Abstract Background Despite evidence that guideline-directed medical therapy (GDMT) improves outcomes in heart failure with reduced ejection fraction (HFrEF), many eligible patients remain untreated in the United States (US). Purpose To explore reasons why patients are not receiving GDMT and physician perceptions in management of their patients. Methods We conducted a cross-sectional survey of HF treatment practices (Adelphi Real World Heart Failure Disease Specific Programme) between August 2022 and February 2023, following publication of the 2022 US HF guidelines recommended that patients with HFrEF receive: angiotensin receptor/neprilysin inhibitors (ARNI), beta-blocker, mineralocorticoid receptor antagonists (MRA), and SGLT-2 inhibitors (SGLT2i). A total of 63 cardiologists and 39 primary care physicians in the US provided clinical and treatment patterns data on adult patients with HFrEF (ejection fraction ≤ 40%) and completed an attitudinal survey detailing reasons for treatment initiation. Results The study group included 323 patients with HFrEF (median age of 67 years [IQR 56-74]; 39% females) of which 59.4% were White, 19.8% African American and 9.6% Hispanic; half of the sample was insured by Medicare (50.2%), followed by commercial insurance (36.5%). GDMT prescription rates are presented in Table 1. Overall, 57.3% were not prescribed ARNI (185/323), 16.4% (53/323) were not prescribed a beta-blocker; 71.5% (231/323) were not prescribed MRA, and 65.3% (211/323) were not prescribed SGLT2i. Among patients not receiving GDMT, the most frequently reported physician reason for not prescribing ARNIs (54.1%), beta-blockers (43.4%), MRAs (54.5%) or SGLT-2is (53.6%) was physician deemed the patient to be clinically stable (Table 2). Most physicians (93.5%) reported being satisfied with treatment for patients with HFrEF and most (80.3%) believed that their patients with HFrEF were fully compliant with their treatments. Most physicians (91.2%) stated that they based their treatment decisions on both clinical experience and laboratory tests, as opposed to laboratory tests/imaging only (9.8%) or personal judgement only (16.7%). Conclusions In this cohort of patients with HFrEF from the US, the most common primary reason physicians reported for their patients not receiving GDMT was that the patient was clinically stable. Patient medication costs, contraindications, and proven intolerance were each reported as primary reasons for non-treatment in only a small minority of cases. These data suggest a strong culture of clinical inertia and lack of therapeutic urgency as the dominant driver of large gaps in use of GDMT in the US.GDMT prescriptions in HFrEF (n = 323)Physician-reasons for no GDMT