From the Guidelines
An electrocardiogram (EKG or ECG) is a non-invasive diagnostic test that records the electrical activity of the heart, essential for evaluating heart rhythm, detecting heart attacks, and assessing other cardiac conditions. The test involves placing electrodes on the chest, arms, and legs to capture electrical signals from different angles. A standard EKG has 12 leads that provide a comprehensive view of heart activity. The resulting waveform shows key components: P waves (atrial depolarization), QRS complex (ventricular depolarization), and T waves (ventricular repolarization). Abnormalities in these patterns can indicate various conditions like arrhythmias, myocardial infarction, electrolyte imbalances, or structural heart disease.
Interpretation of EKG
The interpretation of an EKG requires careful analysis of the waveform, including measuring intervals between waves, examining wave morphology, and analyzing the heart's electrical axis 1. The EKG is critical in adding support to the clinical suspicion of coronary artery disease (CAD) and providing prognostic information based on the pattern and magnitude of abnormalities 1.
Clinical Application
In clinical practice, the EKG is used to diagnose and manage various cardiac conditions, including acute coronary syndromes, arrhythmias, and heart failure. The EKG can also be used to monitor the effects of treatment and adjust therapy as needed. The EKG is a fundamental tool in cardiology, and its interpretation requires a thorough understanding of the underlying physiology and pathology of the heart.
Limitations and Considerations
While the EKG is a valuable diagnostic tool, it is not without limitations. A completely normal EKG does not exclude the possibility of an acute coronary syndrome, and a skilled physician is required to integrate clinical data and provide a differential diagnosis 1. The EKG should be interpreted in the context of the patient's clinical presentation, medical history, and other diagnostic tests.
Key Points
- The EKG is a non-invasive diagnostic test that records the electrical activity of the heart.
- The test involves placing electrodes on the chest, arms, and legs to capture electrical signals from different angles.
- A standard EKG has 12 leads that provide a comprehensive view of heart activity.
- Abnormalities in the EKG waveform can indicate various conditions like arrhythmias, myocardial infarction, electrolyte imbalances, or structural heart disease.
- The EKG is critical in adding support to the clinical suspicion of CAD and providing prognostic information based on the pattern and magnitude of abnormalities.
From the Research
Interpretation of an Electrocardiogram (EKG)
The interpretation of an Electrocardiogram (EKG) is a crucial diagnostic tool in guiding management in patients with suspected myocardial infarction (MI) 2. The 12-lead ECG remains the most immediately accessible and widely used initial diagnostic tool for evaluating patients with chest pain 3, 4.
ECG Patterns and Acute Coronary Syndromes
The ECG recorded during acute myocardial ischemia is of diagnostic, therapeutic, and prognostic significance, typically showing either predominant ST-segment elevation (STE) or no predominant STE 3. Patients with STE are classified as having either aborted myocardial infarction (MI) or ST-elevation MI (STEMI) based on the absence or presence of biomarkers of myocardial necrosis 3.
Diagnostic Significance of ECG
The information obtained from the 12-lead ECG at presentation should be complemented by repeated ECGs, especially during symptoms indicative of ischemia, and by comparing the findings with reference ECGs 3. The prehospital ECG can improve the diagnosis of an acute coronary syndrome, with ST segment and T and Q wave abnormalities suggestive of myocardial ischemia or infarction being more common in patients with acute coronary syndromes 5.
Clinical Application of ECG Interpretation
Careful interpretation of the ECG might yield subtle features suggestive of ischemia, facilitating more rapid triage of patients with subtle acute coronary occlusion or identification of ST-elevation MI mimics (pseudo ST-elevation MI patterns) 2. The electrocardiogram continues to be an invaluable tool in the initial evaluation of patients with chest pain, allowing clinicians to make faster and better decisions than ever before 4.
Challenges in ECG Interpretation
However, patients with critical illness may present with ECG findings that are difficult to distinguish from acute coronary syndrome, highlighting the need for careful consideration of clinical characteristics and significance of ECG patterns 6.