Cardio & Respiratory Wk 12 - Lesson 91

What is an ectopic pacemaker?

abnormal pacemaker elsewhere in the heart that takes over from the SA node, leading to an irregular heartbeat

What is hyperkalemia?

high levels of potassium in the blood, which can disrupt heart rhythm

What is ischemia?

reduced blood flow to heart tissue, often leading to arrhythmias due to oxygen deprivation

What is myocardial infarction?

heart attack; death of a section of heart muscle due to loss of blood supply, which can cause arrythmias

What is myocarditis?

inflammation of the heart muscle, which can lead to arrythmias

What is premature contraction, premature impulses, or ectopic beats?

early heartbeat originating from the atria or ventricles disrupting the normal heart rhythm

What is the reentry circuit?

circular path of electrical impulses that can lead to tachycardia and other arrythmias

What is sinus node dysfunction?

abnormal function of the sinoatrial node, leading to irregular heart rhythms

What is syncope?

fainting or loss of consciousness due to a temporary reduction in blood flow to the brain

What is the torsades de pointes?

specific type of abnormal heart rhythm that can lead to sudden cardiac arrest

What is triggered activity?

impulse initiation in cardiac fibers that is dependent of afterdepolarizations

What are the two basic mechanisms that underline cardiac arrhythmias?

disturbances of automaticity or impulse formation & disturbance of conduction

What are the three ways that you can have disturbances of automaticity?

all of the above

3 multiple choice options

What does abnormal pacemaker activity lead to?

bradycardia or tachycardia

What does formation of electrical impulse in cells that are not normally automatic contribute to?

ectopic beats

What are the two main mechanisms of triggered activity?

early afterdepolarizations and delayed depolarizations

What is the clinical implication of EADs?

implicated in developing torsades de pointes and other long QT syndromes

What is the clinical implication of DADs?

associated with conditions of calcium overload; lead to ventricular and atrial tachyarrhythmias

What factors influence triggered activity?

electrolyte imbalances, ischemia and hypoxia, medications, ANS

What do disturbances of conduction lead to?

bradycardia and tachyarrhythmias

What type of nervous stimulation causes bradyarrhythmia?

parasympathetic

What type of nervous stimulation causes tachyarrhythmia?

sympathetic

What kind of electrolyte disturbances cause bradyarrhythmias?

hyperkalemia

What kind of electrolyte disturbances cause tachyarrhythmias?

hypokalemia

How does your body temperature change with bradyarrhythmia's and tachyarrhythmias?

hypothermia with bradyarrhythmia's and fever with tachyarrhythmia's

What endocrine abnormality occurs with bradyarrhythmia?

hypothyroidism

What endocrine abnormality occurs with tachyarrhythmia?

hyperthyroidism

What diseases cause bradyarrhythmia?

sick sinus syndrome, heart failure by damage of ion channels or GAP junctions

What diseases cause tachyarrhythmia?

heart failure by mechanical stretch, hypovolemia, drugs like catecholamines, atropine, glycopyrrolate

What is hyperkalemia related to in cats?

urethral obstruction because urinary excretion of potassium is reduced

What are the clinical manifestations of hyperkalemia in cats?

changes in cell membrane excitability, muscle weakness, cardiac electrical conduction abnormalities

What phase can EAD occur in?

phase 2-3

When does EAD occur?

happens with slow heart rates and slow repolarization and hypokalemia because then the cells have more time to return to their resting membrane potential which leaves them vulnerable to another action potential

How does EAD occur?

reactivates L-type of Ca channels

What does EAD lead to?

polymorphic ventricular tachycardia (torsades des pointes)

What phase does DAD occur?

phase 4

How does DAD occur?

activation of Na voltage gated channels causing depolarization because of calcium overload and and fast heart rate

What do DADs cause?

ventricular tachyarrhythmias

What does prolongation of P-R interval mean?

first-degree AV blocks

What is a second-degree AV block?

dropped beat

What is third-degree AV block?

when conduction is completely blocked

What animal can dropped beat be physiologic?

equine

3 multiple choice options

What can conduction through abnormal or diseased cardiac tissue result in?

re-entry

What is the most common mechanism for tachyarrhythmia?

re-entry

What are the requirements for re-entries?

all of the above

3 multiple choice options

What happens during re-entry?

there is a block in the fast pathway which allows the slow pathway to depolarize and nothing keeps it from going around and around continuously

What are some other normal working rhythms?

sinus arrhythmia and wandering pacemaker

What is sinus arrhythmia?

regularly irregular where bradycardia occurs during exhalation and tachycardia occurs during inhalation

What is the mnemonic used for sinus arrythmia?

BETI

What animal is BETI normal and not normal?

relaxed dogs and not good in cats

What is wandering pacemaker?

normal variation in the amplitude of P-waves in dog's corresponding to the respiratory cycle

When do you have a taller P wave with wandering pacemaker?

during fast heart rate and inhalation

What are the components of normal working rhythms?

heart rate, sinus rhythm, QRS complexes, P waves

What body system function influences a relaxed dog's regularly irregular heart rhythm?

mechanic of ventilation

3 multiple choice options

What leads show QRS complexes that appear upright, tall, and narrow?

II, III, aVF

What leads show upright P waves?

I, II, III, aVF

What is the AV node?

gatekeeper

How do see if there is a ventricular ectopic complex?

not associated with a preceding P wave

What are ventricular premature complexes?

common in dogs and cats; arise from ectopic focus within the ventricle

What do ventricular premature complexes look like on ECG?

QRS is wide and bizarre in shape

What is ventricular tachycardia?

run of four or more VPCs

What are supraventricular premature complexes?

arise from ectopic focus above the ventricular myocardium

What do supraventricular premature complexes look like on ECG?

normal QRS complexes but seen prematurely

What is supraventricular tachycardia?

run of four or more SVPCs

What is atrial fibrillation?

most common type of supraventricular arrhythmia in small animals and horses; ectopic generation of action potentials causes a high atrial rate leading to functional failure of both atria

What happens with the ventricles during atrial fibrillation?

ventricles remain pumping blood

What type of dogs is atrial fibrillation more common in?

larger breed dogs

What is the most common cause of atrial fibrillation?

atrial dilation and re-entries

What happens when an animal develops atrial fibrillation?

it is nearly always permanent and continuous

What kind of waves are seen in atrial fibrillation?

f waves

What type of arrythmias could be more life-threatening?

ventricular