Cardiac Arrythmias

Question 1

What is tachycardia?

Answer 1

Fast heart rate; it is caused by increased body temperature, stimulation by sympathetic nerves or toxic conditions of the heart.

Question 2

What is endogenously mediated tachycardia?

Answer 2

fast heart beat that is a result of exercise. Can include increased heart rate and cardiac output; filling time is reduced, but stroke volume does not fall.

Question 3

Why does stroke volume not fall during exercise?

Answer 3

the systolic interval is reduced, and more blood is filled during the diastole. Less is stored in the veins and more in the heart (and therefore, more is pumped).

Question 4

What is brachycardia?

Answer 4

A slow heart rate. It is caused by excercise, vagal stimulation or baroreceptors in carotid sinus syndrome.

Question 5

What are spillover signals?

Answer 5

signals from the medulla (inspiratory expiratory) that increase and decrease the number of impulses transmitted through sympathetic and vagus nerves to the heart.

Question 6

What is a sinoatrial block?

Answer 6

When the impulse from the sinus node is blocked before it enters the atrial muscles.

Question 7

What are characteristics of sinoatrial block?

Answer 7

NO P WAVE; no last third of diastole, new rhythm picked up in the AV node.

Question 8

What is an atrioventricular block?

Answer 8

Block by of the AV node; impulses cannot pass from the atria to the ventricles.

Question 9

What causes an atrioventricular block?

Answer 9

ischmeia of AV node, compression of AV bundle, inflammation of AV node, stimulation by vagus nerve

Question 10

What is a first degree AV block?

Answer 10

prolonged PR interval ( > 20 sec)

Question 11

What is a second degree AV block?

Answer 11

prolonged PR interval ( 20 - 45 sec), QRST wave is missing, 2:1 rhythmn.

Question 12

What is a complete AV block?

Answer 12

When the AV signal is completely blocked. Ventricles establish their own signal at the AV node, and ventricles may not beat for 5 to 30 seconds.

Question 13

What is Stokes-Adams syndrome caused by?

Answer 13

Complete AV block and lack of blood for 5 to 30 seoncds; occurs to lack of blood to the brain until the ventricles beat again.

Question 14

What is a partial intraventricular block?

Answer 14

electrical alternans; an alternation in the AMPLITUDE of P waves, QRS complexes or T waves casued by blockages of impulses in the Purkinje fibers.

Question 15

What are premature contractions?

Answer 15

contractions that occur before they should. They are caused by ectopic foci such as ischemias, calcified plaques or irriation of the conduction system or nodes.

Question 16

What is paroxysmal tachycardia?

Answer 16

Tachycardia caused by rapid, rhythmical discharges of impluses that spread in all directions throughout the heart. They begin and end suddenly.

Question 17

When does ventricular fibrillation occur?

Answer 17

When there are abnormal cardiac impulses in the ventricular muscle mass; no coordinated contraction of muscles occurs and heart does not contract enough to pump blood.

Question 18

Why do the normal depolarization waves die out during fibrillation?

Answer 18

The heart muscle that has already contracted is in the refractory period and cannot respond to being stimulated by the existing depolarization waves.

Question 19

What does fibrillation occur as a result of?

Answer 19

circus movements

Question 20

What are circus movements?

Answer 20

three different conditions that cause the impulse to travel around the circle.

Question 21

What are the three circus movements?

Answer 21

pathway around ventricle is too long, length of pathway is constant but velocity of conduction slows down; refractory period is greatly shortened.

Question 22

If the pathway around the ventricles is too long, what occurs?

Answer 22

the muscle is no longer in the refractory period and undergo another repolarization (this would usually not occur)

Question 23

What causes the conduction velocity of the impulse to slow down?

Answer 23

blockage of the purkinje system, ischemia or high potassium levels.

Question 24

What causes the refractory period of the muscle to be shortened?

Answer 24

drugs (epinephrine, repetitive electrical stimulation)

Question 25

Can atrial and ventriculr fibrillation occur separately from one another?

Answer 25

yes

Question 26

What causes atrial fibrillation?

Answer 26

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