Chapter 2 - ECGSupraventricular Rythms

Early beats arising from above the ventricles.PAC, PJC

Normal Sinus Rhythm

Sinus ArrythmiaIrregular rhythm (R-R). Can be caused by respiration. HR increases with inspiration (vagal nerve depressed) and decreases with expiration (vagal nerve stimulated). Phasic SA – due to respirations vs. Non-phasic SA not due to respirations

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). Occurs suddenly with abrupt termination, but slower than SVT with only a rate of 120-150. Depolarizing “spins” around the SA node, circling repeatedly causing a high heart rate at rest.

Sinus Bradycardia cause: fitness, meds, disease

In this example, the heart rate is 34 beats · min–1.

Sinus Pauses – Difficult to know why“ a delay occuring before the appearance of a P wave”

• 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.

Sinus Pause

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.