Myocardial Composition in Light-Chain Cardiac Amyloidosis More Than 1 Year After Successful Therapy

Functional Status and Quality of Life in Light-Chain Amyloidosis: Advanced Imaging, Longitudinal Changes, and Outcomes

BACKGROUND

In light-chain (AL) amyloidosis, whether functional status and heart failure-related quality of life (HF-QOL) correlate with cardiomyopathy severity, improve with therapy, and are associated with major adverse cardiac events (MACE) beyond validated scores is not well-known.

OBJECTIVES

The authors aimed to: 1) correlate functional status and HF-QOL with cardiomyopathy severity; 2) analyze their longitudinal changes; and 3) assess their independent associations with MACE.

METHODS

This study included 106 participants with AL amyloidosis, with 81% having AL cardiomyopathy. Functional status was evaluated using the NYHA functional class, the Karnofsky scale, and the 6-minute walk distance (6MWD), and HF-QOL using the MLWHFQ (Minnesota Living with Heart Failure Questionnaire). Cardiomyopathy severity was assessed by cardiac 18F-florbetapir positron emission tomography/computed tomography, cardiac magnetic resonance, echocardiography, and serum cardiac biomarkers. MACE were defined as all-cause death, heart failure hospitalization, or cardiac transplantation.

RESULTS

NYHA functional class, Karnofsky scale, 6MWD, and MLWHFQ were impaired substantially in participants with recently diagnosed AL cardiomyopathy (P < 0.001), and correlated with all markers of cardiomyopathy severity (P ≤ 0.010). NYHA functional class, 6MWD, and MLWHFQ improved at 12 months in participants with cardiomyopathy (P ≤ 0.013). All measures of functional status and HF-QOL were associated with MACE (P ≤ 0.017), independent of Mayo stage for 6MWD and MLWHFQ (P ≤ 0.006).

CONCLUSIONS

Functional status and HF-QOL were associated with AL cardiomyopathy severity, improved on therapy within 12 months, and were associated with MACE, independently of Mayo stage for 6MWD and MLWHFQ. They may be validated further in addition to prognostic scores and as surrogate outcomes for future studies.

Amyloids and the Heart: An Update

Amyloids consist of fibrils that can be formed by a large variety of different precursor proteins. In localized amyloidosis, amyloids accumulate at the production site with a single organ being affected, whereas in systemic amyloidosis several organs are affected, with the heart being the most common, followed by the kidneys, liver, and the nervous system. The two most frequent systemic amyloidosis types affecting the heart in the vast majority (>95%) of cases are immunoglobulin light chain (AL) amyloidosis and transthyretin (TTR) amyloidosis (ATTR amyloidosis). Patients with amyloid cardiopathy (CA) often present with non-specific heart failure symptoms as well as other clinical manifestations depending on the organ or systems involved. However, there are some findings associated with amyloidosis called "red flags" (clinical, echocardiographic, magnetic resonance imaging), which may assist in guiding the physician to the correct diagnosis. The present state-of-the-art review summarizes the features of the various cardiac phenotypic expressions of amyloidosis, proposes a simplified pathway for its diagnosis, and highlights the rapidly evolving therapeutic landscape.

Myocardial Characteristics, Cardiac Structure, and Cardiac Function in Systemic Light-Chain Amyloidosis

BACKGROUND

In systemic light-chain (AL) amyloidosis, cardiac involvement portends poor outcomes.

OBJECTIVES

The authors' objectives were to detect early myocardial alterations, to analyze longitudinal changes with therapy, and to predict major adverse cardiac events (MACE) in participants with AL amyloidosis using cardiac magnetic resonance imaging (MRI).

METHODS

Recently diagnosed participants were prospectively enrolled. AL amyloidosis with and without cardiomyopathy (AL-CMP, AL-non-CMP) were defined based on abnormal cardiac biomarkers and wall thickness. MRI was performed at baseline, 6 months in all participants, and 12 months in participants with AL-CMP. MACE were defined as all-cause death, heart failure hospitalization, and cardiac transplantation. Mayo stage was based on troponin T, N-terminal pro-B-type natriuretic peptide, and difference in free light chains.

RESULTS

This study included 80 participants (median age 62 years, 58% men). Extracellular volume (ECV) was abnormal (>32%) in all participants with AL-CMP and in 47% of those with AL-non-CMP. ECV tended to increase at 6 months (median +2%; AL-CMP P = 0.120; AL-non-CMP P = 0.018) and returned to baseline values at 12 months in participants with AL-CMP. Global longitudinal strain (GLS) improved at 6 months (median -0.6%; P = 0.048) and 12 months (median -1.2%; P < 0.001) in participants with AL-CMP. ECV and GLS were strongly associated with MACE (P < 0.001) and improved the prognostic value when added to Mayo stage (P ≤ 0.002). No participant with ECV ≤32% had MACE, while 74% of those with ECV >48% had MACE.

CONCLUSIONS

In patients with systemic AL amyloidosis, ECV detects subclinical myocardial alterations. With therapy, ECV tends to increase at 6 months and returns to values unchanged from baseline at 12 months, whereas GLS improves at 6 and 12 months in participants with AL-CMP. ECV and GLS offer additional prognostic performance over Mayo stage. (Molecular Imaging of Primary Amyloid Cardiomyopathy [MICA]; NCT02641145).

Mechanisms of left ventricular systolic dysfunction in light chain amyloidosis: a multiparametric cardiac MRI study

Background

Cardiac systolic dysfunction is a poor prognostic marker in light-chain (AL) cardiomyopathy, a primary interstitial disorder; however, its pathogenesis is poorly understood.

Purpose

This study aims to analyze the effects of extracellular volume (ECV) expansion, a surrogate marker of amyloid burden on myocardial blood flow (MBF), myocardial work efficiency (MWE), and left ventricular (LV) systolic dysfunction in AL amyloidosis.

Methods

Subjects with biopsy-proven AL amyloidosis were prospectively enrolled (April 2016-June 2021; Clinicaltrials.gov ID NCT02641145) and underwent cardiac magnetic resonance imaging (MRI) to quantify rest MBF by perfusion imaging, LV ejection fraction (LVEF) by cine MRI, and ECV by pre- and post-contrast T1 mapping. The MWE was estimated as external cardiac work from the stroke volume and mean arterial pressure normalized to the LV myocardial mass.

Results

Rest MBF in 92 subjects (62 ± 8 years, 52 men) with AL amyloidosis averaged 0.87 ± 0.21 ml/min/g and correlated with MWE (r = 0.42; p < 0.001). Rest MBF was similarly low in subjects with sustained hematologic remission after successful AL amyloidosis therapy (n = 21), as in those with recently diagnosed AL amyloidosis. Both MBF and MWE decreased by ECV tertile (p < 0.01 for linear trends). The association of ECV with MWE comprised a direct effect (84% of the total effect; p < 0.001) on MWE from adverse interstitial remodeling assessed by ECV and an indirect effect (16% of the total effect; p < 0.001) mediated by MBF. There was a significant base-to-apex gradient of rest MBF in subjects with higher amyloid burden.

Conclusions

In AL amyloidosis, both MBF and MWE decrease as cardiac amyloid burden and ECV expansion increase. Both structural and vascular changes from ECV expansion and myocardial amyloid burden appear to contribute to lower MWE.

Light-Chain Cardiac Amyloidosis: Cardiac Magnetic Resonance for Assessing Response to Chemotherapy

OBJECTIVE

Cardiac magnetic resonance (CMR) is a diagnostic tool that provides precise and reproducible information about cardiac structure, function, and tissue characterization, aiding in the monitoring of chemotherapy response in patients with light-chain cardiac amyloidosis (AL-CA). This study aimed to evaluate the feasibility of CMR in monitoring responses to chemotherapy in patients with AL-CA.

MATERIALS AND METHODS

In this prospective study, we enrolled 111 patients with AL-CA (50.5% male; median age, 54 [interquartile range, 49-63] years). Patients underwent longitudinal monitoring using biomarkers and CMR imaging. At follow-up after chemotherapy, patients were categorized into superior and inferior response groups based on their hematological and cardiac laboratory responses to chemotherapy. Changes in CMR findings across therapies and differences between response groups were analyzed.

RESULTS

Following chemotherapy (before vs. after), there were significant increases in myocardial T2 (43.6 ± 3.5 ms vs. 44.6 ± 4.1 ms; P = 0.008), recovery in right ventricular (RV) longitudinal strain (median of -9.6% vs. -11.7%; P = 0.031), and decrease in RV extracellular volume fraction (ECV) (median of 53.9% vs. 51.6%; P = 0.048). These changes were more pronounced in the superior-response group. Patients with superior cardiac laboratory response showed significantly greater reductions in RV ECV (-2.9% [interquartile range, -8.7%-1.1%] vs. 1.7% [-5.5%-7.1%]; P = 0.017) and left ventricular ECV (-2.0% [-6.0%-1.3%] vs. 2.0% [-3.0%-5.0%]; P = 0.01) compared with those with inferior response.

CONCLUSION

Cardiac amyloid deposition can regress following chemotherapy in patients with AL-CA, particularly showing more prominent regression, possibly earlier, in the RV. CMR emerges as an effective tool for monitoring associated tissue characteristics and ventricular functional recovery in patients with AL-CA undergoing chemotherapy, thereby supporting its utility in treatment response assessment.

Quantification of right ventricular amyloid burden with 18F-florbetapir positron emission tomography/computed tomography and its association with right ventricular dysfunction and outcomes in light-chain amyloidosis

AIMS

In systemic light-chain (AL) amyloidosis, quantification of right ventricular (RV) amyloid burden has been limited and the pathogenesis of RV dysfunction is poorly understood. Using 18F-florbetapir positron emission tomography/computed tomography (PET/CT), we aimed to quantify RV amyloid; correlate RV amyloid with RV structure and function; determine the independent contributions of RV, left ventricular (LV), and lung amyloid to RV function; and associate RV amyloid with major adverse cardiac events (MACE: death, heart failure hospitalization, cardiac transplantation).

METHODS AND RESULTS

We prospectively enrolled 106 participants with AL amyloidosis (median age 62 years, 55% males) who underwent 18F-florbetapir PET/CT, magnetic resonance imaging, and echocardiography. 18F-florbetapir PET/CT identified RV amyloid in 63% of those with and 40% of those without cardiac involvement by conventional criteria. RV amyloid burden correlated with RV ejection fraction (EF), RV free wall longitudinal strain (FWLS), RV wall thickness, RV mass index, N-terminal pro-brain natriuretic peptide, troponin T, LV amyloid, and lung amyloid (each P < 0.001). In multivariable analysis, RV amyloid burden, but not LV or lung amyloid burden, predicted RV dysfunction (EF P = 0.014; FWLS P < 0.001). During a median follow-up of 28 months, RV amyloid burden predicted MACE (P < 0.001).

CONCLUSION

This study shows for the first time that 18F-florbetapir PET/CT identifies early RV amyloid in systemic AL amyloidosis prior to alterations in RV structure and function. Increasing RV amyloid on 18F-florbetapir PET/CT is associated with worse RV structure and function, predicts RV dysfunction, and predicts MACE. These results imply a central role for RV amyloid in the pathogenesis of RV dysfunction.

The Significance of Parametric Mapping in Advanced Cardiac Imaging

Cardiac magnetic resonance imaging has witnessed a transformative shift with the integration of parametric mapping techniques, such as T1 and T2 mapping and extracellular volume fraction. These techniques play a crucial role in advancing our understanding of cardiac function and structure, providing unique insights into myocardial tissue properties. Native T1 mapping is particularly valuable, correlating with histopathological fibrosis and serving as a marker for various cardiac pathologies. Extracellular volume fraction, an early indicator of myocardial remodeling, predicts adverse outcomes in heart failure. Elevated T2 relaxation time in cardiac MRI indicates myocardial edema, enabling noninvasive and early detection in conditions like myocarditis. These techniques offer precise insights into myocardial properties, enhancing the accuracy of diagnosis and prognosis across a spectrum of cardiac conditions, including myocardial infarction, autoimmune diseases, myocarditis, and sarcoidosis. Emphasizing the significance of these techniques in myocardial tissue analysis, the review provides a comprehensive overview of their applications and contributions to our understanding of cardiac diseases.

State-of-the-Art Imaging of Infiltrative Cardiomyopathies: A Scientific Statement From the American Heart Association

Infiltrative cardiomyopathies comprise a broad spectrum of inherited or acquired conditions caused by deposition of abnormal substances within the myocardium. Increased wall thickness, inflammation, microvascular dysfunction, and fibrosis are the common pathological processes that lead to abnormal myocardial filling, chamber dilation, and disruption of conduction system. Advanced disease presents as heart failure and cardiac arrhythmias conferring poor prognosis. Infiltrative cardiomyopathies are often diagnosed late or misclassified as other more common conditions, such as hypertrophic cardiomyopathy, hypertensive heart disease, ischemic or other forms of nonischemic cardiomyopathies. Accurate diagnosis is also critical because clinical features, testing methodologies, and approach to treatment vary significantly even within the different types of infiltrative cardiomyopathies on the basis of the type of substance deposited. Substantial advances in noninvasive cardiac imaging have enabled accurate and early diagnosis. thereby eliminating the need for endomyocardial biopsy in most cases. This scientific statement discusses the role of contemporary multimodality imaging of infiltrative cardiomyopathies, including echocardiography, nuclear and cardiac magnetic resonance imaging in the diagnosis, prognostication, and assessment of response to treatment.

Prognostic Value of Left Ventricular 18 F-Florbetapir Uptake in Systemic Light-Chain Amyloidosis

Background

Myocardial immunoglobulin light-chain (AL) amyloid deposits trigger heart failure, cardiomyocyte stretch and myocardial injury, leading to adverse cardiac outcomes. Positron emission tomography/computed tomography (PET/CT) with 18 F-florbetapir, a novel amyloid-targeting radiotracer, can quantify left ventricular (LV) amyloid burden, but its prognostic value is not known. Therefore, we aimed to evaluate the prognostic value of LV amyloid burden quantified by 18 F-florbetapir PET/CT and to identify mechanistic pathways mediating its association with outcomes.

Methods

Eighty-one participants with newly-diagnosed systemic AL amyloidosis were prospectively enrolled and underwent 18 F-florbetapir PET/CT. LV amyloid burden was quantified using 18 F-florbetapir LV percent injected dose (%ID). Mayo AL stage was determined using troponin T, N-terminal pro-B-type natriuretic peptide (NT-proBNP), and difference between involved and uninvolved free light chain levels. Major adverse cardiac events (MACE) were defined as all-cause death, heart failure hospitalization, or cardiac transplantation within 12 months.

Results

Among participants (median age 61 years, 57% males), 36% experienced MACE. Incidence of MACE increased across tertiles of LV amyloid burden from 7% to 63% (p<0.001). LV amyloid burden was significantly associated with MACE in univariable analysis (hazard ratio 1.45, 95% confidence interval 1.15-1.82, p=0.002). However, this association became non-significant in multivariable analyses adjusted for Mayo AL stage. Mediation analysis showed that the association between 18 F-florbetapir LV %ID and MACE was primarily mediated by NT-proBNP (p<0.001), a marker of cardiomyocyte stretch and component of Mayo AL stage.

Conclusion

In this first study to link cardiac 18 F-florbetapir uptake to subsequent outcomes, LV amyloid burden estimated by LV %ID predicted MACE in AL amyloidosis. But this effect was not independent of Mayo AL stage. LV amyloid burden was associated with MACE primarily via NT-pro-BNP, a marker of cardiomyocyte stretch and component of Mayo AL stage. These findings provide novel insights into the mechanism through which myocardial AL amyloid leads to MACE.

Clinical Perspective

In systemic light-chain (AL) amyloidosis, cardiac involvement is the key determinant of adverse outcomes. Usually, prognosis is based on the Mayo AL stage, determined by troponin T, N-terminal pro-B-type natriuretic peptide (NT-proBNP), and the difference between involved and uninvolved immunoglobulin free light chain levels (dFLC). Cardiac amyloid burden is not considered in this staging. In the present study, we used the amyloid-specific radiotracer 18 F-florbetapir to quantify left ventricular (LV) amyloid burden in 81 participants with newly-diagnosed AL amyloidosis and evaluated its prognostic value on major adverse outcomes (MACE: all-cause death, heart failure hospitalization, or cardiac transplantation within 12 months). We found that higher LV amyloid burden by 18 F-florbetapir positron emission tomography/computed tomography (PET/CT) was strongly associated with MACE. However, this association became non-significant after adjustment for the Mayo AL stage. Mediation analysis offered novel pathophysiological insights, implying that LV amyloid burden leads to MACE predominantly through cardiomyocyte stretch and light chain toxicity (by NT-proBNP), rather than through myocardial injury (by troponin T), also considering the severity of plasma cell dyscrasia (by dFLC). This mediation by NT-proBNP may explain why the association with outcomes was non-significant with adjustment for Mayo AL stage. Together, these results establish quantitative 18 F-florbetapir PET/CT as a valid method to predict adverse outcomes in AL amyloidosis. These results support the use of 18 F-florbetapir PET/CT to measure the effects of novel fibril-depleting therapies, in addition to plasma cell therapy, to improve outcomes in systemic AL amyloidosis.

A compartment-based myocardial density approach helps to solve the native T1 vs. ECV paradox in cardiac amyloidosis

Cardiovascular magnetic resonance (CMR) plays an important clinical role for diagnosis and therapy monitoring of cardiac amyloidosis (CA). Previous data suggested a lower native T1 value in spite of a higher LV mass and higher extracellular volume fraction (ECV) value in wild-type transthyretin amyloidosis (ATTRwt) compared to light-chain amyloidosis (AL)-resulting in the still unsolved "native T1 vs. ECV paradox" in CA. The purpose of this study was to address this paradox. The present study comprised N = 90 patients with ATTRwt and N = 30 patients with AL who underwent multi-parametric CMR studies prior to any specific treatment. The CMR protocol comprised cine- and late-gadolinium-enhancement (LGE)-imaging as well as T2-mapping and pre-/post-contrast T1-mapping allowing to measure myocardial ECV. Left ventricular ejection fraction (LV-EF), left ventricular mass index (LVMi) and left ventricular wall thickness (LVWT) were significantly higher in ATTRwt in comparison to AL. Indexed ECV (ECVi) was also higher in ATTRwt (p = 0.041 for global and p = 0.001 for basal septal). In contrast, native T1- [1094 ms (1069-1127 ms) in ATTRwt vs. 1,122 ms (1076-1160 ms) in AL group, p = 0.040] and T2-values [57 ms (55-60 ms) vs. 60 ms (57-64 ms); p = 0.001] were higher in AL. Considering particularities in myocardial density, "total extracellular mass" (TECM) was substantially higher in ATTRwt whereas "total intracellular mass" (TICM) was rather similar between ATTRwt and AL. Consequently, the "ratio TICM/TECM" was lower in ATTRwt compared to AL (0.58 vs. 0.83; p = 0.007). Our data confirm the presence of a "native T1 vs. ECV paradox" with lower native T1 values in spite of higher myocardial mass and ECV in ATTRwt compared to AL. Importantly, this observation can be explained by particularities regarding myocardial density that result in a lower TICM/TECM "ratio" in case of ATTRwt compared to AL-since native T1 is determined by this ratio.

State of the Art: Quantitative Cardiac MRI in Cardiac Amyloidosis

Cardiac amyloidosis (CA) is characterized by amyloid infiltration in the myocardial extracellular space, causing heart failure. Patients with CA are currently underdiagnosed. Cardiac involvement is significantly associated with the prognosis and treatment decision-making for CA. Early identification and accurate stratification are the crucial first step in patient management. Comprehensive cardiac MRI-based evaluation of the cardiac structure, function, and myocardial tissue characterization assesses cardiac involvement by tracing disease processes. Emerging quantitative tissue characterization techniques have introduced new measures that can identify early staged CA and monitor disease progression or response after treatment. Quantitative cardiac MRI is becoming an instrumental tool in understanding CA, which leads to changes in individualized patient care. This review aimed to discuss the quantitative cardiac MRI-based assessment of CA using established and emerging techniques. EVIDENCE LEVEL: 5 TECHNICAL EFFICACY: Stage 3.