Impact of Tafamidis on Delaying Clinical, Functional, and Structural Cardiac Changes in Patients with Wild-Type Transthyretin Amyloid Cardiomyopathy

Background: This study aimed to evaluate the effect of treatment with tafamidis on clinical, laboratory, functional, and structural cardiovascular imaging parameters at the 12-month follow-up timepoint in patients with wild-type transthyretin amyloid cardiomyopathy (ATTRwt-CM) and to assess the response to treatment in terms of disease progression. Methods: Patients with ATTRwt-CM undergoing treatment with tafamidis for >12 months were included. The patients underwent a comprehensive evaluation (including echocardiography, cardiac magnetic resonance imaging, six-minute walking test, assessment of quality of life, and laboratory tests) at baseline and the 12-month follow-up timepoint. Disease progression was assessed using a set of tools proposed by an international panel of experts, evaluating three main domains (clinical, biochemical, and structural). Results: The study cohort consisted of 25 patients (mean age of 75.9 ± 6.1 years, with 92% males). At the 12-month follow-up timepoint, an improvement in quality of life calculated with the KCCQ overall score (64 ± 20 vs. 75 ± 20, p = 0.002) and a reduction in pulmonary artery pressure (34 ± 10 mmHg vs. 30 ± 5 mmHg, p-value = 0.008) and in native T1 time were observed (1162 ± 66 ms vs. 1116 ± 52 ms, p-value = 0.001). Clinical, biochemical, and structural disease progression was observed in 6 (24%), 13 (52%), and 7 (28%) patients, respectively. Overall disease progression was observed in two patients (8%). Conclusions: This study described the impact of tafamidis treatment on clinical, laboratory, and functional parameters. Disease progression, assessed using a multiparametric tool recommended by a recent position paper of experts, was observed in a minority of patients.


Introduction
Transthyretin amyloid cardiomyopathy (ATTR-CM) is a progressive and potentially fatal disease caused by TTR misfolding and aggregation into insoluble amyloid fibrils that deposit in the myocardium, leading to infiltrative cardiomyopathy and heart failure (HF) [1,2].Two forms of ATTR have been described: hereditary ATTR (ATTRh) caused by pathogenic variants in the TTR gene and wild-type ATTR (ATTRwt) where no pathogenic variant is identified [3].The pathogenesis of ATTR amyloidosis is associated with the destabilization of the tetrameric TTR protein [4].Tetramer dissociation is the rate-limiting step in TTR aggregation, which also requires subsequent monomer misfolding to produce soluble misfolded TTR aggregates and insoluble aggregates, including amyloid fibrils [4].In ATTR-CM, the deposition of TTR amyloid in the myocardium leads to a progressive increase in myocardial wall thickness and impairment in diastolic function [5][6][7].
Tafamidis is a TTR kinetic stabilizer that inhibits tetramer dissociation [8].In a randomized controlled study, namely, the Transthyretin Cardiomyopathy Clinical Trial (ATTR-ACT; ClinicalTrials.govidentifier: NCT01994889), Maurer et al. showed that treatment with tafamidis was associated with a significant reduction in mortality and cardiovascularrelated hospitalization and smaller decline in the functional capacity and quality of life of patients with ATTR amyloidosis compared to placebo [8].The post-hoc analysis of the ATTR-ACT trial and reports from single centers showed that treatment with tafamidis may attenuate the decline in cardiac function [9][10][11][12].These studies mainly focused on basic echocardiographic parameters, with limited data regarding the impact of tafamidis treatment on improving the overall disease using a multiparametric approach, including ECG, echocardiography, cardiac magnetic resonance (CMR), biomarkers, functional capacity, and quality of life.
Recently, a consensus document from an international expert panel recommended a set of clinically feasible tools for the long-term monitoring of patients with ATTR-CM, including thresholds for defining disease progression and the frequency of measurements [13].However, the implementation of these tools in clinical practice has never been reported.
This study aimed to evaluate the effect of treatment with tafamidis on clinical, laboratory, functional, and structural cardiovascular imaging parameters at the 12-month follow-up timepoint in patients with ATTRwt-CM and assess the response to treatment in terms of clinical, biochemical, and structural progression using the clinical tools for long-term monitoring proposed by a recent consensus document.

Methods
An observational, longitudinal, and prospective cohort design was employed.This study adhered to the principles of the Helsinki Declaration and received approval from the ethics committee of our institution.All patients provided written informed consent.

Study Population
The study population consisted of consecutive patients with ATTRwt-CM, who were prospectively evaluated at the Inherited and Rare Cardiovascular Disease Clinic of the University of Campania "Luigi Vanvitelli"-Monaldi Hospital (Naples, Italy) between March 2018 and December 2023.ATTRwt-CM was defined by positive 99mTc-hydroxy methylene-diphosphonate scintigraphy (i.e., grade 2 or 3 cardiac uptake) in the absence of monoclonal gammopathy or by a cardiac biopsy containing TTR amyloid in the presence of monoclonal gammopathy [14].Genetic testing was performed to exclude a pathogenic or likely pathogenic variant in the TTR gene.

Eligibility Criteria
To be eligible for enrollment, patients had to meet the following inclusion criteria: diagnosis of ATTRwt-CM; therapy with tafamidis 61 mg once daily for 12 months; and complete clinical, biochemical, functional, and imaging assessment at baseline and follow-up evaluations.Patients diagnosed with ATTRh-CM and those without complete serial evaluations during follow-up were excluded.

Clinical Investigation and Data Collection
Patients who initiated treatment with tafamidis underwent a comprehensive cardiovascular assessment, including clinical history, physical examination, ECG, echocardiography, CMR, six-minute walking test (6-MWT), assessment of quality of life using the Kansas City Cardiomyopathy Questionnaire (KCCQ), and laboratory assessment.This assessment was performed at baseline evaluation (corresponding to the introduction of tafamidis treatment) and at the one-year follow-up timepoint.

Echocardiography
All patients underwent standard transthoracic echocardiography using a Vivid E9 ultrasound system (GE Healthcare, Horten, Norway) equipped with an M5S 3.5-MHz transducer.Two-dimensional, color-Doppler, pulsed-wave, and continuous-wave Doppler data were acquired and stored on a dedicated workstation for offline analysis (EchoPAC Version 204, GE Vingmed Ultrasound, Norway).Chamber quantification followed current recommendations [15].The myocardial contraction fraction (MCF) was calculated as the ratio of stroke volume (SV) to myocardial volume, obtained through three-dimensional (3D) analysis and LV mass calculations [16].LV peak systolic longitudinal strain (LS) and 2D speckle tracking (2D-ST) strain measurements were performed, and the LV global longitudinal strain (GLS) was calculated [17].The relative regional strain ratio (RRSR) was calculated [18], and myocardial work (MW) and related indices were estimated using vendor-specific software [19].Diastolic parameters were collected by wave and tissue Doppler, and pulmonary artery systolic pressure (PASP) was estimated [20].The tricuspid annular plane systolic excursion (TAPSE) was measured, and right ventricular pulmonary artery uncoupling was defined using the TAPSE/PASP ratio [21].The pulmonary artery flow and RV fractional area change (FAC) were measured, and RV myocardial deformation parameters were calculated using the Q-Analysis software package [22].RV global and free wall longitudinal strain values were obtained.To avoid interobserver variability, echocardiographic evaluations were performed by the same operator (G.P.).

Cardiac Magnetic Resonance
CMR examinations were conducted on a 1.5 Tesla scanner (MAGNETOM Avanto, Siemens Healthcare GmbH, Erlangen, Germany) following standard protocols, which included late gadolinium enhancement (LGE) imaging (0.1 mmol/kg gadobutrol; Gadovist, Bayer Vital GmbH, Leverkusen, Germany) and T1 mapping using the modified Look-Locker inversion (MOLLI) sequence.CMR imaging included cine-imaging, pre-and postcontrast T1 mapping, and additional calculations of extracellular volume fraction (ECV) values [23].CMR evaluation was performed at the time of therapy initiation ± 3 months.

Laboratory Assessment
Serum levels of sodium, creatinine, hemoglobin, albumin, high-sensitivity cardiac troponin I (HS-TnI), and N-terminal pro-B-type natriuretic peptide (NT-proBNP) were measured from peripheral venous blood samples in all patients using standard commercially available assays.The estimated glomerular filtration rate was calculated using the CKD-EPI equation [24].Patients with ATTRwt-CM were staged according to the staging systems proposed by Gillmore et al. [25].

Quality of Life and Functional Capacity
The HF-related health status was quantified by the KCCQ score, which includes symptom frequency, physical limitations, social limitations, and quality-of-life domains [26].The scores ranged from 0 to 100, with 100 signifying better health status.The patients completed the KCCQ guided by nurses, who were unaware of the baseline assessment.
Functional capacity was assessed using the 6-MWT.It was performed indoors using a 30-meter corridor, which was marked every 3 meters, and the turnaround points were marked with a cone.

Assessment of Disease Progression
Disease progression was evaluated after 12 months using a set of clinically feasible tools for the long-term monitoring of patients with ATTR-CM proposed by an international panel of experts [13].The assessment of disease progression was performed using a set of 11 features across three main domains: clinical domain (including the assessment of clinical and medical history, NYHA class, quality of life, and functional capacity); biochemical domain (including the assessment of biomarkers and laboratory markers); and structural domain (including the assessment of ECG and echocardiographic parameters).Disease progression was defined as the presence of at least one marker in each of the three domains.

Statistical Analysis
Body surface area (BSA) was calculated from height and weight.The normally distributed continuous variables are described as mean ± standard deviation with two group comparisons conducted using the Student's t-test.The changes in continuous laboratory or imaging parameters were assessed using the paired Student's t-test.Skewed data are described as the median (interquartile range [IQR]), with two group comparisons performed using the Wilcoxon rank-sum test.The categorical variables are listed as a number (percentage), with group comparisons conducted using the χ 2 test or Fisher's exact test.A significance level (p-value) of 0.05 (two-sided test) was used for all the comparisons.All statistical analyses were performed using IBM SPSS Statistics for Macintosh, Version 27.0.

Study Population, Functional Status, and Biochemical Parameters
Between March 2018 and December 2023, 81 patients with ATTRwt-CM were diagnosed.Of these, 20 patients had a NYHA class III or IV and were considered not eligible to initiate tafamidis, while 33 patients started tafamidis but had not completed a 12-month follow-up at the time of the study analysis.Thus, the study population fulfilling the inclusion criteria comprised 28 patients (Table 1).Among these, three patients who died from cardiovascular causes (two due to worsening HF and one from an embolic stroke as the first manifestation of a new onset of atrial fibrillation) were unable to complete the 12-month follow-up and were excluded from the data comparison.The study flow chart is shown in Figure 1.
Demographic data and functional and biochemical parameters in patients with ATTRwt-CM at baseline and 12 months after follow-up are summarized in Table 2.The patients treated with tafamidis showed a significant improvement in quality of life according to the KCCQ score (64 ± 20 vs. 75 ± 20, p = 0.002) after a 12-month follow-up, while no other statistically significant differences were observed between other clinical, functional, and laboratory parameters.

CMR Parameters
CMR imaging examinations were available at baseline and 12 months after treatment in 17 out of 25 patients (68% of the total population).In the remaining eight patients, the exams were not available due to claustrophobia (n = 1; 12.5%) or were discarded due to poor image quality caused by artifacts from the device, which limited the consistency of native and post-contrast T1-mapping measurements (n = 7, 87.5%).At 12 months of follow-up, a reduction in native T1 time and an improvement in RV volume were observed (Table 4).

Assessment of Disease Progression during 12 Months of Follow-up
Disease progression was assessed according to the recommended measurement tools for detecting ATTRwt-CM progression in patients treated with tafamidis, and the results are shown in Tables 5 and 6.After 12 months of treatment with tafamidis 61 mg, clinical progression was observed in six patients, with a prevalence of 24%.In particular, one patient exhibited worsening HF, requiring a significant increase in diuretic treatment, associated with a class increase in the NYHA functional class; one patient experienced worsening HF, necessitating hospitalization, coupled with a significant reduction in 6-MWT.In addition, four patients demonstrated a decrease of at least 30 m in 6-MWT.
Biochemical progression was observed in 13 patients, with a prevalence of 52%.In particular, one patient displayed a significant increase in HS-TnI serum levels; one patient exhibited increases in both HS-TnI and NT-proBNP serum levels; four patients showed at least one stage increase in the NAC staging system score; two patients demonstrated a significant increase in NT-proBNP serum levels; two patients displayed an increase in both the NT-proBNP level and NAC score; and one patient presented all three parameters of biochemical progression.
Structural progression was observed in seven patients, with a prevalence of 28%.In particular, one patient showed an increase in LV wall thickness; one patient experienced a decrease in LVEF; three patients demonstrated an isolated increase in diastolic functioning grade; one patient exhibited an increase in diastolic functioning grade associated with a new onset of atrial fibrillation; and one patient showed a reduction in LVEF associated with an advance in diastolic functioning grade and a new onset of atrial fibrillation.
Considering the presence of at least one parameter for each of the three clinical, biochemical, and structural domains, the overall progression was observed in two patients, with a prevalence of 8% (n = 2/25) in our cohort study 12 months after the initial treatment with tafamidis.However, if cardiovascular deaths are considered as events due to disease progression, the final prevalence of disease progression during treatment with tafamidis 61 mg in our cohort of patients with ATTRwt-CM was equal to 18% (n = 5/28).

Discussion
In this study, our aim was to assess the impact of tafamidis 61 mg treatment after 12 months of follow-up in patients with ATTRwt-CM across various parameters, including clinical status, physical performance, quality of life, and functional and structural cardiac remodeling, and to assess the response to treatment in terms of clinical, biochemical, and structural progression using recommended clinical tools for the long-term monitoring of treatment with tafamidis.
Tafamidis, recognized for its ability to reduce cardiovascular mortality and hospitalization due to HF, stands as the first disease-modifying drug approved for treating patients with ATTR-CM and a history of HF [5,8].The treatment is designed to stabilize the TTR protein, thus preventing its dissociation into monomers, a critical step in fibrillogenesis, and to inhibit the extracellular deposition of amyloid substance, thereby halting the progression of organ damage established by the amyloid burden present at the initiation of treatment.
Monitoring disease progression in patients on tafamidis is challenging and currently lacks best-practice guidance.In our study, we applied a set of clinically feasible tools for the long-term treatment monitoring of patients with ATTR-CM, as suggested by Garcia-Pavia et al. [13].At the 12-month follow-up timepoint since the start of tafamidis treatment in ATTRwt-CM, only 8% of patients experienced disease progression, suggesting a stabilizing effect of tafamidis treatment on the progressive functional and structural cardiac deterioration typically observed in these patients.Moreover, it was observed that tafamidis treatment in ATTRwt-CM stabilizes functional and structural cardiac parameters, although there is no evidence of favorable reverse remodeling, and the results of the present study are consistent with the post-hoc analysis of the ATTR-ACT trial and recent observational studies.
Specifically, a post-hoc analysis of the ATTR-ACT trial [9] investigated the effect of tafamidis 80 mg treatment on cardiac function over 30 months.The analysis, which focused on changes in echocardiographic parameters such as LVEF, LV SV, LV GLS, and E/E ′ , demonstrated less pronounced worsening in these measures among patients receiving tafamidis compared to those on placebo, reaffirming the ability of tafamidis treatment to mitigate the decline in LV systolic and diastolic functions over time.
Moreover, Giblin et al. [12] conducted a retrospective study to investigate the impact of tafamidis on myocardial function over 12 months of treatment using serial speckle tracking echocardiography.Their study, comparing 23 patients treated with ATTR-CM to 22 untreated subjects, demonstrated that GLS and MW-derived parameters deteriorated significantly more in the untreated group compared to those treated with tafamidis.Notably, no significant differences were observed between the groups in terms of other echocardiographic parameters, indicating the stabilization effect of tafamidis on myocardial function over one year.
Similarly, Rettl et al. [11] explored the effect of tafamidis treatment on myocardial strain in patients with ATTR-CM.Their study, involving patients treated with tafamidis free acid 61 mg or tafamidis meglumine 20 mg compared to untreated patients, revealed stable measurements in those treated with tafamidis, while untreated patients exhibited significant deterioration in various strain parameters (e.g., LV GLS, RV GLS, and LA reservoir strain).Those differences between the groups (treated vs. untreated) were more pronounced in patients treated with tafamidis free acid 61 mg.
Ichikawa et al. [27] conducted a similar study on 42 patients with ATTR-CM treated with tafamidis and reached the same conclusion.Their subgroup analyses further confirmed the ability of tafamidis treatment to prevent both structural and functional cardiac deterioration over time, irrespective of age and disease stage.
Additionally, Chamling et al. [28] examined the effect of tafamidis treatment after one year of therapy using cardiac MRI.They compared serial multiparametric CMR parameters between treated and untreated patients with ATTRwt-CM.While parameters such as LV wall thickness, LVEF, native T1 time, and ECV values remained unchanged in the tafamidis group, untreated patients exhibited a reduction in LVEF, along with slight increases in LV mass, native T1 time, and ECV.Serum NT-proBNP levels increased in both groups, with a higher increase observed in untreated patients compared to treated ones.Our study revealed a reduction in native T1 time values on cardiac MRI, which was not observed in other studies.Although it may be related to the reduction in inflammatory-based cytotoxic damage and interstitial edema induced by circulating monomers, the cause of this result is unclear.
In the ATTR-ACT trial [8], tafamidis treatment significantly reduced the decline in functional capacity, health status, and quality of life compared to untreated patients.Our study observed different effects of treatment on quality of life compared to those described in the ATTR-ACT trial.While the ATTR-ACT trial showed a reduction in decline, our study demonstrated a significant improvement in QoL after a shorter follow-up period.
These discrepancies could be attributed to differences in the inclusion criteria of the study populations.In the ATTR-ACT trial, patients with a NYHA class ranging from I to III were enrolled, whereas, in our study, patients with NYHA class III were excluded, following the inclusion criteria for tafamidis prescription currently enforced in Italy.The presence of patients at a less advanced stage of the disease could explain the more pronounced positive effect of the treatment on the patients' quality of life.

Study Limitations
This study had several limitations.First, this study was not placebo-controlled or randomized.Second, echocardiographic evaluations were performed by a single operator, but intra-observer variability was not specifically assessed.Third, patients were enrolled during a 5-year period, when supportive heart failure and arrhythmias management dramatically changed over time.Fourth, CMR was not performed in nearly one-third of the patients.Finally, it is unclear whether the statistically significant differences in PASP at echocardiography and the T1 value at CMR between baseline and follow-up evaluations are a real phenomenon induced by the treatment with tafamidis or the result of a multiplecomparison problem.

Conclusions
Patients with ATTRwt-CM typically undergo a progressive decline over time.This study described the impact of tafamidis treatment on clinical, laboratory, and functional parameters.Disease progression, assessed using a multiparametric tool recommended by a recent position paper of experts, was observed in a minority of patients.

Table 1 .
Demographic data and functional, biochemical, and echocardiographic parameters of the study cohort at the baseline evaluation.

Table 2 .
Demographic data and functional and biochemical parameters of the study cohort at baseline and the 12-month follow-up timepoint.

Table 3 .
Morphological and functional echocardiographic parameters of the study cohort at baseline and the 12-month follow-up timepoint.

Table 4 .
Morphological and functional cardiac magnetic resonance parameters of the study cohort at baseline and the 12-month follow-up timepoint.

Table 5 .
Proportion of patients with disease progression during 12 months of follow-up.

Table 6 .
Patients with clinical, biochemical, and structural progression during 12 months of follow-up.