ECG

Question 1

Types of cardiac cells

Answer 1

1) myocardial = working cells(contraction)
2) pacemaker cells = specialized for electrical conduction system
- spontaneously generate and conduct impulses

Question 2

phases of cardiac action potential

Answer 2

Phase 0 = Na+ rushing into cell(depolarization)
- responsible for QRS complex
Phase 1 = K rushing out of cell(brief early repolarization)
Phase 2 = Ca moving into cell(plateau phase)
- ST segment
Phase 3 = repolarization(Na-K pump)(Final rapid repolarization)
- T wave
Phase 4 = returns to polarization(resting)

Question 3

Hypercalemia

Answer 3

too much K+

- bradycardia

Question 4

hypocalemia

Answer 4

low K+

• dysrythmia, changes in ST(depression)
• from diuretic medication

Question 5

absolute refractory period

Answer 5

cells cannot be stimulated to conduct an electrical impulse

- period from onset of QRS complex to peak of T wave

Question 6

relative refractory period

Answer 6

cardiac cells can be stimulated if stimulus is strong enough

- downslope of T wave

Question 7

supernormal period

Answer 7

weaker than normal stimulus can cause cardiac cells to depolarize
- end of T wave

Question 8

Pacemaker sites

Answer 8

SA node = 60-100 bpm(normal sinus rhythm)
AV(junctional ectopic focus = 40-60 bpm
Ventricular ectopic focus = 20-40 bpm(purkinje fibers and bundle branch)

Question 9

P wave

Answer 9

atrial depolarization

Question 10

QRS complex

Answer 10

ventricle depolarization and atrial repolarization

- less than 0.1 seconds

Question 11

ST segment and T wave

Answer 11

repolarization

• ST elevation = MI or injury
• ST depression = ischemia

Question 12

PR interval

Answer 12

less than 0.2 seconds

• time for impulse from SA node through AV node
• atrial and atrioventricular node depolarization

Question 13

QT interval

Answer 13

systolic phase of heart

- electrical systole

Question 14

7 steps for basic EKG interpretation

Answer 14

1) general rhythm = regular or irregular
2) rate = both general and specific
3) P wave = present or absent(are they identical)
4) Interval = PR interval(.12-.2 secs), QRS interval(.06-.1 secs), QT interval(<.4 secs)
5) origin = supraventricular(SA&AV nodes) or ventricular
6) rhythm interpretation = name of the rhythm and location of any abnormalities
7) hemodynamic compromising?

Question 15

Sinus Tachycardia

Answer 15

rate >100bpm

- caused by anxiety, thyroid toxicosis, fever

Question 16

sinus bradycardia

Answer 16

rate < 60 bpm

- athletes, B-blockers, vomiting, valsalva stimulation, hypotension

Question 17

sinus arrhythmia

Answer 17

irregular rhythm with impulses originating in the SA node(supraventricular)

Question 18

premature atrial contraction

Answer 18

PAC

• regular with premature beats(premature P waves)
• peaked P waves

Question 19

paroxysmal atrial tachycardia

Answer 19

sudden onset tachycardia(150-250 bpm)

Question 20

Wandering atrial pacemaker

Answer 20

“wandering atrial pacemaker”

• P wave changes in size, shape, and direction from beat to beat(at least three different P wave configurations)
• rhythm is irregular

Question 21

atrial flutter

Answer 21

250-350 bpm(atrial rate)

• multiple activations of P wave, but does not cause QRS
• AV node prevents ventricle from contracting and reducing output

Question 22

Atrial fibrillation

Answer 22

350-450 bpm(atrial rate)

• atrium quivers and doesn’t contract fully so all blood does not go into ventricle = decreased Q
• tend to develop clots so pt’s on blood thinner

Question 23

Paroxysmal junctional tachycardia

Answer 23

• sudden onset tachycardia(150-250 bpm)
• P wave absent or inverted
• from emotional stress, hypoxia

Question 24

premature ventricular contraction

Answer 24

PVC = originates suddenly in an ectopic focus in a ventricle producing a giant ventricle complex

• bigeminy = PVC every 2 beats
• trigeminy = PVC every 3 beats
• quadrigeminy = PVC every 4 beats
• couplet = 2 PVC’s in a row
• triplet = 3 PVC’s in a row

Question 25

Ventricular tachycardia

Answer 25

greater than 40 bpm - all signals from the ventricle - no P wave, origin from ventricle - emergency situation

Question 26

ventricular flutter

Answer 26

250-350 bpm - no effective cardiac output - no relaxation stage

Question 27

ventricular fibrillation

Answer 27

greater than 350 bpm

Question 28

1st degree AV block

Answer 28

PR interval > 0.2 sec and constant - generally benign - one P wave per QRS

Question 29

2nd degree AV block

Answer 29

Mobitz 1 or Wenckebach(type 1) | - PR interval progressively lengthens until missing QRS

Question 30

2nd degree AV block(type 2)

Answer 30

Mobitz 2 - PR interval are constant and within normal limits for those conducted beats - some P waves are not followed by QRS complex - need pacemaker to correct otherwise will progress to 3rd degree

Question 31

3rd degree AV block

Answer 31

AV dissociation, complete heart block | - atrial rate and ventricular rate are regular but not matched(independently)

Question 32

Bundle branch block

Answer 32

one ventricle depolarizes slightly later than the other, causing two joined QRS's(one for right ventricle and one for left ventricle)

Question 33

ischemia

Answer 33

T wave inversion

Question 34

Injury(acute)

Answer 34

ST segment elevation - returns to baseline with time - ST elevation associated with Q waves indicates an acute infarct

Question 35

infarction

Answer 35

significant Q wave | - 1mm wide or 1/3 amplitude of QRS

Question 36

sinus rhythm with ST segment depression

Answer 36

depression > 2mm boxes

Question 37

Torsades de pointes

Answer 37

complexes gradually increase then gradually decrease causing a classical spindle shaped progression of waves

Question 38

Rhythm

Answer 38

1) regular 2) regular but interrupted by premature beats 3) regular but interrupted by pauses 4) irregular 5) regularly irregular

Question 39

Rate

Answer 39

1) regular = one HR 2) irregular = range from slowest to fastest, plus mean rate 3) regular but interrupted by premature beats = one HR(ignore premature rates) 4) regular by interrupted by pauses = range from slowest to fastest, plus mean rate 5) if it has two origins, calculate the rate from each origin separately

Question 40

P wave

Answer 40

1) present 2) absent 3) shape 4) relationship with QRS complexes 5) is each followed by a QRS 6) do all P waves look the same

Question 41

Intervals

Answer 41

1) PR < .2 sec 2) QRS < .1 sec and same shape 3) QT < .4 sec

Question 42

origin

Answer 42

1) supraventricular = SA node, atrium, junction | 2) ventricular