Prospective, randomized, multicenter, open-label clinical trial to evaluate the safety and efficacy of Sacubitril/Valsartan (Sac/Vals) compared to no initiation of the drug in patients with transthyretin cardiac amyloidosis (ATTR) and heart failure with reduced ejection fraction (LVEF ≤40%). The primary objective is to determine the impact of Sac/Vals treatment on systolic function by assessing the change in LVEF on echocardiogram at 12-month follow-up.

Transthyretin cardiac amyloidosis (ATTR) has emerged as a prevalent and underdiagnosed cause of heart failure (HF), affecting patients both with preserved left ventricular ejection fraction (LVEF) and with systolic dysfunction. It remains unclear whether this population benefits from standard treatments for HF with reduced LVEF or whether treatment with renin-angiotensin system inhibitors and neprilysin might even be harmful in ATTR.

The investigators plan to conduct a prospective, randomized, multicenter, open-label clinical trial to evaluate the safety and efficacy of Sacubitril/Valsartan (Sac/Vals), as recommended in current HF guidelines, versus no treatment in patients with ATTR and heart failure with reduced ejection fraction (HFrEF), including those with LVEF ≤40%.

Approximately 114 patients from four Spanish centers will be randomized 1:1 to receive Sac/Vals treatment (up to the maximum tolerated dose) or to not initiate the drug, with stratification by center and tafamidis treatment. It has been included a run-in period with a low dose of Sac/Vals to assess tolerance prior to randomization. Patients will have scheduled follow-up visits at 3, 6, and 12 months, during which clinical, functional, analytical, electrocardiographic, and echocardiographic variables will be evaluated.

The primary objective is to determine the impact of Sac/Vals treatment on systolic function in patients with ATTR and HFrEF by assessing the change in LVEF on echocardiogram at 12 months. Improvement in LVEF will be defined as an increase of ≥5% from the baseline echocardiogram to the 12-month follow-up.

Inclusion Criteria:

• Patients ≥ 18 years of age of both sexes.
• Patients diagnosed with ATTR cardiac amyloidosis as indicated in guidelines, both in its hereditary form (ATTRv) or wild-type form (ATTRwt).
• Patients initially evaluated or under follow-up in Cardiomyopathy/Heart Failure/Amyloidosis Units at participating centers.
• Heart failure and reduced ejection fraction: LVEF ≤40%, in functional class I, II, or III according to the New York Heart Association (NYHA).

Exclusion Criteria:

• NYHA Functional Class IV.
• Stage 4 and 5 chronic kidney disease (creatinine clearance by CKD-EPI <30 mL/min/1.73m²).
• Hyperkalemia (blood potassium levels > 5.4 mmol/L).
• Hypotension defined as systolic blood pressure (SBP) <100 mmHg on two consecutive measurements.
• Treatment with ACE inhibitors, ARBs, or sacubitril/valsartan at the time of enrollment.
• History of angioedema or hypersensitivity to ACE inhibitors or ARBs.
• Treatment with TTR gene silencers or diflunisal.
• Participation in another clinical trial.
• Pregnancy, breastfeeding, or fertile women unwilling to use adequate contraception throughout the study duration.
• Any condition that, in the investigator's opinion, compromises participation in the study.

Under agreement, individual or aggregated patient data could be shared with other scientific groups for scientific projects. Data can be shared only for scientific purposes and in full compliance with Personal Data Protection requirements in the EU.

After study scientific publication

Under request to Study Chair

The analysis of the echocardiogram will be performed by evaluators blinded to the treatment and the timing of the imaging.