Symptom/Sign: Tachycardia
Classifications and external resources

ICD-10	R00.0
ICD-9	785.0
MeSH	D013610

Tachycardia refers to rapid beating of the heart. A symptom' (from Greek σύμπτωμα, "accident misfortune that which befalls" from συμπίπτω, "I befall" from A Sign is an indication of some fact or quality and a medical sign is an objective indication of some medical fact or quality that is detected by a Physician The International Statistical Classification of Diseases and Related Health Problems (most commonly known by the abbreviation ICD) provides codes to classify Diseases The International Statistical Classification of Diseases and Related Health Problems 10th Revision ( ICD -10) is a coding of diseases and signs symptoms abnormal findings R00-R69 - Symptoms and Signs (R00-R09 Circulatory and Respiratory systems ( Abnormalities of Heart beat The International Statistical Classification of Diseases and Related Health Problems (most commonly known by the abbreviation ICD) provides codes to classify Diseases The following is a list of codes for International Statistical Classification of Diseases and Related Health Problems. Medical Subject Headings ( MeSH) is a huge Controlled vocabulary (or metadata system for the purpose of indexing journal articles and books The heart is a muscular organ in all Vertebrates responsible for pumping Blood through the Blood vessels by repeated rhythmic By convention it is defined as a heart rate greater than 100 beats per minute in adults. Measuring heart rate The Pulse rate (which in most people is identical to the heart rate can be measured at any point on the body where an Artery 's pulsation For the 2008 British film by Noel Clarke see Adulthood (film. Tachycardia may be normal, such as in exercise and stress, or abnormal, such as in cardiac arrhythmias. Dysrhythmia redirects here For the American band see Dysrhythmia (band. However, depending on the mechanism of the tachycardia and the health status of the person, tachycardia may be harmful and require medical treatment. In extreme cases, tachycardia can be life threatening.

Tachycardia can be harmful in three ways. First, if the heart is pumping too fast for an extended period of time it will change the balance of oxygen and carbon dioxide in the hemoglobin in the blood; this is normal during exercise but when resting this is quite dangerous. Second, when the heart beats too rapidly, it may pump blood less efficiently as there is less time for the myocardium to relax between contractions. Myocardium is the muscular tissue of the Heart. Relationship to other layers The other tissues of the heart are the Endocardium Third, the faster the heart beats, the more oxygen and nutrients the heart requires. Oxygen (from the Greek roots ὀξύς (oxys (acid literally "sharp" from the taste of acids and -γενής (-genēs (producer literally begetteris the This may leave patients feeling out of breath or cause angina in those suffering from ischemic heart disease. Angina pectoris, commonly known as angina, is severe Chest pain due to Ischemia (a lack of blood and hence Oxygen supply of the heart Ischaemic or ischemic heart disease (IHD or myocardial ischaemia, is a Disease characterized by reduced blood supply to the heart muscle

Contents 1 Haemodynamic responses 2 Autonomic and endocrine causes 3 Cardiac Arrhythmias 3.1 Sinus tachycardia 3.2 Ventricular tachycardia 3.3 SVT Rhythms 3.3.1 Atrial fibrillation 3.3.2 AV nodal reentrant tachycardia (AVNRT) 3.3.3 AV reentrant tachycardia 3.3.4 Junctional tachycardia 4 Treatments 5 References 6 External links

Haemodynamic responses

The body contains several feedback mechanisms to maintain adequate blood flow and blood pressure. Feedback is a circular causal Process whereby some proportion of a system's output is returned (fed back to the Input. Blood pressure is also the title of a short story by Damon Runyan in Guys and Dolls and Other Stories If blood pressure decreases, the heart beats faster in an attempt to raise it. This is called reflex tachycardia. A reflex action, also known as a reflex, is an involuntary and almost instant movement in response to stimulus.

This can happen in response to a decrease in blood volume (through dehydration or bleeding), or an unexpected change in blood flow. Blood volume is the Volume of Blood (both Red blood cells and plasma) in a person's Circulatory system. Dehydration ( hypohydration) is the removal of Water ( hydro in ancient Greek) from an object Bleeding, technically known as hemorrhaging / haemorrhaging (see American and British spelling differences) is the loss of Blood from Blood flow is the flow of Blood in the Cardiovascular system. The most common cause of the latter is orthostatic hypotension (also called postural hypotension), a sudden drop of blood pressure that occurs with a change in body position (e. Orthostatic hypotension (also known as postural hypotension, and colloquially as head rush or a dizzy spell) is a form of Hypotension in which Orthostatic hypotension (also known as postural hypotension, and colloquially as head rush or a dizzy spell) is a form of Hypotension in which g. , going from lying down to standing up). When tachycardia occurs for this reason, it is called postural orthostatic tachycardia syndrome (POTS). Postural orthostatic tachycardia syndrome (often referred to as just postural tachycardia syndrome or POTS) is a condition of Dysautonomia, and more specifically

Fever, hyperventilation and infection leading to sepsis are also common causes of tachycardia, primarily due to increase in metabolic demands and compensatory increase in heart rate. Fever (also known as pyrexia, from the Greek pyretos meaning fire or a febrile response, from the Latin word Febris In Medicine, hyperventilation (or overbreathing) is the state of Breathing faster and/or deeper than necessary bringing about lightheadedness and other An infection is the detrimental Colonization of a host Organism by a foreign Species. Sepsis is a serious medical condition characterized by a whole-body inflammatory state (called a Systemic inflammatory response syndrome or SIRS caused Metabolism is the set of Chemical reactions that occur in living Organisms in order to maintain Life.

Autonomic and endocrine causes

An increase in sympathetic nervous system stimulation causes the heart rate to increase, both by the direct action of sympathetic nerve fibers on the heart and by causing the endocrine system to release hormones such as epinephrine (adrenaline), which have a similar effect. The Sympathetic Nervous System ( SNS) is a branch of the Autonomic nervous system along with the Enteric nervous system and Parasympathetic nervous The Sympathetic Nervous System ( SNS) is a branch of the Autonomic nervous system along with the Enteric nervous system and Parasympathetic nervous The endocrine system is an integrated system of small organs that involve the release of extracellular signaling molecules known as Hormones The endocrine system is instrumental Hormones (from Greek ὁρμή - "impetus" are chemicals released by cells that affect cells in other parts of the body Increased sympathetic stimulation is usually due to physical or psychological stress (the so-called "fight or flight" response), but can also be induced by stimulants such as amphetamines. Stimulant drugs are Drugs that temporarily increase alertness and awareness Amphetamine, and related drugs such as Methamphetamine are a group of drugs that act by increasing levels of Norepinephrine, Serotonin, and Dopamine

Endocrine disorders such as pheochromocytoma can cause epinephrine release and tachycardia independent of the nervous system. Among the hundreds of endocrine diseases (or endocrinological diseases) are Adrenal disorders Adrenal insufficiency A phaeochromocytoma ( pheochromocytoma in the US is a Neuroendocrine tumor of the medulla of the Adrenal glands (originating in the Chromaffin Hyperthyroidism is also known to cause tachycardia. Hyperthyroidism is the term for overactive tissue within the Thyroid gland resulting in overproduction and thus an excess of circulating free thyroid hormones Thyroxine

Cardiac Arrhythmias

The Cardiac Arrhythmias lead ECG can help distinguish between the various types of tachycardias, generally distinguished by their site of pacemaker origin:

• Sinus tachycardia, which originates from the Sino-atrial (SA) node, near the base of the superior vena cava
• Ventricular tachycardia, any tachycardia which originates in the ventricles. Sinus Tachycardia (also colloquially known as sinus tach or sinus tachy) is a rhythm with elevated rate of impulses originating from the Sinoatrial The Sinoatrial node (abbreviated SA node or SAN, also called the sinus node) is the impulse generating (pacemaker tissue located in the Right atrium The superior vena cava is a large yet short Vein that carries deoxygenated Blood from the upper half of the body to the Heart 's Right atrium Ventricular tachycardia ( V-tach or VT) is a Tachycardia, or fast heart rhythm that originates in one of the ventricles of the Heart
• Supraventricular tachycardia (SVT), which is a tachycardia paced from the Atria or the AV node. A supraventricular tachycardia ( SVT) is a rapid rhythm of the Heart in which the origin of the electrical signal is either the atria or SVT rhythms include:
  • Atrial fibrillation
  • AVNRT or AV nodal reentrant tachycardia
  • AVRT or AV reentrant tachycardia
  • Junctional tachycardia

It is sometimes useful to classify tachycardias as either narrow complex tachycardias (often referred to as supraventricular tachycardias) or wide complex tachycardias. Atrial fibrillation ( AF or afib) is a Cardiac arrhythmia (abnormal heart rhythm that involves the two upper chambers ( atria) of the Heart AV nodal reentrant tachycardia ( AVNRT) is a type of Tachycardia (fast rhythm of the Heart. "Narrow" and "wide" refer to the width of the QRS complex on 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.

Sinus tachycardia

The most common type of tachycardia is sinus tachycardia, which is the body's normal reaction to stress, including fever, dehydration, or blood loss (shock). Sinus Tachycardia (also colloquially known as sinus tach or sinus tachy) is a rhythm with elevated rate of impulses originating from the Sinoatrial It is a technical narrow complex tachycardia. A supraventricular tachycardia ( SVT) is a rapid rhythm of the Heart in which the origin of the electrical signal is either the atria or In the absence of heart disease, it tends to have a narrow QRS complex on the ECG. Treatment is generally directed at identifying the underlying cause.

Ventricular tachycardia

Main article: Ventricular tachycardia

Ventricular tachycardia (VT or V-tach) is a potentially life-threatening cardiac arrhythmia that originates in the ventricles. Ventricular tachycardia ( V-tach or VT) is a Tachycardia, or fast heart rhythm that originates in one of the ventricles of the Heart It is usually a regular, wide complex tachycardia with a rate between 120 and 250 beats per minute. Ventricular tachycardia has the potential of degrading to the more serious ventricular fibrillation. Ventricular fibrillation ( V-fib or VF) is a condition in which there is uncoordinated contraction of the Cardiac muscle of the ventricles in the Ventricular tachycardia is a common, and often lethal, complication of a myocardial infarction (heart attack). Myocardial infarction ( MI or AMI for acute myocardial infarction) also known as a heart attack, occurs when the blood supply

Exercise-induced ventricular tachycardia is a phenomenon related to sudden deaths, especially in patients with severe heart disease (ischaemia, acquired valvular heart and congenital heart disease) accompanied with left ventricular dysfunction. A cardiac arrest, also known as cardiorespiratory arrest, cardiopulmonary arrest or circulatory arrest, is the abrupt cessation of normal circulation of In Medicine, ischemia ( Greek ισχαιμία, isch- is restriction hema or haema is Blood) is a restriction Valvular heart disease is any disease process involving one or more of the valves of the heart (the aortic and mitral valves on the left and the pulmonary A congenital heart defect (CHD is a defect in the structure of the Heart and Great vessels of a Newborn. In the Heart, a ventricle is a heart chamber which collects Blood from an atrium (another heart chamber that is smaller than a ventricle and ^[1] A case of a death from exercise-induced VT was the death on a basketball court of Hank Gathers, the Loyola Marymount basketball star, in March 1990. Eric "Hank" Gathers ( February 11, 1967, in Philadelphia &ndash March 4, 1990 in Los Angeles) was an Loyola Marymount University (LMU is a comprehensive co-educational private Roman Catholic Jesuit university in Los Angeles California, United States Basketball is a team Sport in which two teams of five active players each try to score points against one another by propelling a ball through a 10 feet (3 m Events in March American Red Cross Month Fire Prevention month ( The Philippines) Women's History Month ( United Year 1990 ( MCMXC) was a Common year starting on Monday (link displays the 1990 Gregorian calendar) ^[2]

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. The second ( SI symbol s) sometimes abbreviated sec, is the name of a unit of Time, and is the International System of Units A minute is a Unit of measurement of Time or of Angle. The minute is a unit of Time equal to 1/60th of an Hour or 60 Paroxysmal tachycardia is a form of Tachycardia which has begins and ends in an Acute (or Paroxysmal manner Ventricular fibrillation ( V-fib or VF) is a condition in which there is uncoordinated contraction of the Cardiac muscle of the ventricles in the

SVT Rhythms

Main article: Supraventricular tachycardia

Atrial fibrillation

Atrial fibrillation is one of the most common cardiac arrhythmias. A supraventricular tachycardia ( SVT) is a rapid rhythm of the Heart in which the origin of the electrical signal is either the atria or Atrial fibrillation ( AF or afib) is a Cardiac arrhythmia (abnormal heart rhythm that involves the two upper chambers ( atria) of the Heart It is generally an irregular, narrow complex rhythm. However, it may show wide QRS complexes on the ECG if a bundle branch block is present. A bundle branch block refers to a defect of the Heart 's electrical conduction system. At high rates, the QRS complex may also become wide due to the Ashman phenomenon. First described by Gouaux and Ashman in 1947 Ashman phenomenon, also known as Ashman beats, describes a particular type of wide complex Tachycardia (fast rhythm of 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 is present). However, new onset atrial fibrillation tends to present with rates between 100 and 150 beats per minute.

AV nodal reentrant tachycardia (AVNRT)

AV nodal reentrant tachycardia is the most common reentrant tachycardia. AV nodal reentrant tachycardia ( AVNRT) is a type of Tachycardia (fast rhythm of the Heart. It is a regular narrow complex tachycardia that usually responds well to vagal maneuvers or the drug adenosine. A supraventricular tachycardia ( SVT) is a rapid rhythm of the Heart in which the origin of the electrical signal is either the atria or Adenosine is a Nucleoside composed of a Molecule of Adenine attached to a Ribose sugar molecule ( Ribofuranose) moiety via a β-N9- However, unstable patients sometimes require synchronized cardioversion. Synchronized electrical cardioversion is the process by which an abnormally fast Heart rate or Cardiac arrhythmia is terminated by the delivery of a therapeutic dose Definitive care may include catheter ablation. Catheter ablation is an invasive procedure used to remove a faulty electrical pathway from the Hearts of those who are prone to developing Cardiac arrhythmias such as

AV reentrant tachycardia

AV reentrant tachycardia (AVRT) requires an accessory pathway 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 Tachycardia, or fast heart rhythm that originates in one of the ventricles of the Heart Most antiarrhythmics are contraindicated in the emergency treatment of AVRT, because they may paradoxically increase conduction across the accessory pathway.

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.

Treatments

Treatment of tachycardia is usually directed at chemical conversion (with antiarrhythmics), electrical conversion (giving external shocks to convert the heart to a normal rhythm) or use of drugs to simply control heart rate (for example as in atrial fibrillation). Antiarrhythmic agents are a group of Pharmaceuticals that are used to suppress fast rhythms of the Heart ( Cardiac arrhythmias) such as Atrial fibrillation Atrial fibrillation ( AF or afib) is a Cardiac arrhythmia (abnormal heart rhythm that involves the two upper chambers ( atria) of the Heart

The treatment modality used depends on the type of tachycardia and the hemodynamic stability of the patient. If the tachycardia originates from the sinus node (sinus tachycardia), treatment of the underlying cause of sinus tachycardia is usually sufficient. On the other hand, if the tachycardia is of a potentially lethal origin (ie: ventricular tachycardia) treatment with anti arrhythmic agents or with electrical cardioversion may be required. Below is a brief discussion of some of the main tachyarrhythmias and their treatments.

The electrocardiac management of atrial fibrillation and atrial flutter is either through medications or electrical cardioversion. Pharmacologic management of these arrhythmias typically involves diltiazem or verapamil as well as beta-blocking agents such as atenolol. The decision to use electrical cardioversion depends heavily on the hemodynamic stability of the presenting patient; in general those patients who are unable to sustain their systemic functions are electrically converted although conversion to a normal sinus rhythm can be performed with amiodarone. An interesting type of atrial fibrillation which must be carefully managed is when it appears in combination with Wolff-parkinson White. In this case, calcium channel blockers, beta-blockers and digoxin must be avoided to prevent precipitation of ventricular tachycardia. Here, procainamide or quinidine are often used. Of note: patients who have been in atrial fibrillation for more than 48 hours should not be converted to normal sinus rhythm unless they have been anti-coagulated to an INR of 2-3 for at least 4 weeks.

In the case of narrow complex tachycardias (junctional, atrial or paroxysmal), the treatment in general is to first give the patient adenosine (to slow conduction through the AV node) and then perform vagal maneuvers to slow the rhythm. If this does not convert the patient, amiodarone, calcium channel blockers or beta-blockers are commonly employed to stabilize the patient. Again as in atrial fibrillation, if a patient is unstable, the decision to electrically cardiovert him/her should be made.

With wide complex tachyarrhythmias or ventricular tachyarrhythmias, in general most are highly unstable and cause the patient significant distress and would be electrically converted. However one notable exception is monomorphic ventricular tachycardia which patients may tolerate but can be treated pharmacologically with amiodarone or lidocaine.

Above all, the treatment modality is tailored to the individual, and varies based on the mechanism of the tachycardia (where it is originating from within the heart), on the duration of the tachycardia, how well the individual is tolerating the fast heart rate, the likelihood of recurrence once the rhythm is terminated, and any co-morbid conditions the individual is suffering from.

References

External links

• Postural Orthostatic Tachycardia Syndrome - overview from Dysautonomia Information Network
• Heart Arrhythmias Respond to Ablation UCLA Healthcare

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