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Electrocardiographic evolution of posterior acute myocardial infarction: importance of early precordial ST-segment
Insights
Isolated precordial ST-segment depression in non-Q-wave acute myocardial infarction (AMI) can indicate evolving posterior AMI. This finding was associated with higher creatine kinase (CK) levels and more severe ST depression, suggesting a distinct clinical subgroup.
Area of Science:
- Cardiology
- Electrocardiography
- Myocardial Infarction
Background:
- Precordial ST-segment depression is typically associated with anterior non-Q-wave acute myocardial infarction (AMI).
- It is generally not considered an indicator for acute thrombolytic therapy.
Purpose of the Study:
- To investigate the incidence and implications of isolated precordial ST-segment depression in patients with non-Q-wave AMI.
- To determine if this electrocardiographic finding predicts the evolution of posterior AMI.
Main Methods:
- Analysis of 544 patients with creatine kinase (CK)-MB-confirmed non-Q-wave AMI from the Diltiazem Reinfarction Study.
- Serial electrocardiograms and CK-MB levels were monitored in 50 patients with isolated precordial ST-segment depression (V1-V4).
- Evolution of posterior AMI was defined by specific R wave and R:S ratio criteria in leads V1 and V2.
Main Results:
- 40% (23 of 50) of patients with isolated precordial ST-segment depression evolved electrocardiographic evidence of posterior AMI.
- Posterior AMI evolution occurred by day 3 in 78% of these patients, with no abnormal CK-MB elevations.
- Patients with evolving posterior AMI had significantly higher peak CK values and greater ST-segment depression in precordial leads compared to those with only anterior AMI features.
Conclusions:
- Isolated precordial ST-segment depression in non-Q-wave AMI may signify an evolving posterior myocardial infarction.
- This subgroup exhibits distinct electrocardiographic and biochemical profiles.
- Further investigation into the management of this specific patient group is warranted.
Abstract:
Precordial ST-segment depression is typically observed in anterior non-Q-wave acute myocardial infarction (AMI), and is generally not regarded as an indication for acute thrombolytic therapy. Of 544 patients with creatine kinase (CK)-MB-confirmed non-Q-wave AMI randomized to the prospective multicenter Diltiazem Reinfarction Study, 50 patients (9.2%) had isolated precordial ST-segment depression of 1 mm or more in 2 or more contiguous precordial electrocardiographic leads (V1-V4). Serial electrocardiograms recorded at study entry (mean 50.5 hours after onset of chest pain), on study day 2, study day 3 and at predischarge showed that in 23 of 50 patients (40%) electrocardiographic evidence of posterior AMI evolved, defined as an R wave of 0.04 second or more in lead V1 and an R:S greater than or equal to 1 in lead V2. In 18 of these 23 patients (78%), posterior AMI had evolved by study day 3, and none had an abnormal reelevation of CK-MB (every 12-hour sampling) for up to 14 days of hospitalization. Compared with the remaining 27 patients who had electrocardiographic features of anterior non-Q-wave AMI only, the 23 with initial precordial ST segment depression in whom posterior AMI developed had significantly higher mean peak CK values (1,051 +/- 172 vs 663 +/- 89 IU, p less than 0.009) and greater mean precordial ST-segment depression in lead V1 (0.28 vs + 0.19 mm, p = 0.01), in lead V2 (1.3 vs 0.26 mm, p = 0.003) and in lead V3 (2.0 vs 0.93 mm, p = 0.0004).(ABSTRACT TRUNCATED AT 250 WORDS)