How do I interpret an electrocardiogram (EKG)?

From the Guidelines

Interpreting an electrocardiogram (EKG) requires a systematic analysis of cardiac electrical activity, starting with checking the rate, rhythm, and axis, and then examining the P waves, PR interval, QRS complex, ST segment, T waves, and QT interval, as outlined in the American Heart Association's recommendations 1. To break down an EKG, follow these steps:

• Check the rate by counting the number of QRS complexes in a 6-second strip and multiplying by 10 for beats per minute.
• Determine the rhythm by assessing whether the intervals between QRS complexes are regular or irregular.
• Examine the axis, which is the direction of electrical flow.
• Look at the P waves, which represent atrial depolarization, and ensure they are present and upright in leads I and II.
• Measure the PR interval, which should be between 0.12-0.20 seconds, and the QRS complex, which should be between 0.06-0.10 seconds.
• Check the ST segment, which should be isoelectric, and the T waves, which should be upright in leads I and II.
• Measure the QT interval, which should be less than half the preceding RR interval. Some key patterns to look for include:
• ST elevation, which may indicate myocardial infarction
• Q waves, which may indicate prior infarction
• T wave inversions, which may indicate ischemia
• Prolonged QT, which may indicate electrolyte abnormalities or medication effects
• Widened QRS, which may indicate bundle branch blocks When interpreting an EKG, it's essential to consider the clinical context and compare with previous EKGs if available, as recommended by the American College of Physicians 1. Regular practice with normal and abnormal EKGs is also crucial for developing proficiency, as pattern recognition is a key skill in accurate interpretation, according to the American Heart Association's guidelines 1. By following these steps and considering the clinical context, you can accurately interpret an EKG and make informed decisions about patient care.

From the Research

Interpreting an Electrocardiogram (EKG)

To interpret an electrocardiogram (EKG), it is essential to follow a systematic approach. Here are the key points to consider:

• A 12-lead EKG graphically displays the heart's electrical activity and is the most common clinical tool for detecting and diagnosing heart disease 2.
• The responsibility for correctly interpreting an EKG lies with the physician, who should be able to recognize patient-dependent errors, operator-dependent errors, and artifact 2.
• Current EKG tracings should always be compared with previous tracings to ensure an accurate interpretation result 2.
• A stepwise approach is recommended to guide the primary care physician's approach to the systematic interpretation of EKG tracings 3.

Key Components of EKG Interpretation

When interpreting an EKG, the following components should be examined:

• The presence, extent, and severity of myocardial ischemia can be determined from the EKG in acute coronary syndromes 4.
• ST-segment elevation on the EKG and symptoms compatible with acute myocardial ischemia/infarction should prompt referral for emergent reperfusion therapy 4.
• Up-sloping ST-segment depression with positive T waves may indicate regional subendocardial ischemia associated with severe obstruction of the left anterior descending coronary artery 4.
• Widespread ST-segment depression, often associated with inverted T waves and ST-segment elevation in lead aVR during episodes of chest pain, may represent diffuse subendocardial ischemia caused by severe coronary artery disease 4.

Education and Training in EKG Interpretation

Education and training in EKG interpretation are crucial for healthcare professionals, including:

• Web-based ECG-interpretation programs can be an effective way to learn and practice ECG interpretation, especially for undergraduate medical students 5.
• Triage nurses can accurately interpret the EKG in the emergency department to identify patients at high risk of acute cardiovascular events, with a sensitivity of 84.6% and a specificity of 43.5% 6.
• Improving the ability of triage nurses to interpret the EKG can have a positive impact on clinical management 6.