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ECG Interpretation
Supraventricular Tachycardia:
Mechanisms, Diagnosis, & Management
William A. Shapiro, M.D.
http://anesthesia.ucsf.edu/shapiro
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Normal Sinus Rhythm
Normal sinus rhythm results from the initiation of an
electrical signal (the cardiac impulse) by cells of the
sinus node at a rate appropriate to the age and state of
activity of the individual, and then the propagation of
that signal in an orderly manner through the atria, AV junction, ventricular specialized conducting system
and the ventricular myocardium
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Cardiac Conduction System
Bachmann’s bundle
Sinus node
Internodal pathways
AV node
Bundle of His
Left bundle branch
Posterior division
Anterior division
Right bundle branch
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Purkinje fibers
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Arrhythmia
An arrhythmia reflects either abnormally rapid or
slow impulse initiation by the sinus node, or
interruption of the sinus rhythm by impulses
originating from some other site in the heart,
either for short or long periods of time
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Mechanisms of Arrhythmias
• Reentry
• Automaticity
– Altered normal automaticity
– Abnormal automaticity
• Triggered Rhythms due to DAD (delayed
after depolarizations
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Causes of Arrhythmias
• Physiologic and Pathologic Processes
– Vagal stimulation, Fever, Hypothermia
– Electrolyte abnormalities, CNS problems
– Hypovolemia, Pain, anaphylaxis, etc.
• Preexisting Cardiac & Pulmonary Disease
– Acute coronary syndrome, HTN, AODM
– COPD, hypoxia, hypercarbia
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Supraventricular Tachycardia
Definition
• All forms of tachycardia (rate > 100 bpm) that arise above the
bifurcation of the His bundle. Paroxysmal = sudden onset.
• Require AVN or atrial tissue, or both, for initiation and
maintenance of the arrhythmia.
• Typically (P)SVT has a narrow QRS complex, but the QRS
complex may be wide at baseline, or become wide due to rate
dependent BBB.
• Most reviews exclude A-fib & A-flutter, and MAT.
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Supraventricular Tachycardia
Incidence/Prevalence
• Prevalence is distinct from incidence.
• Prevalence is a measurement of all individuals affected
by the disease within a particular period of time,
whereas;
• Incidence is a measurement of the number of new
individuals who contract a disease during a particular
period of time.
Reference: http://en.wikipedia.org/wiki/Prevalence
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Supraventricular Tachycardia
Incidence/Prevalence
• Incidence (new cases): 35 cases per 100,000 persons
per year.
• Prevalence (all affected): 2.25 per 1000 (excluding
atrial fibrillation, atrial flutter, and multifocal atrial
tachycardia).
• Increases with age and the presence of CV disease.
• Not usually associated with structural heart disease.
Delacrétaz E. Supraventricular Tachycardia. N Engl J Med. 2006
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Supraventricular Tachycardia
Symptoms
• Palpitations: A trigger is usually not identified.
• Feeling of heart pounding in the chest and neck.
• Anxiety, light-headedness, dyspnea.
• Syncope and chest pain are uncommon, but may
indicate CAD, especially in older patients.
• Psychological stress is very common.
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Supraventricular Tachycardia
Mechanisms
• Reentry- approx 90% of all SVT. Either reentry within the AVN
(60%) or using an accessory bypass tract (30%). Almost all
reentrant SVTs are started with a PAC.
• Atrial focus- approx 10%. Automaticity or Triggered activity
• Important concepts- conduction time and refractory period.
• Fast conduction typically has a long refractory period.
• Slow conduction typically has a sort refractory period.
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Supraventricular Tachycardia
Onset of SVT
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Supraventricular Tachycardia
Mechanisms
Ferguson JD. Contemporary Management of Supraventricular Tachycardia. Circulation. 2003
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Supraventricular Tachycardia
Is this Sinus Rhythm or SVT?
What’s missing?
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are needed to see this picture.
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Supraventricular Tachycardia
What’s happening here?
QuickTime™ and a
decompressor
are needed to see this picture.
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Supraventricular Tachycardia
Classification
• AV Node DependentReentry- approx 90% of all SVT. Either reentry within the
AVN (60%) or using an accessory bypass tract (30%).
• AV Node IndependentAtrial focus- approx 10%. Automaticity or Triggered activity.
• Thinking of SVT in this way can help with treatment.
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Treatment of All
Cardiac Arrhythmias
All arrhythmias that are
hemodynamically significant
require immediate cardioversion,
defibrillation, or cardiac pacing
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Supraventricular Tachycardia
Treatment
• AV Node DependentVagotonic maneuvers- CSM, facial emersion in water,
coughing, straining, etc.
Drugs- Adenosine: 6 or 12 mg., verapamil: 5 mg up to 15 mg
Diltiazem, beta blockers may also be used on the AVN.
Ibutilide, procainamide, and flecainide, affect the bypass tract
• AV Node IndependentHeart rate control is the goal. Beta Blockers- sotalol.
• Catheter ablation considered a long term option.
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Supraventricular Tachycardia
Not Discussed
• Atrial Fibrillation
• Atrial Flutter
• Multifocal Atrial Tachycardia
• Sinus Node Arrhythmias
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Supraventricular Tachycardia
References
• Fox DJ, et al. Supraventricular Tachycardia: Diagnosis and Management.
Mayo Clin Proc. 2008;83(12):1400-11
• Delacrétaz E. Supraventricular Tachycardia. N Engl J Med. 2006;354:1039-51
• ACC/AHA/ESC guide-lines for the management of patients with supraventricular arrhythmias. J Am Coll Cardiol. 2003 Oct 15;42(8):1493-531
• Ferguson JD, et al. Contemporary Management of Paroxysmal Supraventricular
Tachycardia. Circulation 2003;107:1096-1099
• Salerno JC, et al. Supraventricular Tachycardia. Arch Pediatr Adolesc Med.
2009;163(3):268-274
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