Text of Chapter 2 - ECG Supraventricular Rythms Early beats arising from above the ventricles. PAC, PJC
Chapter 2 - ECGSupraventricular RythmsEarly 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 RythmA. 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, diseaseIn this example,
the heart rate is 34 beats min1.
Sinus Pauses Difficult to know why a delay occuring before the
appearance of a P wave Failure of SA Node to depolarizeNote: after
pause rhythm resumes with a P wave that is normal with a normal
SA Block depolarization does not escape from the SA NodeNote:
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. *=
Junctional Premature Complex or PJCPremature beats w/- or absent
P waves due to origin at or near the AV NodeSometime difficult to
decide origin so both terms will work.