Hierarchical linear modelling was used to evaluate the influence of nurse staffing, work environment, and nurse and patient variables on system outcomes based on data collected in Canadian cardiac and cardiovascular inpatient units. Staffing utilization levels below 80% at the unit level and less overtime optimized perceived care quality and the completion of therapeutic interventions. Fewer patients per nurse improved perceived care quality and reduced longer-than-expected length of stay. Nurse reports of greater resource adequacy were associated with less absenteeism and fewer uncompleted or delayed nursing interventions. System outcomes were also influenced by patient characteristics (health, pre-operative education, nursing diagnoses); nurse characteristics (experience, expertise, health, effort-reward imbalance); and work-environment factors (autonomy, unit instability).