Chapter 20 - The Heart - ECG/EKG

Question 1

What does ECG stand for?

Answer 1

Electrocardiogram

Question 2

the electrical events in the heart are powerful enough to be detected by ____ on the surface of the body

Answer 2

electrode

Question 3

Clinicians can use an ECG to assess the performance of which 3 things?

Answer 3

-a specific nodal
-conducting components
-contractile components

Question 4

Briefly explain the 5 steps of impulse conduction through the heart

Answer 4

1. SA node activity begins and atrial activation begins
2. The stimulus spreads across the atrial surfaces and reaches the AV node
3. 100msec delay at the AV node to allow for atrial contraction

4.impulse travels towards the interventricular septum within the AV bundle, to the bundle branches, to the Purkinje fibers, and then through the moderator band the impulse travels to the papillary muscles of the right ventricle

5. The impulse is distributed by the Purkinje fibers throughout the ventricular myocardium. Atrial contraction is complete and ventricular contraction begins

Question 5

Step 1 — SA node activity and atrial activation – represents what on the ECG?

Answer 5

nothing. just a flat line

Question 6

Step 2 – The stimulus spreads across the atrial surfaces and reaches the AV node — what does this step represent on the ECG?

Answer 6

the p wave – smallest wave

Question 7

Step 3 — there is a 100msec delay to allow for atrial contraction to begin – what is this step represented by on the ECG?

Answer 7

P-R interval. flat line

Question 8

step 4 – the impulse travels along interventricular septum to the bundle branches, Purkinje fibers, and to the papillary muscles by way of the moderator band — what is this step represented by on the EKG?

Answer 8

The Q wave —- downwards wave. Ventricular depolarization begins

Question 9

Step 5 – Atrial contraction is complete and ventricular contraction begins – what is this represented by on the ECG?

Answer 9

the QRS complex — completion of ventricular depolarization

Question 10

the small P wave accompanies the…

Answer 10

depolarization of the atria

Question 11

What does the T wave represent on an EKG?

Answer 11

Occurs after the ventricles contract
indicates when the ventricles have repolarized after contracting

Question 12

the QRS complex appears as the ventricles…

Answer 12

depolarize. complex, strong signal

Question 13

the ventricles begin contracting shortly after the peak of the ___ wave

Answer 13

R

Question 14

why is atrial repolarization not apparent on an ECG?

Answer 14

because it occurs while the ventricles are depolarizing and the QRS complex masks this electrical event

Question 15

Explain the P-R interval

Answer 15

extends from the start of atrial depolarization to the start of the QRS complex (ventricular depolarization)

Question 16

Extension of P-R to more than 200msec can indicate damage to…..

Answer 16

the conducting pathways or the AV node

Question 17

the Q-T interval indicates the time required for…

Answer 17

the ventricles to undergo a single cycle of depolarization and repolarization