Highlights
- The ANSWER-HF trial is the first randomized, double-blind study to evaluate Angiotensin Receptor-Neprilysin Inhibition (ARNI) specifically in Chronic Chagas Cardiomyopathy (CCC).
- Sacubitril-valsartan did not achieve a statistically significant improvement in Left Ventricular Ejection Fraction (LVEF) compared to enalapril over 6 months.
- Significant reductions in NT-proBNP and a favorable hierarchical win ratio (1.80) suggest that sacubitril-valsartan possesses biological activity in this specific HFrEF etiology.
- The trial confirms the safety and feasibility of evidence-based pharmacological interventions in a historically neglected and high-risk patient population.
The Neglected Burden of Chagas Cardiomyopathy
Chronic Chagas cardiomyopathy (CCC), caused by the protozoan parasite Trypanosoma cruzi, remains a major public health challenge in Latin America and is increasingly recognized in non-endemic regions due to global migration. Unlike other forms of Heart Failure with reduced Ejection Fraction (HFrEF), CCC is characterized by an intense inflammatory process, extensive myocardial fibrosis, and a high prevalence of conduction system disturbances and apical aneurysms. Historically, patients with CCC have been underrepresented or entirely excluded from major landmark trials that established the current pillars of HFrEF therapy, such as PARADIGM-HF.
Consequently, clinicians have often extrapolated data from ischemic or idiopathic dilated cardiomyopathy to treat Chagasic patients, despite the distinct pathophysiology and typically worse prognosis associated with CCC. The ANSWER-HF trial (Angiotensin Receptor-Neprilysin Inhibition in Chagas Cardiomyopathy With Reduced Ejection Fraction) was designed to bridge this evidence gap by providing high-quality randomized data on the efficacy and safety of sacubitril-valsartan in this specific cohort.
Study Design and Methodology
ANSWER-HF was a randomized, double-blind, controlled trial conducted across multiple centers in Brazil. The study enrolled 190 patients with confirmed CCC and HFrEF, defined by an LVEF of less than 40% and NYHA functional class II-IV symptoms. Participants were randomized in a 1:1 ratio to receive either sacubitril-valsartan (target dose 97/103 mg twice daily) or enalapril (target dose 10 mg twice daily).
The primary endpoint was the change in LVEF from baseline to 6 months, as assessed by 3D echocardiography or magnetic resonance imaging. To provide a more comprehensive assessment of clinical and biochemical response, the researchers utilized a hierarchical secondary endpoint analyzed via the win ratio method. This hierarchy included cardiovascular death, heart failure hospitalization, change in N-terminal pro-B-type natriuretic peptide (NT-proBNP), and change in LVEF. Other secondary outcomes included the 6-minute walk distance (6MWD) and safety parameters such as hypotension, hyperkalemia, and renal dysfunction.
Key Findings: Remodeling and Biomarkers
Primary Outcome: Left Ventricular Ejection Fraction
At the 6-month mark, both groups showed modest improvements in LVEF. The sacubitril-valsartan group experienced a mean increase of 2.1%, while the enalapril group saw an increase of 1.2%. The between-group difference of 0.9 percentage points (95% CI: -0.9 to 2.6) did not reach statistical significance (P = 0.36). This suggests that over a relatively short period of six months, sacubitril-valsartan does not induce superior reverse remodeling compared to standard ACE inhibition in the context of the fibrotic environment typical of Chagas disease.
Biomarkers and the Win Ratio
Despite the neutral primary endpoint, several secondary analyses provided evidence of the biological impact of ARNI therapy. Most notably, NT-proBNP levels—a robust surrogate for myocardial wall stress—were significantly lower in the sacubitril-valsartan group. The geometric mean ratio was 0.68 (95% CI: 0.57-0.81; P < 0.001), indicating a 32% greater reduction in NT-proBNP compared to enalapril. This biochemical signal is consistent with the findings of the PARADIGM-HF and PIONEER-HF trials in other HFrEF populations.
The hierarchical win ratio analysis further supported the potential benefit of sacubitril-valsartan, yielding a win ratio of 1.80 (95% CI: 1.27-2.63). This indicates that when considering a composite of hard clinical outcomes, biomarkers, and remodeling, patients on sacubitril-valsartan were nearly twice as likely to have a better clinical trajectory than those on enalapril.
Safety and Functional Capacity
Functional capacity, as measured by the 6-minute walk distance, did not differ significantly between the two arms. From a safety perspective, the trial was reassuring. Rates of symptomatic hypotension, renal impairment, and hyperkalemia were comparable between sacubitril-valsartan and enalapril. This is particularly important for CCC patients, who often have lower baseline blood pressure and are more prone to bradyarrhythmias and hyperkalemia due to concomitant use of mineralocorticoid receptor antagonists (MRAs).
Expert Commentary: Interpreting the Neutral Primary Outcome
The failure to meet the primary endpoint of LVEF change deserves careful interpretation. Chagas cardiomyopathy is notoriously fibrotic; the myocardial replacement by collagen may limit the degree of mechanical reverse remodeling achievable within a 6-month window. Experts suggest that while LVEF is a standard metric, it may not fully capture the clinical stabilization provided by neprilysin inhibition in this population. The robust NT-proBNP reduction suggests that the drug is effectively modulating the neurohormonal axis, even if the structural changes take longer to manifest.
Furthermore, the use of the win ratio highlights a shift in how heart failure trials are analyzed. By prioritizing death and hospitalization over LVEF change, the win ratio provides a more patient-centric view of the data. The significant win ratio in ANSWER-HF suggests that sacubitril-valsartan may indeed be superior to enalapril if studied in a larger, longer-term outcome-driven trial.
One limitation of the study is its sample size (n=190) and duration. While appropriate for a Phase II/III surrogate endpoint trial, it was not powered to detect differences in mortality or hospitalization. Additionally, the baseline LVEF of 30.1% reflects a population with advanced disease, where the potential for significant recovery is naturally constrained.
Conclusion: A New Era for Chagasic HFrEF Research
The ANSWER-HF trial represents a landmark in the study of neglected tropical diseases. It successfully demonstrates that rigorous, double-blind randomized trials are both feasible and safe in the Chagasic population. While sacubitril-valsartan did not prove superior to enalapril in increasing LVEF over six months, the significant reduction in NT-proBNP and the positive win ratio provide a strong signal of clinical activity.
For clinicians, these results suggest that sacubitril-valsartan is a safe and biologically active alternative to ACE inhibitors in patients with CCC and HFrEF. For the research community, ANSWER-HF serves as a foundational study that paves the way for larger, international trials aimed at definitive clinical outcomes. The era of evidence-based medicine for Chagas cardiomyopathy has finally arrived, offering hope for millions of patients who have long been on the margins of cardiovascular innovation.
Funding and clinicaltrials.gov
The ANSWER-HF trial was supported by institutional grants and funding from the Brazilian Ministry of Health and Novartis. The trial is registered at clinicaltrials.gov with the identifier NCT04853758.
References
- Madrini V Jr, et al. Sacubitril-Valsartan vs Enalapril in Heart Failure Due to Chagas Disease: Primary Results of ANSWER-HF Randomized Trial. J Am Coll Cardiol. 2025. doi: 10.1016/j.jacc.2025.10.053.
- McMurray JJ, et al. Angiotensin-neprilysin inhibition versus enalapril in heart failure. N Engl J Med. 2014;371(11):993-1004.
- Fernandes F, et al. Chagas Heart Disease: An Overview of Diagnosis, Manifestations, and Treatment. Global Heart. 2020;15(1):45.
- Bocchi EA, et al. 1st Brazilian Guidelines for Chagas Cardiomyopathy. Arq Bras Cardiol. 2016;107(1 Suppl 3):1-29.