Gaies M, et al. - In this observational analysis including all cardiac ICU admissions that did not include cardiac surgery, researchers aimed to measure case-mix adjusted cardiac ICU medical mortality rates and evaluate variation across cardiac ICUs in the Pediatric Cardiac Critical Care Consortium. They used variables present at cardiac ICU admission and developed a case-mix adjusted model. Age, underweight, prior surgery, time of and reason for cardiac ICU admission, high-risk medical diagnosis or comorbidity, mechanical ventilation or extracorporeal membrane oxygenation at admission, and pupillary reflex were final model covariates. They validated this model by using bootstrap resampling (1,000 samples). For the validated model, 0.87 was the C-statistic, and it was well calibrated. Important case-mix variation was indicated by the expected mortality that ranged from 2.6% to 8.3%. This is the first report of variation in this case-mix adjusted quality metric within this patient population across Pediatric Cardiac Critical Care Consortium cardiac ICUs.