Background: Quantifying guideline-directed medical therapy (GDMT) intensity is foundational for improving heart failure (HF) care. Existing measures discount dose intensity or use inconsistent weighting., Methods: The Kansas City Medical Optimization (KCMO) score is the average of total daily to target dose percentages for eligible GDMT, reflecting the percentage of optimal GDMT prescribed (range, 0-100). In Change the Management of Patients With HF, we computed KCMO, HF collaboratory (0-7), and modified HF Collaboratory (0-100) scores for each patient at baseline and for 1-year change in established GDMT at the time (mineralocorticoid receptor antagonist, β-blocker, ACE [angiotensin-converting enzyme] inhibitor/angiotensin receptor blocker/angiotensin receptor neprilysin inhibitor). We compared baseline and 1-year change distributions and the coefficient of variation (SD/mean) across scores., Results: Among 4532 patients at baseline, mean KCMO, HF collaboratory, and modified HF Collaboratory scores were 38.8 (SD, 25.7), 3.4 (1.7), and 42.2 (22.2), respectively. The mean 1-year change (n=4061) for KCMO was -1.94 (17.8); HF collaborator, -0.11 (1.32); and modified HF Collaboratory, -1.35 (19.8). KCMO had the highest coefficient of variation (0.66), indicating greater variability around the mean than the HF collaboratory (0.49) and modified HF Collaboratory (0.53) scores, reflecting higher resolution of the variability in GDMT intensity across patients., Conclusions: KCMO measures GDMT intensity by incorporating dosing and treatment eligibility, provides more granularity than existing methods, is easily interpretable (percentage of ideal GDMT), and can be adapted as performance measures evolve. Further study of its association with outcomes and its usefulness for quality assessment and improvement is needed., Competing Interests: Disclosures Drs Khan and Sherrod are supported by the National Heart, Lung, and Blood Institute under award T32H110837. Dr Ikemura received an unrestricted research grant for the Department of Cardiology, Keio University School of Medicine from Bristol Myer Squibb. Dr Sauer reports industry relationships with Abbott, Boston Scientific, Biotronik, Bayer, Amgen, CSL Vifor, Acorai, Story Health, General Prognostics, Impulse Dynamics, and Edwards Lifesciences. He also serves as advisory board member and owns stock in ISHI digital health company. Dr Fonarow reports consulting for Abbott, Amgen, AstraZeneca, Bayer, Boehringer Ingelheim, Cytokinetics, Eli Lilly Johnson & Johnson, Medtronic, Merck, Novartis, and Pfizer. Dr Butler reports consulting for Abbott, American Regent, Amgen, Applied Therapeutic, AstraZeneca, Bayer, Boehringer Ingelheim, Bristol Myers Squibb, Cardiac Dimension, Cardior, CVRx, Cytokinetics, Edwards, Element Science, Innolife, Impulse Dynamics, Imbria, Inventiva, Lexicon, Lilly, LivaNova, Janssen, Medtronics, Merck, Occlutech, Novartis, Novo Nordisk, Pfizer, Pharmacosmos, Pharmain, Roche, Sequana, SQ Innovation, and Vifor. Dr DeVore reports research funding through his institution from Biofourmis, Bodyport, Cytokinetics, American Regent Inc, the National Institutes of Health and the National Heart, Lung, and Blood Institute, Novartis, and Story Health. He also provides consulting services for and/or receives honoraria from Abiomed, Cardionomic, LivaNova, Natera, NovoNordisk, Story Health, and Zoll. Dr Lund is supported by Karolinska Institutet, the Swedish Research Council (grant 523-2014-2336), the Swedish Heart Lung Foundation (grants 20150557 and 20190310), and the Stockholm County Council (grants 20170112 and 20190525). Dr Lund reports the following relationships with industry: grants, consulting, honoraria: Abbot, Alleviant, AstraZeneca, Bayer, Biopeutics, Boehringer Ingelheim, Edwards, Merck/MSD, Novartis, Novo Nordisk, OrionPharma, Owkin, Pharmacosmos, Vifor Pharma; stock ownership: AnaCardio. Dr Chan is supported by the National Heart, Lung, and Blood Institute under award R01HL160734 and is a consultant for Optum Rx. Dr Spertus has provided consultative services on patient-reported outcomes and evidence evaluation to Alnylam, AstraZeneca, Bayer, Merck, Janssen, Bristol Myers Squibb, Edwards, Kineksia, 4DT Medical, Terumo, Cytokinetics, Imbria, and United Healthcare; holds research grants from Bristol Myers Squibb, Abbott Vascular, and Janssen; owns the copyright to the Seattle Angina Questionnaire, Kansas City Cardiomyopathy Questionnaire, and Peripheral Artery Questionnaire; and serves on the Board of Directors for Blue Cross Blue Shield of Kansas City. The other authors report no conflicts.