Related Experiment Video

Updated: Aug 5, 2026

Behavioral Determination of Stimulus Pair Discrimination of Auditory Acoustic and Electrical Stimuli Using a Classical Conditioning and Heart-rate Approach
10:50

Behavioral Determination of Stimulus Pair Discrimination of Auditory Acoustic and Electrical Stimuli Using a Classical Conditioning and Heart-rate Approach

Published on: June 6, 2012

An Abrupt Doubling of Heart Rate

Mazen M Kawji1

  • 1Cardiovascular Institute, Order of Saint Francis, Ottawa, Illinois, USA.

JACC. Case Reports
|July 30, 2026
PubMed

Insights

Sinoatrial exit block, a type of sick sinus syndrome, can manifest in varying degrees. A rare case highlights that a doubling or halving of heart rate may suggest 2:1 sinoatrial block and sinus node dysfunction.

Area of Science:

  • Cardiology
  • Electrophysiology
  • Internal Medicine

Background:

  • Sinoatrial (SA) exit block is a manifestation of sick sinus syndrome, where the sinus node impulse fails to depolarize the atria or causes delayed depolarization.
  • SA exit block presents with varying severity, including first-, second-, and third-degree types.

Purpose of the Study:

  • To present a rare case of sinoatrial block.
  • To discuss the diagnostic implications of this rare condition in a patient with complex comorbidities.

Main Methods:

  • Case report detailing a patient with atrial fibrillation and other cardiac and medical comorbidities.
  • Clinical assessment of cardiac conduction abnormalities, specifically focusing on SA conduction and atrioventricular (AV) conduction.

Main Results:

  • The patient presented with atrial fibrillation and other comorbidities, complicating management.
  • While other conduction abnormalities were present, no evidence of atrioventricular disease was found.

Conclusions:

  • A doubling or halving of the heart rate should raise suspicion for 2:1 sinoatrial block.
  • This pattern indicates underlying sinus node dysfunction and SA exit block.
Abstract

Keywords:
atrial fibrillationbradycardiaelectrocardiogram

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