Cardiac Amyloidosis – An Underdiagnosed Cause of Heart Failure with Preserved Ejection Fraction – Updated Diagnosis and Treatment Options

Contact address: Roxana Cristina RIMBAS, Department of Cardiology, Emergency University Hospital, 169 Splaiul Independentei, 050098, Bucharest, Romania. E-mail: roxana.rimbas@umfcd.ro 1 „Carol Davila” University of Medicine and Pharmacy, Bucharest, Romania 2 Department of Cardiology, Emergency University Hospital, Bucharest, Romania ABSTRACT Cardiac amyloidosis (CA) still represents a frequently missed cause of heart failure with preserved ejection fraction (HFpEF). In the light of many new and effective therapies for immunoglobulin light chain amyloidosis (AL) and for transthyretin amyloidosis (ATTR), screening for amyloidosis as an important and potentially treatable diagnosis under the HFpEF becomes mandatory. A step-by-step algorithm for CA in HF patients was already provided by the guidelines. This review summarizes the role of all imaging modalities and biomarkers in the diagnosis and prognosis of both subtypes, the algorithm for diagnosis of CA, and new therapeutic options. It is the fi rst Romanian publication which intends to bring altogether the current recommendations in the diagnosis and management of CA.


INTRODUCTION
Heart failure with preserved ejection fraction (HFpEF), as defi ned by ESC 2016 guideline and new 2019 scoring system, is still a major healthcare problem 1,2 . HF guidelines and recent studies provides us a large body of therapeutic options for patients with HF with reduced left ventricular ejection fraction (LVEF) (HFrEF). However, specifi c treatments to improve the outcome of patients with HFpEF are still lacking 1,2 . One of the most important factors that might explain this paradox, is that HFpEF comprises a large variety of underlying etiologies, such as hypertension, obesity, diabetes, sleep apnea syndrome, and also infi ltrative cardiomyopathies like amyloidosis 3 .
Amyloidosis still represents a frequently missed cause of HF 1,3 . Cardiac involvement is the most important factor infl uencing the prognosis in this multisystem disease 4 . The prevalence of cardiac amyloidosis (CA) among patients with HFpEF is reported to be 13% to 17% 5 , and approximately 14-16% of patients with aortic stenosis (AS) undergoing transcatheter aortic valve implantation (TAVI) have occult cardiac amyloidosis6, and a higher prevalence than 6% seen in surgical aortic valve replacement cohorts. 7 In the light of many new and effective therapies for immunoglobulin light chain amyloidosis (AL) and for transthyretin amyloidosis (ATTR), screening for amyloidosis as an important and potentially treatable diagnosis under PATHOPHYSIOLOGY Depending on the type of infi ltrating protein, amyloidosis can be divided into three main groups: AL, TTR, and AA amyloidosis, but there are also another rare types reported. Isolated atrial amyloidosis and secondary systemic amyloidosis are also seen 11 . Approximately 5% of elderly patients with HFpEF have at least moderate amyloid infi ltration in their LV 11 . Organ damage results from the deposition of misfolded proteins in the interstitium of affected organs 5,12,[16][17][18] . Amyloid deposits generate organ dysfunction due to pro-apoptotic and direct cardiotoxicity effects of circulating precursors, mechanical disruption and oxidative stress in affected organs. Organ tropism is not yet completely understood 19 . Cardiac involvement is predominantly found in AL (75%) and TTR wild type amyloidosis (96%), but may occur also in other types of amyloidosis [19][20][21][22] . Table 1 summarizes all types of amyloidosis reported till now, responsible protein, organs affected, and important general information about each type.  mm, has a sensitivity of 72% and a specifi city of 91% to diagnose CA. In AL CA low voltage is seen in the majority of cases, whereas only 25% of patients with ATTR subtype (even less depending on the mutation) have low-voltage 52 . However, the presence of low voltage is associated with worse outcome 55 . A corrected QT duration >440 msec and a Sokolow-Lyon index <1.5 mm were found to have a sensitivity and specificity of 85% and 100%, respectively 56 .
Other ECG features of CA include intraventricular conduction delays and blocks 57,58 . These features were seen more in ATTR as compared to AL subtype. The presence of intraventricular conduction blocks, particularly as they progress over time, refl ect a worsening of the disease and higher mortality especially in AL subtype 59 . Decreased heart rate variability is particularly found in AL CA, and in some mutations of the ATTR subtypes, associated with autonomic dysfunction 59,60 . Reduced heart rate variability on a 24-hour Holter predicts high short-term mortality in AL subtype, but limited data are available in ATTR subtypes on mortality 59,60 . Fragmented QRS is also seen in CA and was associated with worse prognosis 57 . TRANSTHORACIC ECHOCARDIO-GRAPHY. As in all cardiomyopathy, 2D TTE is the fi rst line imaging modality that provides two-dimensional measure of cardiac structure and function. It may add a high index of suspicion for CA in patient with HFpEF, non-obstructive hypertrophic cardiomyopathy, disproportionated hypertrophy to the degree of hypertension, and restrictive cardiomyopathy. Although echocardiographic signs are not always present, classic fi ndings suggestive for CA include LV wall thickening, small LV cavity size, bi-atrial enlargement, thickened valves, elevated right pulmonary pressure, atrial septum thickness, restrictive trans mitral pattern, and pericardial effusion [61][62][63] (Figure 1). The appearance of the LV walls has been classically described as ''sparkling''. In addition, there is thickening of the right ventricular (RV) wall 48,49 ,61-63 . In patients with HFpEF, presence of severe LV thickening should trigger consideration of CA, especially if there is a discordance between wall thickness and QRS voltage on ECG 48,49 . Diastolic dysfunction is attributed to increased stiffness as a result of amyloid deposition, and progresses with the degree of myocardial infi ltration, ranging from impaired relaxation to a restrictive pattern in patients with advanced disease 43 .
Recently, evaluation of myocardial deformation indices, by 2D STE have been shown to be sensitive in with exertional syncope or pre-syncope due to low stroke volume which is associated with poor prognosis 5,12,[41][42][43][44] . However, in most of the patients syncope is caused by hypotension due to autonomic dysfunction 41 . The reduced ventricular fi lling limits stroke volume and can progress to low-output heart failure [41][42][43][44] . Atrial involvement may cause thrombus formation, even in patients with sinus rhythm, which may cause systemic embolism 18,[40][41][42] . Microvascular angina due to perivascular infi ltration is also frequently observed.
Typical angina may occur leading to misdiagnosis as CAD [44][45][46] . Moreover, persistent elevated troponin levels are frequently found in patients with amyloidosis, but do not show a crescendo-decrescendo pattern. 45 This is particularly relevant in clinical practice, since patients with cardiac amyloidosis, often undergo unnecessary coronary angiography, which usually shows no signifi cant atherosclerotic epicardial coronary disease 46,47 .
Patients with CA often are diagnosed with HFpEF, which can appear phenotypically as hypertrophic cardiomyopathy. The high level of suspicion for CA comes in patients without longstanding hypertension or ischemia 16,18,19 . ATTR subtype might be present in older persons who have been hospitalized for HF, elevated troponin levels, or NT-proBNP that are out of proportion 48,49 . It is signifi cant that in addition to symptoms of cardiomyopathy, other systemic phenotypes such as polyneuropathy and gastrointestinal or renal disorders may be present. Table 2 summarizes red fl ag clinical fi ndings suggestive for amyloidosis, with systemic and cardiac infi ltration.
ELECTROCARDIOGRAPHY. Electrocardiography (ECG) is the simplest and common adjunctive diagnostic tool for CA. The low voltage on limb leads is the most common fi nding, followed by pseudo-infarct pattern and atrioventricular blocks 51,52 . In biopsy-proven primary CA the low voltage on ECG was present in 46 to 56% of patients, and a pseudo-infarct pattern in 47-60% of all patients. The pseudo-infarct patterns were anterior (36%), inferior (12%), and lateral (14%). Concomitant low voltage and pseudo-infarct pattern were present in 25% of patients 52,53 . Atrial arrhythmias are also very common in CA patients. Atrial fi brillation and fl utter are the most common arrhythmias [52][53][54] . The presence of the above-mentioned fi ndings on ECG or the reverse relationship between the thickness of LV walls and voltages of limb leads strongly supported the diagnosis of CA. It has been reported that the low voltage on limb leads associated with IVS thickness >19.8 the well-validated cardiac biomarkers (NT-proBNP and troponin) for survival among patients treated with stem cell transplantation (SCT). A cut off of -17% was identifi ed as the value that best discriminated survivors from non survivors 72 . GLS has been shown to predict all-cause mortality, especially with values less than -14.8%, and provide incremental value beyond standard clinical and echocardiographic parameters among patients with AL amyloidosis 73 . Data in ATTR are scarce regarding myocardial deformation analysis and prognosis. Recently, Nocioka et al. showed that all LA strain functions were severely impaired in CA and correlated with a greater LV systolic and diastolic dysfunction. 75 Moreover, current evidence reported that absent atrial contractility in AL patients leads to a high incidence of thrombus formation even in sinus rhythm patients. 75 Recognition of this complication is crucial for timely initiation of anticoagulant therapy.
Lastly, abnormal RV strain is also an independent predictor of death beyond diastolic fi lling pattern. However, all of the cohorts consisted mainly of patients with AL subtype, with limited data on ATTR [71][72][73][74] .
There is now emerging evidence highlighting a potential role for new myocardial work (MW) analysis, the detection of subclinical impairment of LV systolic function in amyloidosis, without CAD. Global longitudinal strain (GLS) in CA presents a pathognomonic sign named "apical sparing pattern" or 'cherry-on-top' pattern on the bull's eye plot ( Figure 2 and Figure  3). This is a sensitive and specifi c fi nding that can be used to distinguish amyloidosis from other causes of LV hypertrophy [67][68][69][70][71] . Pagourelias et al. found that the LVEF to GLS ratio has the best accuracy to detect CA in patients with LV hypertrophy, with a sensitivity of 89.7% and specifi city of 91.7%, independent of disease subtype 68,69 .
Moreover, identifying patients with poor prognosis is fundamental to ensure adequate treatment and timely referral to specialized centers. Multiple echocardiographic parameters have shown prognostic value 72 . Conventional measurements such as greater wall thickness 35 , decreased LVEF 73 , restrictive diastolic pattern, increased E/E' ratio and RV involvement 13 had all prognostic value 74 . Recently, there is an increased level of evidence that GLS, left atrial (LA) dysfunction and RV dysfunction are independent and powerful prognostic markers in patients with CA 72 . GLS has been validated to provide additional information beyond

CARDIAC MAGNETIC RESONANCE.
CMR is considered as a "gold standard" for accurate assessment of the LVEF, chamber volumes, myocardial fi brosis and oedema, prior to the onset of LV dysfunction. Regardless of the type of amyloidosis, CMR has emerged as a useful tool in the diagnosis, risk stratifi cation, and prognosis of CA, because of its superior spatial resolution and tissue characterization capabilities. 74 Cine CMR imaging is considered the gold standard for measurement of LV and RV, structure as well as global and regional function. 61 Typical CMR fi ndings in CA include LV hypertrophy, restrictive LV pattern (preserved LVEF, non-dilated ventricles, enlarged atria, restrictive fi lling pattern), atrial septal hypertrophy, and mild pericardial effusions. 35 It has been reported that LV hypertrophy is more prominent in ATTR than in AL amyloidosis. 80 Recently, several CMR fi ndings have been observed in CA, such as RV involvement with a novel STE measures of LV systolic function, derived from LV pressure-strain loop analysis, which may be more sensitive than GLS in the diagnosis and prognosis of CA ( Figure 2 and Figure 3). By integration of afterload, MW might have a superior benefi t in the evaluation of the prognosis of patients. In CA, the progressive infi ltration of the myocardium explains the development of a restrictive cardiomyopathy, with decreased cardiac output and a progressive drop in blood pressure [76][77][78][79] . Global work index and effi ciency, derived by MW analysis, showed both a good correlation with NT-proBNP, eGFR and troponin, and peak oxygen consumption 76,79 . Furthermore, MW indices seem to predict all-cause mortality in CA better than LVEF, even among patients with atrial fi brillation. These indexes might be better used to assess effi ciency of the treatment, than GLS or LVEF, because loading conditions are variable over time [76][77][78][79] . with severe altered deformation mainly at the basal and midventricular segments and relatively preserved at the apex, with a typical "apical sparing" strain or "cherry-on-top" pattern. Panel B: Myocardial work analysis plot of the global work index (GWI) showing severe reduction of the GWI, with a similar "apical sparing" pattern, and an important reduction of the global work effi ciency (GWE). Panel C: Myocardial work analysis with low global constructive work (CW) (green bars), also with even lower CW at the basal level, and higher wasted work (blue bars); Panel D: Strain -pressure loops representing GWI (red curve) and a comparative lower WI curve in a basal segment (green curve).

Roxana Cristina RIMBAS et al. Heart Failure and Amyloidosis
sensitive inversion recovery (PSIR) imaging, the tissue with the least gadolinium will always be nulled and thus PSIR reconstruction images are more reliable and should always be used to assess LGE in CA. 75 The mechanism of LGE in CA is due to infi ltration of the amyloid protein and fi brosis caused by ischemia due to capillary obstruction by amyloid deposits. 35 In amyloidosis, LGE can occur in 3 possible patterns: no LGE, sub-endocardial enhancement, and transmural enhan-hypertrophy and a typically reduced LV indexed stroke volume, as a better measurement of systolic function than LVEF and concentric remodelling. 81 The unique advantage of CMR in the diagnosis of CA arise from its ability to give information about myocardial tissue composition, using late-gadolinium enhancement (LGE) technique, T1 and T2 mapping, and extracellular volume (ECV) using gadolinium enhancement T1 mapping. 82 Moreover, with phase- with RV involvement). 80 A cut-off of 9 was proved to differentiate prognosis in AL amyloidosis patients with a subendocardial LGE pattern 82,83 . Patients with a subendocardial LGE-QALE score <9 have a better prognosis, similar to the patients with no apparent cardiac involvement and no LGE, whereas a value ≥9 implies a worse prognosis, similar to the transmural LGE. 83 The use of LGE is relatively contraindicated in patients with severe renal failure.
Native T1 mapping can overcome these limitations as it measures direct quantitative signal from the myocardium, particularly through assessment the degree of fi brosis. 82 Furthermore, contrast-enhanced T1 mapping enables calculation of the ECV fraction. 35 Patients with CA (both AL and ATTR) have a signifi cantly increased native T1 relaxation time and ECV compared with other cardiac causes such as LV hypertrophy or phenotypically similar Anderson Fabry disease 35 and have shown high diagnostic precision for the detection of both amyloidosis subtypes. 34,74 Moreover, native T1 and ECV are signifi cantly elevated even in patients with amyloidosis without cardiac involvement on conventional or LGE imaging, emphasizing their utility as early disease markers (Figure 4). 84 ECV was found to correlate strongly with the presence of LGE, and therefore may be an independent predictor of mortality. 85 Ne-cement, which can be identifi ed as the amyloid starts to accumulate 80 . Moreover, atrial LGE is a strong clue to the presence of CA, and is associated with atrial contractile dysfunction. 61 Several studies have suggested that the LGE pattern may help in differentiating the two subtypes of CA, with transmural LGE being more prevalent in TTR amyloidosis as opposed to sub-endocardial LGE, which appears to be more prevalent in AL amyloidosis. In addition, RV LGE and atrial LGE was found to be more present in patients with ATTR compared to AL amyloidosis, underlining the global effect in ATTR amyloid. 80 However, current recommendations draw attention that this technique cannot reliably differentiate subtype. 34 Patterns of LGE have also been associated with prognosis, transmural LGE in AL amyloidosis patients being associated with the poorest prognosis. 80 Moreover, the Query Amyloid Late Enhancement (QALE) score was recently validated as a prognostic score in patients with AL amyloidosis. 80 QALE score was based on patterns of LGE in the LV at 3 levels (base, mid ventricle, and apex) and in the RV free wall. The maximum LV LGE score at each level is 4 (maximum LV LGE score 12), plus 6 if RV LGE is present and ranged from 0 (no LGE in the left or right ventricle) to 18 (global transmural LV LGE for the diagnosis of TTR-CA, without the need for tissue biopsy, but after monoclonal protein has been exluded. 34 BIOPSY -GOLD STANDARD FOR DIAGNOSIS. Presence of monoclonal protein is an important differential diagnostic clue for AL and TTR-CA. However, up to 40% of TTR-CA patients have monoclonal gammopathy of unknown signifi cance 88 . In such cases, a defi nitive diagnosis should be made by tissue biopsy. The sensitivity of abdominal fat pad aspiration is around 85%, rectal biopsy is 75-85%, and bone marrow biopsy about 50% in detecting systemic amyloidosis 89,90 . Amyloid, using the Congo red stain, looks pink with normal lighting, and demonstrates apple-green birefringence under polarized light ( Figure  6). The various types of amyloid are indistinguishable using light microscopy. It is therefore essential to perform additional studies to identify the type of protein involved, since the prognosis and treatment of amyloidosis is completely different 25,91 . Amyloid can be speciated using light microscopy or immunogold electron microscopy after reacting the specimen with specifi c antiserum. Mass spectroscopy is considered the current reference standard of classifi cation of amyloid 90 . If suspicion is high and the preceding tests are not defi nitive, biopsy of the affected organs can be considered, but the risks need to be weighed carefully in light of the tendency of amyloidosis patients to suffer hemorrhagic complications. It is usually best to proceed with vertheless, native T1 mapping and ECV have shown to add incremental value in risk-stratifi cation of patients with CA and for disease surveillance monitoring. 34 BONE TRACER CARDIAC SCINTIGRAPHY. Bone scintigraphy with 99m Tcpyrophosphate ( 99m Tc-PYP) or 99m Tc-3,3-diphosphono-1,2-propanodicarboxylic acid ( 99m Tc-DPD), have a high level of diagnostic accuracy in differentiation of CA subtypes (AL and ATTR). 34 To note that even there is no direct comparison between these tracers, bone scintigraphy with or 99m Tc-hydroxymethylene diphosphonate ( 99m Tc-HMDP) has a lowest sensibility in detecting CA. 34 TTR amyloidosis has been shown to have avidity for these radiotracers, whilst AL amyloidosis has at most minimal avidity 86 ( Figure 5). Moreover, 99m Tc-PYP scanning may be of additional help in the 20% of patients with ATTR who have an unrelated monoclonal gammopathy of unknown signifi cance (MGUS), a condition known as wild-type transthyretin amyloidosis (ATTRwt), because the presence of MGUS may lead to an incorrect diagnosis of AL amyloidosis. 87 On planar images, cardiac retention can be evaluated using a visual scoring method that compares the degree of cardiac uptake with bone uptake (0=absent cardiac uptake; 1=mild uptake less than that of bone; 2=moderate uptake equal to that of bone; and 3=high uptake greater than that of bone). 35 A positive result is defi ned as grade 2 or higher, and is highly specifi c tation-related mortality and poor overall survival 35,73 .
The most recent guidelines for staging patients with systemic AL amyloidosis suggest that overall mortality correlates with three serum assays: plasma free light chain difference (dFLC) greater than 18 mg/dL, NTproBNP >332 ng/L or BNP >100 ng/l, and cardiac troponin-T >0.035 ng/mL. All patients should have their cardiac biomarker risk calculated at diagnosis. This system allows determination of patients as low risk (stage I) (eligible for aggressive therapies such as autologous SCT), intermediate risk (stage II) and high risk (stage III) (often die early before any chance of response to therapy). In the Stage III group, a very high NTproBNP (>8500ng/L) or BNP (>800ng/L) have a very poor prognosis, with a median survival rate of 3.5 months 30,[93][94][95] .
These biomarkers are also useful for the quantification of organ response to treatment. Decrease in NTproBNP with more than 30% and >300ng/l decrease in patients with baseline NTproBNP ≥650ng/l, or clinical improvement, is considered a positive response to treatment, whereas an increase of NTproBNP (>30% and >300ng/l), or cTn increase ≥33%, or LVEF decrease ≥10% is considered a progression of CA 96,97 .
If there is clinical suspicion for CA and no plasma cell dyscrasia is found on laboratory results, should consider a workup for ATTR. No plasma or urinary biomarker is available for the diagnosis of ATTR. NT-proBNP is elevated early in ATTR amyloidosis before cardiac symptoms appear, especially among asymptomatic carriers of a TTR gene mutation or in patients with neurological symptoms only. Three staging system are available for ATTR, however their clinical the least invasive procedures fi rst. Endo-myocardial biopsy is the current gold standard diagnostic method for CA, which may not be feasible and indicated in all cases, because of the associated risk 90 .
BIOMARKERS. Although the fi rst step is clinical suspicion, typical diagnostic algorithms begin with determining whether the patient has a plasma cell dyscrasia. For AL amyloidosis serum protein electrophoresis with immunofi xation electrophoresis (SPEP/ IFE) is a frequently used screening test. However, it can be normal in 25% of those with CA because either the pathogenic light chains are produced in small amounts or they are completely fi ltered by the kidneys and therefore not detected in the serum 34 . When used in combination with SPEP/IFE, a 24-hour urine collection with urine protein electrophoresis and IFE can detect 90% of those affected by amyloidosis. The immunofi xation studies determine whether abnormal proteins are present, and the serum free light chain assay quantify the number of abnormal proteins. Biopsy is mandatory for a confi rmatory diagnosis of AL amyloidosis 34 .
Serum cardiac biomarkers like troponin and BNP/ NTproBNP are often persistently elevated in patients with CA, disproportionately to the degree of HF signs 34. Moreover, these biomarkers are frequently used in patients with CA for risk stratifi cation, to better discriminate between groups with different outcomes, enabling better prognostic classifi cation. 35,73 Survival decrease with higher levels of troponin and NTproBNP, and patients with advanced CA (elevated both troponin and NTproBNP levels) are often not considered for SCT, because of high risk for transplan- CARDIAC AMYLOIDOSIS ALGORITHM FOR DIAGNOSIS. AL amyloidosis carries the worst prognosis, with a median survival time of 4 to 6 months after a patient is diagnosed with heart failure. ATTR is characterized by years of relative stability despite progressing disease, for 3 to 10 years after diagnosis, depending on their therapeutic options 34,37,49 . In this light, it is essential to differentiate both subtypes Multiple algorithms have been proposed over time, using clinical suspicion, imaging modalities, and organ biopsy. Figure 7 summaries an adapted and modifi ed algorithm based on the most recently published guidelines 16,34,35,49 .

MODERN TREATMENT OF CARDIAC AMYLOIDOSIS
Management of CA comprises of general therapeutic principles targeting HF and cardiac-associated complications, as well as diseases modifying therapies aiming at repressing the underlying pathological substrate, amyloid formation and deposition 100 (Table 3).
HEART FAILURE AND SUPORTIVE TREATMENT. Diuretic agents are considered to play a key role in HFpEF with CA due to their effect in relieving congestive symptoms 65 . Nonetheless, their use must be done with caution, since these patients exhibit poor ventricular compliance and require higher intracardiac fi lling pressures 101 . Hence, in CA increased reduction in preload by an irrational utilization of diuretic therapy, may lead to decreased cardiac output, systolic blood pressure, and orthostasis 101 . Early anticoagulation could be benefi cial in high-risk CA patients, due to the higher incidence of mortalityassociated intra-cardiac thrombosis and thromboembolic events, observed in these patients 102 . However, at present, there are no guideline recommendations for anticoagulation in patients with CA. Atrial fi brillation, intracardiac thrombosis and thromboembolic events are indications for anticoagulation, irrespective of the CHA2DS2-VASC score 103 . The selection of anticoagulation type must be guideline-driven, according to benefi t-risk assessment. Direct oral anticoagulants are recommended over vitamin K antagonists, in the absence of contraindications 1,101 . Currently, there is no evidence supporting the use of conventional HF medications in the setting of HFpEF with CA 5 . Betablockers, angiotensin-converting enzyme inhibitors, angiotensin receptor blockers, and angiotensin receptor-neprilysin inhibitors are poorly tolerated in patients with CA, and should be used with caution 101 . utility has not been tested prospectively. They use NTproBNP level >3000 pg/ml as a negative prognostic marker, one adds TpT >0.05 ng/ml, and the other one eGRF <45 ml/min. If both parameters are normal Stage 1, if one is abnormal stage 2, and of both are abnormal stage 3. Median survival from diagnosis in untreated patients with TTR-CA is under 4 years. In patients with NT-proBNP >3000 ng/L and eGFR <45 mL/min/1.73m 2 , survival was <2 years 64,65 . All staging systems are vulnerable to renal impairment, drugs, and atrial fi brillation as cardiac biomarkers are elevated under these conditions. BNP should be preferred in patients with end-stage renal failure. As levels of cardiac biomarkers are increased by immunomodulatory drugs, their interpretation requires caution 37,49 . Staging systems for other forms of cardiac amyloidosis, especially AA and ApoAI/II amyloidosis, are not available, yet.
Beyond cardiac involvement, staging systems have only been defi ned for renal involvement in AL amyloidosis that typically is characterized by proteinuria and impaired renal function. A reduced eGFR (<50 ml/ min/1.73 m 2 ) and proteinuria (> 5 g/d) were shown to predict the 2-year risk for the onset of dialysis in AL amyloidosis for stages I, II, and III with 0-3% (both criteria are not fulfi lled), 11-25% (one criterion fulfi lled), and 60-75% (both criteria fulfi lled) 49,64,65 .
If TTR-CA is identifi ed, then genetic sequencing of the TTR gene is required to defi ne ATTRv versus AT-TRwt disease. Differentiating ATTRv from ATTR wt is critical because confi rmation of ATTRv should trigger genetic counseling and potential screening of family members. The identifi cation of the Val122Ile mutation suggests aggressive progression and a need for closer follow-up. 34 In Romania, up to this date, the most prevalent mutation in hereditary ATTR is Glu54Gln mutation. Patients with the Glu54Gl mutation present with a mixed phenotype, with clinical onset in the fourth decade. Distal paresthesia and carpal tunnel syndrome are initial manifestations, with signifi cant cardiac involvement and autonomic dysfunction occurring after diagnosis. 98 PET/SPECT QUANTIFICATION. To date, few published studies have used quantitative SPECT TTR-CA. In a small single-center study using quantitative SPECT, it was demonstrated that SPECT accurately differentiated CA from other cardiac diseases 99 . Caobelli et al. found that quantitative cardiac SPECT is practical, can make the diagnosis of TTR-CA, and provides information that is not identical to visual score from scintigraphy, in grade 2 and 3 patients 99 .
with CA. Patients with indication of pacemaker placement, for whom a high rate of the RV stimulation fraction is anticipated, or who already exhibit reduced LVEF and intraventricular conduction disturbances according to the established guideline criteria, are candidates for CRT system implantation 101,107 .
Regarding primary prevention implantable cardioverter defi brillator (ICD) implantation, a small retrospective cohort study, on 19 patients with ATTR cardiomyopathy and reduced LVEF 108 , suggested lack of outcome benefi t from ICD placement in these patients. In the paucity of consensus guideline recommendations on the use of primary prevention ICD in CA, routine use of ICD remains controversial 108 . For secondary prevention, ICD implantation decision is based on the current guidelines for management of ventricular arrhythmias and prevention of sudden cardiac death (IIA/C recommendation) 109 . In terms of catheter ablation procedures, patients with CA have shown higher relapse rates after catheter ablation compared to control patients 110 . Ablate-and-pace strategy could represent a therapeutic approach for rate control in patients with atrial arrhythmias, in spite of limited data available on the therapeutic impact in subjects with CA 101 .

AMYLOID SPECIFIC THERAPIES
AL AMYLOIDOSIS. The main target of AL amyloidosis therapy is to suppress the abnormal amyloidogenic plasma cell clone, in order to arrest the progressive end-organ deterioration 111 . Common therapeutic approaches in Al amyloidosis are conventional antiplasma cell systemic chemotherapy and high-dose chemotherapy followed by autologous SCT 19 . Their outcome depends on the degree of cardiac involvement at the time of diagnosis, and on the established hematologic and organ response to therapy 19,100 . Since cardiac involvement is the primary determinant of prognosis Their use is limited, since they have not been demonstrated to improve outcomes 101 . In the setting of CA and HFrEF, therapeutical approach with drugs interfering the neurohormonal system, can be taken into account, based on an individualized management 101 . Recommendations for digoxin use in CA are limited because of the narrow therapeutic window 104 .
LV assist device placement, as a bridge to heart transplantation or as a destination therapy, represents a therapeutic approach in ATTR cardiomyopathy-related advanced HF, in patients with no extracardiac involvement 104 . However, the advanced CA, leading to small LV dimension, poses additional challenges to the implantation technique, and it has been shown to be less responsive to assist device support 105 . Moreover, data provided by the United Network for Organ Sharing registry show an inferior 1-year survival rate in subjects undergoing heart transplant for CA (subjects with both AL and ATTR types), compared to those undergoing heart transplant for other etiologies of restrictive cardiomyopathy 104,106 .
Patients with CA are at risk of developing atrial and ventricular rhythm disorders, as well as conductance disturbances 106 . Permanent pacemaker placement is indicated in patients with CA and symptomatic bradycardia, certain types of atrio-ventricular blocks, or history of syncope of undetermined origin 101,104 . In a retrospective study, conducted by Algalarrondo et al, in asymptomatic patients with familial amyloid polyneuropathy, who developed conduction disorders in the course of the disease, prophylactic cardiac pacing prevented major cardiac events in 25% of the studied subjects 106 . The study highlights specifi c electrophysiological criteria for proper patient selection, and suggests the potential benefi t of prophylactic pacemaker implantation in high-risk population 106 .
General guideline recommendations for cardiac resynchronization therapy (CRT) also apply to patients  logical strategies for AL amyloidosis. The humanized anti-CD 38 monoclonal antibody daratumumab showed positive results in patients with AL amyloidosis and advanced cardiac involvement, who relapsed after high-dose chemotherapy and SCT, or did not respond to the last-administered chemotherapy scheme 48,101 . Recently, there were published the safety-run in results of ANDROMEDA phase 3 trial which evaluated daratumumab combined with cyclophosphamide and dexamethasone-bortezomib (CyBorD) versus CyBorD alone in newly diagnosed AL amyloidosis. Daratumumab-CyBorD was well tolerated, with no new safety concerns versus the intravenous formulation, and demonstrated robust hematologic and organ response. 113 Among the newly developed pharmacological agents, a revolutionary approach in reversing organ damage and restoring function could be represented by monoclonal antibodies targeting amyloid deposits 48. Several ongoing clinical trials are addressing monoclonal antibodies that may enhance phagocytic clearance of amyloid burden 48 . The IgG1 kappa monoclonal antibody, NEOD001, showed favorable results as a single agent, in phase I/II trial (NCT01707264), with good cardiac response, in patients with previously treated AL amyloidosis but biomarker evidence of on-going organ deterioration 111,115 .
TTR AMYLOIDOSIS. Once considered an untreatable pathology, the management approach of TTR amyloidosis evolved from supportive treatment, to orthotopic liver transplant for the specifi c treatment of ATTRv, and at present, to the development of a series of novel disease-modifying therapeutic strategies. These new targeted medicines, some of them at different stages of clinical studies, can interfere with the production of both amyloidogenic wild-type and mutated transthyretin, or reduce the formation of amyloid fi brils, potentially improving the outcomes of patients with confi rmed ATTR amyloidosis 111 . The novel therapeutic options for ATTR amyloidosis include drugs that inhibit TTR gene expression, transthyretin tetramer stabilizers, and molecules that inhibit oligomer aggregation and tetramer dissociation or affect degradation and reabsorption of amyloid fi bers 104,111 .
Drugs that stabilize the transthyretin tetramer. Previously published randomized controlled trials documented the effi cacy of two orally administered transthyretin tetramer stabilizers in variant ATTR-related neuropathy, difl unisal and tafamidis 111 . Difl unisal is a non-steroidal anti-infl ammatory drug that inhibits in AL amyloidosis, cardiologists play a pivotal role in the selection of eligible candidates for SCT, optimal care by guiding cardiac-specifi c therapies (appropriate diuretic doses), and monitoring of cardiovascular complications. Long-term cardiac follow-up is crucial in the management of patients with AL amyloidosis (assessment of clinical progression of cardiomyopathy by means of increasing cardiac biomarkers values and worsening of LV systolic function parameters). At present, there is no specifi c cardiac pharmacological agent available for AL cardiomyopathy 101 .
Chemotherapy drugs. The vast majority of chemotherapy regimens used in AL amyloidosis have evolved from multiple myeloma treatment schemes 100 . The therapeutic armamentarium has expanded from melphalan-prednisone scheme, as the standard fi rstline regimen, high-dose dexamethasone-based regimens combined with alkylating agents (melphalan or cyclophosphamide), high-dose melphalan followed by autologous SCT, to the new chemotherapy agents, such as proteasome inhibitors, and novel immunomodulatory drugs 48 . The choice of chemotherapy regimen must be individualized, taking into account the tolerability, effi cacy, and the stage of CA, as the main prognostic determinant 48 . Patients with advanced AL cardiomyopathy are restricted from high-dose chemotherapy with autologous SCT 48 .
The specifi c agents are: bortezomib, carfi lzomib, and ixazomib 111 . The most studied proteasome inhibitor in the treatment of AL amyloidosis is bortezomib. It increases overall hematologic response, greater partial response, and enhancement of progression-free and overall survival in the bortezomib-containing chemotherapy regimen 48,112 . Bortezomib could be a valid option in patients with advanced cardiomyopathy, 67% of patients surviving 2 years after displaying a partial hematologic response 111 . This agent has not been associated with direct cardiovascular toxicity 48,112 .
Immunomodulator agents. Another class of pharmacological agents used in the treatment of AL amyloidosis is represented by immunomodulators: thalidomide, lenalidomide, and pomalidomide 111 . Patients with AL amyloidosis have showed poor tolerability profi les to immunomodulator agents, with a wide range of adverse effects, from cytopenia and infections, to venous thromboembolism and arrhythmias 111 . Considering their toxicity, immunomodulators are reserved for cases of refractory or relapsed AL disease 111 .
Immunotherapy. Monoclonal antibodies targeting plasma cells are among the most novel pharmaco-trial, in adults with stage 1-2 hereditary transthyretin amyloidosis with polyneuropathy, with or without cardiomyopathy, showed that Inotersen determines an improvement in the course of neuropathy, compared with placebo. In contrast to Tafamidis, these two gene silencers agents can be administered in patients with ATTRv amyloidosis and advanced stages of neuropathy. Hitherto, Patisiran and Inotersen have not been approved for the treatment of ATTRwt and isolated cardiac amyloidosis 120,121 .
Drugs that inhibit oligomer aggregation and tetramer dissociation. Epigallocatechin gallate is a natural polyphenol of green tea that disaggregates amyloid deposits, thus stabilizing the tetrameric structure of wild-type and mutated transthyretin 111 . A small observational report of patients ATTR cardiomyopathy showed positive cardiac results, in terms of signifi cant reduction of LV myocardial mass and interventricular septal thickness 111 .
Drugs that affect degradation and reabsorption of amyloid fi bers. Doxycycline and tauro-urso-deoxycholic acid are two molecules that act as fi bril disruptors 111 . The combination of these two agents showed preliminary favorable results in the therapy of both ATTR and AL amyloidosis 111 . The most recent pharmacological agents assessed as fi bril disruptors are specifi c monoclonal antibodies, classifi ed into specifi c anti-TTR fi brils antibodies and anti-serum amyloid P component (anti-SAP) antibodies 111 . Anti-ATTR antibodies have been studied in vitro, but at present, there are no human trials available 111 . Miridesap and Dezamizumab are anti-SAP antibodies. They bind to serum amyloid P protein, and thus trigger the clearance of amyloid 8 . The clinical trials assessing their therapeutic effect in patients with amyloidosis were terminated due to a change in benefi t/risk profi le 104 .
In conclusion, Tafamidis is the drug of choice in patients with ATTRwt and ATTRv cardiomyopathy with stage 1 neuropathy or isolated cardiac or neurologic involvement, while Patisiran is indicated in ATTRv cardiomyopathy and advanced neuropathy or isolated neurologic involvement, and Inotersen is recommended in ATTRv with neurologic involvement and stage 1-2 neuropathy [118][119][120][121] .
Regarding the therapeutic management of patients with concomitant aortic stenosis and cardiac amyloidosis, two recently published multicenter studies showed that TAVI improved outcome in patients with AS-amyloid, compared to medical therapy, with indistinguishable results from lone AS patients. Therefore, amyloid fi brils formation, by stabilizing wild-type and mutated transthyretin tetramers 111 . Relatively to ATTR cardiomyopathy, at present, Difl unisal has been studied in a small, single-arm trial, that showed no changes in the assessed cardiac structure and function parameters (LVEF and mass index) at 12-month follow-up 116 . However, in a small retrospective cohort of patients with ATTR cardiomyopathy, Difl unisal showed an improvement in cardiac structure and function, evaluated by GLS, and a decrease in troponin I value 117 . Tafamidis acts on reducing transthyretin dissociation into monomers that polymerize into amyloid fi brils, by stabilizing TTR tetrameric architecture 111 . It is the only drug specifi cally assessed in patients with ATTR cardiomyopathy 101 . In a multicenter, international, doubleblind, placebo-controlled, phase 3 randomized study that enrolled 441 patients with HF due to wild-type or variant ATTR cardiomyopathy, Maurer et al identifi ed a lower rate of cardiovascular-related hospitalizations, a lower composite outcome of all-cause mortality, and reduction in the decline of functional capacity and quality of life, in the Tafamidis group, as compared to placebo 111,118 . Tafamidis has been approved for the treatment of ATTRwt and ATTRv cardiomyopathy 101 . However, the benefi cial cardiac effects of Tafamidis were more prevalent in patients with NYHA class I/ II heart failure than in those with class III, and the effi cacy and safety in patients with NYHA class IV have not been demonstrated 104,118,119 . Therefore, the published evidence highlights the importance of timely diagnosis of ATTR-associated cardiac disease, early therapeutic approach and proper medication compliance during follow-up 111 . Moreover, at present, Tafamidis is the only pharmacological agent approved for the therapy of ATTRwt and ATTRv cardiomyopathy 117 .
Drugs that inhibit TTR gene expression. Patisiran, a small interfering ribonucleic acid (siRNA) and Inotersen, an antisense oligonucleotide (ASO), are novel molecules that silence the gene expression of both wild-type and mutated transthyretin, being approved for the specifi c treatment of variant ATTR-related polyneuropathy 104,111 . The APOLLO study, a phase 3 placebo-controlled trial, showed that Patisiran may stop or reverse the progression of cardiac manifestations of hereditary ATTR amyloidosis, by decreasing mean left ventricular wall thickness, global longitudinal strain, N-terminal prohormone of brain natriuretic peptide, and adverse cardiac outcomes compared with placebo at 18 months 120 . The NEURO-TTR study, a phase 3, double-blind, placebo-controlled sion should point towards amyloid cardiomyopathy. A step-by-step algorithm for CA in HF patients was already provided by the guidelines. Cardiac magnetic resonance and bone scintigraphy might provide pathognomonic fi ndings and help amyloid typing. Biomarkers such as Troponin and NT-proBNP elevation has a prognostic value in CA. Early diagnosis of cardiac involvement and prompt therapeutical management portends a more favorable outcome in patients with amyloidosis. New treatment opinions are available for both AL and TTR amyloidosis and can slow down the progression of HF. Once considered an incurable disease, CA has become a treatable condition by the development of novel disease-modifying therapeutical agents that target various pathophysiological mechanisms. Referral to hematology in AL amyloidosis is essential, for consideration of chemotherapy or autologous stem cell transplant. Tafamidis and patisiran have been shown to be effective in ATTR, the choice being decided based on ATTR phenotype. Whenever possible, patients should be treated in the setting of clinical studies and ongoing research. Referral to specialized centers is strongly encouraged.
TAVI procedure should not be denied from patients with aortic stenosis and cardiac amyloid depositions 122,123 .

Transplantation
Heart transplant consideration in patients with advanced AL and TTR cardiomyopathy should take into account the extent of extracardiac amyloid organ dysfunction and the risk of immunosuppression complications 100 . Based on previous published results, isolated heart transplant could represent a therapeutic approach in patients with V122I TTR mutation-associated cardiomyopathy 105 . In the majority of cases, this particular population exhibits no extracardiac amyloid end-organ involvement 105 .
Orthotopic liver transplant has been considered the fi rst-line therapeutic option in patients with ATTRv in an attempt to arrest end-organ involvement and amyloid formation, since 95% of circulating TTR protein is developed by the liver 48,105 . The majority of liver transplants have been performed in patients with Val30Met variant and neuropathic phenotype, with a reported survival of more than 50% at 20 years 48 . However, orthotopic liver transplantation did not halt progressive cardiac deterioration resulting from the deposition of wild-type TTR protein 48,124 .
Liver-heart transplantation could represent a therapeutic approach in patients with ATTR v with cardiomyopathy and mutations associated with extracardiac amyloid involvement 124 . According to published data, combined liver-heart transplantation resulted in a higher survival rate than isolated heart transplantation 105 .
Autologous stem cell transplantation. Highdose chemotherapy and autologous SCT could be a suitable option for selected patients with AL amyloidosis, age <65, proper performance status, and adequate kidney and cardiac function 48 . Thus, a tailored approach and a thorough cardiac assessment are mandatory for selecting suitable candidates. However, published data have showed that only 20 to 25% of patients with AL amyloidosis are suitable for SCT based on eligibility criteria 19 . A series of observational studies revealed an overall survival of 10 years after SCT 124 .

CONCLUSIONS
Cardiac amyloidosis is an underdiagnosed cause of HFpEF. Evidence of ventricular thickening on echocardiography or a discordance between ECG and echo fi ndings in HFpEF without a clear history of hyperten-