Lecture 8: Cardiac Arrhythmias

Question 1

What is tachycardia?

Answer 1

HR > 100 beats/minute

Question 2

What causes tachycardia?

Answer 2

Increased body temperature (increase of 10 beats/1˚C)

Stimulation of heart by sympathetic nerves

Toxic conditions of the heart

Question 3

What is bradycardia?

Answer 3

HR < 60 beats/minute

Question 4

What causes bradycardia?

Answer 4

Athletic heart

Vagal stimulation

Sensitive carotid baroreceptors in carotid sinus syndrome

Question 5

What is sinus arrhythmia?

Answer 5

Spillover signals *****

Question 6

What are characteristics of a sinoatrial block?

Answer 6

Sudden cessation of P wave

Standstill of atria

Ventricles pick up new rhythm originating from AV node

Rate of QRS slowed but not otherwise altered

Question 7

What are characteristics of an atrioventricular block?

Answer 7

Ischemia of AV node/bundle through coronary insufficiency

Compression of AV bundle by scar tissue or calcified portions of heart

Inflammation of AV bundle

Extreme stimulation of heart by vagus nerves

Question 8

What are characteristics of an incomplete atrioventricular block?

Answer 8

“First-degree”

Caused when P-R interval becomes prolonged (>0.2 second increase)

Question 9

T/F: If the P-R wave interval increases to 0.25-0.45 seconds from 0.16 seconds, the QRS-T wave interval may be missing, resulting in dropped beats of ventricles

Answer 9

True

Question 10

What are characteristics of a complete atrioventricular block?

Answer 10

Ventricles establish their own signals (AV node)

5-30 seconds may lapse between AV beats

Resumption of ventriclar beat may be due to ectopic pacemaker abilities of purkinje system

Fainting spells may occur (Stokes-Adams syndrome)

Question 11

T/F: Stokes-Adams syndrome is ischemia of the AV node/bundle through coronary insufficiency

Answer 11

False, Stokes-Adams syndrome is the term for the fainting spells associated with complete atrioventricular block

Question 12

What are the characteristics of a partial intraventricular block?

Answer 12

a.k.a. Electrical alternans

Alternations of the amplitude of P waves, QRS complexes, or T waves

Question 13

What are the characteristics of premature contractions?

Answer 13

Result of ectopic foci (pacemaker)

Local ischemic areas

Calcified plaques

Irritation of conduction system or nodes

Question 14

What are the characteristics of paroxysmal tachycardia?

Answer 14

Begins and ends suddenly and last for few seconds to hours

Pacemaker of heart instantly shifts back to sinus node

Question 15

What is fibrillation?

Answer 15

When the wave going through the hears is slow and gets back to ventricle after refractory period and can generate another signal and cause ventricle to depolarize

Result of “circus movements”

Question 16

What are the 3 different conditions of circus movements?

Answer 16

Pathway around heart is too long (dilated heart)

Length of pathway is same, but velocity of conduction is slower (blocked Purkinje system, ischemia, or high K+ levels)

Refractory period for muscle shortens (drugs [epinephrine] or repetitive electrical stimulation)

Question 17

What is atrial fibrillation caused by?

Answer 17

Enlargement of atria (valve lesions)

Inadequate emptying of ventricles causing blood to back up into atria

*It causes low P waves on ECG