What are the two types of cardiac cells?

Cardiac Myocytes
Pacemaker Cells

What are Cardiac Myocytes?

Cardiac muscle cells

What are the characteristics of Cardiac Myocytes?

Can only contract in response to an external electrical impulse
Bulk of cardiac cells

What are the characteristics of Pacemaker Cells?

Spontaneously depolarize to generate an electrical impulse

What is an example of Pacemaker Cells?

SA & AV node

SA & AV node are examples of what type of cardiac cells?

Pacemaker cells

How many times can the sinal atrial node depolarize every minute?


If the SA node is knocked out, what takes over depolarization of the heart?

AV node

What does the P wave indicate?

Depolarization of the atria

What does the QRS wave indicate?

Depolarization of ventricles

What does the T wave indicate?

Repolarization of ventricles

What wave indicates the depolarization of the atria?

P wave

What wave indicates the depolarization of the ventricles?

QRS wave

What wave indicates the repolarization of the ventricles?

T wave

What is the term for disturbance of cardiac rate and/or rhythm?


What is an arrhythmia?

Disturbance of cardiac rate and/or rhythm

What are some possible causes of Arrhythmia?

Ischemia, hypoxia, acidosis, autonomic changes, electrolyte imbalances, and drugs.

How do electrolyte imbalances cause arrhythmia?

Changes in potassium level can effect heart rhythm almost immediately

What is an example of a arrhythmia cause by a genetic defect?

Faulty ion channels

What is an example of abnormal automaticity?

SA node defects, and Ectopic pacemakers

What is an Ectopic pacemaker?

Is an excitable group of cells that causes a premature heart beat outside the normally functioning SA node of the human heart

SA node defects and ectopic pacemakers are examples of what mechanism of cardiac arrhythmia?

Abnormal automaticity

What is cardiac automaticity?

is the ability of the cardiac muscles to depolarize spontaneously, i.e. without external electrical stimulation from the nervous system

_________ cells become a cluster in the heart during abnormal conditions when other cells are ischemic and begin to fail.


What type of cells can cause abnormal electrical conduction?


What are examples of abnormal conduction of impulses?

AV node defect, Conduction blocks, and Reentry currents.

What is a conduction block?

can be a blockage at any level of the electrical conduction system of the heart

What's another term for conduction block?

Heart Block

What may cause a reentry current?

Ischemic tissue usually conducts impulses in the wrong direction.

What is cardiac retrograde conduction

Transmission of a cardiac impulse backward in the ventricular to atrial direction; particularly, conduction from the atrioventricular node into the atria.

What is sick sinus syndrome?

A heart rhythm disorder characterized by bradycardia or tachycardia

What is atrial fibrillation?

Loss of coordinated contraction of atria

What are examples of atrial arrhythmia's?

Premature atrial beat, atrial tachycardia, atrial flutter and atrial fibrillation.

What is the term we use to describe the loss of coordinated contraction of the atria?

Atrial fibrillation

What is the definition of a premature atrial contraction (PAC)?

a common cardiac arrhythmia characterized by premature heartbeats originating in the atria

What causes PAC?

occur when another region of the atria depolarizes before the sinoatrial node and thus triggers a premature heartbeat.

What would you see on a EKG if a paroxysmal atrial tachycardia occurred?

A double P wave

What is a paroxysmal atrial tachycardia (PAT)?

is a condition where the heart beats too fast because there is an abnormality in the conduction system (electrical system) of the heart.

What would you see on a EKG if a atrial flutter were occurring?

Multiple P waves while QRS waves stay normal.

Why is an atrial flutter so dangerous?

Leads to atrial fibrillation

What are the characteristics of atrial flutter?

Atria firing 250-300
Cardiac output is normal

Cardiac output is ________ during atrial flutter.


What is the most common cardiac arrhythmia?

Atrial fibrillation

What cardiac arrhythmia is characterized by pooling of blood in the atria?

Atrial fibrillation

What causes atrial fibrillation?

rapid, disorganized electrical signals cause the heart's two upper chambers to contract fast and irregularly.

What is the effect of atrial arrhythmia on C.O.?

Leads to ventricular tachycardia but AV node can only conduct impulses up the 1/2 the rate of the atria.

Conduction of atrial impulses will lead to ventricular tachycardia but AV node can only conduct impulses up to _______ the rate of the atria.


What is the most common form of arrhythmia?

Ventricular premature beats

If looking at a EKG what would one look for if looking for premature ventricular contractions (PVC)?

A large QRS wave compared to normal beats

Why is there such a large QRS wave in PVC?

A double ventricular contraction

What is ventricular tachycardia?

Excessive ventricular rate

How does ventricular tachycardia effect C.O.?

Depends on the rate. If too fast the ventricles do not have enough time to fill decreasing C.O.

If a patient had ventricular tachycardia, what would you see on their EKG?

CRAZY QRS waves one right after the other

What would allow for the ventricles to beat at rates of 250 beats/min?

Epotopic depolarization of the ventricles

What is ventricular fibrillation?

Complete loss of ventricular rhythm

What arrhythmia is said to be immediately life threatening?

Ventricular Arrhythmia

In ventricular fibrillation C.O. falls to _________.


What patients are most at risk for ventricular fibrillation?

Tachycardia patients

What is a congenital arrhythmia caused by genetic polymorphism in K+ or Na+ channels?

Torsades de pointes

What drug can cause arrhythmia by affecting K+ or Na+ channels?


What can Quinidine cause?

Arrhythmia by affecting K+ or Na+ channels

What is torsades de pointes?

Congenital arrhythmia caused by genetic polymorphism in K+ or Na+ channels.

What is torsades de pointes characterized by?

QT elongation followed by V. Tachycardia

What are the symptoms of torsades de pointes?

Dizziness and loss of consciousness

What is the risk associated with torsades de pointes?

Ventricular fibrillation and sudden death.

What causes heart block?

Ischemia in the bundle branches

Heart block often occurs due to ischemia in the _____________.

Bundle Branches

What are the characteristics of 2nd degree AV block?

P wave occurs without a QRS because the conduction is so poor the impulse never made it.

What are the characteristics of 3rd degree AV block?

P waves continue to occur but no impulse reaches the ventricles.

In 3rd degree AV Block, if no impulse makes it to the ventricle why do we continue to see QRS?

AV node still fires and purkinje fibers

How do we diagnose arrhythmia?

Signal-averaging EKG

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