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Introduction ⬇

On the line

Identifying type II second-degree AV block

This rhythm strip illustrates type II second-degree AV block. Look for these distinguishing characteristics:

Rhythm

  • Atrial—regular; ventricular—irregular

Rate

  • Atrial—60 beats/min; ventricular—50 beats/min

P wave

  • Normal

PR interval

  • 0.28 second

QRS complex

  • 0.10 second

T wave

  • Normal

QT interval

  • 0.60 second

Other

  • PR and RR intervals constant before a dropped beat with no warning


What Causes It ⬆ ⬇

  • Anterior-wall MI
  • Degenerative changes in the conduction system
  • Severe CAD
Help desk

Distinguishing type II second-degree AV block from nonconducted PACs

An isolated nonconducted P wave (a P wave not followed by a QRS complex, as shown in the shaded areas below) may result from type II second-degree AV block or a nonconducted PAC. Confusing these two arrhythmias can have serious consequences. The former is usually benign, but the latter can be life-threatening.

Second-degree AV block type II

If the P-P interval is constant, including the extra P wave, it's type II second-degree AV block.

Nonconducted PAC

If the P-P interval, including the extra P wave, isn't constant, it's a nonconducted PAC.



What to Look for ⬆ ⬇

  • Usually no symptoms as long as cardiac output is adequate
  • Only occasional dropped beats as long as cardiac output is adequate
  • Evidence of decreased cardiac output (as dropped beats increase)
    • Dyspnea
    • Fatigue
    • Light-headedness
  • Hypotension
  • Slow pulse
  • Regular or irregular rhythm

How It's Treated ⬆

  • Observe the cardiac rhythm for progression to a more severe block.
  • Evaluate the patient for correctable causes (such as ischemia).
  • Reduce myocardial oxygen demands by keeping the patient on bed rest and administering oxygen.
  • Teach the patient and his family about pacemakers, if indicated.
  • If the patient has no serious signs and symptoms:
    • Monitor him continuously, keeping a transcutaneous pacemaker attached to the patient or in the room.
    • Prepare him for transvenous pacemaker insertion.
  • If the patient has serious signs and symptoms:
    • Give IV atropine, dopamine, epinephrine, or a combination of these drugs as ordered for symptomatic bradycardia.
    • Use transcutaneous pacing until a transvenous pacemaker is placed.