Sinus tachycardia is a sinus rhythm of the heart, with an increased rate of electrical discharge from the

sinoatrial node The sinoatrial node (also known as the sinuatrial node, SA node, sinus node or Keith–Flack node) is an ellipse, oval shaped region of special cardiac muscle in the upper back wall of the right atrium made up of Cell (biology), cells known as pa ...

, resulting in a

tachycardia Tachycardia, also called tachyarrhythmia, is a heart rate that exceeds the normal resting rate. In general, a resting heart rate over 100 beats per minute is accepted as tachycardia in adults. Heart rates above the resting rate may be normal ...

, a

heart rate Heart rate is the frequency of the cardiac cycle, heartbeat measured by the number of contractions of the heart per minute (''beats per minute'', or bpm). The heart rate varies according to the body's Human body, physical needs, including the nee ...

that is higher than the upper limit of normal (90–100 beats per minute for adult humans). The normal

resting heart rate Heart rate is the frequency of the heartbeat measured by the number of contractions of the heart per minute (''beats per minute'', or bpm). The heart rate varies according to the body's physical needs, including the need to absorb oxygen and ...

is 60–90 bpm in an average adult. Normal heart rates vary with age and level of fitness, from infants having faster heart rates (110-150 bpm) and the elderly having slower heart rates. Sinus tachycardia is a normal response to physical exercise or other stress, when the heart rate increases to meet the body's higher demand for energy and oxygen, but sinus tachycardia can also be caused by a health problem.

Signs and symptoms

Tachycardia Tachycardia, also called tachyarrhythmia, is a heart rate that exceeds the normal resting rate. In general, a resting heart rate over 100 beats per minute is accepted as tachycardia in adults. Heart rates above the resting rate may be normal ...

is often asymptomatic. It is often a resulting symptom of a primary disease state and can be an indication of the severity of a disease. If the heart rate is too high, cardiac output may fall due to the markedly reduced ventricular filling time. Rapid rates, though they may be compensating for

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 ...

elsewhere, increase myocardial oxygen demand and reduce coronary blood flow, thus precipitating an ischemic heart or valvular disease. Sinus tachycardia accompanying a

myocardial infarction A myocardial infarction (MI), commonly known as a heart attack, occurs when Ischemia, blood flow decreases or stops in one of the coronary arteries of the heart, causing infarction (tissue death) to the heart muscle. The most common symptom ...

may be indicative of

cardiogenic shock Cardiogenic shock is a medical emergency resulting from inadequate blood flow to the body's organs due to the dysfunction of the heart. Signs of inadequate blood flow include low urine production (<30 mL/hour), cool arms and legs, and decreased ...

Cause

Sinus

is usually a response to physiological stress, such as

exercise Exercise or workout is physical activity that enhances or maintains fitness and overall health. It is performed for various reasons, including weight loss or maintenance, to aid growth and improve strength, develop muscles and the cardio ...

, or an increased sympathetic tone with increased catecholamine release, such as stress, fright, flight, and anger. Other causes include: *

Pain Pain is a distressing feeling often caused by intense or damaging Stimulus (physiology), stimuli. The International Association for the Study of Pain defines pain as "an unpleasant sense, sensory and emotional experience associated with, or res ...

Fever Fever or pyrexia in humans is a symptom of an anti-infection defense mechanism that appears with Human body temperature, body temperature exceeding the normal range caused by an increase in the body's temperature Human body temperature#Fever, s ...

Anxiety Anxiety is an emotion characterised by an unpleasant state of inner wikt:turmoil, turmoil and includes feelings of dread over Anticipation, anticipated events. Anxiety is different from fear in that fear is defined as the emotional response ...

Dehydration In physiology, dehydration is a lack of total body water that disrupts metabolic processes. It occurs when free water loss exceeds intake, often resulting from excessive sweating, health conditions, or inadequate consumption of water. Mild deh ...

* Excess

cortisol Cortisol is a steroid hormone in the glucocorticoid class of hormones and a stress hormone. When used as medication, it is known as hydrocortisone. Cortisol is produced in many animals, mainly by the ''zona fasciculata'' of the adrenal corte ...

* Malignant hyperthermia *

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 loss ...

with

hypotension Hypotension, also known as low blood pressure, is a cardiovascular condition characterized by abnormally reduced blood pressure. Blood pressure is the force of blood pushing against the walls of the arteries as the heart pumps out blood and is ...

and shock *

Anemia Anemia (also spelt anaemia in British English) is a blood disorder in which the blood has a reduced ability to carry oxygen. This can be due to a lower than normal number of red blood cells, a reduction in the amount of hemoglobin availabl ...

Hyperthyroidism Hyperthyroidism is a endocrine disease in which the thyroid gland produces excessive amounts of thyroid hormones. Thyrotoxicosis is a condition that occurs due to elevated levels of thyroid hormones of any cause and therefore includes hyperth ...

* Mercury poisoning * Kawasaki disease * Pheochromocytoma *

Sepsis Sepsis is a potentially life-threatening condition that arises when the body's response to infection causes injury to its own tissues and organs. This initial stage of sepsis is followed by suppression of the immune system. Common signs and s ...

Pulmonary embolism Pulmonary embolism (PE) is a blockage of an pulmonary artery, artery in the lungs by a substance that has moved from elsewhere in the body through the bloodstream (embolism). Symptoms of a PE may include dyspnea, shortness of breath, chest pain ...

* Acute coronary ischemia and

Chronic obstructive pulmonary disease Chronic obstructive pulmonary disease (COPD) is a type of progressive lung disease characterized by chronic respiratory symptoms and airflow limitation. GOLD defines COPD as a heterogeneous lung condition characterized by chronic respiratory s ...

* Hypoxia * Intake of

stimulants Stimulants (also known as central nervous system stimulants, or psychostimulants, or colloquially as uppers) are a class of drugs that increase alertness. They are used for various purposes, such as enhancing attention, motivation, cognitio ...

such as

caffeine Caffeine is a central nervous system (CNS) stimulant of the methylxanthine chemical classification, class and is the most commonly consumed Psychoactive drug, psychoactive substance globally. It is mainly used for its eugeroic (wakefulness pr ...

, theophylline,

nicotine Nicotine is a natural product, naturally produced alkaloid in the nightshade family of plants (most predominantly in tobacco and ''Duboisia hopwoodii'') and is widely used recreational drug use, recreationally as a stimulant and anxiolytic. As ...

cocaine Cocaine is a tropane alkaloid and central nervous system stimulant, derived primarily from the leaves of two South American coca plants, ''Erythroxylum coca'' and ''Erythroxylum novogranatense, E. novogranatense'', which are cultivated a ...

, or

amphetamines Substituted amphetamines, or simply amphetamines, are a chemical class, class of compounds based upon the amphetamine structure; it includes all derivative (chemistry), derivative compounds which are formed by replacing, or substitution reacti ...

* Hyperdynamic circulation *

Electric shock An electrical injury (electric injury) or electrical shock (electric shock) is damage sustained to the skin or internal organs on direct contact with an electric current. The injury depends on the Current density, density of the current, tissu ...

Drug withdrawal A drug is any chemical substance other than a nutrient or an essential dietary ingredient, which, when administered to a living organism, produces a biological effect. Consumption of drugs can be via insufflation (medicine), inhalation, drug i ...

* Porphyria * Acute inflammatory demyelinating polyradiculoneuropathy *

Postural orthostatic tachycardia syndrome Postural orthostatic tachycardia syndrome (POTS) is a condition characterized by an abnormally large increase in heart rate upon sitting up or standing. POTS is a disorder of the autonomic nervous system that can lead to a variety of symptoms, ...

Mitral valve prolapse Mitral valve prolapse (MVP) is a valvular heart disease characterized by the displacement of an abnormally thickened mitral valve leaflet into the atria of the heart, left atrium during Systole (medicine), systole. It is the primary form of myxom ...

* Metabolic myopathies

Diagnosis

Sinus tachycardia is usually apparent on an ECG, but if the heart rate is above 140 bpm the P wave may be difficult to distinguish from the previous

T wave In electrocardiography, the T wave represents the repolarization of the ventricles. The interval from the beginning of the QRS complex to the apex of the T wave is referred to as the ''absolute refractory period''. The last half of the T wav ...

and one may confuse it with a

paroxysmal supraventricular tachycardia Paroxysmal supraventricular tachycardia (PSVT) is a type of supraventricular tachycardia, named for its intermittent episodes of abrupt onset and termination. Often people have no symptoms. Otherwise symptoms may include palpitations, feeling li ...

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 (SVT). ...

with a 2:1 block. Ways to distinguish the three are: * Vagal maneuvers (such as carotid sinus massage or Valsalva's maneuver) to slow the rate and identification of P waves * administer AV blockers (e.g.,

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 build ...

, verapamil) to identify

with 2:1 block Heart sounds should also be listened to.

ECG characteristics

* ''Rate'': Greater than or equal to 100. * ''Rhythm'': Regular. * ''P waves'': Upright, in leads I, II and aVL, and negative in lead aVR; * each P wave is followed by a QRS and T waves

Inappropriate sinus tachycardia

In inappropriate sinus tachycardia (also known as chronic nonparoxysmal sinus tachycardia), patients have an elevated resting heart rate and/or exaggerated heart rate in response to exercise. These patients have no apparent heart disease or other causes of sinus tachycardia. IST is thought to be due to abnormal autonomic control. IST is a diagnosis of exclusion.

Postural orthostatic tachycardia syndrome

Usually, in women with no heart problems, this syndrome is characterized by normal resting heart rate but exaggerated postural sinus tachycardia with or without orthostatic hypotension.

Metabolic myopathy

Upon exertion, sinus tachycardia can be seen in some inborn errors of metabolism that result in metabolic myopathies, such as McArdle Disease (GSD-V) and Hereditary myopathy with lactic acidosis (Larsson–Linderholm syndrome). Metabolic myopathies interfere with the muscle's ability to create energy. This energy shortage in muscle cells causes an inappropriate rapid heart rate 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 one such category of metabolic myopathies, muscle glycogenoses (muscle GSDs), individuals are unable to create energy from muscle glycogen, and depending on the muscle GSD, may not be able to utilize blood glucose within the muscle cell either. 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. Mechanis ...

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 glycogenoses 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 b ...

, muscle fatigue and pain, during the aforementioned activities and time frames. Notable in McArdle Disease (GSD-V) is the phenomenon of second wind where after approximately 6–10 minutes of aerobic exercise, such as walking without an incline, the heart rate drops as blood borne fuels, predominantly from free fatty acids, produce energy via oxidative phosphorylation. Rare diseases, such as McArdle disease, are often misdiagnosed. The inappropriate rapid heart rate response to exercise may be misdiagnosed as inappropriate sinus tachycardia (which is a diagnosis of exclusion).

Treatment

Treatment for physiologic sinus tachycardia involves treating the underlying causes of the tachycardia response.

Beta blocker Beta blockers, also spelled β-blockers, are a class of medications that are predominantly used to manage abnormal heart rhythms ( arrhythmia), and to protect the heart from a second heart attack after a first heart attack ( secondary prevention ...

s may be used to decrease tachycardia in patients with certain conditions, such as ischemic heart disease and rate-related angina. In patients with inappropriate sinus tachycardia, careful titration of beta-blockers, salt loading, and hydration typically reduce symptoms. Patients who are unresponsive to such treatment can undergo catheter ablation to potentially repair the sinus node.

Acute myocardial infarction (AMI)

Sinus tachycardia can present in more than a third of the patients with AMI but this usually decreases over time. Patients with sustained sinus tachycardia reflects a larger infarct that are more anterior with prominent left ventricular dysfunction, associated with high mortality and morbidity. Tachycardia in the presence of AMI can reduce coronary blood flow and increase myocardial oxygen demand, aggravating the situation. Beta-blockers can be used to slow the rate, but most patients are usually already treated with beta-blockers as a routine regimen for AMI.

IST and POTS

Beta blockers are useful if the cause is sympathetic overactivity. If the cause is due to decreased vagal activity, it is usually hard to treat and one may consider radiofrequency catheter ablation.