Exam 2 – Cardio Ch 13 Flashcards
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
What are normal causes of sinus arrhythmia?
Increase in heart rate during inhalation
Decrease in heat rate during exhalation
Autonomic input associated with respiration
What are abnormal sinus rhythms?
Tachycardia
Bradycardia
Define tachycardia
Fast heart rate is greater than normal range
What causes tachycardia?
Increased body temperature
Sympathetic stimulation (blood loss, reflex stimulation of the heart)
Toxic conditions
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
Define bradycardia
Slow heart rate lower than normal range
Why is bradycardia present in some athletes?
They have a large stroke volume
What can cause bradycardia?
Vagal stimulation
What is carotid sinus syndrome?
Especially sensitive syndrome that easily triggers vagal stimulation
Define sinoatrial block
In rare instances impulses from SA node are blocked before it enters atrial muscle
What does sinoatrial block cause cessation of?
P wave
What is the new pacemaker in sinoatrial block?
Region of heart with the next fastest discharge rate, usually AV node
Due to cessation of P waves in sinoatrial block, what is occasionally seen?
Atrial standstill
Define atrioventricular block
Impulses through AV node and AV bundle are slowed down or blocked
What causes atrioventricular block?
Ischemia
Compression
AV nodal/AV bundle inflammation
Excessive vagal stimulation
What is the AV bundle also known as?
Bundle of HIS
Describe incomplete heart block first degree block
Long space between P wave and QRS
Prolonged PR interval
What can the PR interval not be longer than in a first degree block?
RR interval
Cannot be longer than space between two beats
Why is a first degree block considered incomplete?
Delay of conduction from atria to ventricles but not actual blockage of conduction
Describe second degree incomplete block
PR interval increased
What is Mobitz Type ! or Wenkebach second degree block?
PR gets longer with each beat until a beat is dropped
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
What happens to atria speed in second degree incomplete block?
It beats faster than ventricles
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