Safe discharge from the cardiac emergency room with a rapid rule-out myocardial infarction protocol using serial CK-MBmass

Objective-To determine whether a new protocol, using a rapid and sensitive CK-MBmass assay and serial sampling, can rule out myocardial infarction in patients with chest pain and decrease their length of stay in the cardiac e mergency room without increasing risk. Design-The combined incidence of cardiac death and acute myocardial infarct ion at 30 days, six months, and 24 months of follow up were compared betwee n patients discharged home from the cardiac emergency room after ruling out myocardial infarction with a CK-MBactivity assay in 1994 and those dischar ged home after a rapid CK-MBmass assay in 1996. Setting-Cardiac emergency room of a large university hospital. Patients-In 1994 and 1996, 230 and 423 chest pain patients, respectively, w ere discharged home from the cardiac emergency room with a normal CK-MB and an uneventful observation period. Results-The median length of stay in the cardiac emergency room was signifi cantly reduced, from 16.0 hours in 1994 to 9.0 hours in 1996 (p < 0.0001). Mean event rates in patients from the 1994 and 1996 cohorts, respectively, were 0.9% (95% confidence interval (CI) -0.3% to 2.1%) <nu> 0.7% (95% CI -0 .1% to 1.5%) at 30 days, 3.0% (95% CI 0.8% to 5.2%) nu 2.8% (95% CI 1.2% to 4.4%) at six months, and 7.0% (95% CI 3.7% to 10.3%) nu 5.7% (95% CI 3.5% to 7.9%) at 24 months. Kaplan-Meier survival analysis showed no difference in mean event-free survival at 30 days, six months, and 24 months of follow up. Conclusions-Using a rule-out myocardial infarction protocol with a rapid an d sensitive CK-MBmass assay and serial sampling, the length of stay of pati ents with chest pain in the cardiac emergency room can be reduced without c ompromising safety.