From the Guidelines
To accurately interpret an Electrocardiogram (EKG), it is essential to follow a systematic step-by-step approach, considering the patient's clinical presentation and symptoms, as emphasized by the 2010 American Heart Association guidelines for cardiopulmonary resuscitation and emergency cardiovascular care 1.
Step-by-Step Approach to EKG Interpretation
When interpreting an EKG, begin by:
- Checking the rate by counting the number of QRS complexes in a 6-second strip and multiplying by 10, or using the 300 method (300 divided by the number of large boxes between consecutive R waves)
- Evaluating the rhythm by examining if P waves and QRS complexes occur regularly
- Assessing the P waves for their presence, morphology, and relationship to QRS complexes
- Measuring the PR interval (normal: 120-200 ms), QRS duration (normal: <120 ms), and QT interval (normal: <450 ms for men, <460 ms for women)
- Calculating the heart's axis by examining leads I and aVF
- Looking for any ST segment elevation or depression that might indicate ischemia or infarction
- Examining T wave morphology for inversions or hyperacute changes
- Checking for pathological Q waves (>1 mm wide and >1/3 the height of the QRS)
- Identifying any additional abnormalities such as bundle branch blocks, hypertrophy patterns, or signs of electrolyte disturbances
Clinical Correlation and Context
It is crucial to remember that EKG findings must always be interpreted in the context of the patient's presentation, including symptoms and clinical signs, such as ventilation, oxygenation, heart rate, blood pressure, level of consciousness, and signs of inadequate organ perfusion 1. This comprehensive approach ensures that critical findings are not missed and that patient management decisions are informed by a thorough understanding of the patient's condition.
Limitations of Computer Interpretation
While computer analyses of EKGs can be useful adjuncts to EKG interpretation, they should not replace a qualified physician in making patient management decisions, as errors in computer interpretation are still common 1. Therefore, it is essential to combine the systematic step-by-step approach to EKG interpretation with clinical correlation and expertise in EKG interpretation to provide the best possible patient care.
From the Research
Interpreting an Electrocardiogram (EKG)
To interpret an EKG, one must understand the different components of the cardiac rhythm. The following steps can be taken:
- Evaluate the main components of cardiac rhythm, using a simple five-step method 2
- Assess the risk of major cardiovascular events or sudden cardiac death when the cause of syncope remains uncertain after initial evaluation 3
- Identify patients with high likelihood of cardiac syncope due to arrhythmic or cardiopulmonary disorder using ECG diagnostic criteria and findings suggestive of cardiac syncope 3
- Use a 12-lead electrocardiogram (ECG) as the only instrumental test recommended for the initial evaluation of patients with suspected syncope 3
ECG Findings and Diagnostic Criteria
ECG findings can disclose an arrhythmia associated with a high likelihood of syncope, avoiding further evaluations and permitting institution of specific treatment in some patients 3. The ECG may show:
- Arrhythmias, which are the most common cardiac causes of syncope 3
- Global ischemia, which is a marker of an adverse outcome in patients with non-ST elevation acute coronary syndromes 4
- ST depression with inverted T waves and lead aVR ST elevation, which is indicative of left main stenosis 4
Clinical Implications of ECG Monitoring
ECG monitoring can have significant clinical implications, including:
- Identifying patients with high likelihood of cardiac syncope due to arrhythmic or cardiopulmonary disorder 3
- Guiding diagnosis, prognosis, and treatment in emergency departments 2
- Allowing for high-quality ECG monitoring with high usability during intensive exercise in athletes 5
- Predicting an unfavorable outcome in patients with acute coronary syndromes 4