ECG Interpretation Differential Diagnosis

To approach the interpretation of an ECG strip, it's crucial to consider various potential diagnoses based on the information that can be derived from the ECG tracing. The following differential diagnosis is organized into categories to help prioritize and not miss critical conditions.

• Single Most Likely Diagnosis

  • Normal Sinus Rhythm: This is often the most common finding on an ECG and represents a normal heart rhythm with a rate between 60-100 beats per minute, a PR interval between 120-200 milliseconds, and a QRS duration of less than 120 milliseconds. Justification: The majority of the population has a normal sinus rhythm, making it the most likely diagnosis in the absence of specific symptoms or ECG abnormalities.

• Other Likely Diagnoses

  • Sinus Tachycardia: Characterized by a heart rate greater than 100 beats per minute with an otherwise normal ECG. Justification: Common in individuals experiencing stress, anxiety, fever, or dehydration.
  • Sinus Bradycardia: Defined by a heart rate less than 60 beats per minute. Justification: Often seen in athletes or individuals with high vagal tone.
  • Atrial Fibrillation: Identified by an irregularly irregular rhythm with no discernible P waves. Justification: Common in older adults, especially those with hypertension, heart failure, or valvular heart disease.

• Do Not Miss Diagnoses

  • ST-Elevation Myocardial Infarction (STEMI): Characterized by ST-segment elevation in two or more contiguous leads, indicating acute myocardial infarction. Justification: Requires immediate medical attention to prevent significant morbidity and mortality.
  • Ventricular Tachycardia: A wide-complex tachycardia that can be life-threatening. Justification: Needs prompt recognition and treatment to prevent cardiac arrest.
  • Wolff-Parkinson-White (WPW) Syndrome: Identified by a short PR interval and the presence of a delta wave. Justification: Can lead to life-threatening tachyarrhythmias if not recognized and managed appropriately.

• Rare Diagnoses

  • Brugada Syndrome: Characterized by a specific pattern of ST-segment elevation in leads V1-V3. Justification: Associated with an increased risk of sudden cardiac death.
  • Long QT Syndrome: Identified by a prolonged QT interval. Justification: Can lead to torsades de pointes, a potentially fatal arrhythmia.
  • Arrhythmogenic Right Ventricular Cardiomyopathy (ARVC): May show epsilon waves in leads V1-V3 and T-wave inversion in the right precordial leads. Justification: A rare cause of sudden cardiac death, particularly in young athletes.

Each of these diagnoses requires careful consideration of the ECG tracing, clinical context, and patient symptoms to ensure accurate interpretation and appropriate management.