TOC | Cardiology   
PSVT (Paroxysmal Supraventricular Tachycardia)         See Supraventricular Tachycardia 2006 (NEJM)      
See also  WPW Syndrome

RX:

  1. Increase vagal tone: carotid sinus massage, induction of gagging by touching the posterior phryns with a tongue blade, valsalva maneuver.
  2. IV Adenosine 6-12 mg bolus. If the initial 6 mg is ineffective, a second bolus of 9 mg can be given after 2-3 min. Transient sinus pauses, aV nodal block, & atrial fibrillation as well as systemic side effects, such as flushing, headache, dyspnea, chest pressure, & nausea, are common with adenosine. They are usually not serious, however, and resolve rapidly.
  3. IV Verapamil 5-10 mg (0.075 to 0.15 mg/kg) bolus over 1-3 min.
    Conversion to sinus rhythm usually occurs within 10 min. If no effect is observe, vagal maneuvers should be repeated, & if ineffective, the same dose may be repeated in 30 min.
    Cardiovasc. side effects associated with its use include sinus bradycardia & transient asystole on conversion (esp. in pts with preexisting sinus node dysfunction), AV block, hypotension, & exacerbation of heart failure. The drug should be be used IV in conjunction with beta-blocking agents, in pts with sick sinus syndrome (unless a pacemaker is in place), or in pts with heart failure unrelated to the rapid heart rate.
  4. IV beta-blocking agents.
  5. Digoxin rapid IV digitalization - 0.5 to 0.75 mg.
  6. Other antiarrhythmic drugs as Flecainide 300 mg PO, IV procainamide 100 mg q2 min to conversion or to a total dose of 2 gm, PO propafenone, amiodarone.
  7. Electrical cardioversion or external pacemaker with rapid atrial stimulation.

Wolff-Parkinson-White  (with/without CHF)
(avoid adenosine, beta blockers, calcium channel blockers, digoxin)
Rate Control †*amiodarone

   

Reentry is the mechanism responsible for the vast majority of cases of PSVT:
AV nodal reentry through the Beta pathway of His bundle ( no P waves are visible)
AV nodal reentry using a concealed bypass tract (inverted retrograde P waves on the T waves)
Intraatrial reentry
In WPW synd. the bypass tract conduct antegradely instead of retrogradely.

AV Nodal Reentrant Tachycardia - the most common cause of PSVT:
It usually presents as a narrow QRS complex with regular rates ranging from 120-250 beats/min. PACs that initiate the arrhythmia are almost always associated with a prolonged PR interval. Retrograde P waves may be absent, buried in the QRS complex, or appear as distortions at the terminal parts of the QRS complex.

RX:

  1. Vagal maneuvers (if no hypotension) as carotid sinus massage, can terminate the arrhythmia in 80% of cases.
  2. If hypotension is present, raising the BP by the cautious use of IV phynylephrine in 0.1 mg increments may terminate the arrhythmia lone or in combination with carotid sinus pressure. if thse Rx are unsuccessful, then
  3. IV adenosine 6-12 mg or verapamil 2.5-10 mg. - agents of first choice.
  4. IV propranolol 0.05-0.2 mg/kg to slow or terminate the tachycardia - agent of second choice.
  5. digoxin has a lower onset of action & should not be used for acute Rx.
  6. Prevention of AV nodal reentry: digoxin, B-blocker, calcium channel blockers, quinidine, flecainide, amiodarone.
  7. Radiofrequency catheter modification of AV nodal function for those who require chronic med. Rx..

Concealed AV bypass tract retrograde Reentrant Tachycardia

These pts manifest the same type of PSVT as in WPW synd, but the bypass tract cannot conduct in an antegrade direction during sinus rhythm or other atrial tachyarrhythmias.
Alteration of the QRS complexes &/or T wave occurs in about 1/3 of such tachycardias. The P wave usually occurs after the QRS complex, because atrial activation must follow vent. activation during AV reentry.

RX: similar to that for AV Nodal Rentry Tachycardia above.

   

POL Outlines in Clinical Medicine 1998

Supraventricular Tachycardias