Cardiac Arrhythmias

Question 1

Circus movements are the basis of heart fibrillation. What is true of them?

Answer 1

Fibrillation may occur when the pathway around the circle is too short

Question 2

What is Tachycardia?

Answer 2

Fast heart rate

Question 3

What does the heart rate have to be to be considered tachycardia?

Answer 3

> 100 beats/min

Question 4

What is bradycardia?

Answer 4

slow heart rate

Question 5

What heart rate defines bradycardia?

Question 6

What causes bradycardia?

Answer 6

1. athletic heart
2. vagal stimulation
3. extremely sensitive carotid baroreceptors in carotid sinus syndrome

Question 7

What are the characteristics of a sinoatrial block

Answer 7

1. sudden cessation of P waves
2. resultant standstill of atria
3. ventricles pick up a new rhythm, usually originating in the AV node
4. rate of QRS is slowed but not otherwise altered

Question 8

What are the conditions causing the atrioventricular block?

Answer 8

1. ischemia of AV node or AV bundle fibers through coronary insufficiency
2. compress of AV bundle by scar tissue or calcified portions of the heart
3. inflammation of the AV node or bundle
4. extreme stimulation of the heart by the vagus nerves

Question 9

What are the two types of incomplete atrioventricular block?

Answer 9

first-degree and second-degree

Question 10

What are the characteristics of a first-degree incomplete atrioventricular block?

Answer 10

when P-R interval increases to greater that 0.20 seconds, the P-R interval is prolonged

Question 11

What is the characteristics of a second-degree incomplete atrioventricular block?

Answer 11

• P-R time interval increases to 0.25 to 0.45
• atrial P wave is present but QRS-T wave may be missing, resulting in dropped beats of the ventricle
• 2:1 rhythm or other variations may develop.

Question 12

What are the characteristics of complete atrioventricular block?

Answer 12

1. ventricles establish their own signal
2. no relation between the rate of the P waves and the rate of the QRS-T complexes
3. Duration of the block is highly variable
4. After AV conduction ceases, ventricles may not start beating on their own for 5 to 30 seconds
5. resumption of the ventricular beat may be due to parts of the purkinje system acting as an ectopic pacemaker.

Question 13

Whats the periodic fainting spells caused by complete atrioventricular blocks cause lack of blood to the brain known as?

Answer 13

Stokes-Adams syndrome

Question 14

Whats the resumption of the ventricular beat called when a complete atrioventricular block occurs?

Answer 14

Ventricular escape

Question 15

What are the characteristics of the partial intraventricular block?

Answer 15

1. referred to as electrical alternans

2. alternation in the amplitude of P waves, QRS complexes, or T waves

Question 16

What are three ectopic foci that causes of premature contractions?

Answer 16

1. local ischemic areas
2. calcified plaques
3. irritation of the conduction system or nodes

Question 17

What is fibrillation?

Answer 17

the twitching of individual muscle fibers in the atria or ventricles and also in recently denervated skeletal muscle fibers

Question 18

What are three different conditions that cause the impulse to travel around the circle in circus movements?

Answer 18

1. the pathway around the circle is too long.
2. the length of the pathway remains constant but the velocity of the conduction slows down
3. the refractory period of the muscle might become greatly shortened

Question 19

What conditions may result in tachycardia?

Answer 19

Toxic conditions of the heart
Increased body temperature
sympathetic nerve simulation

Question 20

How many beats does heart rate increase for every 1 degree F and C?

Answer 20

10 beats and 18 beats respectively

Question 21

Why does an increase in body temperature cause tachycardia?

Answer 21

Increases the metabolism of the SA node thus increasing its excitability

Question 22

What is endogenously mediated tachycardia?

Answer 22

Heart rate increase due to exercise or activeness

Question 23

What are three characteristics of endogenously mediated tachycardia?

Answer 23

• Heart rate increase
• Cardiac output increases
• filling time is reduced but stroke-volume does not fall

Question 24

What are pathologically mediated tachycardia’s characterists?

Answer 24

Heart rate increases

Cardiac output decreases

Question 25

Why would carotid sinus syndrome lower heart rate?

Answer 25

Because these carotid baroreceptors are more sensitive for the syndrome causing them to be more aware of pressure changes and making them stimulate a lower heart rate to lower the pressure

Question 26

What are spillover signals?

Answer 26

the signals from the medullary respiratory center into vasomotor center during inspiratory and expiratory respiratory cycles alternately increase and decrease number of impulses transmitted through sympathetic and vagus nerves to the heart

Question 27

During a Sinoatrial block where do ventricles pick up a new rhythm from usually?

Answer 27

The AV node

Question 28

What is the defining feature in an ECG of a second-degree incomplete AV block?

Answer 28

a 2:1 rhythm of P-waves to QRS wave

Question 29

What is a dropped beat?

Answer 29

a missing QRS wave caused by a second degree AV block

Question 30

What causes the ventricular escape during a complete AV block?

Answer 30

It is due to parts of the purkinje system acting as an ectopic pacemaker

Question 31

What are the causes of atrial fibrillation?

Answer 31

• Enlargement of the atria

- inadequate emptying of the ventricles causing blood to back up into the atria