Chapter 2 - ECGSupraventricular Rythms

Early beats arising from above the ventricles.PAC, PJC

Normal Sinus Rhythm

Sinus ArrythmiaCan be caused by respiration. HR increases with inspiration (vagal nerve depressed) and decreases with expiration (vagal nerve stimulated).

Normal Sinus Rythm

• A. Figure 2.4, page 21.

Sinus Tachycardia and SA Nodal Re-Entrant Tachycardia

If obtained under resting conditions this would be considered:“SA Nodal Re-Entrant Tachycardia” (pg. 23)

Sinus Pauses – Difficult to know why• Failure of SA Node to depolarize

– Note: after pause rhythm resumes with a “P” wave that is normal with a normal QRS.

• SA Block – depolarization does not “escape” from the SA Node– Note: Rhythm resumes with a normal

QRS.

PAC – premature, ectopic beat arising somewhere other than the SA Node. Arises in atria or AV node. P wave morphology is different. PR interval will differ (shorter) due to change in time for conduction to move to ventricles. QRS is normal.

• Blocked or non-conducted PAC. AV node is still in the refractory period.

*= ectopic focus

Junctional Premature Complex or PJC• Premature beats w/- or

absent P waves due to origin at or near the AV Node

• Sometime difficult to decide origin so both terms will work.