ECG Interpretation

Question 1

P wave

Answer 1

Atrial depolarization

Question 2

PR interval

Answer 2

time for the atrial depolarization and conduction from the SA node to the AV node, normal is .12 to .20 seconds

Question 3

QRS complex

Answer 3

Ventricular depolarization and atrial repolarization, normal is .06 to .10 seconds

Question 4

QT interval

Answer 4

time for both ventricular depolarization and repolarization , ranges from .20 to .40 and depends on HR

Question 5

ST segment

Answer 5

Isoelectric period following QRS when the ventricles are depolarized

Question 6

T wave

Answer 6

Ventricular repolarization

Question 7

Where does atrial depolarization begin?

Answer 7

SA node…and spreads normally throughout electrical conduction system

Question 8

Premature atrial contractions (PAC)

Answer 8

Occur when an ectopic focus in the atrium initiates an impulse before the SA node, p wave is premature with abnormal configuration

Question 9

PAC: Clinical Significance

Answer 9

Very common and generally benign but can progress to atrial flutter, tachycardia, or fibrilation
May occur in normal heart due to caffeine, smoking, stress, alcohol and any type of heart disease

Question 10

Atrial flutter

Answer 10

Ectopic, very rapid atrial tachycardia
Atrial rate of 250-350 beats.min; ventricular rate dependent upon AV node conduction
Saw toothed p waves

Question 11

Atrial flutter: Clinical Signifigance

Answer 11

Occurs with valvular disease (especially mitral), ischemic heart disease, cardiomyopathy, HTN, acute MI, chronic obstructive lung disease, and pulmonary emboli
Stagnation of blood may predispose to thrombi in the atria
Palpitations, lightheadedness, and angina due to rapid rate

Question 12

Atrial fibrilation

Answer 12

Common arrythmia where the atria are depolarized b/w 350-600 times/min
ECG shows irregular undulations of ECG baseline without discrete p waves

Question 13

A-fib: Clinical Signifigance

Answer 13

Occurs in healthy hearts and in patients with coronary artery disease, HTN, and valvular disease
Stagnation of blood may predispose to thrombi in the atria
Palpitations, fatigue, dyspnea, lightheadedness, syncope, and chest pain

Question 14

1st degree AV block

Answer 14

PR interval is no longer than.2 seconds but relatively constant from beat to beat

Question 15

1st degree AV block: Clinical Signifigance

Answer 15

No symptoms or significant changes in cardiac function

PR interval mat become prolonged for many reasons including medications that suppress AV conduction

Question 16

2nd degree AV block

Answer 16

AV conduction disturbance in which impulses b/w the atria and ventricles fail intermittently

Question 17

What are the 2 major types of 2nd degree AV block?

Answer 17

Mobitz type I block aka Wenckeback block

Mobitz type II block

Question 18

2nd degree AV block: Clinical Signifigance

Answer 18

Mobitz I- progressive prolongation of PR interval until one impulse is not conducted (generally benigh)
Mobitz II- consecutive PR intervals are the same and normal followed by nonconduction of one or more impulses, more serious condition

Question 19

In Mobitz type II block, what happens to cardiac output if HR is slow?

Answer 19

Decrease in CO with the blocked impulse, 2nd degree AV block can lead to 3rd degree AV block

Question 20

3rd degree AV block (complete heart failure)

Answer 20

All impulses are blocked at the AV node and non are trasmitted to the ventricles
The atria and ventricles are paced independently; atrial rate > ventricular rate

Question 21

3rd degree AV block: Clinical Signifigance

Answer 21

Considered a medical emergency requiring a pacemaker

If the ventricular rate is too slow, the cardia output drops and the pt my faint

Question 22

What are some common causes of a 3rd degree AV block?

Answer 22

Degenerative changes of the conduction systems, digitalis, heart surgery, and acute MI