1. Chapter 4
Atrial Rhythms

2. Atrial Dysrhythmias: Mechanisms
Altered automaticity and triggered activity are disorders in impulse formation. Reentry is a disorder in impulse conduction.

3. Altered Automaticity
Altered Automaticity occurs in normal pacemaker cells and in myocardial working cells that do not normally function as pacemaker sites.

4. Triggered Activity
Triggered Activity results from abnormal electrical impulses that sometimes occur during repolarization, when cells are normally quiet.

5. Reentry
Reentry (reactivation) is a condition in which an impulse returns to stimulate tissue that was previously depolarized.
Reentry requires:
A potential condition circuit or circular conduction pathway
A block within part of the circuit
Delayed conduction within the remainder of the circuit

6. Premature Atrial Complexes (PACs)
A premature atrial complex (PAC) occurs when an irritable site within the atria fires before the next SA node impulse is due to fire.
2 PAC’s

7. Aberrantly Conducted PACs
PACs associated with a wide QRS complex are called aberrantly conducted PACs.
Aberrantly conducted PACs

8. Wandering Atrial Pacemaker
With this rhythm, the size, shape and direction of the P waves vary, sometimes from beat to beat.
Notice all of the P waves are different even in the slightest bit.

9. Multifocal Atrial Tachycardia
When the wandering atrial pacemaker is associated with a ventricular rate greater than 100 bpm, the rhythm is called multifocal atrial tachycardia (MAT).

10. Atrial Tachycardia
An irritable site in the atria fires at a rate of bpm.

11. Atrial Tachycardia
Atrial tachycardia that starts or ends suddenly is called paroxysmal atrial tachycardia (PAT).

12. Synchronized Cardioversion
Synchronized cardioversion is the delivery of shock to the heart by means of a defibrillator to terminate rapid dysrhythmia.

13. AV Nodal Reentrant Tachycardia (AVNRT)
AVNRT is caused by reentry in the area of the AV node.

14. AVNRT
A regular, narrow-QRS tachycardia that starts or ends suddenly is called paroxysmal supraventricular tachycardia (PSVT).

15. AV Reentrant Tachycardia (AVRT)
Preexcitation is a term used to describe rhythms that originate from above the ventricles but in which the impulse travels via a pathway other than the AV node & bundle of His
The most common type of preexcitation syndrome is called Wolff-Parkinson-White (WPW) Syndrome.
Delta Wave

16. Atrial Flutter
Atrial Flutter is an ectopic rhythm in which an irritable site fires regularly at a very rapid rate.

17. Atrial Fibrillation
Atrial Fibrillation occurs because of altered automaticity in one of several rapidly firing sites in the atria or reentry involving one or more circuits in the atria.
These rapid impulses cause the muscles of the atria to quiver (fibrillate).