheral blood stem cell (PBSC) in AL amyloidosis patients is associated with volume overload, arrhythmias and capillary leak syndrome. Plerixafor has a different mechanism of action and has non-overlapping toxicities with G-CSF. We describe our experience in five patients with AL amyloidosis and cardiac involvement who received plerixafor with G-CSF for PBSC mobilization. Median age was 56 years; two patients had undergone heart transplantation within the year prior to HDM/SCT. Three patients received plerixafor after an initial trial of mobilization with G-CSF alone. No patient had any significant toxicities during mobilization and PBSC collection. The median total yield of PBSCs collected was 5.9 × 10(6) CD34+ cells/kg; the median number of leukapheresis days was 2. Neutrophil engraftment after HDM/SCT occurred at a median of nine days, platelet engraftment at a median of 13 days. Plerixafor was effective and well tolerated when used upfront or as rescue for PBSC mobilization in AL amyloidosis patients with cardiac involvement.

How I treat amyloidosis: the importance of accurate diagnosis and amyloid typing

Amyloidosis is a rare group of diseases characterized by deposition of amyloid fibrils in soft tissues. More than 28 types of amyloid have been identified. They all share common ultrastructural and chemical characteristics. Treatments are available for many types but are type specific. Therefore, confirmation and typing of amyloid are essential before initiating treatment. Monoclonal protein studies should be performed on suspected cases, but the diagnosis requires a tissue biopsy. Congo red stain and electron microscopy are helpful to discriminate between amyloid and other pathologic fibrils. Once amyloid is confirmed, typing should be performed. Immunofluorescence and immunohistochemistry are frequently used and are helpful, but this approach has limitations, such as availability, specificity and sensitivity of commercial antibodies. Genetic mutational analysis is vital for ruling in and out hereditary amyloidoses but is unhelpful in nonmutated forms. The most advanced technique of amyloid typing is laser microdissection followed by mass spectrometry. Using proteomics, laser microdissection followed by mass spectrometry can directly identify proteins with or without mutations. Finally, imaging studies, such as cardiac MRI with gadolinium and (123)I-labeled SAP scintigraphy not only assist in evaluation of patients with known amyloidosis but cardiac MRI has detected amyloid in patients previously unsuspected of the disease.