EKG lecture 4 pt 1

Question 1

Describe the Sxs of arrythmia

Answer 1

1) Asymptomatic, incidental findings
2) Clinically apparent symptoms:
Palpitations
Lightheadedness to syncope – decreased C.O.
Angina – 2nd to supply: demand mismatch
Acute HF
ACS/Sudden death

Question 2

List the causes of arrythmias

Answer 2

1) Hypoxia: irritable myocardium – pulmonary disease/PE
2) Ischemia & Irritability: stable angina, ACS, myocarditis (viral)
3) Inherited: prolonged QT, HOCM
4) Sympathetic stimulation: exercise, stress, hyperthyroidism, HF
5) Bradycardia: low cardiac output, tachy-brady (sick sinus) syndrome
6) Electrolyte d/o: hypoK/hyperK
7) Drugs: antiarrhythmic drugs, others
8) Stretch: hypertrophy, dilation – HFrEF, cardiomyopathies, valvular dz
HIISBEDS

Question 3

What are rhythm strips?

Answer 3

View rhythm over longer duration than standard 12 lead

Question 4

When would you use ambulatory monitors? What are 2 different kinds?

Answer 4

1) Intermittent arrhythmias
2) Holter monitor
Zio patch

Question 5

Besides ambulatory monitors, what are the other 3 types of monitors? When would you use them?

Answer 5

1) Event monitor – infrequent arrhythmias, patient initiated based on symptoms
2) Implantable event monitor
3) Consumer oriented HR monitors – smart watch/phone

Question 6

List the 4 different ways to determine HR on an EKG

Answer 6

1) Estimate by 300-150-100-75-60-50-42
2) 300/# of large boxes between R-R interval
3) 1500/# of small boxes between R-R interval
4) For slow/irregular rates, count the # QRS complexes noted on the rhythm strip & multiply by 6 (typical EKG runs for 10 seconds)

Question 7

Arrhythmias of sinus origin (AKA “supraventricular”): List the different kinds

Answer 7

Sinus bradycardia = slow
Sinus tachycardia = fast
Sinus arrhythmia = normal variant
Sinus arrest/exit block………no sinus activity, flat line
Sinus arrest/exit block with junctional escape…..secondary site origin

Question 8

List all the differentials for sinus bradycardia

Answer 8

1) Enhanced vagal tone (seen in athletes, valsalva)
2) Medications – negative chronotropes - B-blocker, CCB, et. al.
3) Opioids
4) Myocardial ischemia
5) Hypothyroidism
6) Hypothermia
7) Hyperkalemia
8) Stroke
9) OSA during apneic episodes
10) Sinus node dysfunction – SSS, sinus arrest
11) Many infectious causes

Question 9

Explain the physiology of sinus arrythmia

Answer 9

Inspiration speeds up the rate (decreased pre-load)
Expiration slows of the heart rate (increased pre-load)

Question 10

Explain sinus arrest and sinus exit block

Answer 10

1) Sinus arrest: sinus node does not fire = flat line
2) Sinus exit block: SA node fires but no propagation = flat line
-Neither above have P-wave or any electrical activity unless an escape beat emerges (atrial, junctional, ventricular).
-Escape beats = inherent pacemakers in most myocardial cell

Question 11

Give an overview of the pacemakers of the heart

Answer 11

1) Normal (sinus pacemaker): SA node 60-100 – “over drives” the other pacers
2) Non-sinus pacemakers (ectopic) result in escape beats – rescue beats if SA node does not fire or propagate a wave of depolarization
a) Atrial pacemakers ~ 60-75/minutes
b) Junctional pacemakers (at or near AV node) ~ 40-60/minute – Most common
c) Ventricular pacemakers ~ 30-45/minute

Question 12

Explain junctional escape

Answer 12

1) Originates near AV node
2) Usual pattern of atrial depolarization does not occur – normal P wave NOT seen
3) Most often, no P wave seen
4) Occasionally a retrograde P wave may be seen – atrial depolarization moving backward from AV node into the atria and axis reverse

Question 13

Occasionally a retrograde P wave may be seen with junctional escape; explain what this means

Answer 13

1) A normal P wave is upright in lead II and inverted in aVR
2) Retrograde P wave is inverted in lead II, upright in aVR … but may be hidden in QRS complex of follow

Question 14

Junctional escape beat: When may it occur? Where does i originate?

Answer 14

1) May follow sinus arrest or sinus exit block
2) Originates at or near AV node, rate of ~ 40-60

Question 15

Junctional escape beat: Explain what it looks like on an EKG

Answer 15

1) P waves may be absent or occasionally retrograde – after QRS
2) QRS is narrow; depolarization progresses down the ventricular conduction system

Question 16

“No P wave; electrically silent until escape beat occurs and restores electrical activity” describes what?

Answer 16

Sinus arrest or exit block

Question 17

Sinus arrest = sinus ___________ clinically

Answer 17

exit block

Question 18

Explain sinus arrest/ sinus exit block

Answer 18

SA node depolarization is not seen on EKG
neither initiates depolarization of atria
so…can’t tell the difference with EKG … result is the same

Medications, infiltrative processes (amyloid, sarcoid), fibrosis, & inflammatory conditions such as Rheumatic fever

Question 19

What are the 2 main causes of non-sinus arrythmias?

Answer 19

1. Ectopic rhythms: enhanced automaticity or d/o of impulse formation
2. Re-entrant rhythms: d/o of impulse transmission

Question 20

Non-sinus rhythms can be single isolated beats or sustained ____________

Answer 20

arrhythmias

Question 21

When do ectopic rhythms occur?

Answer 21

“Fastest Pacer Drives the heart” – under abnormal circumstances, non-sinus pacer can be stimulated to fire faster & faster and over “take over” the normal SA node pacer

Question 22

Ectopic rhythms:
1) Define them
2) Are they always sustained?
3) What causes them?

Answer 22

1) Abnormal rhythms that arise from outside the SA node
2) Single/isolated beats or sustained
2) Enhanced automaticity of a non-sinus node site, either single focus or roving site - essentially disorder of impulse formation

Question 23

What are some common etiologies of ectopic rhythms?

Answer 23

Digitalis toxicity
B-adrenergic stimulation – SABA/LABA (B1 vs. B2 vs. non-cardio select BB)
Caffeine, alcohol
Stimulant drugs – ADHD Rx, cocaine, methamphetamines
Psychological stress

Question 24

Re-entry rhythms:
1) What causes them?
2) Why do they vary in size?

Answer 24

1) Abnormal electrical activity resulting in a reentry loop
2) Within AV node, entire chamber, or if an accessory pathway can involve atria and ventricle

Question 25

1. Are NORMAL P-waves present? - Normal shaped P waves and normal P wave axis (0-70 degrees therefore + in lead II, - in lead aVR.) What are the 3 potential answers to this question? Explain each

Answer 25

1) YES … present and normal axis = then origin of arrhythmia is atrial, likely at or near Sinus node 2) YES … present, abnormal axis or appearance = then origin is atrial other than at or near sinus node, retrograde from junctional or accessory pathway from a ventricular origin 3) NO … no P waves present = then origin is below atria in AV node or ventricles

Question 26

"What is the relationship between the P waves and the QRS complexes?" What may cause this relationship to be abnormal?

Answer 26

A-V dissociation – atria and ventricles depolarize independently of each other, and no association noted

Question 27

How do you answer the question "Is the rhythm regular or irregular (look at rhythm strip)?" What may it help determine?

Answer 27

Usually immediately obvious May be most critical in determining rhythm – think A. fibrillation vs. A. flutter

Question 28

Supraventricular arrythmias: 1) Define these 2) What are 2 different forms? Which is common? 3) How long are they?

Answer 28

1) Arrhythmias originates above the ventricles: Atria or vicinity of AV node (junctional) 2) Single or sustained Single - common and of no clinical significance unless initiate more sustained arrhythmias 3) Seconds or life long

Question 29

Atrial & junctional Premature beats: Describe them

Answer 29

Common Neither indicating pathology Do not require treatment May initiate more sustained arrhythmias Both usually conducted normally to the ventricles with a resulting narrow QRS complex (supraventricular origin)

Question 30

Explain atrial premature beats

Answer 30

Amplitude and duration of 1st P-wave? Different contour of the P wave – depole originates at different site than SA node Timing – 3rd beat is early resulting in a premature atrial contraction

Question 31

Junctional premature beat: What do they look like?

Answer 31

Usually, no visible P wave or occasionally retrograde P wave similar to Junctional escape beats with sinus arrest.

Question 32

What are the 2 forms of junctional premature beat?

Answer 32

Jct premature beat occurs early (A) VS. Jct escape beat occurs late (B)

Question 33

Give examples of Sustained supraventricular arrhythmias

Answer 33

1) AV nodal reentrant tachycardia (AVNRT) – aka paroxysmal supraventricular tachycardia 2) Atrial flutter 3) Atrial fibrillation 4) Multifocal Atrial Tachyccardia (MAT) 5) Paroxysmal Atrial Tachycardia (PAT) – aka ectopic atrial tachy 6) AV reciprocating tachycardia – see preexcitation lecture

Question 34

Describe AV nodal reentrant tachycardia (AVNRT). What are the S/Sx and what is the etiology?

Answer 34

Common Sudden onset - usually initiated by premature supraventricular beat (atrial or jct) Abrupt termination May occur in normal hearts S/S: palpitations, SOB, dizziness, syncope Etiology: Alcohol, coffee, excitement

Question 35

Describe what AVNRT looks like on an EKG

Answer 35

1) Regular rhythm 2) Rate 150-250/minute 3) Most often driven by reentrant circuit within AV node (carotid massage may terminate rhythm) 4) May see retrograde P waves in lead II or III and V1 pseudo-R’, most buried in QRS complex

Question 36

Atrial flutter: 1) Is it normal? 2) What is the rhythm? 3) What is the rate? 4) Explain what is occurring

Answer 36

1) Usually indicates underlying pathology – reentrant rhythm around annulus of tricuspid valve (above AV node) 2) Regular rhythm 3) Rate is faster than AVNRT 4) P waves @ rate 250-300 – flutter waves, best seen in leads II and III Single constant reentrant circuit with regular P waves Carotid massage increases AV nodal block (slows ventricular rate)

Question 37

Atrial flutter: Carotid massage increases AV block from 2:1 to 4:1 but does not ____________ as originate above AV node

Answer 37

terminate

Question 38

Atrial fibrillation: 1) What is it? 2) Describe the P waves 3) What does the AV node do? 4) What may slow ventricular rate?

Answer 38

1) Chaotic atrial activity Multiple tiny reentrant circuits 2) No true P waves 3) AV node only allows periodic impulses thru generating Irregularly Irregular Rhythm usually between 120-180/min (rapid ventricular response) 4) Carotid massage may slow (via increased AV nodal block) ventricular rate