Tachycardia, also called tachyarrhythmia, is a
heart rate
Heart rate (or pulse rate) is the frequency of the heartbeat measured by the number of contractions (beats) of the heart per minute (bpm). The heart rate can vary according to the body's physical needs, including the need to absorb oxygen and excr ...
that exceeds the
normal resting rate.
In general, a resting heart rate over 100
beat
Beat, beats or beating may refer to:
Common uses
* Patrol, or beat, a group of personnel assigned to monitor a specific area
** Beat (police), the territory that a police officer patrols
** Gay beat, an area frequented by gay men
* Battery (c ...
s per minute is accepted as tachycardia in adults.
Heart rates above the resting rate may be normal (such as with
exercise
Exercise is a body activity that enhances or maintains physical fitness and overall health and wellness.
It is performed for various reasons, to aid growth and improve strength, develop muscles and the cardiovascular system, hone athletic ...
) or abnormal (such as with electrical problems within the heart).
Complications
Tachycardia can lead to
fainting
Syncope, commonly known as fainting, or passing out, is a loss of consciousness and muscle strength characterized by a fast onset, short duration, and spontaneous recovery. It is caused by a decrease in blood flow to the brain, typically from ...
.
When the rate of blood flow becomes too rapid, or fast blood flow passes on damaged
endothelium
The endothelium is a single layer of squamous endothelial cells that line the interior surface of blood vessels and lymphatic vessels. The endothelium forms an interface between circulating blood or lymph in the lumen and the rest of the vessel ...
, it increases the friction within vessels resulting in turbulence and other disturbances. According to the
Virchow's triad
Virchow's triad or the triad of Virchow () describes the three broad categories of factors that are thought to contribute to thrombosis.
*Hypercoagulability
*Hemodynamic changes (stasis, turbulence)
*Endothelial injury/dysfunction
It is named a ...
, this is one of the three conditions that can lead to
thrombosis
Thrombosis (from Ancient Greek "clotting") is the formation of a blood clot inside a blood vessel, obstructing the flow of blood through the circulatory system. When a blood vessel (a vein or an artery) is injured, the body uses platelets (thro ...
(i.e., blood clots within vessels).
Causes
Some causes of tachycardia include:
*
Adrenergic storm
An adrenergic storm is a sudden and dramatic increase in serum levels of the catecholamines adrenaline and noradrenaline (also known as epinephrine and norepinephrine respectively), with a less significant increase in dopamine transmission. It ...
*
Anaemia
Anemia or anaemia (British English) is a blood disorder in which the blood has a reduced ability to carry oxygen due to a lower than normal number of red blood cells, or a reduction in the amount of hemoglobin. When anemia comes on slowly, th ...
*
Anxiety
Anxiety is an emotion which is characterized by an unpleasant state of inner turmoil and includes feelings of dread over anticipated events. Anxiety is different than fear in that the former is defined as the anticipation of a future threat wh ...
*
Atrial fibrillation
*
Atrial flutter
Atrial flutter (AFL) is a common abnormal heart rhythm that starts in the atrial chambers of the heart. When it first occurs, it is usually associated with a fast heart rate and is classified as a type of supraventricular tachycardia. Atrial f ...
*
Atrial tachycardia
Atrial tachycardia is a type of heart rhythm problem in which the heart's electrical impulse comes from an ectopic pacemaker (that is, an abnormally located cardiac pacemaker) in the upper chambers ( atria) of the heart, rather than from the sino ...
*
Atrioventricular reentrant tachycardia
Atrioventricular reentrant tachycardia (AVRT), or atrioventricular reciprocating tachycardia, is a type of abnormal fast heart rhythm and is classified as a type of supraventricular tachycardia (SVT). AVRT is most commonly associated with Wolff ...
*
AV nodal reentrant tachycardia
AV-nodal reentrant tachycardia (AVNRT) is a type of abnormal fast heart rhythm. It is a type of supraventricular tachycardia (SVT), meaning that it originates from a location within the heart above the bundle of His. AV nodal reentrant tachycar ...
*
Brugada syndrome
Brugada syndrome (BrS) is a genetic disorder in which the electrical activity of the heart is abnormal due to channelopathy. It increases the risk of abnormal heart rhythms and sudden cardiac death. Those affected may have episodes of syncope ...
*
Circulatory shock
Shock is the state of insufficient blood flow to the Tissue (biology), tissues of the body as a result of problems with the circulatory system. Initial symptoms of shock may include weakness, fast heart rate, fast breathing, sweating, anxiety, a ...
and its various causes (
obstructive shock
Obstructive shock is one of the four types of shock, caused by a physical obstruction in the flow of blood. Obstruction can occur at the level of the great vessels or the heart itself. Causes include pulmonary embolism, cardiac tamponade, and tensi ...
,
cardiogenic shock
Cardiogenic shock (CS) is a medical emergency resulting from inadequate blood flow due to the dysfunction of the ventricles of the heart.Textbooks of Internal MedicinHarrison's Principles of Internal Medicine 16th Edition, The McGraw-Hill Compan ...
,
hypovolemic shock
Hypovolemic shock is a form of shock caused by severe hypovolemia (insufficient blood volume or extracellular fluid in the body). It could be the result of severe dehydration through a variety of mechanisms or blood loss. Hypovolemic shock is a ...
,
distributive shock
Distributive shock is a medical condition in which abnormal distribution of blood flow in the smallest blood vessels results in inadequate supply of blood to the body's tissues and organs. It is one of four categories of shock, a condition where ...
)
*
Dysautonomia
Dysautonomia or autonomic dysfunction is a condition in which the autonomic nervous system (ANS) does not work properly. This may affect the functioning of the heart, bladder, intestines, sweat glands, pupils, and blood vessels. Dysautonomia has m ...
*
Exercise
Exercise is a body activity that enhances or maintains physical fitness and overall health and wellness.
It is performed for various reasons, to aid growth and improve strength, develop muscles and the cardiovascular system, hone athletic ...
*
Fear
Fear is an intensely unpleasant emotion in response to perceiving or recognizing a danger or threat. Fear causes physiological changes that may produce behavioral reactions such as mounting an aggressive response or fleeing the threat. Fear ...
*
Hypoglycemia
Hypoglycemia, also called low blood sugar, is a fall in blood sugar to levels below normal, typically below 70 mg/dL (3.9 mmol/L). Whipple's triad is used to properly identify hypoglycemic episodes. It is defined as blood glucose belo ...
*
Hypovolemia
Hypovolemia, also known as volume depletion or volume contraction, is a state of abnormally low extracellular fluid in the body. This may be due to either a loss of both salt and water or a decrease in blood volume. Hypovolemia refers to the los ...
*
Hyperthyroidism
Hyperthyroidism is the condition that occurs due to excessive production of thyroid hormones by the thyroid gland. Thyrotoxicosis is the condition that occurs due to excessive thyroid hormone of any cause and therefore includes hyperthyroidism ...
*
Hyperventilation
Hyperventilation is irregular breathing that occurs when the rate or tidal volume of breathing eliminates more carbon dioxide than the body can produce. This leads to hypocapnia, a reduced concentration of carbon dioxide dissolved in the blood. ...
*
Inappropriate sinus tachycardia
Inappropriate sinus tachycardia (IST) is a rare type of cardiac arrhythmia within the category of supraventricular tachycardia (SVT). IST may be caused by the Sinoatrial node, sinus node itself having an abnormal structure or function, or it may b ...
*
Junctional tachycardia
Junctional tachycardia is a form of supraventricular tachycardia characterized by involvement of the AV node. It can be contrasted to atrial tachycardia. It is a tachycardia associated with the generation of impulses in a focus in the region of ...
*
Metabolic myopathy
Metabolic myopathies are Myopathy, myopathies that result from defects in biochemical metabolism that primarily affect muscle. They are generally genetic defects that interfere with muscle's ability to create energy. At the cellular level, metaboli ...
*
Multifocal atrial tachycardia
Multifocal (or multiform) atrial tachycardia (MAT) is an abnormal heart rhythm, specifically a type of supraventricular tachycardia, that is particularly common in older people and is associated with exacerbations of chronic obstructive pulmona ...
*
Pacemaker
An artificial cardiac pacemaker (or artificial pacemaker, so as not to be confused with the natural cardiac pacemaker) or pacemaker is a medical device that generates electrical impulses delivered by electrodes to the chambers of the heart eith ...
mediated
*
Pain
Pain is a distressing feeling often caused by intense or damaging stimuli. The International Association for the Study of Pain defines pain as "an unpleasant sensory and emotional experience associated with, or resembling that associated with, ...
*
Panic attack
Panic attacks are sudden periods of intense fear and discomfort that may include palpitations, sweating, chest pain or chest discomfort, shortness of breath, trembling, dizziness, numbness, confusion, or a feeling of impending doom or of losing ...
*
Pheochromocytoma
Pheochromocytoma (PHEO or PCC) is a rare tumor of the adrenal medulla composed of chromaffin cells, also known as pheochromocytes. When a tumor composed of the same cells as a pheochromocytoma develops outside the adrenal gland, it is referred t ...
*
Sinus tachycardia
Sinus tachycardia is an elevated sinus rhythm characterized by an increase in the rate of electrical impulses arising from the sinoatrial node. In adults, sinus tachycardia is defined as a heart rate greater than 100 beats per minute (bpm). The ...
*
Sleep deprivation
Sleep deprivation, also known as sleep insufficiency or sleeplessness, is the condition of not having adequate duration and/or quality of sleep to support decent alertness, performance, and health. It can be either chronic or acute and may vary ...
*
Supraventricular tachycardia
Supraventricular tachycardia (SVT) is an umbrella term for fast heart rhythms arising from the upper part of the heart. This is in contrast to the other group of fast heart rhythms – ventricular tachycardia, which start within the lower cham ...
*
Ventricular tachycardia
Ventricular tachycardia (V-tach or VT) is a fast heart rate arising from the lower chambers of the heart. Although a few seconds of VT may not result in permanent problems, longer periods are dangerous; and multiple episodes over a short period ...
*
Wolff–Parkinson–White syndrome
Wolff–Parkinson–White syndrome (WPWS) is a disorder due to a specific type of problem with the electrical system of the heart. About 60% of people with the electrical problem developed symptoms, which may include an abnormally fast heartbeat, ...
Drug related:
*
Alcohol
Alcohol most commonly refers to:
* Alcohol (chemistry), an organic compound in which a hydroxyl group is bound to a carbon atom
* Alcohol (drug), an intoxicant found in alcoholic drinks
Alcohol may also refer to:
Chemicals
* Ethanol, one of sev ...
(
Ethanol
Ethanol (abbr. EtOH; also called ethyl alcohol, grain alcohol, drinking alcohol, or simply alcohol) is an organic compound. It is an Alcohol (chemistry), alcohol with the chemical formula . Its formula can be also written as or (an ethyl ...
) intoxication
*
Stimulant
Stimulants (also often referred to as psychostimulants or colloquially as uppers) is an overarching term that covers many drugs including those that increase activity of the central nervous system and the body, drugs that are pleasurable and inv ...
s
*
Cannabis
''Cannabis'' () is a genus of flowering plants in the family Cannabaceae. The number of species within the genus is disputed. Three species may be recognized: ''Cannabis sativa'', '' C. indica'', and '' C. ruderalis''. Alternatively ...
*
Drug withdrawal
Drug withdrawal, drug withdrawal syndrome, or substance withdrawal syndrome, is the group of symptoms that occur upon the abrupt discontinuation or decrease in the intake of pharmaceutical or recreational drugs.
In order for the symptoms of with ...
*
Tricyclic antidepressant
Tricyclic antidepressants (TCAs) are a class of medications that are used primarily as antidepressants, which is important for the management of depression. They are second-line drugs next to SSRIs. TCAs were discovered in the early 1950s and wer ...
s
*
Nefopam
Nefopam, sold under the brand name Acupan among others, is a centrally acting, non-opioid painkilling medication, that is primarily used to treat moderate to severe pain.
Nefopam acts in the brain and spinal cord to relieve pain via novel mecha ...
*
Opioid
Opioids are substances that act on opioid receptors to produce morphine-like effects. Medically they are primarily used for pain relief, including anesthesia. Other medical uses include suppression of diarrhea, replacement therapy for opioid us ...
s (rare)
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:
* 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
Ischemia or ischaemia is a restriction in blood supply to any tissue, muscle group, or organ of the body, causing a shortage of oxygen that is needed for cellular metabolism (to keep tissue alive). Ischemia is generally caused by problems wi ...
.
[Harrison's Principles of Internal Medicine, 17th Edition]
Differential diagnosis
![Electrocardiogram of Ventricular Tachycardia](https://upload.wikimedia.org/wikipedia/commons/c/c4/Electrocardiogram_of_Ventricular_Tachycardia.png)
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
The QRS complex is the combination of three of the graphical deflections seen on a typical electrocardiogram (ECG or EKG). It is usually the central and most visually obvious part of the tracing. It corresponds to the depolarization of the ri ...
.
Equal or less than 0.1s for narrow complex. Presented in order of most to least common, they are:
* Narrow complex
**
Sinus tachycardia
Sinus tachycardia is an elevated sinus rhythm characterized by an increase in the rate of electrical impulses arising from the sinoatrial node. In adults, sinus tachycardia is defined as a heart rate greater than 100 beats per minute (bpm). The ...
, which originates from the
sino-atrial (SA) node, near the base of the
superior vena cava
The superior vena cava (SVC) is the superior of the two venae cavae, the great venous trunks that return deoxygenated blood from the systemic circulation to the right atrium of the heart. It is a large-diameter (24 mm) short length vein th ...
**
Atrial fibrillation
**
Atrial flutter
Atrial flutter (AFL) is a common abnormal heart rhythm that starts in the atrial chambers of the heart. When it first occurs, it is usually associated with a fast heart rate and is classified as a type of supraventricular tachycardia. Atrial f ...
**
AV nodal reentrant tachycardia
AV-nodal reentrant tachycardia (AVNRT) is a type of abnormal fast heart rhythm. It is a type of supraventricular tachycardia (SVT), meaning that it originates from a location within the heart above the bundle of His. AV nodal reentrant tachycar ...
**
Accessory pathway mediated tachycardia
**
Atrial tachycardia
Atrial tachycardia is a type of heart rhythm problem in which the heart's electrical impulse comes from an ectopic pacemaker (that is, an abnormally located cardiac pacemaker) in the upper chambers ( atria) of the heart, rather than from the sino ...
**
Multifocal atrial tachycardia
Multifocal (or multiform) atrial tachycardia (MAT) is an abnormal heart rhythm, specifically a type of supraventricular tachycardia, that is particularly common in older people and is associated with exacerbations of chronic obstructive pulmona ...
**
Cardiac Tamponade
Cardiac tamponade, also known as pericardial tamponade (), is the buildup of fluid in the pericardium (the sac around the heart), resulting in compression of the heart. Onset may be rapid or gradual. Symptoms typically include those of obstruct ...
**
Junctional tachycardia
Junctional tachycardia is a form of supraventricular tachycardia characterized by involvement of the AV node. It can be contrasted to atrial tachycardia. It is a tachycardia associated with the generation of impulses in a focus in the region of ...
(rare in adults)
* Wide complex
**
Ventricular tachycardia
Ventricular tachycardia (V-tach or VT) is a fast heart rate arising from the lower chambers of the heart. Although a few seconds of VT may not result in permanent problems, longer periods are dangerous; and multiple episodes over a short period ...
, any tachycardia that originates in the
ventricles
** Any narrow complex tachycardia combined with a problem with the
conduction system
The cardiac conduction system (CCS) (also called the electrical conduction system of the heart) transmits the signals generated by the sinoatrial node – the heart's pacemaker, to cause the heart muscle to contract, and pump blood through the ...
of the heart, often termed "supraventricular tachycardia with
aberrancy"
** A narrow complex tachycardia with an accessory conduction pathway, often termed "supraventricular tachycardia with pre-excitation" (e.g.
Wolff–Parkinson–White syndrome
Wolff–Parkinson–White syndrome (WPWS) is a disorder due to a specific type of problem with the electrical system of the heart. About 60% of people with the electrical problem developed symptoms, which may include an abnormally fast heartbeat, ...
)
** Pacemaker-tracked or pacemaker-mediated tachycardia
Tachycardias may be classified as either narrow complex tachycardias (supraventricular tachycardias) or wide complex tachycardias. Narrow and wide refer to the width of the
QRS complex
The QRS complex is the combination of three of the graphical deflections seen on a typical electrocardiogram (ECG or EKG). It is usually the central and most visually obvious part of the tracing. It corresponds to the depolarization of the ri ...
on the
ECG
Electrocardiography is the process of producing an electrocardiogram (ECG or EKG), a recording of the heart's electrical activity. It is an electrogram of the heart which is a graph of voltage versus time of the electrical activity of the hear ...
. 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.
Sinus
The body has several
feedback mechanism
Feedback occurs when outputs of a system are routed back as inputs as part of a Signal chain (signal processing chain), chain of Causality, cause-and-effect that forms a circuit or loop. The system can then be said to ''feed back'' into itself. ...
s to maintain adequate blood flow and
blood pressure
Blood pressure (BP) is the pressure of circulating blood against the walls of blood vessels. Most of this pressure results from the heart pumping blood through the circulatory system. When used without qualification, the term "blood pressure" r ...
. If blood pressure decreases, the heart beats faster in an attempt to raise it. This is called
reflex
In biology, a reflex, or reflex action, is an involuntary, unplanned sequence or action and nearly instantaneous response to a stimulus.
Reflexes are found with varying levels of complexity in organisms with a nervous system. A reflex occurs ...
tachycardia. This can happen in response to a decrease in blood volume (through
dehydration
In physiology, dehydration is a lack of total body water, with an accompanying disruption of metabolic processes. It occurs when free water loss exceeds free water intake, usually due to exercise, disease, or high environmental temperature. Mil ...
or
bleeding
Bleeding, hemorrhage, haemorrhage or blood loss, is blood escaping from the circulatory system from damaged blood vessels. Bleeding can occur internally, or externally either through a natural opening such as the mouth, nose, ear, urethra, vag ...
), or an unexpected change in
blood flow
Hemodynamics or haemodynamics are the dynamics of blood flow. The circulatory system is controlled by homeostatic mechanisms of autoregulation, just as hydraulic circuits are controlled by control systems. The hemodynamic response continuously m ...
. The most common cause of the latter is
orthostatic hypotension
Orthostatic hypotension, also known as postural hypotension, is a medical condition wherein a person's blood pressure drops when standing up or sitting down. Primary orthostatic hypertension is also often referred to as neurogenic orthostatic hyp ...
(also called
postural hypotension
Orthostatic hypotension, also known as postural hypotension, is a medical condition wherein a person's blood pressure drops when standing up or sitting down. Primary orthostatic hypertension is also often referred to as neurogenic orthostatic hyp ...
).
Fever
Fever, also referred to as pyrexia, is defined as having a body temperature, temperature above the human body temperature, normal range due to an increase in the body's temperature Human body temperature#Fever, set point. There is not a single ...
,
hyperventilation
Hyperventilation is irregular breathing that occurs when the rate or tidal volume of breathing eliminates more carbon dioxide than the body can produce. This leads to hypocapnia, a reduced concentration of carbon dioxide dissolved in the blood. ...
,
diarrhea
Diarrhea, also spelled diarrhoea, is the condition of having at least three loose, liquid, or watery bowel movements each day. It often lasts for a few days and can result in dehydration due to fluid loss. Signs of dehydration often begin wi ...
and severe
infections
An infection is the invasion of tissue (biology), tissues by pathogens, their multiplication, and the reaction of host (biology), host tissues to the infectious agent and the toxins they produce. An infectious disease, also known as a transmiss ...
can also cause tachycardia, primarily due to increase in
metabolic
Metabolism (, from el, μεταβολή ''metabolē'', "change") is the set of life-sustaining chemical reactions in organisms. The three main functions of metabolism are: the conversion of the energy in food to energy available to run cell ...
demands.
Upon exertion,
sinus tachycardia
Sinus tachycardia is an elevated sinus rhythm characterized by an increase in the rate of electrical impulses arising from the sinoatrial node. In adults, sinus tachycardia is defined as a heart rate greater than 100 beats per minute (bpm). The ...
can also be seen in some
Inborn Errors of Metabolism
Inborn errors of metabolism form a large class of genetic diseases involving congenital disorders of enzyme activities. The majority are due to defects of single genes that code for enzymes that facilitate conversion of various substances ( substra ...
that result in
metabolic myopathies, such as
McArdle Disease (GSD-V).
[Lucia A, Martinuzzi A, Nogales-Gadea G, Quinlivan R, Reason S; International Association for Muscle Glycogen Storage Disease study group. Clinical practice guidelines for glycogen storage disease V & VII (McArdle disease and Tarui disease) from an international study group. Neuromuscul Disord. 2021 Dec;31(12):1296-1310. doi: 10.1016/j.nmd.2021.10.006. Epub 2021 Oct 28. Erratum in: Neuromuscul Disord. 2022 Feb 6;: PMID: 34848128.][Scalco RS, Chatfield S, Godfrey R, Pattni J, Ellerton C, Beggs A, Brady S, Wakelin A, Holton JL, Quinlivan R. From exercise intolerance to functional improvement: the second wind phenomenon in the identification of McArdle disease. Arq Neuropsiquiatr. 2014 Jul;72(7):538-41. doi: 10.1590/0004-282x20140062. PMID: 25054987.] 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.
"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."
As skeletal muscle relies predominantly on
glycogenolysis
Glycogenolysis is the breakdown of glycogen (n) to glucose-1-phosphate and glycogen (n-1). Glycogen branches are catabolized by the sequential removal of glucose monomers via phosphorolysis, by the enzyme glycogen phosphorylase.
Mechanism
The ...
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
Tachypnea, also spelt tachypnoea, is a respiratory rate greater than normal, resulting in abnormally rapid and shallow breathing.
In adult humans at rest, any respiratory rate of 1220 per minute is considered clinically normal, with tachypnea be ...
, muscle fatigue and pain, during the aforementioned activities and time frames.
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
Exercise intolerance is a condition of inability or decreased ability to perform physical exercise at the normally expected level or duration for people of that age, size, sex, and muscle mass. It also includes experiences of unusually severe post ...
improve.
An increase in
sympathetic nervous system
The sympathetic nervous system (SNS) is one of the three divisions of the autonomic nervous system, the others being the parasympathetic nervous system and the enteric nervous system. The enteric nervous system is sometimes considered part of th ...
stimulation causes the heart rate to increase, both by the direct action of
sympathetic nerve
The sympathetic nervous system (SNS) is one of the three divisions of the autonomic nervous system, the others being the parasympathetic nervous system and the enteric nervous system. The enteric nervous system is sometimes considered part of the ...
fibers on the heart and by causing the
endocrine
The endocrine system is a messenger system comprising feedback loops of the hormones released by internal glands of an organism directly into the circulatory system, regulating distant target organs. In vertebrates, the hypothalamus is the neu ...
system to release
hormone
A hormone (from the Greek participle , "setting in motion") is a class of signaling molecules in multicellular organisms that are sent to distant organs by complex biological processes to regulate physiology and behavior. Hormones are required ...
s such as
epinephrine (adrenaline), which have a similar effect. Increased sympathetic stimulation is usually due to physical or psychological stress. This is the basis for the so-called
fight-or-flight response
The fight-or-flight or the fight-flight-or-freeze response (also called hyperarousal or the acute stress response) is a physiological reaction that occurs in response to a perceived harmful event, attack, or threat to survival. It was first des ...
, but such stimulation can also be induced by
stimulant
Stimulants (also often referred to as psychostimulants or colloquially as uppers) is an overarching term that covers many drugs including those that increase activity of the central nervous system and the body, drugs that are pleasurable and inv ...
s such as
ephedrine
Ephedrine is a central nervous system (CNS) stimulant that is often used to prevent low blood pressure during anesthesia. It has also been used for asthma, narcolepsy, and obesity but is not the preferred treatment. It is of unclear benefit in ...
,
amphetamines
Substituted amphetamines are a class of compounds based upon the amphetamine structure; it includes all derivative compounds which are formed by replacing, or substituting, one or more hydrogen atoms in the amphetamine core structure with sub ...
or
cocaine
Cocaine (from , from , ultimately from Quechuan languages, Quechua: ''kúka'') is a central nervous system (CNS) stimulant mainly recreational drug use, used recreationally for its euphoria, euphoric effects. It is primarily obtained from t ...
. Certain
endocrine disorders
Endocrine diseases are disorders of the endocrine system. The branch of medicine associated with endocrine disorders is known as endocrinology.
Types of disease
Broadly speaking, endocrine disorders may be subdivided into three groups:
# Endocrin ...
such as
pheochromocytoma
Pheochromocytoma (PHEO or PCC) is a rare tumor of the adrenal medulla composed of chromaffin cells, also known as pheochromocytes. When a tumor composed of the same cells as a pheochromocytoma develops outside the adrenal gland, it is referred t ...
can also cause epinephrine release and can result in tachycardia independent of nervous system stimulation.
Hyperthyroidism
Hyperthyroidism is the condition that occurs due to excessive production of thyroid hormones by the thyroid gland. Thyrotoxicosis is the condition that occurs due to excessive thyroid hormone of any cause and therefore includes hyperthyroidism ...
can also cause tachycardia.
[Barker RL, Burton JR, Zieve, PD eds. Principles of Ambulatory Medicine. Sixth Edition. Philadelphia, PA: Lippinocott, Wilkins & Williams 2003] The upper limit of normal rate for sinus tachycardia is thought to be 220 bpm minus age.
=Inappropriate sinus tachycardia
=
Inappropriate sinus tachycardia
Inappropriate sinus tachycardia (IST) is a rare type of cardiac arrhythmia within the category of supraventricular tachycardia (SVT). IST may be caused by the Sinoatrial node, sinus node itself having an abnormal structure or function, or it may b ...
(IST) is a rare but benign type of cardiac arrhythmia that may be caused by a structural abnormality in the
sinus node
The sinoatrial node (also known as the sinuatrial node, SA node or sinus node) is an oval shaped region of special cardiac muscle in the upper back wall of the right atrium made up of cells known as pacemaker cells. The sinus node is approximat ...
. 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.
Ventricular
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
''Torsades de pointes, torsade de pointes'' or ''torsades des pointes'' (TdP) (, , translated as "twisting of peaks") is a specific type of abnormal heart rhythm that can lead to sudden cardiac death. It is a polymorphic ventricular tachycardia t ...
'' (literally meaning "twisting of the points", due to its appearance on an EKG), which tends to result from a long QT interval.
Both of these rhythms normally last for only a few
second
The second (symbol: s) is the unit of time in the International System of Units (SI), historically defined as of a day – this factor derived from the division of the day first into 24 hours, then to 60 minutes and finally to 60 seconds ...
s to
minute
The minute is a unit of time usually equal to (the first sexagesimal fraction) of an hour, or 60 seconds. In the UTC time standard, a minute on rare occasions has 61 seconds, a consequence of leap seconds (there is a provision to insert a nega ...
s'' (
paroxysmal tachycardia
Paroxysmal tachycardia is a form of tachycardia which begins and ends in an acute (or paroxysmal) manner.
It is also known as "Bouveret-Hoffmann syndrome".
Cause
The cause of this condition is not accurately known, though it is probably of nerv ...
)'', but if VT persists it is extremely dangerous, often leading to
ventricular fibrillation
Ventricular fibrillation (V-fib or VF) is an abnormal heart rhythm in which the ventricles of the heart quiver. It is due to disorganized electrical activity. Ventricular fibrillation results in cardiac arrest with loss of consciousness and no p ...
.
Supraventricular
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.
=Atrial fibrillation
=
Atrial fibrillation is 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 a
bundle branch block
A bundle branch block is a defect in one the bundle branches in the electrical conduction system of the heart.
Anatomy and physiology
The heart's electrical activity begins in the sinoatrial node (the heart's natural pacemaker), which is situat ...
is present. At high rates, the QRS complex may also become wide due to the
Ashman phenomenon
Ashman phenomenon, also known as Ashman beats, describes a particular type of wide QRS complex, often seen isolated that is typically seen in atrial fibrillation. It is more often misinterpreted as a premature ventricular complex.
It is named ...
. 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 an
accessory pathway An accessory pathway is an additional electrical connection between two parts of the heart. These pathways can lead to abnormal heart rhythms or arrhythmias associated with symptoms of palpitations. Some pathways may activate a region of ventricula ...
is present). However, new-onset atrial fibrillation tends to present with rates between 100 and 150 beats per minute.
=AV nodal reentrant tachycardia
=
AV nodal reentrant tachycardia
AV-nodal reentrant tachycardia (AVNRT) is a type of abnormal fast heart rhythm. It is a type of supraventricular tachycardia (SVT), meaning that it originates from a location within the heart above the bundle of His. AV nodal reentrant tachycar ...
(AVNRT) is the most common reentrant tachycardia. It is a regular
narrow complex tachycardia that usually responds well to the
Valsalva maneuver
The Valsalva maneuver is performed by a forceful attempt of exhalation against a closed airway, usually done by closing one's mouth and pinching one's nose shut while expelling air out as if blowing up a balloon. Variations of the maneuver can ...
or the drug
adenosine
Adenosine ( symbol A) is an organic compound that occurs widely in nature in the form of diverse derivatives. The molecule consists of an adenine attached to a ribose via a β-N9-glycosidic bond. Adenosine is one of the four nucleoside building ...
. However, unstable patients sometimes require synchronized
cardioversion
Cardioversion is a medical procedure by which an abnormally fast heart rate (tachycardia) or other cardiac arrhythmia is converted to a sinus rhythm, normal rhythm using electricity or pharmaceutical drug, drugs. Synchronized electrical cardiover ...
. Definitive care may include
catheter ablation
Catheter ablation is a procedure used to remove or terminate a faulty electrical pathway from sections of the heart of those who are prone to developing cardiac arrhythmias such as atrial fibrillation, atrial flutter and Wolff-Parkinson-White syn ...
.
=AV reentrant tachycardia
=
AV reentrant tachycardia (AVRT) requires an
accessory pathway An accessory pathway is an additional electrical connection between two parts of the heart. These pathways can lead to abnormal heart rhythms or arrhythmias associated with symptoms of palpitations. Some pathways may activate a region of ventricula ...
for 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 mimics
ventricular tachycardia
Ventricular tachycardia (V-tach or VT) is a fast heart rate arising from the lower chambers of the heart. Although a few seconds of VT may not result in permanent problems, longer periods are dangerous; and multiple episodes over a short period ...
. Most
antiarrhythmics
Antiarrhythmic agents, also known as cardiac dysrhythmia medications, are a group of pharmaceuticals that are used to suppress abnormally fast rhythms ( tachycardias), such as atrial fibrillation, supraventricular tachycardia and ventricular ta ...
are
contraindicated
In medicine, a contraindication is a condition that serves as a reason not to take a certain medical treatment due to the harm that it would cause the patient. Contraindication is the opposite of indication, which is a reason to use a certain tre ...
in the emergency treatment of AVRT, because they may paradoxically increase conduction across the accessory pathway.
=Junctional tachycardia
=
Junctional tachycardia is an
automatic tachycardia
An automatic tachycardia is a cardiac arrhythmia which involves an area of the heart generating an abnormally fast rhythm, sometimes also called enhanced automaticity. These tachycardias, or fast heart rhythms, differ from reentrant tachycardias ( ...
originating in the AV junction. It tends to be a regular, narrow complex tachycardia and may be a sign of digitalis toxicity.
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.
Unstable means that either important organ functions are affected or
cardiac arrest
Cardiac arrest is when the heart suddenly and unexpectedly stops beating. It is a medical emergency that, without immediate medical intervention, will result in sudden cardiac death within minutes. Cardiopulmonary resuscitation (CPR) and possib ...
is about to occur.
Unstable
In those that are unstable with a narrow complex tachycardia, intravenous
adenosine
Adenosine ( symbol A) is an organic compound that occurs widely in nature in the form of diverse derivatives. The molecule consists of an adenine attached to a ribose via a β-N9-glycosidic bond. Adenosine is one of the four nucleoside building ...
may be attempted.
In all others immediate
cardioversion
Cardioversion is a medical procedure by which an abnormally fast heart rate (tachycardia) or other cardiac arrhythmia is converted to a sinus rhythm, normal rhythm using electricity or pharmaceutical drug, drugs. Synchronized electrical cardiover ...
is recommended.
Terminology
The word ''tachycardia'' came to English from
New Latin
New Latin (also called Neo-Latin or Modern Latin) is the revival of Literary Latin used in original, scholarly, and scientific works since about 1500. Modern scholarly and technical nomenclature, such as in zoological and botanical taxonomy ...
as a
neoclassical compound
Neoclassical compounds are compound words composed from combining forms (which act as affixes or stems) derived from classical Latin or ancient Greek roots. New Latin comprises many such words and is a substantial component of the technical and ...
built from the combining forms ''
tachy-'' + ''
-cardia'', which are from the
Greek
Greek may refer to:
Greece
Anything of, from, or related to Greece, a country in Southern Europe:
*Greeks, an ethnic group.
*Greek language, a branch of the Indo-European language family.
**Proto-Greek language, the assumed last common ancestor ...
ταχύς ''tachys'', "quick, rapid" and καρδία, ''kardia'', "heart". As a matter both of
usage
The usage of a language is the ways in which its written and spoken variations are routinely employed by its speakers; that is, it refers to "the collective habits of a language's native speakers", as opposed to idealized models of how a language ...
choices in the
medical literature
Medical literature is the scientific literature of medicine: articles in journals and texts in books devoted to the field of medicine. Many references to the medical literature include the health care literature generally, including that of denti ...
and of
idiom
An idiom is a phrase or expression that typically presents a figurative, non-literal meaning attached to the phrase; but some phrases become figurative idioms while retaining the literal meaning of the phrase. Categorized as formulaic language, ...
in
natural language
In neuropsychology, linguistics, and philosophy of language, a natural language or ordinary language is any language that has evolved naturally in humans through use and repetition without conscious planning or premeditation. Natural languages ...
, the words ''tachycardia'' and ''tachyarrhythmia'' are 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
and major general dictionaries.
The distinction is that ''tachycardia'' be reserved for the rapid heart rate itself, regardless of cause, physiologic or pathologic (that is, from
healthy response to exercise or from
cardiac arrhythmia
Arrhythmias, also known as cardiac arrhythmias, heart arrhythmias, or dysrhythmias, are irregularities in the heartbeat, including when it is too fast or too slow. A resting heart rate that is too fast – above 100 beats per minute in adults ...
), and that ''tachyarrhythmia'' be reserved for the pathologic form (that is, an arrhythmia of the rapid rate type). This is why five of the previously referenced dictionaries do ''not'' enter cross-references indicating
synonym
A synonym is a word, morpheme, or phrase that means exactly or nearly the same as another word, morpheme, or phrase in a given language. For example, in the English language, the words ''begin'', ''start'', ''commence'', and ''initiate'' are all ...
y between 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.
But the
prescription will probably never be successfully imposed on general
usage
The usage of a language is the ways in which its written and spoken variations are routinely employed by its speakers; that is, it refers to "the collective habits of a language's native speakers", as opposed to idealized models of how a language ...
, 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
Supraventricular tachycardia (SVT) is an umbrella term for fast heart rhythms arising from the upper part of the heart. This is in contrast to the other group of fast heart rhythms – ventricular tachycardia, which start within the lower cham ...
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
AV-nodal reentrant tachycardia (AVNRT) is a type of abnormal fast heart rhythm. It is a type of supraventricular tachycardia (SVT), meaning that it originates from a location within the heart above the bundle of His. AV nodal reentrant tachycard ...
. 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.
See also
*
Postural orthostatic tachycardia syndrome
Postural orthostatic tachycardia syndrome (POTS) is a condition characterized by an abnormally large increase in heart rate upon standing. Symptoms may include lightheadedness, brain fog, blurred vision, weakness, fatigue, headaches, heart ...
*
Metabolic Myopathies
References
External links
{{Authority control
Cardiac arrhythmia
Symptoms and signs: Cardiac