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Related Concept Videos

Decreased pulse rate01:14

Decreased pulse rate

950
Bradycardia is a medical condition in which the heart rate is slower than normal. It occurs when the heart's natural pacemaker, the sinus node, generates slower electrical impulses than the standard rhythm. In adults, bradycardia is diagnosed when the pulse rate falls below 60 beats per minute, indicating a deviation from the normal heart rate range.
There are specific risk factors that can elevate the likelihood of developing bradycardia. Advanced age is a significant factor, with...
950
Dysrhythmias IV: Characteristics of Bradyarrhythmias01:18

Dysrhythmias IV: Characteristics of Bradyarrhythmias

626
Bradyarrhythmias are cardiac rhythm disorders characterized by a slower-than-normal heart rate, typically defined as fewer than 60 beats per minute. Some of which are discussed here:Sinus BradycardiaSinus bradycardia presents a heart rate lower than 60 beats per minute, with a regular rhythm originating from the SA node. The ECG typically shows normal P waves preceding each QRS complex, a normal PR interval (0.12 to 0.20 seconds), and a normal QRS duration (0.06 to 0.10 seconds).First-Degree AV...
626
Dysrhythmias III: Characteristics of Dysrhythmias01:29

Dysrhythmias III: Characteristics of Dysrhythmias

542
Dysrhythmias, also known as arrhythmias, are irregular heart rhythms that result from abnormal electrical activity in the heart, affecting its ability to circulate blood efficiently. Tachyarrhythmias, a subset of dysrhythmias, are characterized by abnormally fast heart rates exceeding 100 beats per minute. Here are some types of tachyarrhythmias with their distinct ECG features:Sinus Tachycardia:Sinus tachycardia presents a regular heart rhythm with an increased rate of 101-180 beats per...
542
Disturbances in Heart Rhythm01:29

Disturbances in Heart Rhythm

3.3K
Arrhythmia or dysrhythmia refers to an abnormal heart rhythm caused by a defect in the heart's conduction system. It can cause the heart to beat irregularly, too quickly, or too slowly, leading to symptoms like chest pain, shortness of breath, and fainting. Factors such as stress, caffeine, alcohol, nicotine, cocaine, certain drugs, congenital defects, diseases, and electrolyte abnormalities can trigger arrhythmias.
Arrhythmias are categorized by their speed, rhythm, and origin. A slow heart...
3.3K
ECG Interpretation of Arrhythmias I: Sinus Arrhythmias01:16

ECG Interpretation of Arrhythmias I: Sinus Arrhythmias

881
Arrhythmias are disturbances in the heart's rhythm that lead to abnormal heartbeats. These irregularities can originate from different parts of the heart and are classified based on their origin and nature.
Types of Arrhythmias
Sinus Node Arrhythmias
Sinus Bradycardia: Originating from the sinoatrial (SA) node, sinus bradycardia involves slower impulses, resulting in a heart rate of less than 60 beats per minute (bpm). Causes include sleep, vagal stimulation, beta-blockers, hypothyroidism,...
881
Dysrhythmias II: Classification of Tachyarrhythmias01:28

Dysrhythmias II: Classification of Tachyarrhythmias

664
Tachyarrhythmias are a type of dysrhythmia where the heart rate exceeds 100 beats per minute. Here are some common types of tachyarrhythmias:Sinus TachycardiaSinus tachycardia originates from increased impulses from the sinus node, leading to an elevated heart rate. It is often triggered by stress, fever, or exercise.Patients may experience palpitations, a sensation of a racing heart, dizziness, and chest discomfort.Causes and Risk Factors: Common causes include physical exertion, emotional...
664

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Updated: Feb 21, 2026

Microelectrode Array Recording of Sinoatrial Node Firing Rate to Identify Intrinsic Cardiac Pacemaking Defects in Mice
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Relative Bradycardia in Scrub Typhus.

Lae Young Jung1,2, Mir Jeon2, Seung Hee Choi3

  • 1Biomedical Research Institute of Chonbuk National University Hospital, Jeonju, Republic of Korea.

The American Journal of Tropical Medicine and Hygiene
|October 11, 2017
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Summary

Most febrile patients with scrub typhus exhibit relative bradycardia (RB), a slower heart rate increase relative to temperature rise. This finding aids in differentiating scrub typhus from other infections.

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Area of Science:

  • Infectious Diseases
  • Cardiology
  • Internal Medicine

Background:

  • Fever commonly causes an increased heart rate.
  • The relationship between temperature and heart rate in scrub typhus is not well-defined.
  • Relative bradycardia (RB) is a less common heart rate response to fever.

Purpose of the Study:

  • To investigate the relationship between heart rate and temperature in febrile patients.
  • To determine the prevalence of relative bradycardia (RB) in scrub typhus.
  • To assess the clinical significance of heart rate response patterns in scrub typhus.

Main Methods:

  • Retrospective analysis of 493 febrile patients with documented scrub typhus.
  • Serological diagnosis and classification based on heart rate response to fever (<10 beats/minute/°C for RB, ≥10 beats/minute/°C for general heart rate increase [GHRI]).
  • Comparison of clinical outcomes including acute kidney injury, systemic inflammatory response syndrome (SIRS), and death between RB and GHRI groups.

Main Results:

  • 68.4% of patients (337/493) presented with relative bradycardia (RB).
  • The RB group had a higher median resting heart rate and lower heart rate at maximum temperature compared to the GHRI group.
  • No significant differences in clinical outcomes (acute kidney injury, SIRS, death) were observed between the RB and GHRI groups.

Conclusions:

  • Relative bradycardia (RB) is a common clinical feature in scrub typhus infections.
  • RB can be a useful diagnostic indicator for differentiating scrub typhus from other infectious diseases.
  • Heart rate response patterns do not appear to significantly impact clinical outcomes in scrub typhus.