SVT and NARROW vs. WIDE COMPLEX TACHYCARDIA

 

Etiology:

  1. Can be a consequence of Acute MI, WPW, MVP or  pt without CAD (e.g. stress, coffee).

S & S:

  1. Sudden onset of palpitations.

DX:

1.      narrow complex Tachycardia (SVT, A.fib, A.flut)

  • HR > 160 bpm
  • +/- P wave, QRS is < 0.12 sec
  • VS may be stable or  unstable

2.     wide complex tachycardia

    a) this can be tachycardia with BBB (also called  SVT with aberrancy), WPW
       or wide complex is in reality VT  

    b) can be 2ry to hyperkalemia, dig  toxicity, quinidine toxicity.

    c) what is important is to differentiate VT from  SVT with aberrancy . Clues that
       favor VT  are:

         1.AV dissociation

         2.Capture beat (a beat with normal QRS)

         3.Fusion beat (a "hybrid" between normal QRS and abnormal QRS)

         4.QRS concordance in V1 - V6 leads, i.e. QRS in these leads are in the
            same orientation.

         5.VS may be stable or  unstable

             6.if pt has hx of CAD VT is more likely

             7. RBBB morphology with QRS > 140 md

             8. LBBB morphology with QRS > 160 ms

             9. extreme LAD

 

Treatment:
1.  Stable narrow complex Tachycardia

    a) Vagal stimulation

    b) If SVT is considered, Adenosine 6 mg IV followed by 12 mg x2 (if needed). Adenosine, although short acting and rarely with significant hemodynamic consequences, should be avoided in 2 & 3 AVB, SSS and should be used with
    caution in pt who is on Carbamezapine (may worsen bradycardia), and asthmatics (causes broncospasm). Pts addicted to caffeine may require higher dose of
    adenosine since xanthines compete with adenosine receptors. Also pts may experience acute, angina-like pain when treated with adenosine, but this does
    not require specific treatment unless protracted. CCB, -blockers and dig  can be
    tried if no response from Adenosine.

    c)  If A.fib or A.flut are considered – CCB, B-blockers and/or Dig are given

2.  Unstable narrow complex SVT (BP, chest pain, CHF)

        a)  Cardioversion with 25 -100 j

3.  Stable wide complex Tachycardia (SVT with aberrancy, VT,  unknown etiology)

        a) Lidocaine  Adenosine  Procainamide  Bretylium. The positive response to Class
            I Antiarrhythmics does not prove that pt had VT.   

    b) Pt should not be treated with CCB since it may cause hemodynamic
        deterioration in case of  VT and in case of A.fib and WPW.

4.  Unstable wide complex Tachycardia

    a) if  BP, CHF, chest pain  synchronized cardioversion with 100 - 200 – 300 - 360 j

    b) if pulsless VT  treated as VF.

 

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