Paroxysmal Supraventricular Tachycardia (SVT)

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Paroxysmal Supraventricular Tachycardia(SVT)
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• Supraventricular Tachycardias
• Start and stop spontaneusly
• gt 100 BPM
• Usually narrow complex, may be wide due to
  aberrant conduction
• Originate above the origin of the bundle of His
• Variable duration
• Causes include
• structural heart disease
• drug toxicity
• electrolyte disturbances (low K)
• lung disease

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• Supraventricular Arrhythmias
• Sinus tachycardia
• Premature atrial complexes
• Premature junctional complexes
• Atrial fibrillation
• Atrial flutter
• Ectopic atrial tachycardia and rhythm
• Multifocal atrial tachycardia
• PSVT
• Junctional rhythms and tachycardia

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• Mechanisms of Supraventricular Arrhythmias
• Enhanced automaticity - normal heart structure or
  organic heart disease, warm-up w/gradual
  acceleration, slows prior to termination,
  suppressed by overdrive pacing, transient nodal
  block w/ADO or CSM
• Triggered activity - delayed after-depolarizations
  (low-amplitude oscillations at end of action
  potential), result of myocardial calcium ion
  influxes, common w/digoxin toxicity or
  catecholamines, initiated/accelerated/terminated
  by rapid atrial pacing, CSM, ADO, verapamil, BB
• Reentrant tachycardia (macro or microreentrant),
  structural heart disease, induced and terminated
  by programmed extrastimulation

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• Three main types of PSVT, they are categorized as
  short RP and long RP tachycardias
• AVNRT AV nodal reentrant tachycardia - short
  RP tachycardia, dual AV nodal conduction
  pathways w/different conduction properties and
  refractory periods, P waves evident following the
  QRS complex, P waves may be buried in the QRS/ST
  segment and thus not visible at all!
• AVRT AV reentrant tachycardia using an
  accessory pathway - short RP tachycardia, P
  waves usually inscribed on the ST segment
• Atrial tachycardia (least common) - long RP
  tachycardia, P waves usually evident
• preceding QRS, in other words the interval from
  the QRS complex to the next P wave is longer
• than the interval from the P wave to the next
  QRS complex

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Regular Narrow Complex Tachycardia

• AV nodal reentry (50)
• AV reciprocating tachycardia (35) with a
  concealed retrograde accessory pathway
• Atrial tachycardia (15)

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RP - PR relationship
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ECG Diagnosis

• Relationship of atrial and ventricular complexes
• RP and PR ratio
• P wave morphology and axis

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ECG Diagnosis

• Mode of initiation
• Response to vagal manuevers
• Response to adenosine
• Influence of bundle branch aberration on
  tachycardia rate

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AVNRT

• Anterograde conduction
• AV node slow pathway
• Posteroseptal right atrium
• Retrograde conduction
• AV node fast pathway
• Anteroseptal right atrium

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AVNRT
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AVNRT
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AVNRT
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Supraventricular Tachycardia
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• Pseudo S waves in leads II and III
• Pseudo R waves in lead V1
• These are typical findings in AVNRT and they
  represent p waves or atrial depolarization

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• After carotid sinus massage normal sinus rhythm
  with normal axis and intervals, adenosine could
  have been used as well

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• Longterm therapy Digoxin, CCBs, b-blockers
• AVNRT can potentially be treated with ablation

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• PSVT due to an accessory pathway
  (Wolff-Parkinson-White syndrome - WPW)
• Second-most common cause of PSVT
• Type of AV reciprocating tachycardia
• Two pathways between atria and ventricles with
  different conducting properties
• Orthodromic using normal pathway to enter the
  ventricle (narrow complex)
• Antidromic antegrade conduction down the
  anomolous pathway (wide complex)

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