Supraventricular tachycardia

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Abdelrahman Ibrahim Abushouk, MD[2]

Synonyms and keywords: SVT

Overview

Classification

Pathophysiology

Causes

Causes by Organ System

Cardiovascular	Air embolism, amyloidosis, aortic regurgitation, aortic stenosis, arteriovenous fistula, atrial ischemia, atrial myxoma, atrial septal defect, cardiac tamponade, cardiac tumors, cardiomyopathy, Chagas heart disease, congestive heart failure, constrictive pericarditis, coronary artery bypass graft surgery, coronary artery disease, dilated cardiomyopathy, Ebstein's anomaly, endocarditis, familial atrial fibrillation, familial atrioventricular nodal reentry tachycardia, heart bypass surgery, heart failure, hemochromatosis, holiday heart syndrome, hypertensive heart disease, hypertrophic cardiomyopathy, hypokalemia, hypotension, hypoxia, ischemic heart disease, Kawasaki disease, left ventricular hypertrophy, Lown-Ganong-Levine syndrome, LQT type 4, Lutembacher syndrome, mahaim fiber tachycardia, mitral regurgitation, mitral valve stenosis, myocardial infarction, myocarditis, neonatal coxsackie myocarditis, open heart surgery, pericarditis, peripartum cardiomyopathy, post cardiac surgery, pulmonary embolism, pulmonary hypertension, rheumatic heart disease, shock, sick sinus syndrome, stroke, temporary cardiac pacing, tricuspid regurgitation, tricuspid stenosis, unstable angina, uremic pericarditis, valvular heart disease, Wolff-Parkinson-White syndrome
Chemical/Poisoning	Breath spray, carbon monoxide poisoning, cyanide, grayanotoxin, mercury poisoning
Dental	No underlying causes
Dermatologic	Psoriatic arthritis
Drug Side Effect	Albuterol, alprazolam, amiodarone, amphetamines, amrinone, atomoxetine, atropine, beta blockers, caffeine, carbamazepine poisoning, cimetidine, clonidine, conivaptan, diazoxide, dicobalt edetate, diltiazem, disopyramide, dobutamine, docetaxel, dopexamine, doxapram, doxorubicin, ephedrine, epirubicin, fentanyl, flecainide, flumazenil, fluvoxamine, guanethidine, hexamethonium, hydralazine, ibutilide, isoprenaline, isoproterenol infusion, lithium, methamphetamines, methyldopa, methylphenidate, methysergide, minoxidil, nelarabine, nicotine, orlistat, palonosetron, paroxetine, phenoxybenzamine, phentolamine, porfimer sodium, pramipexole, procainamide, propafenone, quinidine, ramucirumab, reserpine, ritodrine, romidepsin, salbutamol, salmeterol, sargramostim, sibutramine, theophylline, trimethaphan, type Ia antiarrhythmic agents, type Ic antiarrhythmic agents, type III antiarrhythmic agents, verapamil
Ear Nose Throat	No underlying causes
Endocrine	Amyloidosis, diabetes mellitus, fatigue, hemochromatosis, hyperthyroidism, hypoglycemia, hypothyroidism, pheochromocytoma, thyrotoxicosis
Environmental	No underlying causes
Gastroenterologic	Crohn's disease, hemochromatosis, ulcerative colitis
Genetic	Channelopaties, Emery-Dreifuss muscular dystrophy, hemochromatosis, LQT type 4, muscular dystrophy, myotonic dystrophy
Hematologic	Anemia, fat embolism, fatigue, hemochromatosis
Iatrogenic	Cardiac surgery, cardiac transplantation, incomplete ablation procedures, post cardiac surgery, postoperative complication, surgery
Infectious Disease	Amoebiasis, chagas heart disease, diphtheria, fever, leptospirosis, Lyme disease, myocarditis, myotonic dystrophy, neonatal coxsackie myocarditis, rheumatic fever, salmonella typhosa, sepsis, trichinosis, viral infections
Musculoskeletal/Orthopedic	Emery-Dreifuss muscular dystrophy, fat embolism, hemochromatosis, muscular dystrophy
Neurologic	Diabetic autonomic neuropathy, fat embolism, fatigue, Guillain-Barré syndrome, obstructive sleep apnea, stroke, subarachnoid hemorrhage
Nutritional/Metabolic	Dehydration, hypercapnia, hypervitaminosis D, hypokalemia, hypomagnesemia
Obstetric/Gynecologic	nonimmune hydrops fetalis, peripartum cardiomyopathy, pregnancy
Oncologic	atrial myxoma, bronchogenic carcinoma, cardiac tumors, fatigue, lung cancer, pheochromocytoma
Ophthalmologic	No underlying causes
Overdose/Toxicity	Alcohol overdose, alcohol withdrawal, aminophylline toxicity, binge drinking, carbamazepine poisoning, cocaine overdose, digitalis toxicity, salicylate poisoning, tricyclic antidepressant overdose
Psychiatric	Anxiety, bulimia nervosa, fatigue, panic disorder, psychological stress
Pulmonary	Air embolism, bronchogenic carcinoma, chronic obstructive pulmonary disease, emphysema, fat embolism, hypoxia, lung cancer, pneumonia, sarcoidosis, tension pneumothorax
Renal/Electrolyte	Chronic kidney disease, chronic renal failure, dehydration, electrolyte disturbance, renal insufficiency
Rheumatology/Immunology/Allergy	Amyloidosis, ankylosing spondylitis, collagen vascular disease, juvenile idiopathic arthritis, psoriatic arthritis, reactive arthritis, rheumatic fever, rheumatic heart disease, sarcoidosis, scleroderma, spondyloarthritis
Sexual	No underlying causes
Trauma	Cardiac injury from blunt trauma, drowning, electric shock
Urologic	No underlying causes
Miscellaneous	Binge drinking, drowning, fever, hypothermia, malignant hyperthermia, pain, stress

Differentiating Among the Different Types of Supraventricular Tachycardia

The individual subtypes of SVT can be distinguished from each other by certain physiological and electrical characteristics, many of which present in the patient's EKG. Supraventricular tachycardias must be differentiated from each other because the management strategies may vary:

	Epidemiology	Rate	Rhythm	P waves	PR Interval	QRS complex	Response to maneuvers
Sinus Tachycardia		Greater than 100 bpm	Regular	Upright, consistent, and normal in morphology	0.12–0.20 sec and shortens with high heart rate	Less than 0.12 seconds, consistent, and normal in morphology	May break with vagal maneuvers
Atrial Fibrillation	More common in the elderly, following bypass surgery, in mitral valve disease, hyperthyroidism	110 to 180 bpm	Irregularly irregular	Absent, fibrillatory waves	Absent	Less than 0.12 seconds, consistent, and normal in morphology in the absence of aberrant conduction	Does not break with adenosine or vagal maneuvers
Atrial Flutter	More common in the elderly, after alcohol	75 (4:1 block), 100 (3:1 block) and 150 (2:1 block) bpm, but 150 is more common	Regular	Sawtooth pattern of P waves at 250 to 350 beats per minute	Varies depending upon the magnitude of the block, but is short	Less than 0.12 seconds, consistent, and normal in morphology	Conduction may vary in response to drugs and maneuvers dropping the rate from 150 to 100 or to 75 bpm
AV Nodal Reentry Tachycardia (AVNRT)	Accounts for 60%-70% of all SVTs. 80% to 90% of cases are due to antegrade conduction down a slow pathway and retrograde up a fast pathway.	In adults the range is 140-250 bpm, but in children the rate can exceed 250 bpm	Regular	The P wave is usually superimposed on or buried within the QRS complex	Cannot be calculated as the P wave is generally obscured by the QRS complex	Less than 0.12 seconds, consistent, and normal in morphology	May break with adenosine or vagal maneuvers
AV Reciprocating Tachycardia (AVRT)	More common in males, whereas AVNRT is more common in females, occurs at a younger age.	More rapid than AVNRT	Regular	A retrograde P wave is seen either at the end of the QRS complex or at the beginning of the ST segment	Less than 0.12 seconds	Less than 0.12 seconds, consistent, and normal in morphology	May break with adenosine or vagal maneuvers
Inappropriate Sinus Tachycardia	The disorder is uncommon. Most patients are in their late 20s to early 30s. More common in women.	> 95 beats per minute. A nocturnal reduction in heart rate is present. There is an inappropriate heart rate response on exertion.	Regular	Normal morphology and precede the QRS complex	Normal and < 0.20 seconds	Less than 0.12 seconds, consistent, and normal in morphology	Does not break with adenosine or vagal maneuvers
Junctional Tachycardia	Common after heart surgery, digitalis toxicity, as an escape rhythm in AV block	> 60 beats per minute	Regular	Usually inverted, may be burried in the QRS complex	The P wave is usually buried in the QRS complex	Less than 0.12 seconds, consistent, and normal in morphology	Does not break with adenosine or vagal maneuvers
Multifocal Atrial Tachycardia (MAT)	High incidence in the elderly and in those with COPD	Atrial rate is > 100 beats per minute (bpm)	Irregular	P waves of varying morphology from at least three different foci	Variable PR intervals, RR intervals, and PP intervals	Less than 0.12 seconds, consistent, and normal in morphology	Does not terminate with adenosine or vagal maneuvers
Sinus Node Reentry Tachycardia		100 to 150 bpm	Regular	Upright P waves precede each regular, narrow QRS complex	Short PR interval	Less than 0.12 seconds, consistent, and normal in morphology	Does often terminate with vagal maneuvers unlike sinus tachycardia.
Wolff-Parkinson-White syndrome	Estimated prevalence of WPW syndrome is 100 - 300 per 100,000 in the entire world.	Atrial rate is nearly 300 bpm and ventricular rate is at 150 bpm.	Regular	P wave generally follows the QRS complex due to a bypass tract	Less than 0.12 seconds	Delta wave and evidence of ventricular pre-excitation if there is conduction to the ventricle via ante-grade conduction down an accessory pathway	May break in response to procainamide, adenosine, vagal maneuvers

Differentiating Supraventricular Tachycardia from Ventricular Tachycardia

For a detailed discussion of how to distinguish ventricular tachycardia (VT) from supraventricular tachycardia (SVT), please visit the wide complex tachycardia differential diagnosis page.

In brief, the diagnosis of VT is more likely if:

• There is a history of myocardial infarction, congestive heart failure or structural heart disease
• VT is more common in the elderly
• The electrical axis is -90 to -180 degrees (a “northwest” or “superior” axis)
• The QRS is > 140 msec
• There is AV dissociation. P waves are normal in morphology, upright, but dissociated from the QRS complex (i.e. "march through" the QRS complex)
• There are positive or negative QRS complexes in all the precordial leads
• The morphology of the QRS complexes resembles that of a previous premature ventricular contraction (PVC).
• Rate: More than 100 bpm and usually 150-200 bpm
• Rhythm: The rhythm is regular
• PR interval: Variable PR interval
• Response to Maneuvers: VT does not terminate in response to adenosine or vagal maneuvers

Epidemiology and Demographics

Natural History, Complications and Prognosis

Natural History

The rhythm often ceases abruptly and spontaneously, particularly the most common form AVNRT. An episode generally last seconds to hours.

Complications

• Some patients will develop syncope during episodes of AVRNT. The mechanism of syncope may be due to a reduction of cardiac output and hemodynamic compromise as a result of the short ventricular filling time or alternatively it may be due to transient asystole due to tachycardia-mediated suppression of the sinus node when the rhythm terminates. Those patients who do become symptomatic during episodes of SVT (i.e. have syncope) should avoid activities where the occurrence of hemodynamic compromise would endanger their safety or that of others (like driving).
• In patients with underlying ischemic heart disease, demand-related myocardial ischemia, angina and even myocardial infarction and/or congestive heart failure can occur.
• Tachycardia mediated cardiomyopathy may develop if the SVT is chronic and does not terminate.

Prognosis

SVTs are rarely life threatening and in the absence of underlying structural heart disease, the prognosis is good. Radiofrequency ablation is curative in 95% of cases of AVNRT.

Diagnosis

Symptoms that are common to all types of SVT include the following:

• Anxiety
• Chest pain or sensation of tightness
• Dizziness, or lightheadedness (near-faint), or fainting
• Lightheadedness
• Palpitations (the sensation of the heart racing, fluttering or pounding strongly in the chest or the carotid arteries)
• Shortness of breath
• Syncope in cases of AVNRT
• Sweating

Shown below is an EKG depicting a tachycardia at a rate of 190/min with narrow QRS complexes indicating supraventricular tachycardia.

Copyleft image obtained courtesy of ECGpedia, http://en.ecgpedia.org/wiki/File:De-AW00011.jpg

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Shown below is an EKG recording of a patient who goes from sinus rhythm to a wide complex tachycardia at about 130/min. The wide QRS though disappears after nine complexes and is replaced by narrow complexes at a slightly slower rate. No P wave activity is seen. This is a supraventricular tachycardia with a form of aberrancy. In this case we are probably seeing a rate dependent left bundle branch block or the effect of a left bundle branch block which persists for the nine complexes because of continued block in the left bundle from the depolarizations from the intact right bundle.

Copyleft image obtained courtesy of ECGpedia, http://en.ecgpedia.org/wiki/Main_Page

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Shown below is an example of a EKG demonstrating a rapid heart rate at the rate of nearly 300 beats per minute indicating a paroxysmal supraventricular tachycardia.

Copyleft image obtained courtesy of ECGpedia, http://en.ecgpedia.org/wiki/File:De-AW00012.jpg

Treatment

Acute Treatment

In general, SVT is not life threatening, but episodes should be treated or prevented. While some treatment modalities can be applied to all SVTs with impunity, there are specific therapies available to cure some of the different sub-types. Cure requires intimate knowledge of how and where the arrhythmia is initiated and propagated.

The SVTs can be separated into two groups, based on whether they involve the AV node for impulse maintenance or not. Those that involve the AV node can be terminated by slowing conduction through the AV node. Those that do not involve the AV node will not usually be stopped by AV nodal blocking maneuvers. These maneuvers are still useful however, as transient AV block will often unmask the underlying rhythm abnormality.

AV nodal blocking can be achieved in at least three different ways:

Acute Pharmacotherapy

Another modality involves treatment with medications. Pre-hospital care providers and hospital clinicians might administer adenosine, an ultra short acting AV nodal blocking agent. If this works, followup therapy with diltiazem, verapamil or metoprolol may be indicated. SVT that does NOT involve the AV node may respond to other anti-arrhythmic drugs such as sotalol or amiodarone.

In pregnancy, metoprolol is the treatment of choice as recommended by the American Heart Association.

Prevention

Once the acute episode has been terminated, ongoing treatment may be indicated to prevent a recurrence of the arrhythmia. Patients who have a single isolated episode, or infrequent and minimally symptomatic episodes usually do not warrant any treatment except observation. Patients who have more frequent or disabling symptoms from their episodes generally warrant some form of preventative therapy. A variety of drugs including simple AV nodal blocking agents like beta-blockers and verapamil, as well as antiarrhythmics may be used, usually with good effect, although the risks of these therapies need to be weighed against the potential benefits.

References