Q-wave evolution of a first acute myocardial infarction without significant ST segment elevation

Area of Science:

• Cardiology
• Electrocardiography
• Myocardial Infarction

Background:

• Some patients with acute myocardial infarction (AMI) without ST-segment elevation develop Q-wave infarction.
• It remains unclear if these patients can be identified by admission ECG or if their prognosis differs from non-Q-wave AMI patients.

Purpose of the Study:

• To assess the frequency of Q-wave evolution in patients with non-ST-elevation AMI.
• To identify electrocardiogram (ECG) predictors of Q-wave evolution.
• To evaluate the short-term in-hospital implications of Q-wave evolution.

Main Methods:

• 432 consecutive patients admitted with a first acute myocardial infarction (AMI) without Q waves and with ST-segment amplitudes ≤0.1 mV were analyzed.
• Admission ECGs were assessed for predictors of Q-wave evolution.
• In-hospital outcomes were compared between patients with and without Q-wave evolution.

Main Results:

• Q-wave myocardial infarction evolved in 94 patients (22%) before hospital discharge.
• Specific ECG criteria showed moderate sensitivity and high specificity for predicting anterior, inferior, and posterior Q-wave evolution.
• Patients with Q-wave evolution had higher peak creatine kinase MB levels but experienced a benign in-hospital course with similar risks of severe complications compared to non-Q-wave patients.

Conclusions:

• Approximately one-fifth of patients with non-ST-elevation AMI develop Q-wave infarction.
• Admission ECG findings can help identify patients at risk for Q-wave evolution.
• Q-wave evolution in this patient group does not appear to be associated with a worse in-hospital outcome.