A single heart rate (HR) measurement may inform future prognosis in chronic heart failure with reduced ejection fraction (HFrEF). The importance of elevated HR across serial assessment is uncertain, particularly with well-applied guideline-directed medical therapy (GDMT) with beta blockers (BBs). In this post hoc analysis of 129 patients with chronic HFrEF in sinus rhythm, who had aggressive medication titration over 10.6 months, HR and BB use were assessed at each visit (average of 6 visits per patient). All-cause mortality was assessed. At baseline, 81 subjects (62.8%) had HR ≥70 beats/min; 40 subjects (31.0%) had high HR despite being on ≥50% of GDMT BB dose. At final visit, 30.4% of the subjects still had high HR despite achieving ≥50% target BB dose. There were no significant baseline differences in demographics or BB doses in patients with HR <70 vs HR ≥70 beats/min. In adjusted model in which HR was treated as time-dependent covariate, an increase in HR of 10  beats/min was associated with an increased hazard of all-cause mortality during follow-up (adjusted hazard ratio per 10 beats/min = 2.46; 95% confidence interval 1.46–4.16, p <0.001). In conclusion, in well-managed patients with HFrEF, high HR was frequent even after aggressive medication titration, and often despite being on at least 50% of GDMT BB dose. An increase in HR was associated with worse clinical outcomes (Clinicaltrials.gov NCT#00351390).