EKG/ECG Interpretation

Question 1

What is an electrocardiogram (ECG)?

Answer 1

A graphic representation of the heart’s electrical rhythm recorded from electrodes on the surface of the body.

Question 2

Describe the normal cardiac cycle on a ECG. (pg 191 has a great picture in therapy ed)

Answer 2

P wave = atrial depolarization
PR interval = time required for impulse to travel from the SA node to the AV node
QRS wave = ventricular depolarization and atrial repolarization
ST segment = beginning of ventricular repolarization
T wave = ventricular repolarization
QT interval = time for electrical systole (time for both ventricular depolarization and repolarization)

Question 3

How is heart rate calculated using an ECG strip?

Answer 3

Count the number of intervals between QRS complexes in a 6 second strip and multiply by 10.

Question 4

Atrial depolarization begins in the _____.

Answer 4

SA node

Question 5

What is sinus arrest?

Answer 5

A sinus rhythm with intermittent failure of either SA node impulse formation or AV node conduction that results in the occasional complete absence of P or QRS waves

Question 6

What is a premature ventricular contraction (PVC)?

Answer 6

Premature depolarization arising in the ventricle due to an ectopic focus

Question 7

What is the difference between unifocal and multifocal PVCs?

Answer 7

Unifocal = arise from the same ectopic focus and have the same configuration

Multifocal = arise from different ectopic foci and have different configurations

Question 8

What do PVCs typically look like on a ECG strip?

Answer 8

No P wave, a bizarre and wide QRS that is premature, followed by a long compensatory pause

Question 9

What is the difference between PVCs that occur in bigeminy versus trigeminy?

Answer 9

Bigeminy = normal sinus impulse is followed by a PVC
Trigeminy = PVC occurs after every two normal sinus impulses

Question 10

When are PVCs considered to be serious?

Answer 10

> 6 per minute OR 3 consecutive PVCs

Question 11

What is ventricular tachycardia? How does it appear on an ECG?

Answer 11

3 or more PVCs at a ventricular rate >150 beats/minute

ECG: P waves are absent and QRS complexes are wide and aberrant in appearance

Question 12

When does ventricular tachycardia become a medical emergency? What happens to a patient who is sustained v-tach?

Answer 12

V-tach that lasts greater than 30 seconds is a life threatening arrhythmia that requires immediate medical attention

Sustained v-tach = patients are unable to maintain adequate BP and become very hypotensive

Question 13

What is ventricular fibrillation? How does it appear on an ECG?

Answer 13

Ventricles do not beat in a coordinated fashion, but fibrillate or quiver asynchronously and ineffectively

ECG: Bizarre, erratic activity without QRS complexes

Question 14

What happens to a patient who is in ventricular fibrillation?

Answer 14

No cardiac output
Patient becomes unconscious
Clinical death within 4-6 minutes

Question 15

What is ventricular asystole? How does it appear on an ECG?

Answer 15

Ventricular standstill with no rhythm

ECG: straight line pattern

Question 16

What is atrial flutter? What does it look like on an ECG?

Answer 16

An ectopic, very rapid atrial tachycardia

Atrial rate of 250-350 beats per minute; ventricular rate dependent upon AV node conduction

ECG: Saw-tooth shaped P waves are characteristic

Question 17

What is atrial fibrillation? What does it look like on an ECG?

Answer 17

A common arrhythmia where the atria are depolarized between 350-600 times/min

ECG: irregular RR interval with irregular non-discrete P waves

Question 18

What are atrioventricular blocks?

Answer 18

Abnormal delays or failure to conduct through normal conducting system

Question 19

What is a 1st degree atrioventricular block?

Answer 19

PR interval is longer than 0.2 seconds, but relatively constant from beat to beat

No symptoms or significant change in cardiac function

Question 20

What is a 2nd degree heart block? List the types of 2nd degree AV blocks.

Answer 20

AV conduction disturbance in which impulses between the atria and ventricles fail intermittently

Mobitz type I block (Wenckebach block)
Mobitz type II block

Question 21

What is a Mobitz type I (Wenckebach) AV block?

Answer 21

Progressive prolongation of the PR interval until one impulse is not conducted (dropped)

Longer, longer, longer, drop, now you have a Wenckebach

Question 22

Describe a Mobitz type II AV block.

Answer 22

Consecutive PR intervals are the same and normal followed by nonconduction of one or more impulses (a more serious condition)

Question 23

Describe a 3rd degree heart block.

Answer 23

All impulses are blocked at the AV node and none are transmitted to the ventricles (complete heart block)

Question 24

What interventions are used to treat a 3rd degree heart block?

Answer 24

Atropine

Pacemaker implantation

Question 25

ST segment depression or elevation greater than ____ measured at the J point in ___ consecutive leads is considered abnormal.

Answer 25

Greater than 1mm in 2 consecutive leads is considered abnormal.

Question 26

What does ST segement elevation typically indicate?

Answer 26

Myocardial infarction (STEMI)

Question 27

What influence does hyperkalemia have on ECG waves?(3)

Answer 27

Widens QRS wave
Flattens P wave
T wave becomes peaked

Question 28

What influence does hypokalemia have on ECG waves?(2)

Answer 28

Flattens or inverts T wave

Produces a U wave

Question 29

What influence does hypercalcemia have on ECG waves? (2)

Answer 29

Widens QRS

Shortens QT interval

Question 30

What influence does hypocalcemia have on ECG waves? (1)

Answer 30

Prolongs QT interval