3. Normal Sinus Rhythm (NSR) Rhythm: Regular Rate: 60 – 100 bpm P waves: Upright & uniform; precedes each QRS complex PRI: 0.12 – 0.20 sec; constant QRS: Narrow ( < 0.10 sec); sometimes wide ***Interpretation: Normal Sinus Rhythm

4. Sinus Bradycardia (SB) Rhythm: Regular Rate: < 60 bpm P waves: Upright & uniform; precedes each QRS complex PRI: 0.12 – 0.20 sec; constant QRS: Narrow ( < 0.10 sec); sometimes wide ***Interpretation: Sinus Bradycardia (ST-segment depression ???)

5. Sinus Bradycardia (SB) Normal with relaxation or sleep when parasympathetic effect is dominant over the SNS Common in trained athletes (as low as 35 bpm) Beneficial for some patients with cardiac insufficiencies (decreases the workload of the heart)

7. Sinus Tachycardia (ST) Rhythm: Regular Rate: > 100 bpm; < 160 bpm P waves: Upright & uniform; precedes each QRS complex PRI: 0.12 – 0.20 sec; constant QRS: Narrow ( < 0.10 sec); sometimes wide ***Interpretation: Sinus tachycardia

10. Sinus Arrhythmia (SA) Rhythm: Irregular Rate: 60 – 100 bpm; sometimes slower P waves: Upright & uniform; precedes each QRS complex PRI: 0.12 – 0.20 sec; constant QRS: Narrow (< 0.12 sec); sometimes wide ***Interpretation: Sinus Arrhythmia

11. Sinus Arrhythmia (SA) Normal phenomenon caused by variations in autonomic tone Associated with phases of respiration Inspiration = Rate Increases Expiration = Rate Decreases

12. Sinus Pauses Two Kinds: Both originate from the sinus node Sinus (Exit) Block & Sinus Arrest

13. Sinus Arrest Failure of the SA node to fire; a disorder of automaticity. Failure of the SA node to discharge causes an irregularity of when the rhythm resumes following the pause

14. Sinus Arrest Rhythm: depends on underlying; pauses cause slight irregularity; does not resume on time after pause Rate: depends on underlying P waves: Upright & uniform; precedes each QRS complex PRI: 0.12 – 0.20 sec; constant QRS: Narrow (< 0.12 sec); sometimes wide ***Interpretation: NSR with a sinus arrest (??? Sec)

15. Sinus (Exit) Block Electrical impulse is initiated by the SA node, but is BLOCKED as it exits the sinus node preventing conduction to the atria. SA node discharge not affected; regularity not disturbed after rhythm resumes following the pause

16. Sinus (Exit) Block Rhythm: depends on underlying; pauses cause slight irregularity; resumes on time after pause Rate: depends on underlying P waves: Upright & uniform; precedes each QRS complex PRI: 0.12 – 0.20 sec; constant QRS: Narrow (< 0.12 sec); sometimes wide ***Interpretation: NSR with a sinus exit block (??? Sec)

20. TIME TO WORKOUT!!!