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Nodal and infranodal atrioventricular conduction block: electrophysiological basis to correlate the ECG findings

Bharat K Kantharia1, Arti N Shah

  • 1Professor of Medicine, The University of Texas-Health Science Center at Houston, 6431 Fannin Street, Suite MSB 1.246, Houston, TX 77030, USA; Director, Clinical Cardiac Electrophysiology Fellowship Training Program, 6431 Fannin Street, Suite MSB 1.246, Houston, TX 77030, USA; Director, Cardiac Electrophysiology Laboratories-Memorial Hermann Hospital, 6431 Fannin Street, Suite MSB 1.246, Houston, TX 77030, USA.

Indian Heart Journal
|May 8, 2013
PubMed

Insights

Syncope in a patient with cardiomyopathy was linked to intermittent infra-Hisian block. Electrophysiology revealed alternating conduction patterns and His-Purkinje system abnormalities.

Area of Science:

  • Cardiology
  • Electrophysiology
  • Cardiac Electrophysiology

Background:

  • Dilated non-ischemic cardiomyopathy can present with syncope.
  • Left bundle branch block (LBBB) is a common ECG finding in cardiac disease.

Observation:

  • Telemetry revealed intermittent 2:1 block in sinus rhythm with narrower QRS complexes.
  • Electrophysiological study showed normal atrioventricular nodal conduction (AH interval 79 ms).
  • Alternating sinus beats were blocked infra-Hisian (after His deflection), with normal HV intervals (54 ms) during narrow beats.

Findings:

  • Infra-Hisian block was identified as the cause of syncope.
  • When 1:1 conduction resumed, His-Purkinje system abnormalities manifested as LBBB morphology and prolonged HV intervals (96 ms).

Implications:

  • This case highlights the importance of invasive electrophysiological studies in diagnosing syncope.
  • Understanding infra-Hisian block and His-Purkinje system conduction is crucial for managing cardiac arrhythmias.
  • The study discusses criteria to differentiate nodal from infranodal block based on electrophysiological properties.

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