Study objectives: Increasing pressure to deliver thrombolytic agents quickly to patients with suspected myocardial infarction (MI), along with expanded indications, may contribute to inappropriate administration of these agents, with potentially catastrophic results. We sought to identify the extent to which MI is ruled out in patients given thrombolytic therapy for acute MI and to characterize the clinical course and outcome in such patents.
Methods: We studied 609 consecutive patients admitted to the CCU of an urban teaching hospital who were treated with thrombolytic agents for suspected acute MI between January 1986 and December 1993. In 35 (5.7%), MI was ruled out on the basis of persistently normal serum creatine kinase-MB isoenzyme levels. Hospital course and alternative diagnoses were established by means of chart review and database inquiry.
Results: Patients in whom MI was ruled out were similar to those with MI with regard to baseline demographic and clinical features. Presenting ECGs in patients without MI were less likely to show Q waves (43 versus 64%, P < .02) but more likely to show left ventricular hypertrophy (26 versus 7%, P = .001) and nonspecific ST-segment and T-wave changes (54 versus 32%, P < .01) compared the ECGs of MI patients. Transient ST-segment elevation was detected in 51%. Hospital complications of patients without MI were similar to those of MI patients. No patient in whom MI was ruled out sustained a major hemorrhage. Final diagnoses of patients without MI included unstable angina (n = 20, 57%) undefined chest pain (n = 8, 17%) pericarditis (n = 3), pancreatitis (n = 2), esophagitis (n = 1), and aortic dissection (n = 1). Two patients died, one of aortic dissection and another of pericarditis.
Conclusion: In a consecutive series of CCU patients in whom MI was ruled after thrombolysis, we found no demographic or presenting clinical features to distinguish them from patients in whom MI was diagnosed. Transient ST-segment elevation potentially justifying thrombolytic therapy was present in more than half of the patients in whom MI was ruled out but may have represented transient coronary occlusion, coronary spasm, or other manifestations of unstable angina. In this study, patients in whom MI was ruled out had a high incidence of coronary disease and risk of in-hospital complications similar to that of patients with acute MI. Our findings support the rationale and safety of policies to rapidly and aggressively administer thrombolytic agents in the emergency department.