SAM 6

What does an ECG detect?

Electrical changes from depolarization and repolarization

What is the SA node?

The heart's pacemaker

Where is the SA node?

Right atrium

What does the AV node do?

Delays conduction so ventricles can fill

What do Purkinje fibers do?

Trigger ventricular contraction

What does the P wave represent?

Atrial depolarization

What does the QRS complex represent?

Ventricular depolarization

What does the T wave represent?

Ventricular repolarization

What should you assess when interpreting an ECG?

Rate rhythm P waves PR interval QRS and axis

What is normal sinus rhythm?

Regular rhythm originating from the SA node

What characterizes normal sinus rhythm?

P for every QRS and regular R-R intervals

What causes sinus tachycardia?

Increased sympathetic tone

What causes sinus bradycardia?

Increased vagal tone

What can severe sinus bradycardia cause?

Syncope

What is sinus arrhythmia?

Cyclic speeding and slowing with respiration

Is sinus arrhythmia normal in dogs?

Yes

What is an APC?

Premature ectopic beat from the atria

How does an APC usually appear?

Narrow QRS with a premature P wave

What is SVT?

Rapid regular rhythm from above the ventricles

How does SVT differ from sinus tachycardia?

Often faster and paroxysmal

What is atrial fibrillation?

Chaotic atrial activity

How do you recognize AFib on an ECG?

Irregularly irregular rhythm with no P waves

What does AFib usually have for QRS complexes?

Relatively normal QRS

What commonly causes AFib?

Atrial dilation

What is lone AFib?

AFib in a large-breed dog without structural disease

What is a VPC?

Premature beat arising from the ventricles

How does a VPC appear?

Wide bizarre QRS with no P wave

How do you distinguish an APC from a VPC?

APC narrow QRS and VPC wide QRS

What is a compensatory pause?

Pause equal to 2× normal R-R

What rhythm usually causes a compensatory pause?

VPC

What is a non-compensatory pause?

Pause less than 2× normal R-R

What rhythm usually causes a non-compensatory pause?

APC

What is ventricular tachycardia?

4 or more VPCs in a row

How does VT appear on ECG?

Rapid rhythm with wide bizarre QRS

Why is VT dangerous?

Can cause hypotension syncope and sudden death

What is ventricular fibrillation?

Chaotic ventricular electrical activity

How does VF appear on ECG?

Chaotic baseline with no identifiable QRS

Why is VF an emergency?

The heart is not pumping blood

What is the treatment for VF?

Immediate defibrillation and CPR

What is electrical alternans?

Alternating QRS amplitude

What does electrical alternans suggest?

Pericardial effusion

Why does electrical alternans occur?

The heart swings in the fluid-filled pericardial sac

What is AV block?

Abnormal conduction from atria to ventricles

What is first-degree AV block?

Prolonged PR interval

What happens in second-degree AV block?

Some P waves fail to conduct

What is Mobitz I?

Progressive PR prolongation then dropped beat

What is Mobitz II?

Constant PR with sudden dropped beats

What is third-degree AV block?

Complete failure of atrial impulses to conduct

What characterizes third-degree AV block?

P waves and QRS are dissociated

What is sinus arrest?

Failure of the SA node to discharge

What can long sinus pauses cause?

Syncope

What is sick sinus syndrome?

Sinus node dysfunction with sinus arrest

What can follow sinus arrest in sick sinus syndrome?

Paroxysmal SVT

What is atrial standstill?

Complete absence of atrial activity

What is the key ECG finding in atrial standstill?

No P waves

What can cause atrial standstill?

Severe hyperkalemia

What ECG finding suggests hyperkalemia?

Tall tented T waves

What does a tall P wave suggest?

Right atrial enlargement

What does a wide P wave suggest?

Left atrial enlargement

What can tall R waves suggest?

Ventricular hypertrophy or dilation

What is a premature depolarization?

A heartbeat that starts too early

What is an escape depolarization?

A backup heartbeat after a pause

What is AV dissociation?

Atria and ventricles depolarize independently

What does paroxysmal mean?

Sudden burst with abrupt end

What is the key rule about arrhythmias and disease?

One arrhythmia does not equal one specific disease