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Failure to recognize a His bundle potential in complete atrioventricular block
European Journal of Cardiology
|July 1, 1979
Summary
Electrophysiological studies in complete heart block reveal competing pacemakers. This explains why His potentials are sometimes absent in patients with this cardiac condition.
Area of Science:
- Cardiology
- Electrophysiology
- Cardiac Electrophysiology
Background:
- Complete heart block (CHB) presents diagnostic challenges in electrophysiological studies.
- Understanding the origin of escape rhythms is crucial for diagnosing CHB.
- Identifying the precise location of block and pacemaker origin is key.
Observation:
- Electrophysiological studies in a CHB patient showed variable escape rhythms.
- Narrow QRS escape rhythms were preceded by His potentials with normal HV intervals.
- Wide QRS escape rhythms (left bundle branch block morphology) lacked His bundle activity.
- Intermediate QRS complexes showed His potentials with HV intervals inversely proportional to QRS width.
Findings:
- The observed phenomena are explained by a block proximal to the His bundle.
- Two competing pacemaker foci with similar rates were identified: one junctional, one distal (right bundle branch/ventricle).
- This dual pacemaker competition explains the variable QRS morphology and His potential recording.
Implications:
- A proximal block site combined with a distal dominant pacemaker may commonly cause His potential non-recording in CHB.
- This finding refines the understanding of CHB pathophysiology.
- It aids in interpreting complex electrophysiological recordings in heart block patients.