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 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 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?
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 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 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 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?
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 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.
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.
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
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 a congenital arrhythmia caused by genetic polymorphism in K+ or Na+ channels?
Torsades de pointes
What is torsades de pointes?
Congenital arrhythmia caused by genetic polymorphism in K+ or Na+ channels.
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