Objective: This study aims to investigate the prevalence and prognostic impact of septal hypertrophy in patients hospitalized due to heart failure with mildly reduced ejection fraction (HFmrEF). 

Background: Limited data about septal hypertrophy in patients with HFmrEF is available. 

Methods: A large retrospective registry was used including all consecutive hospitalized patients with HFmrEF (i.e., left ventricular ejection fraction (LVEF) 41 – 49%) from 2016 to 2022 according to current European guidelines. Septal hypertrophy was defined as end-diastolic septal wall thickness ≥ 12 mm. The primary endpoint was the first heart-failure related re-hospitalization at 3 years. Secondary endpoints comprised amongst others in-hospital mortality. Kaplan-Meier, uni- and multivariable Cox regression analyses were applied for statistics.

Results: 687 consecutive patients with HFmrEF were included with a median septal thickness of 12 mm. The prevalence of septal hypertrophy was 53%. Patients with septal hypertrophy presented with significantly higher aminoterminal pro-brain natriuretic peptide (NT-pro BNP) levels compared to patients without (medians 9192 pg/ml vs. 5465 pg/ml; p=0.046). HFmrEF patients with septal wall hypertrophy were associated with an increased risk of heart-failure related re-hospitalization at 3 years (10% vs. 6%; log rank p=0.032; HR= 1.814; 95% CI 1.046 - 3.146; p=0.034) alongside with an increased risk of cardiovascular re-hospitalization (23% vs. 14%; log rank p=0.001; HR= 1.790; 95% CI 1.244 – 2.576; p=0.002). In-hospital mortality was not affected by the presence of septal hypertrophy (3% vs. 3%; p=0.708).

Conclusions: The presence of septal hypertrophy detiorates prognosis in HFmrEF patients.