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Related Concept Videos

Factors Influencing Heart Rate01:30

Factors Influencing Heart Rate

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The heart rate, or pulse rate, is a vital indicator of cardiovascular health. It reflects the number of times the heart beats per minute. Various physiological and environmental factors influence heart rate, increasing or decreasing cardiac output. Understanding these factors is crucial for assessing heart function and identifying potential health issues.
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Cardiac Output I:Effect of Heart Rate on Cardiac Output01:19

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Cardiac Output
Cardiac output (CO) refers to the total amount of blood ejected by one of the ventricles in liters per minute (L/min). In a resting adult, CO ranges from 5 to 6 L/min, adjusting according to the body's metabolic requirements.
Effect of Heart Rate on Cardiac Output
Cardiac output adapts to metabolic demands during stress, physical activity, or illness. The autonomic nervous system regulates heart rate via the sinoatrial node. The parasympathetic nervous system decreases heart...
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Regulation of Heart Rates01:31

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The regulation of heart rate is a complex process controlled by the autonomic nervous system (ANS), hormonal influences, and intrinsic cardiac mechanisms. The ANS has two main components: the sympathetic nervous system (SNS) and the parasympathetic nervous system (PNS).
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Disturbances in Heart Rhythm01:29

Disturbances in Heart Rhythm

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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...
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Dysrhythmias IV: Characteristics of Bradyarrhythmias01:18

Dysrhythmias IV: Characteristics of Bradyarrhythmias

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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...
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Dysrhythmias III: Characteristics of Dysrhythmias01:29

Dysrhythmias III: Characteristics of Dysrhythmias

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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...
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Related Experiment Video

Updated: Nov 25, 2025

Calculating Heart Rate Variability from ECG Data from Youth with Cerebral Palsy During Active Video Game Sessions
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Heart Rate Influence on the QT Variability Risk Factors.

Irena Andršová1, Katerina Hnatkova2, Martina Šišáková1

  • 1Department of Internal Medicine and Cardiology, University Hospital Brno, Faculty of Medicine, Masaryk University, Jihlavská 20, 625 00 Brno, Czech Republic.

Diagnostics (Basel, Switzerland)
|December 19, 2020
PubMed
Summary
This summary is machine-generated.

QT variability index (QTVi) and standard deviation of QT interval durations (SDQT) are influenced by heart rate. SDQT is more reproducible and recommended over QTVi for QT interval variability analysis.

Keywords:
QT variabilityQT variability indexRR variabilitysequential analysis of regression varianceunderlying heart rate

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Area of Science:

  • Cardiology
  • Biomedical Engineering
  • Physiology

Background:

  • QT interval variability is used in risk diagnostics.
  • Physiologic correlates of QT variability, especially in short ECGs, are under-researched.

Purpose of the Study:

  • Investigate QT variability indices (QTVi, SDQT) in short ECGs.
  • Relate these indices to heart rate and RR interval variability (SDRR).

Main Methods:

  • Analysis of 657,287 10-second ECGs from 523 healthy subjects.
  • Calculated QT variability indices (QTVi, SDQT) and SDRR.
  • Statistical analysis of index relationships with heart rate and SDRR.

Main Results:

  • Both QTVi and SDQT are significantly influenced by heart rate (p < 0.00001).
  • QTVi exhibits poor intra-subject reproducibility (CV ~200%).
  • SDQT shows stronger relation to heart rate than SDRR; QTVi is more influenced by heart rate and SDRR than SDQT.

Conclusions:

  • SDQT is a more reliable measure of QT interval variability than QTVi.
  • SDQT is preferable for future applications, particularly when combined with heart rate data.