Topic 9: Cardiac Arrhythmias

ECG shows the instantaneous __ in electrical charge between 2 points.

difference

Depolarization waves move from __ to __ pole, and the movement of electrical current is captured in the __ pole.

-; +; +

Repolarization waves move from __ to __ pole; movement of electrical current is captured in the __ pole.

+; -; -

Both depolarization and repolarization are captured as a __ deflection.

positive

ECG detects activation/depolarization and recovery/repolarization potentials generated by the __, not the __ process.

myocardium; conduction

__ leads determine the difference between leads on the periphery versus the central EKG reading.

Prechordial

__ leads show small electrical activity not clearly shown in other EKGs. It measures the difference between one lead versus the __ of the other two leads.

augmented; sum

The EKG gives information in __ different planes: (2).

2; vertical & horizontal

Which leads are in the vertical plane? Which are in the horizontal plane?

vertical: lead I, II, III & augmented leads

horizontal: prechordial leads

Through an EKG, __ & __ abnormalities can be detected, and the __ of impulses across the myocardium can be mapped.

rhythm; rate; movement

The __ interval is the complete phase of depolarization and repolarization.

QT

An EKG interval shows the __ and __ of the impulse during that time.

strength; duration

What are the two ways heart rate is calculated?

1. 300/(# large boxes bw 2 consecutive R waves)

2. 1500/(# small boxes bw 2 consecutive R waves)

On average, how long is a full cardiac cycle?

25 mm/sec

Placement of EKG leads give __ that measure the direction impulses take during depolarization and repolarization.

vectors

The __ gives the main direction that impulses are taking.

resultant vector/mean electrical axis

The mean electrical axis is normally between __.

0 - 90 degrees (typically at 60)

If the mean electrical axis falls between -30 - -90 degrees, it has a __ axis deviation.

left

If the mean electrical axis falls between 90 - 180 degrees, it has a __ axis deviation.

right

Because of the many leads and vectors created as a result, EKGs can give specificity on __ of defect.

specific locations

__ describes anything that denotes from the normal rhythm of the heart.

arrhythmia

__ describes the normal rhythm of the heart.

sinus rhythm

__ function depresses automaticity of SA nodes and slows conduction, while __ exert the opposite effect.

vagal; sympathetic

What is the normal beats per minute in healthy individuals?

60-100; but can be <60/min (for athletes)

__ have faster heart beats than adults.

infants/children

The pacemaker function of the heart resides with the __ node.

SA

Cardiac arrhythmias are disorders of: (2)

impulse formation &/or impulse conduction

In impulse formation, cardiac automaticity remains __, but involves __ or __ of normal pacemaker mechanism.

normal; speeding; slowing

Sinus __ describes heart rate that is less than 60 bpm.

bradycardia

Sinus bradycardia is normally seem with: (6)

increased vagal tone

decreased sympathetic tone

certain drugs (Digoxin, beta blockers)

hypothermia

hypothyroidism

increased intracranial pressure

Sinus bradycardia is normally benign, unless if associated with: (2)

congestive heart failure or low cardiac output (then needs temporary or permanent electrical pacing)

Sinus __ describes when the heart rate is more than 100 bpm.

tachycardia

Sinus tachycardia is normal in: (4)

childhood

physiologic stress

pain

anxiety

__ is often seen with fever, hypotension, hypovolemia, hypothyroidism, drugs (catecholamines, alcohol, nicotine, caffeine), cardiac ischemia, and shock.

sinus tachycardia

In __, the SA node generates faster impulses for no reason. It can occur in a healthy person due to an __ defect.

chronic inappropriate sinus tachycardia (IST); autonomic

How are abnormal impulse formations treated?

identify and correct obvious cause (in emergency and outpatient setting)

eliminate possible stimulants (coffee, alcohol, tea etc)

medical treatment: Ca channel blockers, beta blockers

__ is characterized by intermittent sinus arrests or short period of atrial flutter followed by sinus arrests.

sick sinus syndrome

Sick sinus syndrome’s clinical expression can show persistent spontaneous __ that is not appropriate for the type of physical activity. It can also demonstrate a __ syndrome.

bradycardia; bradycardia-tachycardia

Sick sinus syndrome is often because of a __ node defect.

SA

How is bradycardia-tachycardia syndrome, in sick sinus syndrome, treated?

pacemaker to prevent bradycardia or drugs to control tachycardia

A latent pacemaker impulse may __ and become the __ pace maker if: (2)

escape; dominant

if: SA node rate slows down or propagation of normal impulse is interrupted

Which premature complex has a P wave that is hidden in the ST-T wave of the preceding beat, producing a camel wave?

premature atrial complex

What occurs as a result of a premature atrial complex?

longer than normal interval before the next sinus beat arrives

In a premature junctional complex, the ectopic beat from the __ captures the __, which is going retrograde/backward, and the __, which is going forward/anterograde.

AV; atria; ventricles

In the premature junctional complex, the premature P wave may occur __ or __ the QRS complex. As a result, there is a longer __ before the next beat.

before; in; pause

Are premature complexes harmful?

no, they are benign and everyone can have them every now and then

Paroxysmal Supraventricular Tachycardia is mostly due to __ in the __ or __ or both.

reentry; atria; ventricles p

Paroxysmal supraventricular tachycardia is defined by its __ QRS complexes with no apparent __ wave.

narrow; P

Why is paroxysmal supraventricular tachycardia defined as paroxysmal?

because onset is sudden and also stops abruptly

Paroxysmal supraventricular tachycardia is often seen in __ that report palpitations, pounding in chest, chest pain or pressure, weakness, SOB, or dizziness.

young adults

How is paroxysmal supraventricular tachycardia treated?

cardioversion if hemodynamically unstable

vagal maneuvers and drugs

Despite a fast heart rate in paroxysmal supraventricular tachycardia, the rhythm is __.

very normal

Atrial flutter has an atrial depolarization rate around 300/min & variable ventricular rate that may be __ or __.

regular; irregular

In atrial flutter, the waves have a __ shape.

new saw (sharp tips)

Atrial flutter is characterized by a:

macro reentrant atrial rhythm (meaning arrhythmia due to large electrical circuit in atria causing atria to beat rapidly and irregularly)

Atrial flutter can occur in health people or people with: (5)

lung disease

pulmonary embolism

alcoholism

hyperthyroidism

mitral valve disease

How is atrial flutter treated? (3)

atrial pacing

cardioversion if unstable

medications (antiarrhythmic drugs, calcium channel blockers, digitalis prep)

__ is characterized by chaotic atrial activity without effective contraction.

atrial fibrillation

Atrial fibrillation may be __ or __.

paroxysmal; chronic

Atrial fibrillation is more common in __ and __.

elderly and men

Atrial fibrillation can eventually cause:

hemodynamic changes in the heart

In atrial fibrillation, what can be seen on an EKG?

no P waves, indicating no atrial activity at all, or fine undulations (rising and falling) resembling an old saw

irregularly irregular ventricular activity: random, no pattern

What is atrial fibrillation often associated with? (4)

cardiac disease

hyperthyroidism

pulmonary embolism

pericarditis

__ describes A-fib in the absence of heart disease or risk factors.

Lone atrial fibrillation

How does A-fib relate to blood clotting?

when there is no P wave, there is a period of no activity until the next impulse. this can cause blood to not effectively be pumped, giving a chance for the heart to come to a complete stop. blood is thus pooled and clotted and can travel to the brain, causing a stroke

What are the goals when treating A-fib? (5)

identify etiology

restore sinus rhythm

control ventricular rate

prevent recurrences

prevent thromboembolic episodes (caused by blood clots)

How is A-fib initially treated?

cardioversion via:

drugs (beta blockers, calcium channel blockers)

defibrillation/electric shock

If drugs or electrical techniques don’t work, what other options will treat A-fib? (2)

1. radiofrequency ablation therapy

2. surgery: maze procedure

What cases of A-fib can undergo radiofrequency catheter ablation therapy? (3)

cases that are paroxysmal, refractory to drugs, after resuscitation sudden cardiac death

__ drugs are also beneficial for patients with A-fib.

anticoagulation

How does the maze procedure work?

creates lesions and ultimately scar tissues that block abnormal electrical impulses from being conducted through the heart

Premature ventricular complexes is due to:

ectopic ventricular foci

What does the EKG for premature ventricular complex (PVC) look like? Do the abnormalities have a pattern?

wide QRS complexes with abnormal shapes and durations

can be occasional, bigeminy, trigeminy, quadrigeminy, or have runs of PVC

What is premature ventricular complex often associated with?

significant heart disease

When premature ventricular complex is present along with myocardial infarction, what can be seen?

more serious rhythm disturbances

If present with __, premature ventricular complexes are treated with __.

cardiac disease; anti-arrhythmics

__ has an EKG showing wide QRS complexes at rates greater than 120 bpm with at least __ in a row.

ventricular tachycardia; 3

Ventricular tachycardia is __ and needs __ treatment via: (2)

life threatening; immediate

cardioversion if pt unstable or drugs

__ is a particular pleomorphic form of V-tach associated with a prolonged QT interval and QRS complexes of changing amplitude and a twisted helix shape.

Torsades de Pointes

Torsades de Pointes is usually __ or __ related.

congenital; drug

__ is chaotic ventricular activity not compatible with life.

ventricular fibrillationI

If ventricular fibrillation is not reversed in __ minutes, irreversible __ damage occurs.

3-5; brain

How is V-fib treated?

electric shock

What abnormal automaticity does this EKG show?

ventricular fibrillation

What are 3 forms of conduction disturbances?

1st degree heart block

2nd degree block

3rd degree/complete heart block

In __ degree heart block, conduction is prolonged but all impulses are conducted.

first

In __ degree heart block, conduction is prolonged until an impulse is not conducted.

second

In second degree heart block, the block is occasionally not preceded by a measurable __ in conduction.

reduction (doesn’t slow down conduction after)

What type of heart block is shown in this EKG?

first degree heart block

In first degree heart block, are other heart diseases usually present? What is it usually associated with?

not always; usually associated with drugs and infectious diseases

Is treatment necessary for first degree heart block?

not usually

What are the two types of second degree heart block?

Mobitz Type I

Mobitz Type II

In Mobitz Type I, PR intervals become progressively __ until:

longer; no impulse/skipped beat followed by impulse starting again

In Mobitz Type I, 2nd degree heart block is associated with __.

myocardial ischemia (may be reversible)

Is Mobitz Type I dangerous?

usually not; usually does not need pacemaker

In Mobitz Type __, there is periodic failure to transmit atrial stimulation (sudden block of a P wave without PR elongation).

II

What does Mobitz Type II indicate?

danger of a serious bradycardia (pace can significantly drop) and requires pacemaker

What type of heart block is shown?

2nd degree Mobitz Type II heart block

In third degree heart block, the atrium and ventricle are depolarizing __ with no __ waves conducted.

independently; P

In complete heart block, what treatment is required?

pacemaker