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Tachycardia

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Tachycardia
Other namesTachyarrhythmia
ECG showingsinus tachycardiawith a rate of about 100 beats per minute
Pronunciation
SpecialtyCardiology
Differential diagnosis

Tachycardia,also calledtachyarrhythmia,is aheart ratethat exceeds thenormal resting rate.[1]In general, a resting heart rate over 100beatsper minute is accepted as tachycardia in adults.[1]Heart rates above the resting rate may be normal (such as withexercise) or abnormal (such as with electrical problems within the heart).

Complications

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Tachycardia can lead tofainting.[2]

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

Causes

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Some causes of tachycardia include:[5]

Drug related:

Diagnosis

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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 relatedischemia.[9]

Differential diagnosis

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12 leadelectrocardiogramshowing aventricular tachycardia(VT)

Anelectrocardiogram(ECG) is used to classify the type of tachycardia. They may be classified into narrow and wide complex based on theQRS 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 theQRS complexon theECG.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

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Main article:Sinus tachycardia

The body has severalfeedback mechanismsto maintain adequate blood flow andblood pressure.If blood pressure decreases, the heart beats faster in an attempt to raise it. This is calledreflextachycardia. This can happen in response to a decrease in blood volume (throughdehydrationorbleeding), or an unexpected change inblood flow.The most common cause of the latter isorthostatic hypotension(also calledpostural hypotension).Fever,hyperventilation,diarrheaand severeinfectionscan also cause tachycardia, primarily due to increase inmetabolicdemands.[citation needed]

Upon exertion,sinus tachycardiacan also be seen in someinborn errors of metabolismthat result inmetabolic myopathies,such asMcArdle'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 onglycogenolysisfor 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 ofexercise intoleranceimprove.[12][13][14]

An increase insympathetic nervous systemstimulation causes the heart rate to increase, both by the direct action ofsympathetic nervefibers on the heart and by causing theendocrinesystem to releasehormonessuch asepinephrine (adrenaline),which have a similar effect. Increased sympathetic stimulation is usually due to physical or psychological stress. This is the basis for the so-calledfight-or-flight response,but such stimulation can also be induced bystimulantssuch asephedrine,amphetaminesorcocaine.Certainendocrine disorderssuch aspheochromocytomacan also cause epinephrine release and can result in tachycardia independent of nervous system stimulation.Hyperthyroidismcan 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
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Main article:Inappropriate sinus tachycardia

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

Ventricular

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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 calledtorsades 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 fewsecondstominutes(paroxysmal tachycardia),but if VT persists it is extremely dangerous, often leading toventricular fibrillation.[19][20]

Supraventricular

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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
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Atrial fibrillationis one of the most common cardiac arrhythmias. In general, it is an irregular, narrow complex rhythm. However, it may show wide QRS complexes on the ECG if abundle branch blockis present. At high rates, the QRS complex may also become wide due to theAshman phenomenon.It may be difficult to determine the rhythm's regularity when the rate exceeds 150 beats per minute. Depending on the patient's health and other variables such as medications taken for rate control, atrial fibrillation may cause heart rates that span from 50 to 250 beats per minute (or even higher if anaccessory pathwayis present). However, new-onset atrial fibrillation tends to present with rates between 100 and 150 beats per minute.[22]

AV nodal reentrant tachycardia
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AV nodal reentrant tachycardia(AVNRT) is the most common reentrant tachycardia. It is a regularnarrow complex tachycardiathat usually responds well to theValsalva maneuveror the drugadenosine.However, unstable patients sometimes require synchronizedcardioversion.Definitive care may includecatheter ablation.[23]

AV reentrant tachycardia
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AV reentrant tachycardia (AVRT)requires anaccessory pathwayfor its maintenance. AVRT may involve orthodromic conduction (where the impulse travels down the AV node to the ventricles and back up to the atria through the accessory pathway) or antidromic conduction (which the impulse travels down the accessory pathway and back up to the atria through the AV node). Orthodromic conduction usually results in a narrow complex tachycardia, and antidromic conduction usually results in a wide complex tachycardia that often mimicsventricular tachycardia.Mostantiarrhythmicsarecontraindicatedin the emergency treatment of AVRT, because they may paradoxically increase conduction across the accessory pathway.[citation needed]

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

Management

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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 orcardiac arrestis about to occur.[10]Stable means that there is a tachycardia, but it does not seem an immediate threat for the patient's health, but only a symptom of an unknown disease, or a reaction that is not very dangerous in that moment.

Unstable

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In those that are unstable with a narrow complex tachycardia, intravenousadenosinemay be attempted.[10]In all others, immediatecardioversionis recommended.[10]

Stable

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If the problem is a simple acceleration of the heart rate that worries the patient, but the heart and the general patient's health remain stable enough, it is possible to correct it by a simple deceleration using some physical maneuvers calledvagal maneuvers.[25]But, if the cause of the tachycardia is chronic (permanent), it would return after some time, unless that cause is corrected.

Besides, the patient should avoid receiving external effects that cause or increase tachycardia.

The same measures than in unstable tachycardia can also be taken, with medications and the type of cardioversion that is appropriate for the patient's tachycardia.[10]

Terminology

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The wordtachycardiacame to English fromNeo-Latinas aneoclassical compoundbuilt from the combining formstachy-+-cardia,which are from theGreekταχύςtachys,"quick, rapid" and καρδία,kardia,"heart". As a matter both ofusagechoices in themedical literatureand ofidiominnatural language,the wordstachycardiaandtachyarrhythmiaare usually used interchangeably, or loosely enough that precise differentiation is not explicit. Some careful writers have tried to maintain a logical differentiation between them, which is reflected in major medical dictionaries[26][27][28]and major general dictionaries.[29][30][31]The distinction is thattachycardiabe reserved for the rapid heart rate itself, regardless of cause, physiologic or pathologic (that is, fromhealthy response to exerciseor fromcardiac arrhythmia), and thattachyarrhythmiabe reserved for the pathologic form (that is, an arrhythmia of the rapid rate type). This is why five of the previously referenced dictionaries donotenter cross-references indicatingsynonymybetween their entries for the two words (as they do elsewhere whenever synonymy is meant), and it is why one of them explicitly specifies that the two words not be confused.[28]But theprescriptionwill probably never be successfully imposed on generalusage,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 thetachycardiaversion as the more commonly used version. Thus SVT is calledsupraventricular tachycardiamore 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 ofAVRTandAVNRT.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

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References

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  3. ^Kushner A, West WP, Pillarisetty LS (2020)."Virchow Triad".StatPearls.Treasure Island (FL): StatPearls Publishing.PMID30969519.Retrieved2020-06-18.
  4. ^Kumar DR, Hanlin E, Glurich I, Mazza JJ, Yale SH (December 2010)."Virchow's contribution to the understanding of thrombosis and cellular biology".Clinical Medicine & Research.8(3–4): 168–172.doi:10.3121/cmr.2009.866.PMC3006583.PMID20739582.
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  17. ^Peyrol M, Lévy S (June 2016). "Clinical presentation of inappropriate sinus tachycardia and differential diagnosis".Journal of Interventional Cardiac Electrophysiology.46(1): 33–41.doi:10.1007/s10840-015-0051-z.PMID26329720.S2CID23249973.
  18. ^Mitchell LB (January 2023)."Torsades de Pointes Ventricular Tachycardia".Merck Manual Profesional Edition.Retrieved19 April2019.
  19. ^Samie FH, Jalife J (May 2001)."Mechanisms underlying ventricular tachycardia and its transition to ventricular fibrillation in the structurally normal heart".Cardiovascular Research.50(2): 242–250.doi:10.1016/S0008-6363(00)00289-3.PMID11334828.
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  21. ^"Types of Arrhythmia".National Heart, Lung, and Blood Institute (NHLBI).U.S. National Institutes of Health. July 1, 2011.Archivedfrom the original on June 7, 2015.
  22. ^Oiseth S, Jones L, Maza E (11 August 2020)."Atrial Fibrillation".The Lecturio Medical Concept Library.Retrieved3 July2021.
  23. ^Katritsis DG (December 2018)."Catheter Ablation of Atrioventricular Nodal Re-entrant Tachycardia: Facts and Fiction".Arrhythmia & Electrophysiology Review.7(4): 230–231.doi:10.15420/aer.2018.7.4.EO1.PMC6304791.PMID30588309.
  24. ^Rosen KM (March 1973). "Junctional tachycardia. Mechanisms, diagnosis, differential diagnosis, and management".Circulation.47(3): 654–664.doi:10.1161/01.CIR.47.3.654.PMID4571060.
  25. ^Page RL, Joglar JA, Caldwell MA, Calkins H, Conti JB, Deal BJ, Estes NM, Field ME, Goldberger ZD, Hammill SC, Indik JH, Lindsay BD, Olshansky B, Russo AM, Shen WK (2016-04-05)."2015 ACC/AHA/HRS Guideline for the Management of Adult Patients With Supraventricular Tachycardia: A Report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines and the Heart Rhythm Society".Circulation.133(14).doi:10.1161/CIR.0000000000000311.ISSN0009-7322.
  26. ^Elsevier,Dorland's Illustrated Medical Dictionary,Elsevier.
  27. ^Merriam-Webster,Merriam-Webster's Medical Dictionary,Merriam-Webster.
  28. ^abWolters Kluwer,Stedman's Medical Dictionary,Wolters Kluwer.
  29. ^Houghton Mifflin Harcourt,The American Heritage Dictionary of the English Language,Houghton Mifflin Harcourt.
  30. ^Merriam-Webster,Merriam-Webster's Collegiate Dictionary,Merriam-Webster, archived fromthe originalon 2020-10-10,retrieved2017-07-22.
  31. ^Merriam-Webster,Merriam-Webster's Unabridged Dictionary,Merriam-Webster, archived fromthe originalon 2020-05-25,retrieved2017-07-22.
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