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Related Concept Videos

Regulation of Heart Rates01:31

Regulation of Heart Rates

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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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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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Anatomy of the Heart01:27

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The human heart is made up of three layers of tissue that are surrounded by the pericardium, a membrane that protects and confines the heart. The outermost layer, closest to the pericardium, is the epicardium. The pericardial cavity separates the pericardium from the epicardium. Beneath the epicardium is the myocardium, the middle layer, and the endocardium, the innermost layer. There are four chambers of the heart: the right atrium, the right ventricle, the left atrium, and the left ventricle.
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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.
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Variability: Analysis01:11

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Measures of variability are statistical metrics that reveal the dispersion pattern within a dataset. They are pivotal in biostatistics, providing insights into the heterogeneity within health and biological data. Variability signifies the degree to which data points diverge from one another, helping researchers understand the potential range of values and associated uncertainty within the data.
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A random variable is a single numerical value that indicates the outcome of a procedure. The concept of random variables is fundamental to the probability theory and was introduced by a Russian mathematician, Pafnuty Chebyshev, in the mid-nineteenth century.
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Related Experiment Video

Updated: Jan 27, 2026

Microelectrode Array Recording of Sinoatrial Node Firing Rate to Identify Intrinsic Cardiac Pacemaking Defects in Mice
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Sinus node dysfunction in patients with Fontan circulation: could heart rate variability be a predictor for pacemaker

Jenny Alenius Dahlqvist1, Urban Wiklund2, Marcus Karlsson2

  • 1Department of Clinical Sciences, Pediatrics, Umeå University, 901 85, Umeå, Sweden. jenny.alenius@umu.se.

Pediatric Cardiology
|March 29, 2019
PubMed
Summary

Heart rate variability (HRV) is higher in Fontan patients with sinus node dysfunction (SND). Severe SND requiring pacemakers may show reduced diurnal HRV, suggesting HRV analysis can aid Fontan patient follow-up.

Keywords:
Congenital heart diseaseFontan circulationHeart rate variabilityPacemakerPoincaré analysisSinus node dysfunction

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Area of Science:

  • Cardiology
  • Pediatric Cardiology
  • Autonomic Nervous System Function

Background:

  • Sinus node dysfunction (SND) is a significant cause of morbidity in patients following Fontan surgery.
  • Heart rate variability (HRV) quantifies autonomic regulation of the heart and is linked to SND in adults.
  • Understanding HRV changes in Fontan patients with SND is crucial for monitoring and management.

Purpose of the Study:

  • To investigate if 24-hour electrocardiographic (ECG) recordings can detect changes in HRV in Fontan patients with SND.
  • To compare HRV parameters between Fontan patients with and without SND, and with healthy controls.

Main Methods:

  • Compared HRV from 24-h ECG recordings in four groups: Fontan patients with SND requiring pacemakers (n=12), Fontan patients with SND without pacemaker indication (n=11), Fontan patients without SND (n=90), and healthy controls (n=66).
  • Analyzed HRV using the Poincaré plot index SD2 and the very low-frequency (VLF) component.

Main Results:

  • Both SND groups exhibited significantly higher SD2 and VLF HRV components compared to healthy controls and Fontan patients without SND.
  • Fontan patients with SND requiring pacemakers showed a trend towards reduced SD2 and VLF compared to those with SND but no pacemaker (p=0.06).
  • These findings suggest altered autonomic regulation in Fontan patients with SND.

Conclusions:

  • Fontan patients with SND demonstrate significantly altered HRV compared to controls.
  • A trend of reduced diurnal HRV in severe SND requiring pacemakers may indicate further autonomic compromise.
  • HRV analysis shows potential as a valuable tool for monitoring the development of SND in Fontan patients.