Background: During the coronavirus disease 2019 (COVID-19) pandemic, Veterans have deferred inpatient care such as coronary revascularization in the context of an acute myocardial infarction. Simultaneously, cardiovascular care has been disrupted, with clinicians less likely to prescribe guideline indicated medications for common cardiovascular conditions such as stable coronary artery disease or heart failure. Excess deaths have also occurred during the COVID-19 pandemic, particularly among vulnerable populations, raising the possibility of suboptimal healthcare utilization or quality of care among those not directly infected by the virus. However, the extent to which cardiovascular healthcare utilization and quality of care have decreased during the pandemic compared with preceding time periods and whether these changes have impacted Veterans’ risk of mortality is unknown. Significance: Cardiovascular disease is the most common condition in the United States and the leading cause of excess, non-COVID deaths during the early pandemic. The proposed work may identify gaps in VA healthcare utilization and quality of care with the potential to directly inform national improvements in cardiovascular care for Veterans, leading to more accessible, higher-quality, more equitable care in the future. In addition, the evaluation of care for cardiovascular disease could serve as a model for future research in other disciplines within Veterans Affairs medical specialty care. Specific Aims: Aim 1: Compare inpatient and outpatient utilization (clinic visits / hospitalizations / diagnostic testing / procedural care) among Veterans with common cardiovascular diagnoses (atrial fibrillation / coronary artery disease / heart failure) during the COVID-19 pandemic compared with expected utilization based on the corresponding 3-year period preceding the pandemic. Aim 2: Compare quality of care (guideline indicated medication / transitions of care) among Veterans with common cardiovascular diagnoses (atrial fibrillation / coronary artery disease / heart failure) during the COVID- 19 pandemic with that expected based on the corresponding 3-year period preceding the pandemic. Aim 3: Evaluate whether potential pandemic-related changes in healthcare utilization and/or process of care quality metrics are associated with an increased risk for the clinical outcomes of all-cause mortality and/or cardiovascular mortality among Veterans with common cardiovascular diagnoses. Methodology: We propose an observational, retrospective, national cohort study of Veterans with cardiovascular disease. The primary data sources will consist of the VA Corporate Data Warehouse (CDW) and the Non-VA Care Program Integrity Tools (PIT) system. Using indirect standardization, we will compare potential decreases in cardiovascular healthcare utilization and quality of care and a potential increase in mortality to that which occurred prior to the pandemic, performing subgroup analyses focused on age,...