Differential Diagnosis for SVT vs Atrial Flutter after Adenosine Administration

After administering adenosine, the primary goal is to determine whether the supraventricular tachycardia (SVT) has converted to a normal sinus rhythm, persisted, or if atrial flutter is present. Here's a differential diagnosis based on the provided categories:

• Single Most Likely Diagnosis
  • Atrial Flutter: Adenosine can help unmask atrial flutter by transiently blocking AV nodal conduction, making it easier to diagnose the typical sawtooth pattern of atrial flutter on the ECG. If the patient's heart rate slows down after adenosine administration but the rhythm doesn't fully convert to sinus rhythm, atrial flutter is a strong consideration.
• Other Likely Diagnoses
  • SVT with AV Nodal Block: Adenosine can cause a temporary block in the AV node, which may slow down or terminate SVT. If the SVT recurs shortly after adenosine administration, it suggests the SVT is not atrial flutter.
  • Sinus Tachycardia: If adenosine administration leads to a brief pause followed by a return to a rapid heart rate but with a normal P-wave axis, sinus tachycardia should be considered, especially if there are underlying conditions that could cause it, such as anxiety, fever, or dehydration.
• Do Not Miss Diagnoses
  • Wolff-Parkinson-White (WPW) Syndrome: Although less common, WPW syndrome can mimic SVT and may not respond typically to adenosine. It's crucial to identify this condition due to its potential for rapid ventricular response and the risk of degenerating into atrial fibrillation.
  • Atrial Fibrillation: Adenosine can sometimes unmask atrial fibrillation, especially if the ventricular response is rapid and irregular. Missing this diagnosis could lead to inappropriate treatment and increased risk of thromboembolic events.
• Rare Diagnoses
  • Junctional Tachycardia: This is a rare form of SVT originating from the AV junction. It might not respond to adenosine in the typical manner and requires careful ECG analysis for diagnosis.
  • Multifocal Atrial Tachycardia: Characterized by an irregular atrial rhythm with multiple P-wave morphologies, this condition is less common and might be uncovered after adenosine administration, especially in patients with severe pulmonary disease.

Each of these diagnoses requires careful consideration of the patient's clinical presentation, ECG findings before and after adenosine administration, and response to the treatment. The key to differentiating among them lies in a thorough understanding of their ECG characteristics and clinical contexts.