What is the approach to interpreting an EKG (electrocardiogram) in a patient with suspected cardiac ischemia or arrhythmia?

From the Guidelines

Interpreting an EKG in patients with suspected cardiac ischemia or arrhythmia requires a systematic approach that evaluates all components of the tracing, with a focus on ST-segment changes, T-wave inversions, and the presence of Q waves, as outlined in the 2012 guidelines for the third universal definition of myocardial infarction 1. When approaching EKG interpretation, it is essential to begin with a standardized method examining rate, rhythm, axis, intervals, and waveform morphology.

• For suspected ischemia, key features to focus on include:
  • ST-segment elevation of ≥1 mm in two contiguous leads, which suggests myocardial infarction
  • ST depression or T-wave inversions, which may indicate ischemia
• When evaluating arrhythmias, it is crucial to:
  • Determine if the rhythm is regular or irregular
  • Identify P waves and their relationship to QRS complexes
  • Measure PR intervals
  • Assess QRS width
  • Distinguish between narrow complex (usually supraventricular) and wide complex (ventricular or aberrantly conducted) rhythms for tachyarrhythmias (>100 bpm)
  • Look for heart rates below 60 bpm and determine if it's sinus bradycardia, heart block, or another mechanism for bradyarrhythmias Always compare with previous EKGs when available, as this helps identify acute versus chronic changes, and consider the clinical context, including symptoms, vital signs, and patient history, which significantly influence EKG interpretation and subsequent management decisions, as emphasized in guidelines such as those from the American College of Cardiology/American Heart Association 1. The use of serial ECGs, as mentioned in the 1992 guidelines for electrocardiography 1, is important for assessing the severity and progression of the underlying cardiovascular disease or dysfunction, and for evaluating response to therapy. Furthermore, the 2006 ACC/AHA/ESC guidelines for management of patients with ventricular arrhythmias and the prevention of sudden cardiac death highlight the importance of considering structural heart disease and the role of echocardiography in patients with ventricular arrhythmias 1. However, the most recent and highest quality study, the 2012 guidelines for the third universal definition of myocardial infarction 1, should guide the approach to EKG interpretation in clinical practice, prioritizing the detection of myocardial infarction and ischemia, and emphasizing the importance of prompt and serial ECG acquisition and interpretation in patients with suspected cardiac ischemia or arrhythmia.

From the Research

Approach to EKG Interpretation

When interpreting an EKG in a patient with suspected cardiac ischemia or arrhythmia, several key factors must be considered:

• The patient's clinical presentation and medical history
• The EKG findings, including any abnormalities in the QRS complexes, ST segments, and T waves
• Comparison to previous EKGs, if available
• The need for prompt recognition and treatment of life-threatening conditions, such as acute coronary syndromes

EKG Findings in Cardiac Ischemia

In patients with suspected cardiac ischemia, the EKG may show:

• ST segment elevation, indicating transmural ischemia and potential acute coronary occlusion 2
• ST segment depression, indicating subendocardial ischemia or non-ischemic causes such as left ventricular hypertrophy
• T wave abnormalities, such as inversion or flattening, which can indicate ischemia or other conditions

EKG Interpretation in Arrhythmias

In patients with suspected arrhythmias, the EKG may show:

• Abnormalities in the cardiac rhythm, such as atrial fibrillation or ventricular tachycardia
• The presence of antiarrhythmic medications, such as amiodarone, which can affect the EKG interpretation 3
• The need for prompt recognition and treatment of life-threatening arrhythmias

Importance of Clinician Competency

Clinician competency in EKG interpretation is crucial for accurate diagnosis and treatment of cardiac conditions:

• Nurses' competency in EKG interpretation varies, and regular training and education are recommended to improve skills and confidence 4
• A standardized and comprehensive EKG interpretation tool is needed to assess clinician competency and ensure accurate diagnosis and treatment

Additional Diagnostic Tools

Additional diagnostic tools, such as stress echocardiography, may be used to evaluate patients with suspected cardiac conditions:

• Stress echocardiography can provide valuable information on cardiac function and perfusion, and can be used to guide diagnosis and treatment 5
• The ABCDE protocol, which includes assessment of regional wall motion abnormality, regional perfusion, diastolic function, and other factors, can provide a comprehensive evaluation of cardiac function 5