Basics of EKG part II

Question 1

What is the normal duration and amplitude of a P wave

Answer 1

• duration: 0.06-0.10 sec
• amplitude: 0.5 - 2.5 mm

Question 2

If amplitude of P wave is > 2.5 mm it suggests

Answer 2

• right atrial enlargement: called “P pulmonale”

Question 3

If width of P wave is > 0.10 sec, it suggests

Answer 3

• Left atrial enlargement
• called “P mitrale”

Question 4

impulses arising from the atria but not the SA node, will produce what

Answer 4

• different looking P waves

Question 5

In rapid rates, the P wave is likely buried where

Answer 5

• in the T wave of the preceeding beat
  
  • when this occurs, T waves are often peaked, notched, or larger than normal

Question 6

What type of P waveform is produced when the atria fires rapidly from one site at a rate of 250-350 bpm

Answer 6

• “F” waves or flutter waves
  
  • often described as a saw tooth pattern
• with atrial flutter, an ectopic site in the atria fires at rate 250-350 bpm

Question 7

What happens to P waves when atria fire rapidly from many sites at a rate > 350 bpm

Answer 7

• “fibrillatory” waves (not getting coordinated contraction)

Question 8

How are inverted P waves produced

Answer 8

• when a P wave arises from the lower right atrium near the AV node, the left atrium, of the AV junction
  
  • ​results in retrograde depolarization of the atria

Question 9

inverted P waves can have what relationship to QRS complex

Answer 9

• immediately preceed, occur during, or follow the QRS complex

Question 10

more P waves than QRS complexes indicates what

Answer 10

• the impulse was initiated in the SA node or atria but was blocked and did not reach the ventricles

Question 11

While there is only one Q wave, there can be more than one R and S wave. What are the second R or S wave called? What if they are small?

Answer 11

• R’ or S’: (R prime or S prime)
• use lower case: “r” or “s”
  
  • small: less than 1 big box

Question 12

how do you measure QRS complexes

Answer 12

• starting point is where first wave of complex starts to move away from baseline
• ending point is where last wave of complex begins to level out at, above, or below baseline

Question 13

tall QRS complexes are usually caused by what heart condition

Answer 13

• hypertrophy of one or both ventricles

Question 14

low voltage QRS complexes are seen in what patient conditions

Answer 14

• obese patients
• hypothyroid patients
• pericardial effusion

Question 15

wide QRS complexes are often a result of

Answer 15

intraventricular conduction defect

Question 16

What is an aberrant conduction

Answer 16

• occurs when electrical impulses reach the bundle branch while it is still refractory after conducting a previous electrical impulse
• results in impulse traveling down the unaffected bundle first, followed by stimulation of the other bundle branch
• causes QRS complex to appear wider than normal

Question 17

List the five step process of ECG analysis

Answer 17

1. rate
2. regularity
3. P waves
4. QRS complexes
5. PR intervals

Question 18

What does the PR interval denote

Answer 18

• depolarization of the heart from the SA node through the atria, AV node and His-purkinje system

Question 19

how is PR interval measured

Answer 19

• distance from beginning of P wave to the beginning of the Q wave

Question 20

what causes short PR intervals

Answer 20

1. impulse originates in the atria close to the AV junction or in the AV junction
2. impulse arises from a supraventricular site but travels through abnormal accessory pathways to the ventricles
   
   • leads to premature ventricular depolarization -> preexcitation

Question 21

what conditions cause longer PR intervals

Answer 21

1. there is a delay in impulse conduction through the AV node

Question 22

What can cause varying PR intervals

Answer 22

1. wandering atrial pacemaker
   
   1. ​pacemaker site moves from beat to beat causing the P waves to appear different and the PR intervals to vary

Question 23

what condition is characterized by PR intervals that are progressively longer until a QRS complex is dropped and then the cycle repeats

Answer 23

2nd degree AV heart block, type I