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Sedentary Work Exerting up to 10 pounds (4.5 kg) of force occasionally and/or a negligible amount of force frequently or constantly to lift, carry, push, pull, or otherwise move objects, including the human body. Sedentary work involves sitting most of the time, but may involve walking or standing for brief periods of time. Jobs are sedentary if walking and standing are required only occasionally and other sedentary criteria are met.

Light Work Exerting up to 20 pounds (9.1 kg) of force occasionally and/or up to 10 pounds (4.5 kg) of force frequently, and/or negligible amount of force constantly to move objects. Physical demand requirements are in excess of those for Sedentary Work. Light Work usually requires walking or standing to a significant degree. However, if the use of the arm and/or leg controls requires exertion of forces greater than that for Sedentary Work and the worker sits most the time, the job is rated Light Work.

Medium Work Exerting up to 50 (22.7 kg) pounds of force occasionally, and/or up to 25 pounds (11.3 kg) of force frequently, and/or up to 10 pounds (4.5 kg) of forces constantly to move objects.

Heavy Work Exerting up to 100 pounds (45.4 kg) of force occasionally, and/or up to 50 pounds (22.7 kg) of force frequently, and/or in excess of 20 pounds (9.1 kg) of force constantly to move objects.

Very Heavy Work Exerting in excess of 100 pounds (45.4 kg) of force occasionally, and/or in excess of 50 pounds (22.7 kg) of force frequently, and/or in excess of 20 pounds (9.1 kg) of force constantly to move objects.

Job Classification

In most duration tables, five job classifications are displayed. These job classifications are based on the amount of physical effort required to perform the work. The classifications correspond to the Strength Factor classifications described in the United States Department of Labor's Dictionary of Occupational Titles. The following definitions are quoted directly from that publication.

Sedentary Work Exerting up to 10 pounds (4.5 kg) of force occasionally and/or a negligible amount of force frequently or constantly to lift, carry, push, pull, or otherwise move objects, including the human body. Sedentary work involves sitting most of the time, but may involve walking or standing for brief periods of time. Jobs are sedentary if walking and standing are required only occasionally and other sedentary criteria are met.

Light Work Exerting up to 20 pounds (9.1 kg) of force occasionally and/or up to 10 pounds (4.5 kg) of force frequently, and/or negligible amount of force constantly to move objects. Physical demand requirements are in excess of those for Sedentary Work. Light Work usually requires walking or standing to a significant degree. However, if the use of the arm and/or leg controls requires exertion of forces greater than that for Sedentary Work and the worker sits most the time, the job is rated Light Work.

Medium Work Exerting up to 50 (22.7 kg) pounds of force occasionally, and/or up to 25 pounds (11.3 kg) of force frequently, and/or up to 10 pounds (4.5 kg) of forces constantly to move objects.

Heavy Work Exerting up to 100 pounds (45.4 kg) of force occasionally, and/or up to 50 pounds (22.7 kg) of force frequently, and/or in excess of 20 pounds (9.1 kg) of force constantly to move objects.

Very Heavy Work Exerting in excess of 100 pounds (45.4 kg) of force occasionally, and/or in excess of 50 pounds (22.7 kg) of force frequently, and/or in excess of 20 pounds (9.1 kg) of force constantly to move objects.

Tachycardia, Paroxysmal Supraventricular


Text Only Home | Graphic-Rich Site | Overview | Risk and Causation | Diagnosis | Treatment | Prognosis | Differential Diagnosis | Specialists | Comorbid Conditions | Complications | Factors Influencing Duration | Length of Disability | Duration Trends | Ability to Work | Failure to Recover | Medical Codes | References

Medical Codes

ICD-9-CM:
427.0 - Paroxysmal Supraventricular Tachycardia
427.1 - Paroxysmal Ventricular Tachycardia

Related Terms

  • Paroxysmal Atrial Tachycardia (PAT)
  • Paroxysmal Atrioventricular Tachycardia
  • Paroxysmal Junctional Tachycardia
  • PSVT
  • Tachycardia

Overview

Paroxysmal supraventricular tachycardia (PSVT) is a disturbance of the normal heart rhythm (tachyarrhythmia), resulting in spontaneously occurring and sporadic (paroxysmal) episodes of regular, rapid heart rate (tachycardia) of more than 100 beats per minute. It develops and ends abruptly, originates in heart tissue that is not in the ventricles, and can last for minutes or hours.

Normally, heart chambers (atria and ventricles) contract in a coordinated way. The electrical signal to contract begins in the sinus (sinoatrial, or SA) node. It is conducted through the upper heart chambers (atria) and stimulates them to contract. It passes through the atrioventricular (AV) node and then travels throughout the ventricles (larger, lower chambers) (through the bundle of His and the Purkinje fibers) and stimulates them to contract.

PSVT occurs from changes in the electrical conduction pathway of the heart. The types of tachycardia that occur depend on where the change in the conduction pathway is initiated. Supraventricular tachycardia (SVT) requires atrial and/or atrioventricular initiation and is classified as either atrial or AV tachyarrhythmia, depending on where it originates; PSVT is an episodic form of SVT that can begin in the atria, the SA node, or the AV node. Symptoms may start and stop suddenly and can last for a few minutes or as long as a day or two.

The 3 types of PSVT are atrioventricular nodal reentry tachycardia (AVNRT); atrioventricular reciprocating tachycardia (AVRT), also known as accessory pathway tachycardia; and sinus tachycardia, including inappropriate sinus tachycardia (IST) and sinus node reentrant tachycardia (SNRT). The most common type of PSVT is AVNRT, diagnosed in 50% to 60% of individuals with tachyarrhythmias (Gugneja). AVNRT occurs when the abnormal conduction pathway originates inside or next to the AV node. AVNRT is usually triggered by premature atrial impulses, and the heartbeat is usually a regular, rapid (120 to 250 beats per minute) rhythm. AVRT occurs when the AV node is bypassed completely and a "shortcut" conduction pathway is used, manifesting in a condition called Wolff-Parkinson-White (WPW) syndrome, which can include atrial fibrillation or atrial flutter. Heart rates can be extremely rapid and may degenerate into ventricular fibrillation and sudden death. Sinus tachycardia originates in the sinoatrial node, which is considered the "pacemaker" node of the heart. IST develops without the presence of structural heart disease and manifests as an elevated resting heart rate and an increase in the heart rate on even modest exercise. SNRT originates as a reentry circuit in or near the sinus node and occurs abruptly with an exaggerated heart rate as high as 150 beats per minute.

An underlying lung or heart disease may cause PSVT. It can occur after a heart attack (myocardial infarction), after lung or heart surgery, or with digitalis toxicity. The abnormal conduction seen in WPW syndrome, however, may be present at birth (congenital).

Incidence and Prevalence: Overall, PSVT occurs in 1 to 3 individuals per 1,000 people. AVNRT is found in 50% to 60% of individuals with a tachyarrhythmia, and AVRT or WPW occurs in 0.1% to 0.3% of the general population (Gugneja).

Source: Medical Disability Advisor



Causation and Known Risk Factors

AVNRT is present in women more often than men and usually occurs in middle-aged or older individuals. AVRT is more common in men than women and presents at a younger age, usually adolescence. The prevalence of PSVT increases with age, but the frequency of accessory pathway SVT decreases with age (Gugneja).

Lifestyle risk factors include excessive use of tobacco (nicotine), caffeine, amphetamines, cocaine, alcohol, and certain medications (e.g., atropine, salbutamol).

Clinical risk factors for PSVT include having rheumatic heart disease, pericarditis, previous heart attack (myocardial infarction), mitral valve prolapse, or preexcitation syndrome. Chronic lung disease and digoxin toxicity can also increase risk.

Source: Medical Disability Advisor



Diagnosis

History: Individuals with PSVT can present with symptoms ranging from mild to severe cardiopulmonary complaints. They may complain of a rapid heartbeat (tachycardia); a sensation of feeling their heartbeat (palpitations); dizziness; lightheadedness; fainting (syncope) or feeling like they may faint (near syncope); neck pounding; shortness of breath; sweatiness (diaphoresis); chest pain; chest tightness; or weakness, fatigue, and nausea. Many individuals with PSVT may complain of anxiety or feeling scared. Personal history may include the use of caffeine, tobacco, recreational drugs, or alcohol. Medical history may include previously diagnosed heart or lung disease, rheumatic fever, prior heart attack, and the use of medications such as atropine and salbutamol that are known to cause tachyarrhythmia. Important diagnostic information includes the time of onset and duration, possible triggers of the episode, previous episodes, and any prior treatment received.
The actual PSVT episode may have ended as abruptly as it began prior to the individual seeking medical care. If the episode continues during physical examination, the heart rate may be greater than 100 beats/minute, with rates of 150 to 200 beats/minute with AVNRT and 150 to 250 beats/minute for AVRT; between episodes, the heart rate is usually normal (60 to 100 beats/minute). The individual typically has a rapid pulse and may appear anxious. Auscultation may reveal abnormal lung sounds such as rales or crackles secondary to congestive heart failure. Signs of poor oxygen perfusion, such as pale skin (pallor), decreased oxygen levels, or confusion, may be observed. Generally, no other specific physical findings are evident. A complete examination may be needed to evaluate preexisting structural heart disease or lung disease. Tachycardia may be the only presenting sign.

Tests: Lab tests include cardiac enzymes to assess for a heart attack in those individuals complaining of chest pain. Additional tests include blood sodium and potassium (serum electrolytes), thyroid hormone levels, a complete blood count (CBC) to assess for anemia, and serum digoxin levels for those individuals on digoxin to check for very high or low levels. A chest x-ray may be needed to check for possible fluid in the lungs (pulmonary edema, pneumonia, heart failure) and heart enlargement (cardiomegaly). An ultrasound of the heart with duplex Doppler (echocardiography) may be done to assess for structural heart defects. Transthoracic echocardiogram and/or cardiac magnetic resonance imaging (MRI) may be needed to investigate possible congenital heart disease.

An electrocardiogram (ECG) usually confirms the diagnosis and helps classify the tachyarrhythmia. Continuous ambulatory monitoring or a 24-hour Holter monitor may be needed to diagnose PSVT because of the sporadic nature of the disorder. WSW syndrome is detected with ECG performed after the tachycardia has terminated.

An intracardiac electrophysiology study (EPS) may be required to confirm that the tachyarrhythmia is caused by PSVT. EPS recordings help map the specific pathways and reentry circuits, allowing classification of the SVT. EPS is performed in conjunction with radiofrequency catheter ablation.

Source: Medical Disability Advisor



Treatment

Many individuals with PSVT require no treatment because the arrhythmia starts and stops spontaneously and may resolve spontaneously. If symptoms develop or there are underlying cardiac disorders, treatment may be initiated in an attempt to interrupt the arrhythmia and convert back to a normal sinus rhythm. Individuals are advised to avoid nicotine, caffeine, recreational drugs, alcohol, fatigue, and stress, all of which are known to provoke tachycardia. Certain medications known to trigger episodes may be discontinued.

For those with PSVT who experience light-headedness or near fainting (near-syncope), the doctor may initiate measures to interrupt the rapid heart rate (tachycardia) by gently massaging one of the carotid arteries (carotid massage) in the neck (used in young people but not advised for older individuals at risk of stroke) and prescribing medications (beta-blockers, calcium channel blockers). Medications such as adenosine or nondihydropyridine calcium channel blockers, procainamide, or amiodarone, may be administered intravenously in hospitalized individuals. Symptomatic individuals (especially those with preexcitation syndrome or incessant tachycardia) may be treated with a procedure that delivers low-voltage, high-frequency electrical energy directly into the heart through a catheter (radiofrequency catheter ablation, catheter ablation). This technique creates a necrotic lesion at specific points in the reentry circuit, determined by the type of SVT, to interrupt the circuit and decrease the heart rate. Catheter ablation may be the only treatment in individuals who cannot tolerate medications. Individuals who are severely symptomatic may require immediate electric shock (cardioversion), which is successful in restoring (converting) PSVT to a normal heart rhythm in many cases.

Pacemakers designed to interrupt or override the tachycardia may be an alternative to ablation or chronic medications for PSVT, but pacemakers are not normally used to correct re-entrant or triggered rhythms. Individuals also may learn self-help measures to slow AV node conduction and interrupt the circuit, such as coughing, plunging their face in ice water (ice water immersion), holding their breath, or attempting to expel breath while deliberately closing the mouth and nose and bearing down (Valsalva maneuver).

Source: Medical Disability Advisor



Prognosis

PSVT is generally not life-threatening unless other cardiac disorders are present. Younger, otherwise healthy individuals who are asymptomatic are usually managed without hospitalization. There is a wide variation in outcome for individuals with PSVT, but most have an excellent outcome, including those who undergo catheter ablation therapy. The success rate for catheter ablation is estimated to be more than 90% (Gugneja). Patients receiving cardioversion are usually unstable with comorbid illness and may have longer hospital stays with intensive treatment. WSW syndrome carries a small risk of cardiac arrest and sudden death.

Source: Medical Disability Advisor



Differential Diagnosis

Source: Medical Disability Advisor



Specialists

  • Cardiologist, Cardiovascular Physician
  • Emergency Medicine Physician
  • Internal Medicine Physician

Source: Medical Disability Advisor



Comorbid Conditions

Source: Medical Disability Advisor



Complications

Complications of PSVT include atrial fibrillation, other arrhythmias, atrioventricular heart block, congestive heart failure, myocardial ischemia and/or infarction, syncope, and sudden death. Rare complications of catheter ablation may include hematoma, bleeding, infection, myocardial infarction, heart block requiring pacemaker insertion, clot formation, stroke, increased risk of malignancy (due to prolonged fluoroscopy times), and death.

Source: Medical Disability Advisor



Factors Influencing Duration

The length of disability depends on the severity of symptoms and frequency of occurrence. The individual's age, response to treatment, associated complications, and adherence to restrictions against nicotine, recreational drugs, alcohol, caffeine, fatigue, and stress, will also influence duration. Individuals with preexisting structural heart disease or chronic lung disease may have longer duration.

Source: Medical Disability Advisor



Ability to Work (Return to Work Considerations)

Asymptomatic, spasmodic tachycardia episodes in otherwise healthy individuals may not require restrictions or special accommodations. The individual may benefit from a less challenging and stressful job and schedule if stress and fatigue are known triggers for an attack. Until recurrent arrhythmia is successfully treated, those who have jobs that entail the safety of others, such as pilots or bus or cab drivers, should be placed in a different job temporarily. Individuals should not hold jobs where there is a danger of falling from heights, or operate moving or heavy machinery. Once the arrhythmia is controlled, no restrictions or accommodations may be required.

Source: Medical Disability Advisor



Failure to Recover

If an individual fails to recover within the expected maximum duration period, the reader may wish to consider the following questions to better understand the specifics of an individual's medical case.

Regarding diagnosis:

  • Does individual have a history of lung or heart disease?
  • Has individual experienced a recent heart attack (myocardial infarction) or undergone lung or heart surgery?
  • Does individual use nicotine, caffeine, recreational drugs, or alcohol?
  • Does individual take the medication digitalis for heart problems? Atropine or salbutamol?
  • Does individual complain of a rapid heartbeat (tachycardia), dizziness, fainting (syncope), shortness of breath, chest pain or tightness, or weakness?
  • Does individual report feeling his or her heartbeat (palpitations) or a sensation of neck-pounding? Does individual report feeling light-headed or about to faint (near-syncope)?
  • Does individual report feeling anxious or scared?
  • Was appropriate lab testing done to rule out other abnormalities or diagnoses such as thyroid dysfunction, electrolyte imbalances, low or high levels of digoxin, or anemia?
  • Was an electrocardiogram (ECG) done?
  • Was continuous ambulatory monitoring for 24 hours (Holter monitor) required due to the sporadic nature of the disorder?
  • Was a diagnosis of PSVT confirmed? Was it classified based on nodal origination?
  • Was an intracardiac electrophysiology study done? If so, what were the results?

Regarding treatment:

  • Was individual treated with medications? Was the treatment successful?
  • Was individual treated with catheter ablation? Did it successfully control episodes? Were there any complications?
  • Did existing underlying heart or lung disease require hospitalization and intensive treatment?
  • Was individual taught self-treatment via vagal maneuvers such as ice immersion, holding his or her breath, and the Valsalva maneuver?

Regarding prognosis:

  • Is individual healthy and asymptomatic other than experiencing episodic PSVT?
  • Does individual have an underlying structural cardiac disorder? Chronic lung disease?
  • Are there any other underlying disorders that could prolong or prevent recovery?
  • Is individual compliant with avoidance of caffeine, recreational drugs, alcohol, nicotine, stress, and fatigue?
  • Is individual compliant with all medication regimens?
  • Have complications of PSVT developed? If so, how will the complication be treated, and what is the expected outcome with treatment?

Source: Medical Disability Advisor



References

Cited

Gugneja, Monika, and Phillip L. Kraft. "Paroxysmal Supraventricular Tachycardia." eMedicine. Eds. Alan D. Forker, et al. 12 Aug. 2009. Medscape. 24 Oct. 2009 <http://emedicine.medscape.com/article/156670-overview>.

General

Mitchell, L. Brent. "Reentrant Supraventricular Tachycardias (SVT, PSVT)." The Merck Manuals Online Medical Library. Jan. 2009. Merck & Co., Inc. 24 Oct. 2009 <http://www.merck.com/mmpe/sec07/ch075/ch075g.html>.

Source: Medical Disability Advisor