Differential Diagnosis for ECG Interpretation

To approach the question of reading an ECG, we must consider various potential diagnoses based on common ECG findings. The differential diagnosis can be categorized as follows:

• Single Most Likely Diagnosis
  • Normal ECG: This is often the most common finding, especially in asymptomatic individuals or those without cardiac history. A normal ECG does not necessarily rule out cardiac disease but indicates no overt abnormalities at the time of the reading.
• Other Likely Diagnoses
  • Atrial Fibrillation: Characterized by an irregularly irregular rhythm, this is a common finding, especially in older adults or those with a history of hypertension, heart failure, or valvular disease.
  • Ventricular Tachycardia: Although less common than atrial fibrillation, VT can be seen in various conditions, including myocardial infarction, cardiomyopathy, or electrolyte imbalances.
  • First-Degree AV Block: This condition, where the PR interval is prolonged, can be seen in healthy individuals but also in those with cardiac conditions or taking certain medications.
• Do Not Miss Diagnoses
  • Acute Myocardial Infarction (MI): ST-elevation or non-ST elevation MI can present with specific ECG changes (ST elevation, Q waves, etc.) and is critical to identify promptly for timely intervention.
  • Wolff-Parkinson-White (WPW) Syndrome: Characterized by a short PR interval and a delta wave, WPW can lead to life-threatening arrhythmias if not recognized and managed appropriately.
  • Long QT Syndrome: This condition, which can lead to Torsades de Pointes, is crucial to identify due to its potential for causing sudden cardiac death.
• Rare Diagnoses
  • Brugada Syndrome: Characterized by specific ST elevation in leads V1-V3, this syndrome can lead to sudden cardiac death and is often diagnosed incidentally on an ECG.
  • Arrhythmogenic Right Ventricular Cardiomyopathy (ARVC): This rare condition can cause ventricular arrhythmias and is diagnosed based on a combination of ECG, imaging, and histological findings.
  • Hyperkalemia: Although not a primary cardiac condition, severe hyperkalemia can cause life-threatening arrhythmias and has distinctive ECG changes (peaked T waves, widened QRS, etc.).

Each of these diagnoses has distinct ECG features and clinical implications, emphasizing the importance of accurate ECG interpretation in clinical practice.