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[Usefulness of adenosine to detect advanced paroxysmal atrioventricular block as a cause of syncope]

Milton E Guevara-Valdivia1, Pedro Iturralde Torres, Alfredo de Micheli

  • 1Departamento de Electrofisiología del Instituto Nacional de Cardiología Ignacio Chávez, INCICH, Juan Badiano No. 1, Col. Sección XVI, Tlalpan, 14080 México, D.F.

Archivos De Cardiologia De Mexico
|November 7, 2002
PubMed

Insights

Adenosine testing can diagnose paroxysmal atrioventricular (AV) block in patients with syncope. This method is effective even when standard electrophysiological studies and other tests are inconclusive, revealing complete AV infra-His block.

Area of Science:

  • Cardiology
  • Electrophysiology

Background:

  • Recurrent syncope in patients can stem from various cardiac causes.
  • Diagnosing intermittent atrioventricular (AV) block poses a significant clinical challenge.

Observation:

  • A 66-year-old male presented with recurrent syncope, exhibiting left anterior fascicle block, right bundle branch block, and first-degree AV block on ECG.
  • Initial investigations including exercise testing, Holter monitoring, tilt testing, and carotid sinus massage were non-diagnostic.
  • Standard electrophysiologic studies failed to reveal abnormalities in the conduction system or induce arrhythmias.

Findings:

  • Intravenous adenosine administration (12 mg) in the patient precipitated complete AV infra-His block.
  • This adenosine-induced block resulted in a significant ventricular asystole of 7.2 seconds.
  • Adenosine testing successfully identified the underlying cause of syncope as paroxysmal AV block.

Implications:

  • Adenosine testing serves as a valuable diagnostic tool for identifying paroxysmal AV block as a cause of syncope.
  • It offers a crucial alternative when conventional electrophysiologic studies and other diagnostic modalities are inconclusive.
  • This approach can improve the diagnostic yield and management of unexplained syncope.

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