Regular paper
Prevalence of coronary occlusion and outcome of an immediate invasive strategy in suspected acute myocardial infarction with and without ST-segment elevation

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Abstract

The prevalence of flow-limiting coronary lesions at the time of presentation in patients with non–ST-segment elevation myocardial infarction (NSTEMI) is unknown. Because rational reperfusion strategies depend on early, accurate identification of coronary flow limitation, we performed coronary angiography at the time of presentation of patients with suspected NSTEMI. We also evaluated outcomes of an immediate interventional strategy. A comparison is made with suspected ST-segment elevation myocardial infarction (STEMI). Unselected consecutive patients with suspected STEMI or NSTEMI were enrolled in a prospective observational cohort study. Suspected STEMI was defined according to standard criteria. Suspected NSTEMI was identified by clinical evaluation of symptoms, electrocardiographic changes, persistence of ischemic pain for >20 minutes despite treatment, and/or hemodynamic instability. Biochemical evidence of myocardial necrosis on presentation was not mandatory. An immediate, around-the-clock invasive strategy was applied. Significant coronary lesions were found in 94% of 279 patients with suspected STEMI and in 90% of 125 patients with suspected NSTEMI, and coronary occlusion or flow limitation was present in 75% and 63% of patients, respectively. Immediate percutaneous coronary intervention was performed in 74% and 60%, respectively, and an additional 13% and 18%, respectively, had coronary artery bypass surgery during the index admission. In-hospital mortalities in the patients with suspected STEMI and NSTEMI were 4.7% and 5.6%, respectively. An additional 1.9% and 2.5% died at 6 months. The prevalence of coronary flow limitation in clinically suspected NSTEMI is almost as high as in suspected STEMI. Short- and long-term outcomes of an immediate invasive strategy are similar for the 2 conditions.

Section snippets

Patients:

We initiated a prospective study on July 1, 1997, to monitor the outcome of a radical shift from a noninvasive to an invasive strategy available 7 days/week, 24 hours/day in the management of patients with STEMI at Royal North Shore Hospital.3 The Interventional Cardiology Unit made the same immediate invasive strategy available to all patients with non–ST elevation acute coronary syndromes if symptoms and/or electrocardiographic abnormalities did not respond to anti-ischemic treatment within

Results

In the absence of prescriptive diagnostic criteria for suspected NSTEMI, the recruitment of patients increased as clinicians gained confidence in diagnosing AMI at the time of presentation on clinical grounds. Figure 1 shows the recruitment of 279 patients with STEMI and 125 with NSTEMI from July 1, 1997 to January 1, 2001. Elimination of age limits contributed to the increase in recruitment after the first year in both groups. The ratio of suspected NSTEMI/STEMI stabilized 2 years after the

Prevalence of NSTEMI:

We describe consecutive patients identified on presentation on the basis of electrocardiographic abnormalities, persistent symptoms, and/or hemodynamic instability. Only a high-risk subset of patients with non–ST-segment acute coronary syndromes is described. Patients believed to have unstable angina rather than infarction were not studied. Some with early resolution of clinical and electrocardiographic abnormalities were not included, even if they ultimately had a confirmed diagnosis of AMI.

Acknowledgements

We thank the staff in the Cardiac Catherization Laboratory, the Coronary Care and Intensive Care Units, and the Department of Cardiothoracic Surgery for their help in the care of patients in this study. We also thank our medical colleagues in the Departments of Cardiology and Emergency Medicine. Their clinical evaluation of patients and enthusiastic support for our infarct angioplasty program made this study possible. Finally, we thank Annie Loxton, BA, and Jacqueline Padley, RN, for their

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