EKG Basics

Question 1

Most anterior portion of the heart?

Answer 1

Right ventricle

Question 2

Conduction pathways between sinus node and AV node?

Answer 2

3 internodal pathways (anterior, middle, posterior) depolarizes RA

Bachmann Bundle which depolarizes in LA

Question 3

Conduction after AV node?

Answer 3

AV node –> HIS bundle –> splits into two branches: RBB and LBB (which gives off left anterior and left posterior fasicles) –> Purkinje fibers –> cardiomyocytes

Question 4

Is the left anterior or posterior fasicle more susceptible to injury? Why?

Answer 4

anterior b/c has less branches coming off it than the posterior branch (so, posterior branch can compensate more easily if a branch is down)

Question 5

what are the intrinsic rates of the following:

Sinus node
AV junction
Ventricles

Answer 5

Sinus node –> 60-100
AV junction –> 40-60
Ventricles –> 20-40

Question 6

lead I - where’s it go?

Answer 6

Right arm to left arm

Question 7

Lead II - where’s it go?

Answer 7

Right arm to left leg

Question 8

Lead III - where’s it go?

Answer 8

left arm to left leg

Question 9

what are the septal leads?

Answer 9

V1 and V2

Question 10

most anterior leads?

Answer 10

V3 and V4

Question 11

when to consider getting right sided leads?

Answer 11

inferior MI

can help diagnose R ventricular MI, which is preload dependent!

Question 12

when to consider posteriors leads?

Answer 12

in setting of ST depression in V1-V3 w/o RBBB

b/c that ST depression is a reciprocal change in the anterior leads of the posterior MI

Question 13

time of one small box?

Answer 13

0.04 sec, or 40 ms

Question 14

time of one large box?

Answer 14

0.2 sec or 200 ms

Question 15

time of 5 big boxes?

Answer 15

1 sec

Question 16

voltage of one small box?

Answer 16

0.1 mV

Question 17

how many boxes to equal 1 mV

Answer 17

2 big boxes

Question 18

width of one small box?

Answer 18

1 mm

Question 19

width of one big box?

Answer 19

5 mm