Introduction: Reducing the number of patients requiring cardiac monitoring would increase system capacity and improve emergency department (ED) patient flow. The Ottawa Chest Pain Rule helps physicians identify chest pain patients who do not require cardiac monitoring and is based on a ‘normal or non-specific’ ECG and being pain-free on initial physician assessment. Our objective was to measure the impact that the implementation of this decision rule would have on cardiac monitoring bed utilization in adult EDs in Calgary. Methods: A convenience sample of patients was prospectively obtained at each of the four Calgary adult emergency sites. All patients presenting with the Canadian Triage Acuity Scale chief complaint of “cardiac pain”, or “chest pain with cardiac features” were captured for inclusion in the study. Real time interviews and survey assessments were conducted with the primary nurse and physician involved in each patient’s care. Results: A total of 61 patients were captured by the study. Physicians identified cardiac as the primary rule-out pathology in 51% of these patients. The average Heart Score of all study patients was 4.2, and 30% of patients were ultimately admitted. Physicians believed that 39% of the 61 patients needed cardiac monitoring, while primary nurses believed that 59% needed monitoring. Of the 61 patients, 59% were triaged to areas providing cardiac monitoring. The application of the Ottawa Rule would have allowed 47% of patients triaged to cardiac monitoring to be taken off cardiac monitoring. This would translate to a total of greater than 74 hours saved or a reduction of 30% of the total cardiac monitored patient time. Conclusion: The Ottawa rule appears to be a low-risk emergency department flow intervention that has the potential to help reduce resource utilization in emergency departments. This change may result in increased emergency department capacity and improved overall patient flow. This simple rule based only on ECG findings and absence of chest pain can easily be applied and implemented without increasing physician workload or increasing risk to patients.