12/8/2014 Medical Physiology CC: EKG/ECG Harold Smulyan

Question 1

What are the 4 elements related to ECG interpretation?

Answer 1

Rate
Rhythm
Conduction
Wave form

Question 2

Sites of potential impulse generation

Answer 2

S-A node
atrial wall
A-V node and transmission system
bundle branches
ventricular myocardium

Question 3

What are the normal characteristics of sinus rhythm?

Answer 3

1. Frequency of the QRS complexes are ~1 per sec indicating normal beating rate
2. Shape of the QRS complex is normal for lead II and its duration is less than 120 ms indicating rapid repolarization of the ventricles via normal conduction pathways
3. Each QRS complex is preceded by a P wave of proper configuration indicating SA nodal origin of the excitation
4. PR interval is less than 200 ms indicating proper conduction delay of the impulse propagation through the AV node
5. QT interval is less than half the R to R interval indicating normal ventricular repolarization