Mortality based on the presenting electrocardiogram in patients with myocardial infarction in the troponin era
Michael C Kontos1, Brett D Roberts, James L Tatum
1Department of Internal Medicine, Cardiology Division, Virginia Commonwealth University, Richmond, Virginia, USA. mkontos@mcvh-vcu.edu
Insights
Initial electrocardiogram (ECG) findings in myocardial infarction (MI) impact outcomes. Even without ST-elevation, specific ECG patterns indicate higher mortality risk in MI patients.
Area of Science:
- Cardiology
- Medical Diagnostics
Background:
- Limited data exists on short-term mortality for myocardial infarction (MI) patients with non-ischemic initial electrocardiogram (ECG) findings.
- Previous studies often excluded patients with normal or nonspecific ECGs, leaving their outcomes unclear, particularly in the current troponin era.
Purpose of the Study:
- To investigate the 30-day mortality rates in patients diagnosed with MI based on initial ECG classifications.
- To assess the relationship between various initial ECG findings and MI size, as estimated by cardiac biomarker levels.
Main Methods:
- 1641 consecutive patients diagnosed with MI using troponin I (TnI) were classified into 8 ECG groups.
- MI size was estimated using creatine kinase-MB (CK-MB) levels.
- 30-day mortality was assessed for each ECG group.
Main Results:
- ST-elevation MI constituted only 22% of cases, with larger infarct sizes.
- Most MIs (78%) had non-ST-elevation ECGs, with smaller infarct sizes; 1/3 diagnosed by TnI elevation alone.
- High-risk ECG groups (ST-elevation, ischemia, LBBB) had >9% mortality, while lower-risk groups averaged 6% mortality (P < .001).
Conclusions:
- ECG findings beyond ischemia predict poor outcomes in MI patients.
- All patients diagnosed with MI should be considered at significant risk, regardless of initial ECG presentation.
Background:
Studies reporting short-term mortality in patients with myocardial infarction (MI) based on the initial electrocardiogram (ECG) are often limited by requiring an ischemic ECG for inclusion. Because few patients with normal or nonspecific findings were included, outcomes in these patients are less clear, especially in the troponin era.
Methods:
Consecutive patients diagnosed as having MI using troponin I (TnI) over a 6-year period were included and classified into 8 mutually exclusive groups based on the initial ECG using standard criteria. Patients were included in only 1 group. The MI size was estimated using multiples of peak creatine kinase-MB (CK-MB), and 30-day mortality rate was assessed.
Results:
Among 1641 patients with MI, patients with ST elevation represented only 22% of all MIs. Patients with ST elevation had the largest MI size, with 2 of 3 having a peak CK-MB greater than 10 times normal. In contrast, most of the patients representing all the other ECG groups had a peak CK-MB less than 5 times normal, with approximately 1 of 3 having no CK-MB elevation and were diagnosed by TnI elevation alone. Patients could be separated into a high-risk group (ST elevation, ischemia, other, or left bundle-branch block), in which mortality rate exceeded 9% (mean, 14%), and a lower-risk group (prior MI, left ventricular hypertrophy, nonspecific changes, and normal), in which the 30-day mortality rate averaged 6% (P < .001; range, 5.23%-7.1%).
Conclusions:
Specific ECG findings other than ischemia portend poor outcomes in patients with MI. Once MI is diagnosed, patients are no longer low risk.
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