Exam 2 – Cardio Ch 13 Flashcards by Anika Eidson

What are causes of cardiac arrhythmias?

Abnormal rhythmicity of the pacemaker
Shift of pacemaker from sinus node
Blocks at different points in the transmission of the cardiac impulses
Abnormal pathways of transmission in the heart
Spontaneous generation of abnormal impulses from any part of the heart

How well did you know this?

Not at all

Perfectly

What are normal causes of sinus arrhythmia?

Increase in heart rate during inhalation
Decrease in heat rate during exhalation
Autonomic input associated with respiration

How well did you know this?

Not at all

Perfectly

What are abnormal sinus rhythms?

Tachycardia

Bradycardia

How well did you know this?

Not at all

Perfectly

Define tachycardia

Fast heart rate is greater than normal range

How well did you know this?

Not at all

Perfectly

What causes tachycardia?

Increased body temperature
Sympathetic stimulation (blood loss, reflex stimulation of the heart)
Toxic conditions

How well did you know this?

Not at all

Perfectly

How does increased body temperature cause tachycardia?

Due to increased rate of metabolism of sinus node which in turn directly increase its excitability and rate of rhythm

How well did you know this?

Not at all

Perfectly

Define bradycardia

Slow heart rate lower than normal range

How well did you know this?

Not at all

Perfectly

Why is bradycardia present in some athletes?

They have a large stroke volume

How well did you know this?

Not at all

Perfectly

What can cause bradycardia?

Vagal stimulation

How well did you know this?

Not at all

Perfectly

What is carotid sinus syndrome?

Especially sensitive syndrome that easily triggers vagal stimulation

How well did you know this?

Not at all

Perfectly

Define sinoatrial block

In rare instances impulses from SA node are blocked before it enters atrial muscle

How well did you know this?

Not at all

Perfectly

What does sinoatrial block cause cessation of?

P wave

How well did you know this?

Not at all

Perfectly

What is the new pacemaker in sinoatrial block?

Region of heart with the next fastest discharge rate, usually AV node

How well did you know this?

Not at all

Perfectly

Due to cessation of P waves in sinoatrial block, what is occasionally seen?

Atrial standstill

How well did you know this?

Not at all

Perfectly

Define atrioventricular block

Impulses through AV node and AV bundle are slowed down or blocked

How well did you know this?

Not at all

Perfectly

What causes atrioventricular block?

Ischemia
Compression
AV nodal/AV bundle inflammation
Excessive vagal stimulation

How well did you know this?

Not at all

Perfectly

What is the AV bundle also known as?

Bundle of HIS

How well did you know this?

Not at all

Perfectly

Describe incomplete heart block first degree block

Long space between P wave and QRS

Prolonged PR interval

How well did you know this?

Not at all

Perfectly

What can the PR interval not be longer than in a first degree block?

RR interval

Cannot be longer than space between two beats

How well did you know this?

Not at all

Perfectly

Why is a first degree block considered incomplete?

Delay of conduction from atria to ventricles but not actual blockage of conduction

How well did you know this?

Not at all

Perfectly

Describe second degree incomplete block

PR interval increased

How well did you know this?

Not at all

Perfectly

What is Mobitz Type ! or Wenkebach second degree block?

PR gets longer with each beat until a beat is dropped

How well did you know this?

Not at all

Perfectly

What is Mobitz Type 2 second degree block?

Some impulses pass through AV node and some do not thus causing “dropped beats”
Fixed number of nonconducted P waves for every QRS complex

How well did you know this?

Not at all

Perfectly

What happens to atria speed in second degree incomplete block?

It beats faster than ventricles

How well did you know this?

Not at all

Perfectly

What species tends to have mild second degree block at rest?

Horses

Describe third degree complete block

Total block through AV node or AV bundle

How are the P waves in a third degree complete block?

Completely dissociated from QRST complexes | AV dissociation

What happens to ventricles in third degree complete block?

Ventricles escape and AV nodal rhythm ensues Spontaneously establish their own signal, usually originating in AV node or AV bundle

Is there a relation between rhythm of P waves and QRST complex in third degree complete block?

No because ventricles escape control from atria and beats at its own natural rate

Describe Stokes-Adams syndrome

Fainting associated with complete AV block

How is the complete AV block in stokes-adams syndrome?

It comes and goes

What happens to ventricles in stokes-adams syndrome?

Ventricles stop contracting for 5-30 seconds because of overdrive suppression meaning they are used to atrial drive

Why does the patient faint from stokes-adams syndrome?

Because of poor cerebral blood flow

What does the ventricle escape in stokes-adams syndrome?

AV nodal or AV bundle rhythm (15-40 beats/min)

What will correct stoke-adams syndrome?

Pacemaker

What happens to the impulse in incomplete intraventricular block (electrical alternans)?

Sometimes blocked and sometimes not in peripheral portions of purkinje system resulting in abnormal QRS waves

What can cause incomplete intraventricular block?

Ischemia Myocarditis Digitalis toxicity

What is incomplete intraventricular block associated with?

Pleural and/or pericardial effusions in animals

What happens to the PR interval in premature atrial contractions?

Shortened if ectopic foci originating the beat are near AV node

Where does the impulse travel in premature atrial contractions?

Through AV node and back toward sinus node causing discharge of the sinus node Next sinus discharge will thus be late

How does an early contraction affect the heart?

It doesn't allow the heart to fill with blood causing a low stroke volume and a weak radial pulse

How does Av nodal or AV bundle premature contractions affect the P waves?

Early and inverted Missing Late and inverted

When the P wave is early and inverted, where is the premature contraction in the AV junction?

High AV junction

When the P wave is missing, where is the premature contraction in AV junction?

Mid AV junction

When the P wave is late and inverted, where is the premature contraction in AV junction?

Low AV junction

Where does the impulse travel in a AV junctional premature contractions?

Backward into atria

What happens to the QRS in premature ventricular contractions?

QRS is prolonged because impulse is conducted through muscle which has slow conduction

What happens to the QRS voltage in premature ventricular contractions?

High because one side depolarizes ahead of the other

What happens to the T wave in premature ventricular contractions?

Inverted because slow conduction causes the area to first depolarize to also repolarize first (opposite of normal)

What causes T wave premature ventricular contractions?

Cigarettes Coffee Lack of sleep

define paroxysmal

A series of rapid heart beats suddenly start and then suddenly stop

What can stop atrial paroxysmal tachycardia?

Vagal reflex | Quinidine or procainmide or lidocaine

What happens to the P wave in atrial paroxysmal tachycardia?

Inverted if origin is near AV node

How does atrial paroxysmal tachycardia?

Occurs by re-entrant pathways

What autonomic discharge occurs in atrial paroxysmal tachycardia?

High sympathetic discharge

What is an atrial flutter?

Single large impulses wave travels around area in one direction

What is the atrial contraction speed in an atrial flutter?

200-350 beats/min

When will the AV node not pass signal in atrial flutter?

Not pass signal until 0.35 seconds elapses after previous signal Therefore, atria may beat 2 or 3 times as rapidly as ventricle

What does atrial fibrillation most often occur without?

Ventricular fibrillation

What is the most frequent cause of atrial fibrillation?

Atrial enlargement due to AV valve dysfunction | This causes a long pathway of conduction which is favorable for circus movements

What happens to the efficiency of ventricular pumping because of atrial fibrillation?

Decreased 20-30 percent

Why does an irregular, fast heart rate occur in atrial fibrillation?

Because of irregular arrival of cardiac impulses at AV node

What does atrial fibrillation sound like?

Tennis shoes in a dryer

When does ventricular paroxysmal tachycardia occur?

Usually does not occur unless there has been ischemic damage

What can fix the problem of ventricular paroxysmal tachycardia?

Quinidine increases refractory period of cardiac muscle

When do circus movements occur in ventricular fibrillation?

If pathway is long If conduction velocity is decreased If refractory period is shortened

What causes a long pathway in ventricular fibrillation?

Dilated heart

What causes decreased conduction velocity in ventricular fibrillation?

Blockade of purkinje system Ischemia of muscle High K+ levels

What causes shortened refractory period in ventricular fibrillation?

Epinephrine release

What is ventricular fibrillation compared to?

Bag of worms

Why is ventricular fibrillation considered a bag of worms?

Some parts of ventricle contract while others relax thus little blood flows out of heart

What is ventricular fibrillation caused by?

Electrical shock or cardiac ischemia

What is ventricular defibrillation?

1000 volts direct current is applied for a few thousandths of a second

Which parts of the heart become refractory during ventricular defibrillation?

All parts of the heart become refractory and remain quiescent for 3-5 seconds until new pacemaker is established

What happens to the heart if used later than one minute after fibrillation?

The heart is too weak to defibrillate and may have to be hand-pumped/CPR

When does cardiac arrest usually occur?

Due to hypoxic conditions in the heart which prevents muscle and conductive fibers from maintaining their electrolyte gradients

Look at ventricular fibrillation diagram

Look at all EKG pictures