Lecture 9: Cardiac Arrhythmias

Question 1

What is tachycardia?

Answer 1

fast heart rate

Question 2

What are the causes of tachycardia?

Answer 2

increased body temperature
stimulation of the heart by sympathetic nerves
toxic conditions of the heart

Question 3

What happens during endogenously mediated tachycardia?

Answer 3

heart rate increases
cardiac output increases
filling time is deducted but stroke volume does not fall

Question 4

What happens during pathologically mediated tachycardia?

Answer 4

heart rate increases

cardiac output decreases

Question 5

What is bradycardia?

Answer 5

slow heart rate

Question 6

What are the causes of bradycardia?

Answer 6

athletic heart
vagal stimulation
extremely sensitive carotid baroreceptors in carotid sinus syndrome

Question 7

What is spillover signals?

Answer 7

signals that alternatively increase and decrease number of impulses transmitted through sympathetic and vagus nerves to the heart

Question 8

What are the characteristics of a sinoatrial block?

Answer 8

sudden cessation of P waves
resultant standstill of atria
ventricles pick up new rhythm, usually originating in AV node
rate of QRS is slowed but not otherwise altered

Question 9

Conditions of atrioventricular block?

Answer 9

ischemia of AV node or AV fibers through coronary insufficiency
compression of AV bundle by scar tissue or calcified portions of the heart
inflammation of the AV node or bundle
extreme stimulation of the heart by the vagus nerves

Question 10

What is first degree incomplete atrioventricular block?

Answer 10

normal PR time interval (0.16 sec)

increases in length with slower heartbeat and decreases with faster heartbeat

Question 11

When PR interval increases to greater than 0.20 seconds, the PR interval is ________ and the pathetic has ______ heart block

Answer 11

prolonged; first degree incomplete

Question 12

What is second degree incomplete atrioventricular block?

Answer 12

PR 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

Question 13

What type of rhythm is present in second degree incomplete atrioventricular block?

Answer 13

2:1 rhythm

Question 14

In a complete atrioventricular block, ventricles establish their _______

Answer 14

own signal

Question 15

How long is the duration of a complete atrioventricular block?

Answer 15

highly variable: seconds to weeks

Question 16

If a complete atrioventricular block occurs, what may resumption of the ventricular beat be due to?

Answer 16

parts of the Purkinje system acting as an ectopic pacemaker

Question 17

Stokes-Adams syndrome

Answer 17

periodic fainting spells due to complete Glock from lack of blood to the brain

Question 18

What is a partial intraventricular block?

Answer 18

electrical alternans

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

Question 19

When do premature contractions occur?

Answer 19

before they should

Question 20

Premature contractions are the result of what?

Answer 20

ectopic foci:
local ischemic areas
calcified plaques
irritation of the conduction system or nodes

Question 21

What is paroxysmal tachycardia?

Answer 21

heart becomes rapid
begins and ends suddenly
pacemaker of the heart instantly shifts back to sinus node

Question 22

What is fibrillation?

Answer 22

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

Question 23

Fibrillation occurs as a result of ___________

Answer 23

circus movements

Question 24

What are the three conditions that causes the impulse to travel around the circle?

Answer 24

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

Question 25

What are the causes of atrial fibrillation?

Answer 25

enlargement of the atria

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

Question 26

Ventricular and atrial fibrillation may occur ________ from one another

Answer 26

separate

Question 27

Circus movements are the basis of heart fibrillation. Which of the following statements is NOT true?
A. Fibrillation may occur when the refractory period of the muscle is greatly shortened.
B. Fibrillation may occur when the pathway around the circle is too short.
C. Fibrillation may occur when the conduction velocity slows down.
D. Fibrillation may occur when the heart becomes dilated.

Answer 27

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

Question 28

Which of the following conditions may result in tachycardia?
A. Toxic conditions of the heart
B. Increased body temperature
C. Sympathetic nerve stimulation
D. All the above
E. BandConly

Answer 28

D. All the above