P and QRS waves

Question 1

Electrocardiogram (ECG)

Answer 1

Graphic record of the electrical potentials produced by cardiac myocytes (voltage over time)
Dx arrythmias

Question 2

Positioning of the ECG

Answer 2

Right lateral recumbency
Black: LA, white: RA, red: LL green: RL

Question 3

Limb leads: frontal plane

Answer 3

Lead 1: right arm to left arm
Lead 2: Right arm to left leg
Lead 3: left arm to left leg

Question 4

Bipolar leads

Answer 4

Contain a negative pole (-) and positive pole
Limb leads 1, 2 and 3

Question 5

Unipolar leads (augmented)

Answer 5

Measures the electric potential @ 1 point with respect to null point
Augmented leads aVR, aVL, and aVF

Question 6

Cardiac conduction system

Answer 6

1. Sinus node (initiation of electrical impulse 60-180 bpm)
2. AV node (only link between atrium and ventricles 40-60 bpm)
3. Purkinje fibers (inherent rate of 20-40 bpm)

Question 7

Rule of ECG

Answer 7

Rapid depol/ repol= narrow tracing
Slow depol/ repol = wide tracing

Question 8

P wave

Answer 8

Organized atrial depolarization
absent or sometimes= no atrial depolarizations

Question 9

What happens when you never see a P wave?

Answer 9

Slow regular ventricular complexes
Atrial flutter or fibrillation
Atrial standstill

Question 10

What happens when you sometimes see a P wave?

Answer 10

P with ventricular complexes
Sinus node disease

Question 11

QRS complex

Answer 11

Ventricular depolarization
Q is first - delfection, R is first + deflection
S always second - or first - after + QRS

Question 12

T wave

Answer 12

Ventricular repolarization
T +, -, or biphasic
Each beat MUST have a T wave

Question 13

Intervals

Answer 13

The amount of time it takes for a wave of conduction to propagate through the heart

Question 14

PR interval

Answer 14

Beginning of P to beginning of Q
Atrial depol and conduction through the AV node

Question 15

QT interval

Answer 15

Beginning of Q to the end of T
Ventricular activity

Question 16

Calculating HR with 25 mm/sec

Answer 16

Average: 30 large boxes= 6 sec
Number of complexes x 10
Instantaneous: 1500/ # small boxes between consecutive R waves

Question 17

Calculating HR with 50 mm/sec

Answer 17

Average: 30 large boxes= 3 sec
Number of complexes x 10
Instantaneous: 3000/ # small boxes between consecutive R waves

Question 18

When is each method for calculating HR used?

Answer 18

Average used to irregular arrhythmias
Instantaneous used to regular rhythms or non-sustained arrhythmias

Question 19

What happens when there ISN’T a P wave for every QRS?

Answer 19

Early: premature, late: escape
Ectopic v. sinus beat
Looks similar: supraventricular/ atrial
Looks different: Ventricular

Question 20

Ventricular premature contractions (VPCs)

Answer 20

No associated P waves
Earlier than expected sinus beat
QRS of ectopics look different from sinus QRS
premature: wide and bizarre

Question 21

Atrial premature contractions (APCs)

Answer 21

No associated P waves
Earlier than the next expected sinus beat
QRS of ectopics look similar to sinus QRS
above the ventricle

Question 22

Ventricular escapes

Answer 22

Some sinus, bradycardia
Ectopics have no associated P wave, late
QRSs of ectopics are wide and bizarre

Question 23

Escape beats: safety mechanism

Answer 23

Sinus mode:P wave, narrow QRS complex
AV node: No P wave, narrow QRS
Ventricle (purkinje): No P, wide QRS
beats generated by pacemakers when sinus rate becomes too slow or arrests

Question 24

Abnormal P waves

Answer 24

P wave + when initiated from sinus node
P wave - from abnorm origin in atrium

Question 25

___________ cells only work as pacemaker if diseased

Answer 25

Atrial myocardial cells *abnormal P waves*

Question 26

1st degree AV block

Answer 26

Prolongation of PR interval (dogs: 0.13, cat: 0.09) Slow conduction in the AV node

Question 27

What caused 1st degree AV block?

Answer 27

Fibrosis in the AV node ↑ vagal tone (physiologic, systemic disease, drugs like betablocks- digoxin) *exception to rule (QRS for every P)*

Question 28

2nd degree Type 1 AV block (Wenckebach)

Answer 28

Gradual prolongation of the PR interval than dropped P *sometimes no QRS for every P*

Question 29

2nd degree Type 2 AV block

Answer 29

Some conduction through the AV node No pattern of PR prolongation Dropped Ps are random *sometimes no QRS for every P*

Question 30

3rd degree AV block

Answer 30

Impulse always blocked in AV node (sinus faster than escape rate) Secondary pacemaker takes over *always no QRS for every P*

Question 31

Bundle branches

Answer 31

Rapidly propagate the wave of depol through the L and R ventricles

Question 32

Left bundle branch block

Answer 32

Right ventricle depol rapidly and normally via the right bundle branch Left ventricle activated late and slowly making QRS wide and bizarre

Question 33

Left ventricular hypertrophy

Answer 33

Sinus rhythm with skinny, tall R waves

Question 34

Right bundle branch block

Answer 34

Left ventricle depol rapidly and normally via left bundle branch Right ventricle activated late and slowly making QRS wide and bizarre

Question 35

Right ventricular hypertrophy

Answer 35

Sinus rhythm with skinny, deep S waves