AL cardiac amyloidosis

Article written and reviewed by Dr Luca Moretti

AL cardiac amyloidosis is cardiac involvement by fibrils formed from monoclonal immunoglobulin light chains produced by a plasma-cell clone or, less commonly, a lymphoplasmacytic clone. Fibrils deposit in the interstitium, but circulating light chains and oligomers also exert direct toxicity on cardiomyocytes. This combination causes stiffness, microvascular disease, arrhythmias and rapid loss of cardiac output. AL heart disease is a hematologic-cardiologic emergency in which time to clone suppression influences survival.

Clone burden may be modest and many patients do not meet the criteria for multiple myeloma, yet the protein produced can damage the heart, kidneys, liver, nerves and other organs. AL therefore belongs to monoclonal gammopathies of clinical significance: the need for treatment derives from protein-mediated injury, not from the number of plasma cells. The small toxic clone explains why an apparently indolent gammopathy must not simply be observed when typed amyloid is present.

The heart is involved in a large proportion of patients and is the principal determinant of early mortality. In stage IIIb, survival can be measured in months if a response is not obtained rapidly, and even effective treatment may arrive too late for an organ with minimal reserve. The therapeutic window requires a parallel pathway: demonstration and typing of the deposit, characterization of the clone, cardiac staging and immediate planning of a tolerable treatment.

A monoclonal component does not establish AL. MGUS becomes more common with age and may coexist with ATTR; conversely, bone scintigraphy can be positive in AL. Diagnosis requires Congo red-positive tissue and reliable typing of the fibril linked to a compatible clone. Proof of light-chain amyloid prevents both unjustified chemotherapy in ATTR with MGUS and fatal delay in true AL.

Clone, fibrils and proteotoxicity

Immunoglobulins consist of heavy and light chains; a clone produces a κ or λ chain with a unique sequence and variable instability. Misfolded fragments form oligomers and beta-sheet fibrils that resist proteolysis and bind to the matrix. Clonal amyloidogenicity cannot be predicted from concentration alone: specific structural properties determine which organs are affected and how aggressively.

In the heart, fibrils expand the interstitium, increase T1 and ECV and disrupt mechanical coupling. Infiltrated small vessels reduce coronary reserve and may cause angina, while atrial and conduction involvement promotes fibrillation and block. Diffuse infiltration reduces longitudinal strain and stroke volume first, then global function, without requiring true cellular hypertrophy.

Soluble light chains activate oxidative stress, alter lysosomes and autophagy and impair contractility. A rapid fall in dFLC may improve biomarkers and stability before fibril burden changes, clinical evidence of the importance of the toxic component. The precursor response is therefore the first objective, whereas cardiac response follows more slowly and depends on accumulated injury.

The clone is usually plasma-cell in origin, with cytogenetic abnormalities such as t(11;14) that may influence response to specific drugs and choices at relapse. Less commonly, AL accompanies a lymphoplasmacytic B-cell clone and a monoclonal IgM, requiring a biologically different strategy. Bone marrow characterization includes morphology, immunophenotyping and FISH and is not limited to confirming that plasma cells are present.

The kidneys and heart are the organs most often involved, but neuropathy, liver, gastrointestinal tract, soft tissues and coagulation may determine tolerance and prognosis. Acquired factor X deficiency, vascular fragility and renal dysfunction increase bleeding risk, while nephrosis and immobility increase thrombosis. The multiorgan profile must be defined before therapy without delaying it for nonessential investigations.

Cardiac presentation and systemic clues

The typical presentation includes rapidly progressive dyspnea, edema, ascites, hypotension and marked exercise intolerance, often with preserved ejection fraction. Blood pressure may be low despite congestion and the patient may poorly tolerate vasodilators or high beta-blocker doses. The blood-pressure-congestion discrepancy reflects low stroke volume and dysautonomia and signals fragile hemodynamic reserve.

Proteinuria or nephrotic syndrome may precede cardiac disease, as may neuropathy, orthostatic hypotension, diarrhea or constipation, weight loss, periorbital purpura and macroglossia. The last two signs suggest AL but are uncommon; their absence does not substantially reduce strong suspicion. Systemic manifestations should be sought actively because patients may not connect carpal tunnel syndrome, bruising or foamy urine with dyspnea.

The ECG often shows low voltage, pseudoinfarction Q waves, conduction abnormalities or atrial fibrillation, but no finding is obligatory. Increased wall thickness with relatively small voltages is a clue; however, hypertension and obesity modify amplitude, and some early AL cases do not have thickened walls. The electrical-anatomic contrast raises suspicion but should not exclude disease when absent.

Echocardiography documents increased wall thickness, dilated atria, a small cavity, reduced strain, right ventricular dysfunction, regurgitation and effusion. Relative apical sparing may occur, but its accuracy is lower in unselected populations and it does not distinguish AL from ATTR. Echocardiographic severity is determined by output, right ventricular function, strain and pressures, not by wall thickness alone.

Troponin and NT-proBNP may be markedly elevated even without pronounced edema, reflecting wall stress, toxicity and renal clearance. A disproportionately high NT-proBNP should be interpreted with eGFR and atrial fibrillation, but in AL it retains strong prognostic value. Biomarker signaling allows cardiac involvement to be recognized before severe systolic reduction and determines therapeutic stage.

From monoclonal protein to tissue proof

Initial screening combines serum immunofixation, urine immunofixation and free light chains. Electrophoresis without immunofixation misses small clones, while the κ/λ ratio widens physiologically in kidney disease and requires appropriate reference ranges and interpretation. Sensitive clonal screening identifies almost all patients with AL, but a positive result still requires demonstration of the deposit.

Abdominal fat-pad biopsy and bone marrow may demonstrate amyloid with limited invasiveness, but their combined sensitivity is not absolute and decreases in specific organ patterns. Kidney, liver or another clinically involved tissue may provide a specimen; endomyocardial biopsy is indicated when the heart is the principal organ and extracardiac sites are negative or inconclusive. Tissue selection balances safety, yield and the need to link the deposit to the phenotype.

Congo red confirms amyloid and mass spectrometry after microdissection identifies its composition. Immunohistochemistry or immunofluorescence can be reliable in expert laboratories but may be equivocal because of background and antibody limitations; light-chain restriction in marrow does not automatically type the deposit. Proteomic typing is particularly important when scintigraphy and gammopathy could suggest competing diagnoses.

Scintigraphy with DPD, PYP or HMDP does not diagnose AL and is not used to exclude it. Grade 0 or 1 uptake is common in AL, but some patients reach grade 2 or 3; if a monoclonal component is present, even intense uptake requires tissue. Lack of specificity in the presence of a clone is why the nonbiopsy ATTR algorithm does not apply in this scenario.

CMR with diffuse LGE, elevated T1 and ECV demonstrates involvement and quantifies burden, but it does not replace typed biopsy for diagnosing AL. In patients with severely reduced renal function, native T1 provides information without contrast. Organ evidence from CMR and etiologic evidence from tissue answer different questions and must be linked.

Cardiac staging and immediate risk

The Mayo 2012 system assigns one point for troponin T at least 0.025 ng/mL, NT-proBNP at least 1800 ng/L and dFLC at least 180 mg/L, defining four stages from I to IV. Thresholds and assays must match the validated system; use of high-sensitivity troponins requires specific equivalents. The Mayo triad integrates cardiac status and clonal burden and stratifies risk, but does not replace assessment of blood pressure, symptoms and organs.

The Mayo 2004 system used troponin and NT-proBNP, and the subsequent European subdivision of stage III defines IIIb with NT-proBNP above 8500 ng/L. Stage IIIb identifies a group with extremely high early mortality and poor representation in trials; extreme values influenced by renal function or atrial fibrillation require judgment but must not be minimized. The IIIb category changes dose, monitoring and urgency; it does not justify abandoning treatment.

Low systolic blood pressure, effusions, right ventricular dysfunction, syncope, arrhythmias, high diuretic requirements and worsening renal function complete the assessment. A modest NYHA class may be misleading in a very sedentary patient, while weight loss may reflect cachexia or dysautonomia. Hemodynamic fragility determines the ability to tolerate corticosteroids, cyclophosphamide and volume shifts during therapy.

dFLC is the absolute difference between involved and uninvolved light chains and reflects clone output better than the ratio alone, but in patients with low baseline dFLC standard response criteria have lower resolution. Quantification should use the same assay and account for renal function and immunosuppression. Functional clonal burden is monitored frequently because failure to fall early may require adjustment of the strategy.

Initial treatment and adaptation to cardiac stage

The goal is to obtain a very rapid and deep hematologic response with tolerable toxicity. Subcutaneous daratumumab combined with cyclophosphamide, bortezomib and dexamethasone, Dara-CyBorD, increased deep hematologic responses and organ responses in the ANDROMEDA trial and has become the reference for many newly diagnosed patients. The daratumumab-CyBorD platform, however, must be modulated according to age, neuropathy, volume status, blood pressure and stage.

Daratumumab is an anti-CD38 antibody that eliminates plasma cells through several mechanisms; the subcutaneous formulation reduces volume and reactions compared with infusion. Bortezomib inhibits the proteasome and produces rapid responses but can worsen neuropathy and dysautonomia; dexamethasone can cause fluid retention, arrhythmias and instability; cyclophosphamide adds cytotoxicity. Tolerance of individual components is assessed separately rather than treating the regimen as indivisible.

Patients with stage IIIb were excluded from ANDROMEDA, so the benefit-risk balance is based on observational data, expert practice and more recent prospective phase 2 data, in the absence of specific randomized evidence. Attenuated starting doses, rapid escalation if tolerated, close monitoring and steroid reduction may be necessary; hospitalization or intensive outpatient therapy depends on stability. The ultra-high-risk strategy prioritizes speed without precipitating heart failure through treatment that is too voluminous or hypotensive.

The t(11;14) translocation is common in AL and may be associated with a less favorable response to bortezomib in some cohorts; venetoclax shows marked activity in relapsed t(11;14) disease, but use and authorization depend on context and do not automatically replace approved first-line therapy. Immunomodulatory drugs may increase NT-proBNP and be difficult to use in advanced cardiac disease. Cytogenetically informed therapy is more established in later lines than as an empirical deviation from initial therapy.

Autologous stem-cell transplantation with high-dose melphalan offers durable responses in selected candidates, but only a minority have sufficient reserve at diagnosis. Blood pressure, biomarkers, organ function, age, performance status and center experience determine eligibility; rigorous selection has reduced procedural mortality. ASCT candidacy is not synonymous with youth or a good ejection fraction and should be reassessed after induction in appropriate cases.

Hematologic response and organ response

Complete response requires negative serum and urine immunofixation and an appropriate FLC ratio; very good partial response requires dFLC below 40 mg/L, whereas partial response requires a reduction greater than 50%. In patients with baseline dFLC of 20-50 mg/L, achieving dFLC below 10 mg/L is considered. Clonal depth is associated with survival, but speed within the first weeks is particularly important in advanced cardiac disease.

Light-chain measurements are performed frequently during induction, generally at each cycle or more often in patients at very high risk. An inadequate response should not be awaited for many months while the heart deteriorates; adherence, dose, biology and a change in therapy are discussed early. The adaptive decision balances urgency with the risk of changing too quickly before the full effect is observed.

Classic cardiac response is a reduction in NT-proBNP greater than 30% and 300 ng/L in patients with a baseline value of at least 650 ng/L; progression is an analogous increase. New continuous and graded criteria improve sensitivity, but renal function, atrial fibrillation and decongestion can alter the peptide. A validated cardiac response should be interpreted after clinical stabilization and is not equivalent to histologic regression of the deposit.

Renal, hepatic and neurologic responses are measured using organ-specific criteria and may follow different timelines. A suppressed clone does not guarantee recovery if fibrosis or injury is advanced, but it reduces continued toxic production and allows the possibility of repair. The clone-organ dissociation should be explained to the patient so that failure of edema to improve immediately is not interpreted as hematologic failure.

Minimal residual disease assessed by flow cytometry or sequencing may refine response depth and be associated with organ outcomes, but its role in guiding every AL decision continues to evolve. Minimal positive immunofixation may be clinically relevant in a fragile heart, while toxicity and quality of life limit intensity. Functional clonal eradication remains the goal, using tools calibrated to the disease rather than copied mechanically from myeloma.

Kidneys, liver, nerves and coagulation

The kidney is frequently involved with albuminuria, nephrotic syndrome and progressive reduction in filtration. Edema may result simultaneously from venous pressure, protein loss and renal retention, so weight alone does not identify the mechanism. Twenty-four-hour proteinuria or protein-creatinine ratio, albumin, eGFR and urinary sediment define the picture; amyloid nephropathy modifies doses, anticoagulation, thrombotic risk and transplantation options.

Hepatomegaly and elevated alkaline phosphatase suggest hepatic deposition, whereas isolated splenomegaly is less specific. Elevated transaminases may reflect congestion or medications and must be distinguished from infiltration; liver biopsy carries bleeding risk and is unnecessary when deposition is already proven elsewhere and organ criteria are coherent. Hepatic attribution integrates laboratory testing, imaging, hemodynamics and procedural safety.

Sensorimotor and autonomic neuropathy causes pain, weakness, diarrhea or constipation, bladder dysfunction and hypotension. Bortezomib can add neurotoxicity, so baseline status and changes must be documented before each cycle. Composite neuropathy requires distinguishing disease, diabetes, deficiencies and drug effects in order to adapt route and frequency without unnecessarily losing clonal efficacy.

Factor X can adsorb to fibrils and produce an acquired deficiency; vascular fragility, cutaneous deposition, liver failure and thrombocytopenia increase bleeding. At the same time, nephrosis, catheters, immobility and dysfunctional atria increase thrombosis. This bidirectional coagulopathy explains why normal PT and platelet count do not complete the assessment before biopsies, anticoagulation or procedures.

Stage IIIb and the first months of treatment

Stage IIIb conventionally identifies very advanced cardiac disease, often with NT-proBNP above 8,500 ng/L in the European system, and carries high early mortality. These patients were excluded from many registration trials, so evidence is less robust and derives from specialist cohorts. Hemodynamic fragility does not eliminate the indication to treat the clone, but requires different speed, initial attenuation and surveillance.

Urgent assessment includes blood pressure, orthostatic response, perfusion, volume status, rhythm, eGFR, electrolytes, troponin, NT-proBNP and ability to receive therapy. Hospitalization or very close follow-up is appropriate when syncope, hypotension, hyponatremia, increasing diuretic need or arrhythmias indicate instability. A high-intensity pathway reduces the time between diagnosis, first dose and recognition of toxicity.

Dexamethasone can worsen fluid retention and arrhythmias; bortezomib requires dose or frequency adjustments according to tolerance; cyclophosphamide and daratumumab require specific assessment of infections, cytopenias and reactions. In the most unstable patients, attenuated initial schedules with escalation if tolerated are often used, avoiding both indiscriminate full dosing and chronic undertreatment. Adaptive dosing seeks a deep response in the shortest time compatible with surviving the first cycles.

Weekly coordination between hematology and cardiology may change diuretics, potassium, prophylaxis, infusion timing and need for reassessment. Light chains often fall before the heart improves, so absence of immediate relief should not interrupt an effective clonal response. The early-risk phase is traversed by supporting the organ while treatment shuts down the toxic source.

Treatment complications and adaptation

Daratumumab may cause administration-related reactions, interfere with immunohematology testing and increase infection risk. Blood typing and red-cell screening before initiation facilitate any later transfusions, while vaccination, immunoglobulins and prophylaxis are considered according to history and infections. Transfusion safety should be planned before the antibody makes laboratory compatibility more complex.

Bortezomib is preferably administered subcutaneously and at a frequency adapted in vulnerable patients; neuropathy, hypotension, ileus and herpes zoster are events to prevent or recognize. Antiviral prophylaxis is routine and new weakness requires assessment rather than simple empirical dose reduction. Monitored neurotoxicity allows therapy to be modified early while preserving as much efficacy as possible.

Diuretics and steroids cause fluctuations in weight, potassium and glucose; nausea or diarrhea reduce absorption and volume; infection and anemia worsen low output. A pre-cycle panel with clinical examination prevents every episode of dyspnea from being attributed to amyloid progression. The differential diagnosis of toxicity distinguishes congestion, sepsis, thromboembolism, arrhythmia, neuropathy and drug reaction.

Autologous stem-cell transplantation offers deep responses in carefully selected patients, but advanced cardiac disease increases procedure-related mortality. Selection, mobilization, melphalan dose and support require expert centers; it is neither mandatory nor automatically superior to modern regimens. Transplant candidacy considers cardiac reserve, other organs, clonal biology and the response already achieved.

Cardiac support during therapy

Loop diuretics control edema and filling pressures, often with a mineralocorticoid receptor antagonist or sequential nephron blockade in resistant cases. Nephrosis, hypoalbuminemia and intestinal congestion reduce oral response; intravenous diuresis and close monitoring may be necessary. Excessive volume removal reduces output, but leaving congestion worsens renal function and absorption. Dynamic decongestion is coordinated with treatment and steroid days.

ACE inhibitors, ARBs and beta-blockers are often poorly tolerated because of hypotension and dysautonomia; non-dihydropyridine calcium-channel blockers and digoxin require particular caution. These are not absolute prohibitions, but the indication must be strong and monitoring close. Minimal pressure reserve makes perfusion the priority and may require discontinuation of drugs previously prescribed for hypertension that is no longer present.

Atrial fibrillation and flutter are anticoagulated unless contraindicated, with simultaneous attention to vascular fragility, coagulopathy and renal function. Before cardioversion, thrombus is sought with transesophageal echocardiography even after adequate anticoagulation because atrial contractility is reduced. The thrombosis-bleeding balance is more complex than in ordinary heart failure and requires reassessment during thrombocytopenia or procedures.

Symptomatic bradyarrhythmias and blocks meeting usual pacing indications require a pacemaker; an ICD may be appropriate for selected secondary prevention, but primary-prevention benefit has not been demonstrated uniformly. Pulseless electrical activity, low output and refractory heart failure remain mechanisms not corrected by a shock. Clonal and cardiac prognosis determines whether a device has enough time and capacity to provide benefit.

Nutrition, physiotherapy, infection prevention, antiviral prophylaxis with specific therapies, thromboprophylaxis and renal dose adjustment are integrated. Dexamethasone may precipitate fluid retention, bortezomib neuropathy and daratumumab reactions or infections; every event must be attributed without confusing it with progression. Anticipated toxicity allows sufficient dose intensity to be maintained while avoiding hospitalizations that interrupt response.

Relapse, transplantation and prognosis

At relapse, the choice depends on the duration and depth of the previous response, refractoriness, t(11;14), organ status, neuropathy and drugs already used. Daratumumab, proteasome inhibitors, venetoclax in t(11;14), pomalidomide and other strategies have variable roles; organ progression may justify therapy before major clonal regrowth. Biologic relapse is interpreted in relation to the risk of new injury, not only with the threshold used in myeloma.

Deposit-directed therapies, clearance antibodies and BCMA-targeted platforms are under study, but do not replace clone suppression outside validated indications. Preliminary results must be distinguished from authorized practice, and patients with advanced stage should be encouraged to enter appropriate trials when feasible. Anti-amyloid research aims to close the gap between hematologic response and organ recovery.

Heart transplantation may be considered in highly selected patients with end-stage cardiac disease, a controllable clone and compatible extracardiac involvement, followed or preceded by a hematologic strategy. Age, nephropathy and the ability to achieve a deep response determine suitability; it is not a solution for uncontrolled systemic disease. The heart-clone sequence is planned by centers experienced in both disciplines.

Prognosis has improved in the bortezomib-daratumumab era, but benefit is not distributed uniformly. Stages I-II may achieve long survival with deep responses, whereas stage IIIb retains high risk in the first months; once the early phase is overcome, a sustained response changes the trajectory. Front-loaded mortality explains why overall averages and results from selected trials may underestimate danger in the most fragile patient.

Communication must combine urgency with the concrete possibility of disease control. Patients need to understand that therapy aims to shut down the light-chain factory, that the heart may take months to respond and that medications and volume management will be adjusted frequently. A hematology-cardiology partnership reduces delays, supports adherence and allows both toxicity and progression to be recognized rapidly.