Instability of ST segments in the early stages of acute myocardial infarction in patients undergoing continuous 12-lead ECG monitoring.

Many patients presenting to the emergency department with suspected acute myocardial infarction (AMI) have an initial 12-lead electrocardiogram (ECG) nondiagnostic for acute injury and thus do not meet any accepted ECG criteria for thrombolytic therapy. Early studies in the use of intracoronary thrombolytic therapy documented that cyclic variations in ST segment magnitudes between normalcy and injury are common during the early phase of AMI and correspond to spontaneous intermittent coronary opening and reocclusion. The reliance on a single ECG to diagnose AMI may mean that many patients with AMI are missed if the initial ECG is obtained during a window of ST segment normalcy. We present 3 patients with AMI who underwent continuous 12-lead ST segment monitoring with frequent serial ECGs whose ST segments periodically normalized during the acute injury phase. We believe continuous 12-lead ST segment monitoring with frequent serial ECGs can aid the physician in identifying patients with AMI who may benefit from thrombolytic therapy and other urgent revascularization techniques.