Lecture 22 and 23

Question 1

Name some things that can be determined by reading an EKG

Answer 1

rate
rhythm
hypertrophy
infarction

Question 2

How do determine HR

Answer 2

1. find R wave that falls on heavy black line
2. count off 300, 150, 100, 75, 60, 50 for each consecutive heavy line
3. Where the next R wave falls determines the rate

Question 3

60-100 beats/min

Answer 3

normal sinus rhythm

Question 4

<60 beats/min

Answer 4

sinus bradycardia

Question 5

> 100 beats/min

Answer 5

sinus tachycardia

Question 6

1. all waves are present in each cardiac cycle and look normal
2. normal distances between similar waves from one cardiac cycle to the next
3. each wave in all cardiac cycle look alike
4. the P-R/P-Q, Q-T, and QRS intervals are normal

Answer 6

normal/regular rhythm

Question 7

ectopic focus discharging spontaneously producing a beat which appears earlier than expected in the rhythm

Answer 7

premature beats

Question 8

originates suddenly in an atrial ectopic focus and produces an abnormal P wave earlier than expected

Answer 8

premature contraction (PAC)

Question 9

originates suddenly in an ectopic focus in a ventricle producing a giant ventricular complex. occurs before a P wave can begin a new cycle. QRS complex is very wide and tall/deep

Answer 9

premature ventricular contraction (PVC)

Question 10

Why is the QRS complex wider and normal during a PVC?

Answer 10

because depolarization originates in the myocardium (instead of conduction system) and therefore depolarization impulse conducted very slowly across both ventricles

Question 11

Why is the QRS taller/deeper than normal during a PVC?

Answer 11

During normal ventricular conduction, the left and right ventricles depolarize simultaneously. As a result, depolarization going toward the left ventricle is somewhat opposed by simultaneous depolarization going toward right ventricle. Therefore, QRS is relatively small. PVC originates in one ventricle which depolarizes before the other and there is no simultaneous opposing depolarization from opposite sides. Therefore, QRS is very large.

Question 12

rate between 250-350 beats/min

Answer 12

flutter

Question 13

1. originates in an atrial ectopic focus
2. P waves occur in rapid succession and each is identical to the next
3. P waves look identical because they arise from the same ectopic focus
4. only occasionally will the atrial stimulus penetrate the AV node and produce a QRS complext

Answer 13

atrial flutter

Question 14

1. is produced by a single ventricular ectopic focus firing at an extremely rapid rate
2. forms a smooth sine wave
3. no P waves or T waves

Answer 14

ventricular flutter

Question 15

rate between 350-450 beats/min

Answer 15

fibrillation

Question 16

1. caused by MANY atrial ectopic foci firing at rapid rates
2. no true P wave-just spikes appear
3. major concern is development of blood clots due to pooling of blood- can live with this

Answer 16

atrial fibrillation

Question 17

1. caused by rapid-rate discharges from many ventricular ectopic foci producing erratic, rapid twitching of the ventricles
2. because so many foci are firing at once, each only depolarized a small area of ventricle and produces “twitching” of ventricle instead of full contraction of ventricle
3. no effective pumping-will directly kill you

Answer 17

ventricular fibrillation

Question 18

electrical blocks which retard or prevent the passage of electrical (depolarization) stimuli

Answer 18

heart block

Question 19

1. the SA node stops its pacing activity for at least once cycle.
2. the P waves identical because the same SA node pacemaker is functioning before and after the pause (missed cycle)

Answer 19

sinus block

Question 20

delay in transmission of the impulse through the AV node

Answer 20

AV block

Question 21

results in longer pause before stimulating the ventricles; P-R interval prolonged (>0.20 seconds)

Answer 21

primary AV block

Question 22

progressive P-R prolongation until QRS is dropped

Answer 22

secondary AV block

Question 23

complete block- complete dissociation of atria and ventricles

Answer 23

tertiary AV block

Question 24

1. caused by block of depolarization in the right or in the left bundle branch
2. normally, the impulse spreads through the right and left bundle branches simultaneously and therefore ventricles contract simultaneously
   3 a block to either of the bundle branches creates a delay of the electrical impulse to that side and causes one ventricle to depolarize than the other
3. results in widened QRS complex often with “rabbit ears” (>0.12 seconds)

Answer 24

bundle branch block

Question 25

1. inverted symmetrical T waves
2. elevated or depressed S-T segments
3. Presence of significant Q waves

Answer 25

ischemia/infarct

Question 26

1. prolonged depolarization of ventricles during ischemia changes pattern of repolarization
2. ventricles repolarize in opposite direction to normal repolarization

Answer 26

inverted symmetrical T waves

Question 27

1. sign of acute injury

2. can return to baseline with time

Answer 27

elevated or depressed S-T segments

Question 28

significant is considered >1 mm deep

Answer 28

presence of significant Q waves make the diagnosis of infarct