Many of the patients with sinus tachycardia remain asymptomatic. But patients with IST may present with features like:

• Fast and regular palpitations
• Dyspnea
• Dizziness
• Lightheadedness 
• Presyncope

Patients with postural orthostatic sinus tachycardia may have additional symptoms including tremor, constipation, and bladder-related problems. They may find it difficult to tolerate extreme heat and cold, be intolerant to exercise, and have chronic fatigue. Tachycardia without any signs of underlying condition may indicate IST. On physical examination, significant findings are related to cardiovascular and respiratory systems. Patients are distressed. Some may present with chest discomfort due to tachycardia. The sinus rhythm will be higher than 100 beats per minute and may go up to 200 beats per minute in young individuals. In older individuals this value may be 150 beats per minute or less.

• Anemia

  Appropriate sinus tachycardia can result from: [ 3 ] Exercise Anxiety Alcohol / caffeine use Drugs (e.g. beta-agonists like dobutamine) Inappropriate sinus tachycardia can result from: Fever Hypotension Hypoxia Congestive heart failure Bleeding Anemia [en.ecgpedia.org]

  […] exclusion of other causes of tachycardia including medications/substances (such as anti-cholinergic, beta-blocker withdrawal, caffeine, and alcohol) or medical conditions (such as panic attacks, pulmonary embolism, fever, hyperthyroidism, hypovolemia, anemia [eurekaselect.com]

  E is for erythrocyte deficiency and the development of anemia regardless of whether it’s a rapid or slow process your patient may become tachycardic. [rebelem.com]

  Also excluded were tachycardia episodes with potential explanation e.g. acute illness, severe pain, fever, acute anemia, hyperthyroidism, pregnancy and history of cardiac arrhythmias. [acrabstracts.org]

• Fatigue

  These people can develop symptoms of palpitations, breathlessness, fatigue, dizziness and, occasionally, blackouts. [cambridgeheartclinic.co.uk]

  We ask about general symptoms (anxious mood, depressed mood, fatigue, pain, and stress) regardless of condition. Last updated: January 31, 2019 [patientslikeme.com]

  dizziness, and alternating periods of bradycardia and atrial tachycardia, which is caused by sinoatrial node dysfunction A constellation of signs and symptoms which may include syncope, fatigue, dizziness, and alternating periods of bradycardia and [icd9data.com]

  Inappropriate sinus tachycardia (IST) is a arrhythmia in which the resting heart rate is abnormally high (greater than 100 beats per minute), and increases rapidly with minimal exertion, accompanied by symptoms of palpitations, fatigue, and exercise intolerance [cardiachealth.org]

• Sepsis

  Note : Normal heart rates in children Newborn : 110 – 150 bpm 2 years : 85 – 125 bpm 4 years : 75 – 115 bpm 6 years+ : 60 – 100 bpm Causes Non-pharmacological Exercise Pain, anxiety Hypoxia, hypercarbia Acidaemia Sepsis, pyrexia Pulmonary embolism Hyperthyroidism [lifeinthefastlane.com]

  Most cases were in poor and middle income countries, but even wealthier nations are dealing with sepsis. What is sepsis? Sepsis is also known as the "hidden killer" because it can be so hard to detect. [bbc.com]

  It may be a response in order to increase cardiac output to compensate for hypovolemia, anemia, hypoxemia, hypoglycemia, fever, or sepsis. [openanesthesia.org]

  Note: Normal heart rates in children Newborn: 110 – 150 bpm 2 years: 85 – 125 bpm 4 years: 75 – 115 bpm 6 years+: 60 – 100 bpm Causes Non-pharmacological Exercise Pain, anxiety Hypoxia, hypercarbia Acidaemia Sepsis, pyrexia Pulmonary embolism Hyperthyroidism [litfl.com]

• Unconsciousness

  If it does, you may notice: Dizziness Lightheadedness Rapid heartbeat or palpitations Chest pain (angina) Shortness of breath Unconsciousness Cardiac arrest Treatment Not everyone needs treatment for atrial tachycardia, but treatment should be considered [ucihealth.org]

  Common symptoms include: Dizziness Palpitations Shortness of breath Nausea Lightheadedness Falling unconscious Cardiac arrest, in extreme cases Treatment options The cause of your ventricular tachycardia will inform your treatment options. [heart.org]

  Symptoms No matter which type of tachycardia you have, you may feel: Dizziness Lightheadedness Shortness of breath Chest pain Heart palpitations In extreme cases, you could become unconscious or go into cardiac arrest. [webmd.com]

• Hyperthermia

  Other causes include: Pain Fever Anxiety Dehydration Malignant hyperthermia Hypovolemia with hypotension and shock Anemia Heart failure Hyperthyroidism Mercury poisoning Kawasaki disease Pheochromocytoma Sepsis Pulmonary embolism Acute coronary ischemia [en.wikipedia.org]

  Additionally drug related pathologic causes to consider include allergy/anaphylaxis, malignant hyperthermia, or alcohol withdrawal. [openanesthesia.org]

• Exertional Dyspnea

  dyspnea, and nasal discharge. [nigjcardiol.org]

  Case Report A 51-years- old man was admitted in our department with symptoms of exertional and non exertional dyspnea, palpitation, light headedness, orthopnea, giddiness and lethargy. [aclr.com.es]

• Abdominal Pain

  […] en Amlodipine Common side effects Headache, oedema (for example ankle swelling), feeling tired, sleepiness, feeling sick, dizziness, abdominal pain, palpitations (a quicker or irregular heart beat), nausea, flushing mt Matul din it-tneħħija gradwali tad-dazji [glosbe.com]

  At that time she had complained of repeated attacks of upper abdominal pain and intolerance to fatty foods. [pubs.rsna.org]

  Symptoms include: chest pain difficulty breathing profuse sweating dizziness pain or discomfort in the upper body mental confusion or panics abdominal pain dizziness vomiting blackouts See your doctor as soon as possible if you’re experiencing any symptoms [healthline.com]

  It blunts orthostatic tachycardia 31 and may improve chronic symptoms in most patients, 32 but has side-effects including diarrhoea and abdominal pain that can limit its tolerability. [aerjournal.com]

• Tachycardia

  Tachycardia induced cardiomyopathy is a potentially lethal cause of heart failure generally because of atrial tachycardia and less frequently ventricular tachycardia. [ncbi.nlm.nih.gov]

  Sinus tachycardia ECG readout of an individual with sinus tachycardia. Here the heart rate is around 150. [en.wikipedia.org]

  after the exclusion of medical conditions causing sinus tachycardia. [clinicaltrials.gov]

  Inappropriate sinus tachycardia. Olshansky B, Sullivan RM. J Am Coll Cardiol 2013;61:793-801. 3. Inappropriate sinus tachycardia, postural orthostatic tachycardia syndrome, and overlapping syndromes. Brady PA, Low PA, Shen WK. [dysautonomiainternational.org]

• Heart Disease

  It is often a resulting symptom of a primary disease state and can be an indication of the severity of a disease[3]. If the heart rate is too high, cardiac output may fall due to the markedly reduced ventricular filling time[4]. [en.wikipedia.org]

  Structural heart disease and other causes of tachycardia were discarded. Electrocardiographic, Holter monitoring, exercise tolerance and quality of life determinations were performed. [ncbi.nlm.nih.gov]

  Reducing the risk of heart diseases is the best way to prevent the development of this condition. Those who have any form of heart disease or metabolic diseases should monitor and treat the condition. [symptoma.com]

  Continue reading → Tags: Costochondritis, depression, Grand Rounds, heart attack symptoms, Inappropriate Sinus Tachycardia, Lyme disease, misdiagnosis, panic disorder, Tick-Borne Relapsing Fever, women and heart disease [myheartsisters.org]

• Orthostatic Hypotension

  A tilt table test is then required to exclude autonomic disorders that can mimic IST: postural orthostatic tachycardia syndrome (POTS) or orthostatic hypotension. [heartracing.com]

  Postural orthostatic tachycardia syndrome[edit] 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. [en.wikipedia.org]

  […] from a recumbent to a standing position (or > 40 bpm in individuals 12 to 19 years of age); and (3) the absence of orthostatic hypotension (> 20 mm Hg drop in systolic blood pressure). [cambridgeheartclinic.co.uk]

• Sweating

  […] to the most prominent symptoms of palpitations, fatigue and exercise intolerance, IST can also be associated with a host of other symptoms including a drop in blood pressure upon standing, blurred vision, dizziness, tingling, shortness of breath, and sweating [cardiachealth.org]

  […] l-operazzjoni, it-tagħbija eċċ., jistgħu ukoll jiġu msemmija taħt din l-intestatura en Immune system disorders Uncommon-Urticaria, rash Very rare-Anaphylactic reactions Symptoms of generalised hypersensitivity may include generalised skin rash, itching, sweating [glosbe.com]

  Fatigue Resting heart rate of greater than 100bpm Sleeping heart rate of 70 – 90bpm Minimal exertion, heart rate will rapidly reach 150bpm Potentially related symptoms: Drop in blood pressure upon standing Blurred vision Dizziness Syncope Pre-syncope Sweating [heartrhythmalliance.org]

  Symptoms of arrhythmias include fast or slow heart beat skipping beats lightheadedness or dizziness chest pain shortness of breath sweating your doctor can run tests to find out if you have an arrhythmia. [icd9data.com]

• Myalgia

  […] flushing, pruritus, urticaria, face oedema, angioneurotic oedema, rhinitis, bronchospasm, tachypnea, wheezing, hypertension, hypotension, tachycardia, palpitations, abdominal pain, nausea, vomiting, infusion-related pain including pain at the extremities, myalgia [glosbe.com]

• Blurred Vision

  In addition to the most prominent symptoms of palpitations, fatigue and exercise intolerance, IST can also be associated with a host of other symptoms including a drop in blood pressure upon standing, blurred vision, dizziness, tingling, shortness of [cardiachealth.org]

  Symptomatic Tachycardia• If cardiac output falls and compensatory mechanisms fail – Will experience symptoms • Hypotension • Syncope • Blurred vision • Chest pain and palpitations • Nervousness or anxiety • Heart failure – JVD – crackles 9. [slideshare.net]

• Dysautonomia

  (A more general dysautonomia would explain why symptoms with IST most often seem out of proportion to the increase in heart rate.) [verywellhealth.com]

  We suspected prolonged sinus tachycardia due to dysautonomia caused by HHV6 encephalomyelitis. [ncbi.nlm.nih.gov]

  I googled my symptoms and I discovered dysautonomia, which is a dysfunction in the autonomic nervous symptom. Along with dysautonomia, I also read about inappropriate sinus tachycardia (IST). [sclero.org]

  There is a thorough discussion of POTS in the section on Dysautonomia on this website. [njfaint.com]

• Headache

  This had progressed from a discomfort while lying down, noted immediately after her most recent procedure, to continuous headache as if “hanging upside down.” [innovationsincrm.com]

  In addition to rapid heart rate, IST can cause: shortness of breath chest pains dizziness or fainting headaches trouble exercising anxiety Causes Doctors aren’t sure about the exact cause of IST, but it likely involves a combination of factors, including [healthline.com]

  […] en Amlodipine Common side effects Headache, oedema (for example ankle swelling), feeling tired, sleepiness, feeling sick, dizziness, abdominal pain, palpitations (a quicker or irregular heart beat), nausea, flushing mt Matul din it-tneħħija gradwali tad-dazji [glosbe.com]

  Sufferers also experience exhaustion/fatigue, hypersensitivity, vision problems, headaches and even anxiety symptoms. [change.org]

  Possible symptoms include: Sensation of a rapid heartbeat, which may be uncomfortable Shortness of breath Dizziness Fainting Chest pain Anxiety Headaches Decreased ability to exercise The symptoms of IST may look like other health problems. [saintlukeskc.org]

• Somnolence

  […] xaħmin/ Aċtu lawriku en Less frequent adverse reactions of levodopa/carbidopa therapy are irregular heart rhythm and/or palpitations, orthostatic hypotensive episodes, bradykinetic episodes (the 'on-off ' phenomenon), anorexia, vomiting, dizziness, and somnolence [glosbe.com]

Electrocardiography (ECG) is the confirmatory diagnostic test for the different forms of sinus tachycardia. Differentiation between the different types like sinus node re-entry tachycardia and IST are important for deciding on the treatment regimen. ECG also helps to add more information regarding the cardiovascular cause of the condition. IST is characterized by heart rate of 100 beats per minute or more, followed by P-wave axis and morphology similar to that during sinus rhythm. In IST, the heart rate tends to become normal during sleep. Those with postural orthostatic sinus tachycardia show symptoms during upright posture. These patients may show an increase of <30 beats from baseline when in upright posture, but may not have a significant change in blood pressure during head upright tilt test.

• Hypoglycemia

  It may be a response in order to increase cardiac output to compensate for hypovolemia, anemia, hypoxemia, hypoglycemia, fever, or sepsis. [openanesthesia.org]

  Severe hypoglycemia-induced lethal cardiac arrhythmias are mediated by sympathoadrenal activation. Diabetes. 2013 Oct;62(10):3570-81. [PMC free article: PMC3781452] [PubMed: 23835337] 46. Hoffman RS. [ncbi.nlm.nih.gov]

  G stands for glucose and if your patient develops hypoglycemia then they may have sympathoadrenal activation causing tachycardia as well as others symptoms such as tremors, diaphoresis, weakness, altered mental status and even seizures, coma and death [rebelem.com]

  aortic or mitral regurgitation, myocardial infarction, POTS, and vasovagal episodes), pulmonary (e.g., pneumonia, pulmonary embolism), psychological (e.g., anxiety, panic disorder) etiologies, and physiologic contributors (e.g., pain, dehydration, hypoglycemia [eplabdigest.com]

• Sinus Arrhythmia

  ECGs were analysed for cardiac arrhythmias (sinus tachycardia, sinus arrhythmia, premature atrial/ventricular complexes, atrial fibrillation/flutter) and respiratory sinus arrhythmia. [ncbi.nlm.nih.gov]

  Related Topics Sinus rhythm Sinus arrhythmia Sinus bradycardia LITFL Further Reading ECG Library Basics – Waves, Intervals, Segments and Clinical Interpretation ECG A to Z by diagnosis – ECG interpretation in clinical context ECG Exigency and Cardiovascular [lifeinthefastlane.com]

  Keywords: Clinical syndrome, symptoms, diagnosis, tachycardia, EKG, IST, sinus, arrhythmia, tachycardia. [eurekaselect.com]

Those with normal sinus tachycardia due to physical or mental exertion may not need any specific treatment. For other forms of sinus tachycardia, identifying and controlling the underlying cause is the main aim of any form of treatment. Non-pharmacologic strategies like increasing fluid consumption, high salt diet, and keeping the head at an elevated position during sleep help to expand plasma volume. Compression stockings with an ankle pressure of 30 mmHg is also recommended.

Beta blockers are the most common medications used in the management of symptomatic forms of normal sinus tachycardia, particularly those related to emotional stress or related to anxiety. They are also suggested for tachycardia with underlying congestive cardiac failure. But initial dosage and dosing intervals are carefully planned and monitored to avoid decompensation. Beta blockers are useful in IST as well. In case of postural orthostatic form of sinus tachycardia, beta blockers are combined with fludrocortisone. But this is generally done only after the failure of non-pharmacologic measures. Calcium channel blockers are also used in the management of symptomatic sinus tachycardia. This is useful in patients who are intolerant to beta blockers. It is effective in patients with sinus tachycardia secondary to acute myocardial infarction, and also in patients with IST. Alpha receptor agonists, central sympatholytic agents, and barbiturates are used for the management of postural orthostatic form of tachycardia.

Invasive therapy is generally not used in the treatment of normal and postural orthostatic sinus tachycardia. Catheter modification is occasionally used in the management of refractory forms of IST. This removes the cephalic region of the sinus node, but may lead to bradycardia and also the need for permanent pacing. Catheter modification is a useful strategy in the management of sinus node re-entry tachycardia, particularly in those patients who do not respond to drug therapy and those who have frequent episodes of tachycardia.

Prognosis of the different types of sinus tachycardia may depend on the underlying disease, if any. Those with normal sinus tachycardia have a good prognosis. Many studies have shown that high resting heartrate as an indicator of adverse prognosis. And this particularly true of patients with cardiovascular disease. Progressive increase in heartrate is associated with increased risk of cardiovascular and coronary mortality.

Sinus tachycardia is often a physiologic response to stresses including fever, anxiety, pain, hypoxia, hyperthyroidism, and hypovolemia [2]. Stimulants like nicotine and caffeine, and certain medications like salbutamol and atropine, are also implicated as etiological factors in normal sinus tachycardia. Drugs like cocaine, amphetamines, and ecstasy can also cause sinus tachycardia.

In IST the baseline sinus rate may be elevated even in the absence of a physiologic stressor. Adults with IST may show elevated rate of resting heart beat, and minimal exercise may bring in an exaggerated response. Thus, IST is considered to be caused by hypersensitivity to autonomic stimuli or due to sinus node abnormality [3]. Some other causes of sinus tachycardia include congestive heart failure, pulmonary embolism, acute myocardial infarction, cardiogenic shock, and inflammation.

Normal sinus tachycardia is the most common among sinus tachycardia. Symptomatic physiologic normal sinus tachycardia is more prevalent among females, while the other forms, including pathologic and pharmacologic, are present equally among males and females. IST is more common among females, and the average age of onset is about 30 years [4]. Postural orthostatic sinus tachycardia is also reported to be more prevalent among females [5]. There is no age or gender preference in sinus node re-entry tachycardia. Other epidemiological characteristics of the condition are lacking.

Rate of impulses from the sinus node is regulated by the autonomic tone, temperature, availability of oxygen, blood pH, and other hormonal factors. Sinoatrial nodal cells have an unstable membrane potential, and generate an impulse once every second [6]. Most of the pharmacological and pathological etiological factors of sinus tachycardia result in faster depolarization of pacemaker by stimulating the beta adrenergic receptors which results in a faster heartbeat. Physiological causes of increase in heartbeat is driven by catecholamines.

In IST, the sinus nodal cells show enhanced automaticity [7]. Excess of sympathetic with reduced parasympathetic tone also lead to IST. Abnormality in the baroreceptor reflex to orthostatic stress results in postural orthostatic sinus tachycardia. Even in the presence of a peripheral vascular resistance, and exaggerated tachycardia response is often lodged during orthostatic stress in this condition [8]. Orthostatic tachycardia may also be caused by an exaggerated sympathetic response to physiological stimuli. Intrinsic sinus node abnormalities may also affect the normal sinus rhythm [9]. In many other forms the pathophysiologic mechanisms are not clear. Patients who have orthostatic intolerance often show reduced venous compliance, particularly in the legs. This may lead to the specific symptoms [10].

The best way to prevent sinus tachycardia is to reduce the risk of cardiovascular disease. Those who have an underlying heart disease should monitor it carefully and treat the condition. Avoiding causes like alcohol, caffeine, and nicotine also goes a long way in preventing the development of sinus tachycardia.

Sinus tachycardia is a common sinus rhythm, in which the rhythm exceeds 100 beats per minute in adults. This results from an increase in the number of impulses arising from the sinus node. The prognosis of the condition is not too good, particularly in patients with cardiovascular diseases [1]. Although very common, sinus tachycardia is often overlooked. Normal heart beat rate in adult ranges from 60 to 100 beats per minute, while in infants it may be 110-150 beats per minute. The increased rate gradually slows down in children as they grow older. Sinus tachycardia may be classified into four distinct forms of rhythm disturbances:

• Normal sinus tachycardia
• Inappropriate sinus tachycardia (IST)
• Postural orthostatic tachycardia syndrome
• Sinus node re-entry tachycardia (SNRT) 

Electrophysiological studies are often used to assess the origin and extent of conduction abnormalities. Patients may be asymptomatic or present with variable clinical manifestations.

Sinus tachycardia is a condition in which the heart rate is elevated, usually above 100 beats per minute. This rate is higher than the normal resting heart rate of an individual, which ranges from 60-100 beats per minute. It may go up to 200 beats per minute in younger individuals, while it may be around 150 beats in older people. Increase in heart rate is usually a response to physiological conditions like exercise, anger, and emotional stress. Some other causes of sinus tachycardia include pain, fever, inflammation, anxiety, dehydration, heart failure, hyperthyroidism, lack of oxygen, and chronic pulmonary disease. Thus sinus tachycardia generally reflects an underlying condition or an effect of certain medication. Many forms of sinus tachycardia is found to be more common among females when compared to males.

Sinus tachycardia may remain asymptomatic, but many may present with features like dizziness, lightheadedness, and palpitations. Patients who have underlying heart disease may not be able to tolerate sinus tachycardia. Tremor, constipation, and bladder-related problems are also noted as symptoms in some patients. Prognosis of this condition depends on the severity of underlying condition. In general, sinus tachycardia has a good prognosis. But, progressive increase in heart rate is associated with many heart diseases.

Electrocardiography (ECG) is the most important tool in the diagnosis of this condition along with the clinical symptoms. Identifying the underlying cause of the disease is very important in deciding on appropriate treatment strategy. If the condition is caused by certain medications, slow tapering of the medication is suggested. Some of the common medications used in the treatment include beta blockers and calcium channel blockers. Invasive procedures like catheter modification is used only in cases of refractory sinus tachycardia. Sinus tachycardia is treated without any specific medication as well. Those with normal sinus tachycardia due to physical or mental exertion may not need a specific treatment. Non pharmacologic strategies like increased fluid consumption, having a high salt diet, and keeping the head at an elevated position during sleeping helps to relieve the symptoms. Compression stockings with an ankle pressure of 30 mmHg is also recommended. Reducing the risk of heart diseases is the best way to prevent the development of this condition. Those who have any form of heart disease or metabolic diseases should monitor and treat the condition. Avoiding the use of causative factors like nicotine, alcohol and caffeine is also important.

1. Yusuf S, Camm AJ. The sinus tachycardias. Nat Clin Pract Cardiovasc Med. 2005;2(1):44-52. 
2. Tintinalli JE, Kelen GD, Stapczynski JS. Emergency Medicine: A Comprehensive Study Guide. 5th ed. New York, NY: McGraw Hill; 2000.
3. Josephson ME, Zimetbaum PJ, Buxton AE, Marchlinski FE. Tachyarrhythmias. Harrison TR, Resnik WR, Isselbacher KJ, et al, eds. Harrison’s Online [serial online]. New York, NY: McGraw-Hill; 2001.
4. Krahn AD, Yee R, Klein AJ, Morillo C. Inappropriate sinus tachycardia: evaluation and therapy. J Cardiovasc Electrophysiol 1995;6:1124-1128. 
5. Low PA, Opfer-Gehrking TL, Textor SC, et al. Postural tachycardia syndrome (POTS). Neurology. 1995;45:S19-25. 
6. De Fransesco D. Pacemaker mechanisms in cardiac tissue. Ann Rev Physiol. 1993;55:455-472. 
7. Morillo CA, Klein GJ, Thakur RK, Li H, Zardini M, Yee R. Mechanism of inappropriate sinus tachycardia. Role of sympathovagal balance. Circulatiuon. 1994;90-873-877. 
8. Farquhar WB, Taylor JA, Darling SE, Chase KP, Freeman R. Abnormal baroreflex responses in patients with idiopathic orthostatic intolerance. Circulation. 2000;102:3086-3091. 
9. Singer W, Shen WK, Opfer-Gehrking TL, Textor SC, McPhee BR, Hilz MJ, Low PA: Evidence of an intrinsic sinus node abnormality in patients with postural tachycardia syndrome. Mayo Clin Proc 2002;77:246–252.
10. Freeman R, Lirofonis V, Farquhar WB, Risk M: Limb venous compliance in patients with idiopathic orthostatic intolerance and postural tachycardia.J Appl Physiol 2002;93:636–644.