Abstract Cardiac inotrope medications used to augment heart contractility during recovery from cardiac surgery carry steep tradeoffs between risks (e.g., myocardial ischemia, malignant arrhythmia) and benefits (e.g., enhanced perfusion to vital organs). Inotrope use is often locally standardized within hospitals based on institutional preferences, rather than individualized to patient-specific risks and benefits. While inotropes are necessary for a minority of patients with advanced cardiogenic shock to survive past the operating room, on average, inotropes are independently associated with 3-fold increased mortality (absolute rate 5.0%) and major complications (18%). For the majority of the 300,000 US patients undergoing cardiac surgeries each year, limited evidence exists to support or refute the ability of inotropes to improve outcomes. As a result, inotrope practice patterns vary widely across institutions, contributing to wide variation in rates of mortality and complications. There is a critical need to understand inotrope use in modern, generalizable cardiac surgery populations, and identify patient-specific contexts in which inotropes are helpful versus harmful. Without such information, unwarranted variation in inotrope use for cardiac surgery will remain high, and opportunities to reduce risk of major complications related to their use (or non-use) will be missed. A paradigm shift to address this need remains possible through (i) availability of preoperative patient risk factor data, detailed minute-to-minute perioperative data, and high-quality outcomes registry data; and (ii) channels to access frontline clinicians capable of describing local practice patterns, structural factors, and attitudes towards inotrope use. Such an understanding requires integration of multicenter cardiac surgery research and quality collaboratives to validate findings in a large, contemporary cardiac surgical cohort, while engaging clinician stakeholders in the process. We propose a multicenter study which leverages the integration of two unique, mature research and quality improvement collaboratives built upon standardized national registries: the Multicenter Perioperative Outcomes Group (MPOG) and the Society for Thoracic Surgeons (STS) Adult Cardiac Surgical Database. MPOG uses nurse-validated, detailed minute-to-minute intraoperative and early ICU data from the EHR for research and quality improvement. With University of Michigan as the Coordinating Center and guided by Research Director PI Mathis, MPOG has integrated over 21 million patient records across >40 health systems in 23 states and provides quality improvement feedback reports to >7,000 frontline anesthesiology clinicians. In addition, MPOG has integrated each member hospital’s STS clinical registry to create a unique national “MPOG-STS” dataset. We will (i) identify patient, clinician, and institution phenotypes associated with inotrope practice patterns (choice, timing) in cardiac surgery; (i...