Lecture 8 Cardiac Arrhythmias Flashcards Preview

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Flashcards in Lecture 8 Cardiac Arrhythmias Deck (45)
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Which of the following conditions may result in tachycardia?

a. Toxic conditions of the heart

b. Increased body temp.

c. Sympathetic nerve stimulation

d. All of the Above

e. B and C only

d. All of the Above


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

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


What is the definition of Tachycardia?

Fast heart rate (> 100 beats/min)


What are the causes of Tachycardia?

Increased body temp Stimulation of the heart by sympathetic nerves Toxic conditions of the heart


The results of Endogenously Mediated Tachycardia (i.e. exercise) include:

Increased HR Increased cardiac output Reduced filling time, but stroke-volume does not fall (ejection fraction increases)


The results of Pathologically mediated tachycardia include:

Increased HR Decreased cardiac output


What is the definition of Bradycardia?

Slow heart rate (


What are the causes of Bradycardia?

Athletic heart Vagal stimulation Extremely sensitive carotid baroreceptors in carotid sinus syndrome


Identify the ECG

Sinus Bradycardia


What type of signals alternately increase and decrease number of impulses transmitted through sympathetic and vagus nerves to the heart?

Spillover signals

From medullary repiratory center into vasomotor center during inspiratory and expiratory respiratoty cycles


What is this called?

Sinus Arrhythmia


Characteristics of Sinoatrial Block (5):

Sudden cessation of P waves

Resultant standstill of atria

Ventricles pick up a new rhythm, usually originating in the AV node

Rate of QRS is slowed but not otherwise altered

Ventricles will still fill but won't have last third of pumping effect from atria


Identify the ECG

Sinatrial nodal black (lead III)


What are conditions that cause atrioventricular blockage?

Ischemia of AV node or AV bundle fibers through coronary insufficiency

Compression of AV bundle by scar tissue or clacified portions of the heart

Inflammation of the AV node or bundle

Extreme stimulation of the heart by the vagus nerve 


What are the two types of incomplete atrioventricular block?




What is the normal P-R time interval?

0.16 sec


What determines if a patient has a first degree incomplete heart block?

When the P-R interval increases to geater than 0.20 seconds


What determines a Second-Degree block?

P-R time intercal increases to 0.25 to 0.45 secs

Atrial P wave is present but QRS-T wave may be missing, resulting in dropped beats of the ventricle


Identify the ECG

Prolonged P-R interval (first degree A-V heart block) (lead II)


Identify the ECG 

Second degree A-V block


Describe what happens in a complete atrioventricular block

(WARNING: Very wordy)

Ventricles establish their own signal 

No relation between rate of P waves and rate of QRS-T complexes

Duration of block is highly variable (secs to weeks)

After AV conduction ceases, ventricles may not start beating on their own for 5-30 secs

Resumption of the ventricular beat may be due to parts of the Purkinje system acting as an ectopic pacemaker 

Patients often faint due to lack of blood to brain until ventricles escape


The periodic fainting spells are reffered to as

Stokes-Adams Syndrome 


Identify the ECG

Complete A-V block


A partial intraventricular black is referred to as what?

"electrical alternans"


What does the term "electrical alternans" refer to?

An alteration in the amplitude of P waves, QRS complexes, or T waves


Identify the ECG 

Partial Intraventircular Block (electrical alternans)


Most premature contractions are the result of: 

ectopic foci


Give examples of ectopic foci (3)

Local ischemic areas

Calcified plaques 

Irritation of the conduction system or nodes 


Identify the ECG 

Atrial Premature Beat


Identify the ECG 

A-V nodal premature contraction