The Task Force has been spearheading the initiative to standardize the lexicon of cardiovascular medicine to enhance the use of clinical data, improve clinical communication, optimize quality assurance and improvement, assess outcomes, enhance process improvement efforts, and facilitate clinical research, development, and analysis of registries. Because the ACC and AHA are committed to updating existing standards as needed to maintain their currency and promote harmonization with other standards as health information technology and clinical practice evolve, this document is provided as an update of the 2005 ACC/AHA key data elements and definitions for chronic heart failure.1 The goal of this publication is to provide new data elements consistent with practice guidelines and updated terminology and attributes in compliance with current methodology of the Task Force2 and current policies of the ACC and AHA regarding harmonization of data across organizations and disciplines. Heart failure (HF) data standards are of critical importance to clinical providers, investigators, administrators, healthcare services and institutions, regulators, legislators, and payers more than ever as a result of: 1) increasing prevalence and burden of HF3,4; 2) increased focus on performance metrics for HF5; 3) increasing need for large data sets to examine comparative effectiveness and safety of treatment strategies in real world patients6; 4) increased recognition of healthcare disparities that require understanding of patient, healthcare delivery, and system variables7; 5) growing need for new effective preventive and treatment strategies in HF targeted for different stages or types of HF8; subgroups of interest and comorbidities requiring better classification and documentation of patient and treatment variables; 6) need for improved communication and for shared decision-making and transitions of care between different levels of care and providers9,10; 7) development of models for prediction of therapeutic benefit and outcomes11; 8) universally understandable data for individualization of therapies and management strategies for patients with complex HF by different providers; and 9) development and conduct of future registries, at both hospital and national levels, by providing a list of major variables, outcomes, and definitions. Approximately 6.2 million persons ≥20 years of age in the United States have HF, with approximately 1 million new HF cases diagnosed annually, and the prevalence continues to rise.3,12 Despite improvements in age-adjusted HF-related survival rates between 2000 and 2012, there has been a recent increase in mortality rates for all age and sex subgroups.12–14 HF remains as the primary diagnosis in >1 million hospitalizations annually, and the total cost of HF care in the United States exceeds $30 billion annually, with over half of these costs spent on hospitalizations.15 The mortality rates after hospitalization for HF remains high, at approximately 20% to 25% at 1 year, with similar mortality rates for heart failure with preserved ejection fraction or heart failure with reduced ejection fraction.16 The clinical syndrome of HF may result from different causes. Thus, despite a common syndrome of HF, different etiologies may imply different prognosis and varying treatment strategies, underlining the importance of specific data elements for emphasizing these differences in HF.8 Similarly, the syndrome of HF commonly overlaps with other cardiovascular diseases, such as coronary artery disease, hypertension, valvular disease, and primary myocardial disease, which are common causes of HF. Specifying these data elements for patients with HF is important for clinical care, performance improvement, research, and endpoints. Standardized data elements and definitions across studies can help accelerate and facilitate research in HF through dissemination and sharing of relevant information, comparisons, pooled analyses, and meta-analyses.17 In clinical care, a broad spectrum of clinicians provides a continuum of care for patients with HF, ranging from primary care/family medicine providers, HF specialists and/or cardiologists, cardiac and transplant surgeons, interventional cardiologists, electrophysiologists, advanced practice providers such as nurse practitioners and physician assistants, pharmacists, hospitalists, home healthcare providers, palliative care specialists and nurses, hospice specialists and nurses, social workers, and cardiac rehabilitation specialists to investigators, who must communicate with each other through a common vocabulary. Care of patients with HF may take place in specialized clinics delivered by a variety of providers previously mentioned, necessitating care coordination comprising common terminology with a patient-centered approach.18 Furthermore, HF is a chronic problem, and patients are likely to transition through different stages of HF, which requires recognition and definition of these states with common terminology standardized across different providers and encounters of care. Similarly, given the recent emphasis on quality performance measurement initiatives, particularly those for which institutions and providers are compared against each other or against benchmarks, and reimbursement strategies and penalties that are attached to such metrics, the necessity for reliable, risk adjustable, and analyzable data is gaining more importance for the professional community, as well as for payers, regulators, legislators, and consumers.5,19,20 The writing committee envisions that the data elements might be useful in these broad categories: Clinical programs, such as HF clinics, where many clinicians work together to achieve specific goals for the care and care coordination of patients with HF. Transitions of care, in which patients with HF move through different locations and levels of care (ie, inpatient, outpatient [eg, home, rehabilitation center, nursing home], palliative care, and hospice) or progress through different stages of HF (Stages A to D), with providers ranging from HF specialists, cardiac transplant physicians, home healthcare or palliative care providers, and primary care providers. Clinical registries, for ongoing care, prospective epidemiologic and comparative effectiveness research, pre- or postmarket analysis for efficacy and safety in populations of interest. Clinical research, particularly prospective randomized clinical trials where eventual pooled analysis or meta-analysis is anticipated. Quality performance measurement initiatives, provider or institutional based or external, retrospective, or prospective. Organization and design of electronic medical information initiatives, such as EHRs, pharmacy databases, computerized decision support, and cloud technologies incorporating health information. Public health policy, healthcare coverage, insurance coverage, and legislation development to provide appropriate and timely care for patients with HF and to prevent disparities in HF care. The data element tables are also included as an Excel file in the Online Data Supplement. 1.1. Special Considerations Several points are important to recognize regarding the scope of this document. First, given the magnitude of additional data elements that cardiac transplantation and mechanical circulatory support device therapies would entail, the writing group decided to focus on HF and not include cardiac transplantation and mechanical circulatory support data elements in detail in this document. Second, the data elements were not differentiated for chronic HF versus acute decompensated HF; or for inpatient, outpatient, palliative care, or hospice status, because HF is a chronic condition that is not an episodic event, and a patient can transition from one status to the other through his/her life time. The writing committee considered data elements pertinent to the full range of care provided to these patients and are intended to be useful for all care venues. Third, the data elements were not differentiated for new onset incident versus prevalent cases or number of encounters, and databases can be built and customized according to users’ needs to capture such information. Fourth, the writing committee would like to alert the readers to the existence of other documents and guidelines with which we tried to harmonize and are likely to complement the content of our document, including the “2020 AHA/ACC Key Data Elements and Definitions for Coronary Revascularization,”21 “2019 ACC/AHA/ASE Key Data Elements and Definitions for Transthoracic Echocardiography,”22 “2014 ACC/AHA Key Data Elements and Definitions for Cardiovascular Endpoint Events in Clinical Trials,”23 “2013 ACCF/AHA Guideline for the Management of Heart Failure,”24 “2017 ACC/AHA/HFSA Focused Update of the 2013 ACCF/AHA Guideline for the Management of Heart Failure,”9 Centers for Medicare & Medicaid Services (https://www.medicare.gov/hospitalcompare/search.html), and The Joint Commission core HF performance measures; meaningful use criteria; The Agency for Healthcare Research and Quality's quality indicators for HF; Get With The Guidelines and National Cardiovascular Data Registry CathPCI Registry data elements. We made every attempt to use guideline- and evidence-based definitions. Finally, we did not include data element fields for entry of calculated risk scores, as databases can be programmed and customized to calculate risks scores according to the user’s objective as different risk models can be used for different purposes. The intent of this writing committee was not to be overly prescriptive.