Abstract Background QRS prolongation is an established prognostic marker in heart failure (HF). In contrast, the role of QRS width progression over time has been incompletely explored. The current study investigates the role of QRS width progression over time on clinical status and identifies underlying predictors. Methods Datasets of ≥ 2 consecutive visits from 100 attendees to our HF clinic between April and August 2021 were analysed for changes in QRS complex duration. Results In total 240 datasets were stratified into tertiles based on change in QRS duration (mm/month) (1st tertile: − 1.65 [1.50] ‘regression’; 2nd tertile 0.03 [0.19] ‘stable’, 3rd tertile 3.57 [10.11] ‘progression’). The incidence of the combined endpoint HF hospitalisation and worsening of symptomatic heart failure was significantly higher in the group with QRS width progression (3rd tertile) compared with the stable group (2nd tertile; log-rank test: p = 0.013). These patients were characterised by higher plasma NT-pro-BNP levels (p = 0.008) and higher heart rate (p = 0.007). A spline-based prediction model identified patients at risk of QRS width progression when NT-pro-BNP and heartrate were > 837 pg/ml and > 83/bpm, respectively. These markers were independent of guideline-directed medical HF therapy. Patients beyond both thresholds had a 14-fold increased risk of QRS width progression compared to those with neither or either alone (HR: 14.2 [95% 6.9 – 53.6]; p < 0.0001, p for interaction = 0.016). Conclusions This pilot study demonstrates that QRS width progression is associated with clinical deterioration of HF. NTproBNP plasma levels and heart rate indicate patients at risk QRS width progression, independently of HF therapy. Graphic abstract