Episodes of fast heartbeat can last for few minutes to 1 to 2 days until the condition gets treated. Increased heartbeat of more than 150 – 279 beats/minutes causes poor cardiac output, which in turn gives rise to the following signs and symptoms [7]:

• Shortness of breath
• Dizziness
• Palpitations
• Chest pain with dyspnea
• Nausea
• Diaphoresis
• Syncope

Infants, who have developed SVT, showcase poor feeding habits, lethargy, and loss of interest in feeding and shallow breathing.

• Fatigue

  Sudden onset of an accelerated heart rate can cause palpitations, light-headedness, chest discomfort, anxiety, dyspnea, or fatigue. [ncbi.nlm.nih.gov]

  SVT does not always cause problems, but in more serious cases it can result in symptoms such as light-headedness, fainting, chest pain, shortness of breath, and fatigue. [uabmedicine.org]

  Cardiac arrhythmias also may cause light-headedness, fainting, chest pain, shortness of breath, fatigue or no symptoms at all. [hopkinsmedicine.org]

• Nausea

  Common symptoms include: Chest discomfort Shortness of breath Fatigue Lightheadedness or dizziness Pulsations in the neck Unpleasant awareness of the heartbeat (palpitations) Fainting, more severe chest pain, and nausea are less common symptoms. [cedars-sinai.org]

• Right Flank Pain

  A 60-year-old woman developed severe right flank pain following straightforward catheter ablation for SVT. This was caused by a spontaneous right adrenal haemorrhage, which, after much delay, was eventually recognised as the cause of her symptoms. [ncbi.nlm.nih.gov]

• Tachycardia

  His bundle tachycardia Junctional ectopic tachycardia Junctional ectopic tachycardia (fast heart beat) Junctional ectopic tachycardia, postoperative Paroxysmal atrial tachycardia Paroxysmal atrial tachycardia (heart beat disorder) Paroxysmal junctional [icd9data.com]

  Atenolol was effective for the tachycardia. At 2 years follow up, cardiac function was normal and tachycardia had not recurred. [ncbi.nlm.nih.gov]

  Supraventricular tachycardia does not include those tachycardia rhythms that originate from the ventricles (ventricular tachycardias) such as ventricular tachycardia or ventricular fibrillation. [emedicinehealth.com]

  tachycardia OR narrow-complex tachycardia OR junctional tachycardia.mp.)] [bestbets.org]

• Palpitations

  Specialty Cardiology Symptoms Palpitations, feeling faint, sweating, shortness of breath, chest pain. Classification D ICD-10: I47.1 ICD-9-CM: 427.89, 427.0 MeSH: D013617 Cardiac Disorders – Open Directory Project [en.wikipedia.org]

  Despite its commonality, presentation of SVT can be nonspecific and varies based upon age with infants demonstrating fussiness or irritability and older children reporting vague perceptions of tachycardia or palpitations. [ncbi.nlm.nih.gov]

  Common presentations include palpitations, chest pain, anxiety, shortness of breath and light headedness. Rarely, it presents with syncope. Assessment Treatment Discharge Criteria Further References and Resources [aci.health.nsw.gov.au]

• Heart Disease

  This is the first report of PSVT as an adverse reaction to DEX in a paediatric patient without heart disease. [ncbi.nlm.nih.gov]

  Flecainide and propafenone should be avoided in patients with left bundle branch block, or ischemic or structural heart disease (Class III). [acc.org]

  This arrhythmia is associated with the following conditions [12, 23, 11] : Rheumatic heart disease Hypertension Ischemic heart disease Pericarditis Thyrotoxicosis Alcohol intoxication Mitral valve prolapse and other disorders of the mitral valve Digitalis [emedicine.medscape.com]

• Irregular Heart Rhythm

  Published on May 17, 2019 Paroxysmal supraventricular tachycardia (PSVT) is a type of arrhythmia—or irregular heart rhythm—that affects around 1.7 million Americans. This type of arrhythmia causes the heart to beat too quickly. [youtube.com]

  Implantable loop recorder: This small device, implanted just under the skin of the chest, is automatically triggered by an irregular heart rhythm, but can also be triggered manually. [baptisthealth.com]

  Supraventricular tachycardia (pronounced sue-prah-ven-TRIK-yu-lar tack-ih-CAR-dee-ah) is a problem with the heart’s electrical activity that causes an irregular heart rhythm. Tachycardia is a broad term used to describe fast heart rates and rhythms. [seattlechildrens.org]

  The ventricles are usually able to respond to this signal, but the result is an irregular heart rhythm. PACs are common and may occur as the result of stimulants such as coffee, tea, alcohol, cigarettes, or medications. [piedmont.org]

• Monoplegia

  Ventricular fibrillation, monoplegia, hemiplegia, and cervicomediastinal haematoma are reported complications of carotid sinus massage. [bestbets.org]

• Polyuria

  The patient may complain of shortness of breath, anxiety and occasionally polyuria due to elevated atrial pressure releasing atrial natriuretic peptide. The tachycardia typically ranges between 140-280 bpm and is regular in nature. [lifeinthefastlane.com]

  Polyuria can occur after termination of the episode (due to the release of atrial natriuretic factor). AVNRT may cause or worsen heart failure in patients with poor left ventricular function. [af-ablation.org]

  This phenomenon is less likely in SVTs in which the AV interval is greater, as occurs in accessory pathway-mediated SVTs, because the pressure gradient is usually lower. 4 Polyuria associated with episodes of tachycardia is due to the increased release [revespcardiol.org]

• A preliminary physical examination will be done to determine the heart rate. Physical examination would also reveal a forceful pulse rate in the neck. Heart rate in individuals with SVT would be above 100 – 250 beats/minute. Children would have a higher heart beat and would also show signs of poor blood circulation. 
• Conducting electrocardiography (ECG) is important for diagnosing SVT. If this test is carried out during an episode of SVT, then appropriate diagnosis can be made and other causes of rapid heartbeat can also be ruled out [8].
• In addition to ECG, more specialized tests such as electrophysiology to diagnose the exact location in the heart that is triggering SVT would also be necessary. Imaging studies such as chest radiography, transthoracic echocardiography and MRI of heart are also indicated in diagnosing other associated conditions such as pulmonary edema, congenital heart disease and cardiomegaly [9].

• Inverted P Wave

  Inverted P waves are sometimes seen after the QRS complex. These are called retrograde p waves. The heart fills during diastole, and diastole is normally 2/3 the cardiac cycle. [acls-algorithms.com]

  Retrograde (inverted) P waves may also be seen. 5. [clinicaladvisor.com]

The following methods are involved in the treatment of supraventricular tachycardia:

• Physical maneuvers: This is the method of choice when the atrioventricular node is involved in the causation of SVT. Physical maneuvers work by increasing the intra thoracic pressure which in turn affects the pressure sensor in the arch of the aorta. The valsavar maneuver should be primarily tried in order to end the episode of SVT. In this, the individuals are asked to hold their breath and simultaneously exhale forcibly similar to the process of bowel straining.
• Medications: Medications such as adenosine, is indicated if physical maneuvers does not bring about any positive effect [10]. 
• Cardioversion: Electrocardioversion is used in cases when other treatment methods did not bring about any desired effect. It is one of the most effective modes for restoring sinus rhythm.

In majority of cases, prognosis of the condition mainly depends on the underlying heart disease. Individuals with SVT having a structurally normal heart, have an excellent prognosis. In cases, when SVT occurs due to Wolff-Parkinson-White syndrome, there is a certain percentage of sudden death due to development of atrial fibrillation [6].

Patients with paroxysmal SVT are at an increase risk of developing heart failure, myocardial ischemia and pulmonary edema. Individuals, who do not have any congenital heart defect and are suffering from SVT, are at least risk of sudden death.

SVT has many causes among which the noted cause is Wolff-Parkinson-White syndrome which can be inherited. It can be caused by other underlying diseases like chronic obstructive pulmonary disease (COPD) or heart failure. Prolonged intake of medicines like digoxin or theophylline, and heart surgery can also predispose to the development of the condition.

Anatomically, the heart has a total of 4 chambers, constituting of 2 atria and 2 ventricles. A heartbeat occurs as a result of electrical signal that is produced by the sinoatrial node. These electrical signals spread across the muscles of the heart causing it to contract, thereby producing a “beat”. Any disturbance in this pathway causes abnormal electrical signals to be transmitted to heart, and this gives rise to the condition known as supraventricular tachycardia. Tachycardia means fast heartbeat and supraventricualr means the region above the ventricles. Therefore, fast heartbeat that originates within the ventricles is termed as supraventricualr tachycardia [2]. 

Paroxysmal SVT occurs in about 1 – 3 cases per 1000 individuals. In other words, it has a prevalence rate of 0.2%. Of the several types, atrial fibrillation is the most common type affecting approximately 3 million individuals of US. Statistics have revealed that, by the year 2050, atrial fibrillation will affect more than 7.5 million people.
The incidence of Wolff-Parkinson-White syndrome is estimated to occur in about 3 out of every 1000 individuals [3] [4].

There are two mechanisms that trigger the onset of SVT; re-entry and automaticity. In the re-entry mode, individuals experience a sudden increase in the heartbeats; which is characterized by about 150 – 200 beats per minute. In the automaticity mode, there is a gradual increase in heartbeat. Such a type of condition occurs majorly due to generation of the heart’s own electrical signal.

Supraventricular tachycardia can also occur as a result of abnormal electrical activity in the heart due to congenital defect; a condition known as Wolff-Parkinson-White syndrome. In this syndrome, there is a “bypass tract” that bypasses the atrioventricular node, which in turn results in transmission of the fast heartbeat directly to the ventricles. This creates several loops of overlapping signals which predisposes an individual to develop SVT [5].

There is no way to prevent the onset of SVT. However, to prevent the recurrence of SVT in the future, medications such as verapamil and beta-blockers are used. These drugs along with anti-arrhythmics can also be given for preventing recurrence of SVT episodes.

Supraventricular tachycardia (SVT) is a potentially life threatening condition, demanding immediate medical attention. SVT often refers to paroxysmal supraventricular tachycardia which is an episodic disorder with an abrupt onset and termination. Medications and other therapies help in controlling the occurrence of SVT [1].

• Definition: Supraventricular tachycardia is a condition wherein there is rapid heartbeat of more than 150 – 200 beats/min that originates from above the ventricles. This occurs due to improper electrical activity in the heart which causes development of SVT.
• Cause: Abnormal electrical activity in the heart causes SVT. If infants have congenital defect in the structure of the heart, it is a favorable sign for the development of SVT. In addition, other factors such as excessive consumption of alcohol and caffeine, smoking and use of illicit drugs can also trigger episodes of SVT.
• Symptoms: Symptoms of SVT include shortness of breath, palpitations, anxiety, and development of discomfort in the chest, rapid pulse rate and dizziness. In severe cases, individuals can also faint due to SVT.
• Diagnosis: A preliminary physical examination to determine the heart rate will be done. Following this, electrocardiogram will also be carried out. Imaging studies such as chest radiography, cardiac MRI and transthoracic echocardiography are also indicated in diagnosis of SVT.
• Treatment: Physical maneuvers are the preliminary line of treatment for SVT. If these don’t work then medications and cardioversion techniques may have to be employed.

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4. Chugh SS, Havmoeller R, Narayanan K, et al. Worldwide epidemiology of atrial fibrillation: a Global Burden of Disease 2010 Study. Circulation 2014; 129:837.
5. Trohman RG. Supraventricular tachycardia: implications for the intensivist. Crit Care Med. Oct 2000;28(10 Suppl):N129-35.
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7. Wood KA, Drew BJ, Scheinman MM. Frequency of disabling symptoms in supraventricular tachycardia. Am J Cardiol. Jan 15 1997;79(2):145-9.
8. Farre J, Wellens HJ. The value of the electrocardiogram in diagnosing site of origin and mechanism of supraventricular tachycardia. In: Wellens HJJ, Kulbetus HE, eds. What's New in Electrocardiography. The Hague, Belgium; Martinus Nijhoff; 1981:131-71.
9. Xie B, Thakur RK, Shah CP, Hoon VK. Clinical differentiation of narrow QRS complex tachycardias. Emerg Med Clin North Am. May 1998;16(2):295-330. 
10. Camm AJ, Garratt CJ. Adenosine and supraventricular tachycardia. N Engl J Med 1991; 325:1621.