3. AV Node P Waves See Overhead Slide 4-1

4. Premature Junctional Contraction A premature junctional contraction (PJC) is an earl beat that originates in the AV junction. As a result of increased automaticity within junctional cells

5. Premature Junctional Contraction Rhythm: Premature ectopic beat causes slight irregularity Rate: Overall HR depends on rate of underlying rhythm P waves: P wave may be inverted, come after the QRS complex, or be lost in the QRS complex. PRI: 0.12 – 0.20 sec on regular beat; ectopic beat is visible PRI will be < 0.12 sec; if P wave is late or not visible there will be no PRI. QRS: Narrow (< 0.12 sec); sometimes wide

6. Junctional Escape Beat An ectopic junctional beat that occurs late within an underlying rhythm P wave will be inverted (before the QRS), hidden (within the QRS), or late & inverted (after the QRS)

7. Junctional Escape Beat Common after a pause in the underlying rhythm: Sinus arrest Sinus (exit) block Nonconducted PAC Mobitz I

8. Junctional Rhythm Appears secondary to depression of the SA node Occurs when the SA node is firing at a rate lower than that of the inherent rate of the AV node Or if the electrical impulse of the SA node fails to reach the AV node If the AV node does receive an impulse within 1 – 1.5 seconds, it is triggered to fire resulting in a junctional escape beat or rhythm

9. Junctional Rhythm Causes: Disease of the SA node Acute MI Drug Effects (digitalis, quinidine, BB’s, or CCB’s) May also occur with Complete Heart Block

10. Junctional Rhythm Rhythm: Regular Rate: 40 – 60 bpm (impulse originates from AV junction) P waves: Consistently either inverted before QRS, hidden in QRS complex, or inverted & after the QRS complex PRI: usually < 0.12 sec but may be 0.12 – 0.20 sec; if P wave is late or not visible there will be no PRI QRS: Narrow (< 0.12 sec); sometimes wide

11. Junctional Rhythm

12. Accelerated Junctional Rhythm Causes: Enhanced automaticity secondary to digitalis toxicity Damage to the AV node secondary to acute inferior wall MI, heart failure, acute rheumatic fever, myocarditis, valvular heart disease, and cardiac surgery (especially valve surgery)

13. Accelerated Junctional Rhythm

14. Junctional Tachycardia Causes: Enhanced automaticity secondary to digitalis toxicity Damage to the AV node secondary to acute inferior wall MI, heart failure, acute rheumatic fever, myocarditis, valvular heart disease, and cardiac surgery (especially valve surgery)

15. Junctional Tachycardia Often confused with SVT if the rate is very fast causing the P wave to become hidden If a P wave cannot be differentiated, then it is acceptable to use the term Paroxysmal SVT or PSVT to describe the rhythm

16. Junctional Tachycardia Rhythm: Regular (usually) Rate: 101 – 180 bpm (impulse originates from AV junction) P waves: Consistently either inverted before QRS, hidden in QRS complex, or inverted & after the QRS complex PRI: usually < 0.12 sec but may be 0.12 – 0.20 sec; if P wave is late or not visible there will be no PRI QRS: Narrow (< 0.12 sec); sometimes wide

17. TIME TO WORKOUT!!!