cardiac arrhithmias ( chapter 13)

Question 1

Common causes of abnormalities in rhythmicity

Answer 1

abnormal pacemaker, shift of pacemaker to different spot, blocks at different points of impulse spread, abnormal pathways of impulse, spontaneous generation of spurious impulses in any part of heart.

Question 2

Tachycardia

Answer 2

Fast heart beat.( more than 100/ min.), Sympathetic stimulation causes it

Question 3

how many beats does heart rate rise per degree fahrenheit with a fever?

Answer 3

10 beats per degree

Question 4

Bradycardia

Answer 4

slow heart rate ( less than 60 beats/min.) Common in athletes, Vagus nerve slows heart down.

Question 5

what is carotid sinus syndrome?

Answer 5

pressure receptors in carotid sinus are excessively sensative. Causes bradychardia

Question 6

sinus arrhythmia

Answer 6

Results from conditions that alter strengths of the sympathetic and parasympathetic nerve signals. ( not a constistant beat, its all over the place)

Question 7

sinoatrial block

Answer 7

impulse from sinus node is blocked before entering the atrial muscle. ( ECG shows sudden cessation of p waves with standstill of atria)

Question 8

Atrioventricular block

Answer 8

problem with the transition from the a-V node to the ventricles

Question 9

name some causes of the atrioventricular block problems

Answer 9

ischemia of AV node or AV budle fibers, compression of AV bundle by scar tissue or calcified spots on heart, inflammation of AV node or AV bundle, extreme stimulation of heart by vagus nerve

Question 10

first degree AV block

Answer 10

when P-R interval increases to greater than .2 second. Its a delay of conduction from the atria to the ventricles but not actual blockage. ( acute rheumatic heart disease causes this)

Question 11

second degree

Answer 11

P-R interval increases to .25-.45 second. Action potential sometimes is not strong enough to get passed to ventricles. So you see P waves but no QRS-T complex. This develops a 2:1, 3:2, 3:1 rhythm

Question 12

Third degree

Answer 12

( complete block)- impulse is not passed to ventricles. Ventricles create its own new pacemaker. P waves are now dissociated with QRS-T complex

Question 13

Stokes adams syndrome

Answer 13

When AV conduction ceases and ventricles stop beating for 5-30 seconds. Eventually they start ( ventricular escape) but sometimes brain damage occurs.

Question 14

incomplete intraventricular block

Answer 14

partial intraventricular block every other heart beat

Question 15

premature contractions

Answer 15

also called extrasystole, premature beat, or ectopic beat

Question 16

what causes premature contractions?

Answer 16

ischemia, calcified plaques at different points of heart, toxic irritation of AV node/ purkinje fibers by caffeine or other drugs

Question 17

pulse deficit

Answer 17

heart contracts before ventricles fill up all the way. This results in a low stroke volume

Question 18

ECG of A-V bundle premature contractions

Answer 18

P wave is missing. It is superimposed onto the QRS-T complex

Question 19

ECG of premature ventricular contractions

Answer 19

QRS complex is usually considerably prolonged. This is cause the implulse is conducted through slowly conducted muscle rather than purkinje fibers. QRS also has a high voltage because it passes through both ventricles simultaneously. The T wave also has an electrical potential polarity exactly opposite to that of QRS

Question 20

what causes disorders of cardiac repolarization?

Answer 20

inherited- mutations of sodium or potassium channel gates.

acquired- associated with plasma electrolyte disturbances like hypomagnesemia, hypokalemia, or hypocalcemia

Question 21

parazymal tachycardia

Answer 21

Heart rate becomes rapid in paraxysms( lasting small period of time). It can be stopped by a vagal reflex( pressing on neck) or by quinidine or lidocaine.

Question 22

atrial paraxysmal tachycardia

Answer 22

??

Question 23

AV nodal paraxysmal tachycardia

Answer 23

??

Question 24

Ventricular paraxysmal tachycardia

Answer 24

is serious for 2 reasons. First, it only occurs if there is damage in the ventricles. Second, this condition usually initiates ventricular fibrilation

Question 25

ventricular fibrilation

Answer 25

very serious. Ventricular chamber neither enlarges nor contracts.

Question 26

Atrial fibrilation

Answer 26

Atria become useless as primers but blood still flows passively into the ventricles. The ventricle efficiency is decreased by 20-30 % ECG shows no P-wave

Question 27

Atrial flutter

Answer 27

rapid contractions of atria between 200-350 beats/ minute. Signals reach the AV node at the same time and not all of them are allowed to move on .This results in 2 or 3 beats of the atria for every 1 of the ventricles