Tachycardia

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Tachydysrhythmias
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Tachycardia
Other namesTachyarrhythmia
ECG showing sinus tachycardia with a rate of about 100 beats per minute
Pronunciation
SpecialtyCardiology
Differential diagnosis

Tachycardia, also called tachyarrhythmia, is a heart rate that exceeds the normal resting rate.[1] In general, a resting heart rate over 100 beats per minute is accepted as tachycardia in adults.[1] Heart rates above the resting rate may be normal (such as with exercise) or abnormal (such as with electrical problems within the heart).

Complications

Tachycardia can lead to

fainting.[2]

When the rate of blood flow becomes too rapid, or fast blood flow passes on damaged endothelium, it increases the friction within vessels resulting in turbulence and other disturbances.[3] According to the Virchow's triad, this is one of the three conditions that can lead to thrombosis (i.e., blood clots within vessels).[4]

Causes

Some causes of tachycardia include:[5]

Drug related:

Diagnosis

The upper threshold of a normal human resting heart rate is based on age. Cutoff values for tachycardia in different age groups are fairly well standardized; typical cutoffs are listed below:[7][8]

  • 1–2 days: Tachycardia >159 beats per minute (bpm)
  • 3–6 days: Tachycardia >166 bpm
  • 1–3 weeks: Tachycardia >182 bpm
  • 1–2 months: Tachycardia >179 bpm
  • 3–5 months: Tachycardia >186 bpm
  • 6–11 months: Tachycardia >169 bpm
  • 1–2 years: Tachycardia >151 bpm
  • 3–4 years: Tachycardia >137 bpm
  • 5–7 years: Tachycardia >133 bpm
  • 8–11 years: Tachycardia >130 bpm
  • 12–15 years: Tachycardia >119 bpm
  • >15 years – adult: Tachycardia >100 bpm

Heart rate is considered in the context of the prevailing clinical picture. When the heart beats excessively or rapidly, the heart pumps less efficiently and provides less blood flow to the rest of the body, including the heart itself. The increased heart rate also leads to increased work and oxygen demand by the heart, which can lead to rate related ischemia.[9]

Differential diagnosis

electrocardiogram showing a ventricular tachycardia
(VT)

An

electrocardiogram (ECG) is used to classify the type of tachycardia. They may be classified into narrow and wide complex based on the QRS complex.[10] Equal or less than 0.1s for narrow complex.[11] Presented in order of most to least common, they are:[10]

Tachycardias may be classified as either narrow complex tachycardias (supraventricular tachycardias) or wide complex tachycardias. Narrow and wide refer to the width of the

ECG. Narrow complex tachycardias tend to originate in the atria, while wide complex tachycardias tend to originate in the ventricles. Tachycardias can be further classified as either regular or irregular.[citation needed
]

Sinus

Main article: Sinus tachycardia

The body has several

metabolic demands.[citation needed
]

Upon exertion, sinus tachycardia can also be seen in some inborn errors of metabolism that result in metabolic myopathies, such as McArdle's disease (GSD-V).[12][13] Metabolic myopathies interfere with the muscle's ability to create energy. This energy shortage in muscle cells causes an inappropriate rapid heart rate in response to exercise. The heart tries to compensate for the energy shortage by increasing heart rate to maximize delivery of oxygen and other blood borne fuels to the muscle cells.[12]

"In McArdle's, our heart rate tends to increase in what is called an 'inappropriate' response. That is, after the start of exercise it increases much more quickly than would be expected in someone unaffected by McArdle's."[14] As skeletal muscle relies predominantly on glycogenolysis for the first few minutes as it transitions from rest to activity, as well as throughout high-intensity aerobic activity and all anaerobic activity, individuals with GSD-V experience during exercise: sinus tachycardia, tachypnea, muscle fatigue and pain, during the aforementioned activities and time frames.[12][13] Those with GSD-V also experience "second wind", after approximately 6–10 minutes of light-moderate aerobic activity, such as walking without an incline, where the heart rate drops and symptoms of exercise intolerance improve.[12][13][14]

An increase in

endocrine disorders such as pheochromocytoma can also cause epinephrine release and can result in tachycardia independent of nervous system stimulation. Hyperthyroidism can also cause tachycardia.[15] The upper limit of normal rate for sinus tachycardia is thought to be 220 bpm minus age.[citation needed
]

Inappropriate sinus tachycardia
Main article: Inappropriate sinus tachycardia

Inappropriate sinus tachycardia (IST) is a diagnosis of exclusion,[16] a rare but benign type of cardiac arrhythmia that may be caused by a structural abnormality in the sinus node. It can occur in seemingly healthy individuals with no history of cardiovascular disease. Other causes may include autonomic nervous system deficits, autoimmune response, or drug interactions. Although symptoms might be distressing, treatment is not generally needed.[17]

Ventricular

Main article: Ventricular tachycardia

Ventricular tachycardia (VT or V-tach) is a potentially life-threatening cardiac arrhythmia that originates in the ventricles. It is usually a regular, wide complex tachycardia with a rate between 120 and 250 beats per minute. A medically significant subvariant of ventricular tachycardia is called torsades de pointes (literally meaning "twisting of the points", due to its appearance on an EKG), which tends to result from a long QT interval.[18]

Both of these rhythms normally last for only a few seconds to minutes (paroxysmal tachycardia), but if VT persists it is extremely dangerous, often leading to ventricular fibrillation.[19][20]

Supraventricular

Main article: Supraventricular tachycardia

This is a type of tachycardia that originates from above the ventricles, such as the atria. It is sometimes known as paroxysmal atrial tachycardia (PAT). Several types of supraventricular tachycardia are known to exist.[21]

Atrial fibrillation

accessory pathway is present). However, new-onset atrial fibrillation tends to present with rates between 100 and 150 beats per minute.[22]

AV nodal reentrant tachycardia

AV nodal reentrant tachycardia (AVNRT) is the most common reentrant tachycardia. It is a regular narrow complex tachycardia that usually responds well to the Valsalva maneuver or the drug adenosine. However, unstable patients sometimes require synchronized cardioversion. Definitive care may include catheter ablation.[23]

AV reentrant tachycardia

contraindicated in the emergency treatment of AVRT, because they may paradoxically increase conduction across the accessory pathway. [citation needed
]

Junctional tachycardia

Junctional tachycardia is an automatic tachycardia originating in the AV junction. It tends to be a regular, narrow complex tachycardia and may be a sign of digitalis toxicity.[24]

Management

The management of tachycardia depends on its type (wide complex versus narrow complex), whether or not the person is stable or unstable, and whether the instability is due to the tachycardia.[10] Unstable means that either important organ functions are affected or cardiac arrest is about to occur.[10]

Unstable

In those that are unstable with a narrow complex tachycardia, intravenous adenosine may be attempted.[10] In all others immediate cardioversion is recommended.[10]

Terminology

The word tachycardia came to English from

usage, not only because much of the existing medical literature ignores it even when the words stand alone but also because the terms for specific types of arrhythmia (standard collocations of adjectives and noun) are deeply established idiomatically with the tachycardia version as the more commonly used version. Thus SVT is called supraventricular tachycardia more than twice as often as it is called supraventricular tachyarrhythmia; moreover, those two terms are always completely synonymous—in natural language there is no such term as "healthy/physiologic supraventricular tachycardia". The same themes are also true of AVRT and AVNRT. Thus this pair is an example of when a particular prescription (which may have been tenable 50 or 100 years earlier) can no longer be invariably enforced without violating idiom. But the power to differentiate in an idiomatic way is not lost, regardless, because when the specification of physiologic tachycardia is needed, that phrase aptly conveys it.[citation needed
]

See also

References

  1. ^
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    .
  2. ^ Thompson EG, Pai RK, eds. (2 June 2011). "Passing Out (Syncope) Caused by Arrhythmias". CardioSmart. American College of Cardiology. Archived from the original on 2020-06-13. Retrieved 2020-04-13.
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  5. ^ "Supraventricular Tachycardias". The Lecturio Medical Concept Library. 9 September 2020. Retrieved 2 July 2021.
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  8. ^ Kantharia BK, Sharma M, Shah AN (17 October 2021). "Atrial Tachycardia: Practice Essentials, Background, Anatomy". MedScape. WebMD LLC.
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  14. ^ a b Wakelin A (2017). Living With McArdle Disease (PDF). International Assoc. of Muscle Glycogen Diseases (IAMGSD). p. 15.
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  16. PMID 35710196
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  17. S2CID 23249973
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  18. ^ Mitchell LB (January 2023). "Torsades de Pointes Ventricular Tachycardia". Merck Manual Profesional Edition. Retrieved 19 April 2019.
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  20. S2CID 207215117
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  21. ^ "Types of Arrhythmia". National Heart, Lung, and Blood Institute (NHLBI). U.S. National Institutes of Health. July 1, 2011. Archived from the original on June 7, 2015.
  22. ^ Oiseth S, Jones L, Maza E (11 August 2020). "Atrial Fibrillation". The Lecturio Medical Concept Library. Retrieved 3 July 2021.
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  25. ^ Elsevier, Dorland's Illustrated Medical Dictionary, Elsevier.
  26. ^ Merriam-Webster, Merriam-Webster's Medical Dictionary, Merriam-Webster.
  27. ^ a b Wolters Kluwer, Stedman's Medical Dictionary, Wolters Kluwer.
  28. ^ Houghton Mifflin Harcourt, The American Heritage Dictionary of the English Language, Houghton Mifflin Harcourt.
  29. ^ Merriam-Webster, Merriam-Webster's Collegiate Dictionary, Merriam-Webster, archived from the original on 2020-10-10, retrieved 2017-07-22.
  30. ^ Merriam-Webster, Merriam-Webster's Unabridged Dictionary, Merriam-Webster, archived from the original on 2020-05-25, retrieved 2017-07-22.

External links

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