Lecture 5: Kirk and Arrhythmia's

Question 1

Draw a sinus rhythm and explain which part represents what

Answer 1

Sinus rhythm shown in picture below

P wave: atrial depolarization

QRS complex: ventricular depolarization

T wave: ventricular repolarization

Question 2

Explain the rule of 300

aka how to count Heart Rate on the EKG

Answer 2

Count the number of BIG boxes between QRS complex peaks

Then do this math:

(300/ the number of boxes in between QRS peaks) = HR

Question 3

In a sinus rhythm explain where the heart rate is being paced from

Answer 3

In sinus rhythm, the SA node or the “pacemaker” is the fastest of the automaticity points in the heart, and therefore controls the entire system’s pace

The SA node normally beats about 60-100 beats/min

Question 4

Explain the wave of automaticity in the heart?

Which beats fastest, and then go down from there

Answer 4

SA Node (60-100)

Atrial Foci (60-80)

Junctional Foci (aka the AV node itself… 40-60)

Ventricular Foci (20-40)

Question 5

Explain “sinus arrhythmia”

Answer 5

Sinus arrhythmia: (non pathological) variability in heart rate caused primarily by respiratory changes in parasympathetic/”vagal” nerve activity to the SA node

Inspiration causes increase in HR by inhibition of PSNS activity (stretch receptors in lung feed back and decrease HR)

Expiration causes decrease in HR caused by stimulation of parasympathetic nerve activity

Question 6

What are the four questions you should ask while evaulating every EKG?

What does the answer to each question tell you?

Answer 6

1. Are normal P waves present? (is the origian the atria/junctional (supraventricular) or in the ventrical)
2. Are the QRS complexes narrow or wide? (narrow is < 0.12 seconds, it is conducted by His-Perkinje system) or not?
3. What is the relationship between P waves and QRS complexes? (is there AV dissociation?)
4. Is the rhythm regular or irregular?

Question 7

Explain what an “Escape Beat” is:

An escape beat is essentially a loss of the __________, causing a ______ to kick in and take over

Answer 7

An “Escape Beat” is essentially loss of the SA node overdrive pacing, causing a downstream automaticity foci to kick in and take over (when it is normally overridden by the SA node)

So, you will have a transient Sinus Block, followed by a pause on the EKG and then an automaticity focus where the escape beat kicks in and takes over

Question 8

Sinus Block:
- SA node firing is __________

• ______ to determine whether SA node failed to fire or fails to cause atrial depolarization
• Difference between sinus arrest and sinus exit block?

Answer 8

Sinus Block:
- SA node firing is not picked up on the EKG

• No way to determine whether SA node failed to fire (aka “sinus arrest”) or fails to cause atrial depolarization (aka “sinus exit block”)
• Sinus arrest means that the AV node failed to fire at all, but Sinus exit block means that the SA node did fire but failed to depolarize the atia

Way to tell the difference on the EKG is whether or not the escape beat pick up on the same pattern (sinus exit block because still paced by SA node)… but this is a unreliable method

Question 9

Explain an Atrial Escape Beat

Also draw what it will look like on an EKG

Answer 9

Atrial Escape Beat:

In an atrial escape beat, there will be a long pause followed by a P’ wave

This is because the SA node stops pacing, and some atrial pacemaker will kick in and take over (aka the P’)

Question 10

Explain a “Junctional Escape Beat”

What will that look like on an EKG?

Answer 10

“Junctional Escape Beat” : this essentially means there is a pause in SA node firing, and the “junction”/AV node picks up and causes a ventricular depolarization

On the EKG, there will be a pause followed by a QRS complex… note there is no P’ wave

In this case you can get retrograde P waves from the AV node firing

Question 11

Explain what a ‘Ventricular Escape Beat’ is

What will that look like on the EKG?

Answer 11

Ventricular Escape Beat:

There will be an SA pause followed by a WIDE QRS complex

This is because some ectopic pacemaker in the ventricles is picking up the slack…you don’t get a nice narrow QRS complex indicating that the wave of depolarization travelled down the His-Perkinje system… because it clearly did not

Question 12

Explain the difference between escape beats and escape rhythms

Answer 12

Escape rhythms will NOT return back to normal sinus rhythm

AKA beats go back to normal afterwards

Question 13

Explain what an atrial escape rhythm is

What will that look like on an EKG?

Answer 13

Atrial Escape Rhythm:

P’ waves will all look different, because there might be different atrial pacemaker kicking in each time

The HR will also be slower than normal

Question 14

Escape rhythms occur with ______

(meaning a very sick SA node)

Answer 14

Escape rhythms occur with sinus arrest

(a very sick SA node)

Question 15

Explain “Junctional Escape Rhythms”

What will they look like on the EKG?

Answer 15

“Junctional Escape Rhythms” mean that there will be no P’ wave

Ends up in a slower HR (even slower thatn atrial escape rhythm)

Question 16

“Ventricular Escape Rhythms”

What do they look like on an EKG

Answer 16

‘Ventricular Escape Rhythms”:

There is no p waves and ends up in WIDE QRS complexes

VERY slow heart rate

Question 17

Ventricular Escape Rhythms:

• Also called _____________ (involves total failure of the SA node and all automaticity foci)
• Rare and dangerous
• Results in fainting called “________”
• Essential a final, futile attempt of ______

Answer 17

Ventricular Escape Rhythm:

• Also called “downward displacement of the pacemaker”
• Rare and dangerous
• Results in fainting (“Stokes-Adam Syndrome”)
• Essentially a final, futile attempt to sustain life

last ditch attempt for the ventricles to save the heart, doesn’t last long, BP will plummet and CO will go down

Question 18

Premature Beats:

• AKA ______ beats
• Beats that occur _______
• Originates from ________ foci
• Atrial/Junctional/ Ventricular
• Some are _____ others are serious
• Can be caused by ______ toxicity or ____ stimulation

Answer 18

Premature Beats:

• AKA ectopic beats
• Beats that occur earlier than expected
• Originates from irritable foci
• Atrial/Junctional/Ventricular
• Some are innocuous, others are serious
• Can be caused by digitalis toxicity or beta adrenergic stimulation (like asthma inhalers)

Question 19

What does a Premature Atrial Beat look like on an EKG and what does a Premature Junctional Beat look like on an EKG?

Answer 19

PAB: p’ followed by a QRS that happens to be earlier than normal

PJB: QRS wave that comes in without a p’ wave earlier than normal

Question 20

Explain what a “Blocked PAC” is

What will it look like on the EKG?

Answer 20

Blocked PAC:

• the SA node fires so early that the AV node is not repolarized yet, therefore you get a P wave with no QRS complex to go with it

The ventricles are not yet repolarized and therefore can’t fire

Question 21

PVC:

Ventricular Foci Become Irritable Because:

• Low ____
• Low ____
• Other pathologies (like _____)

Answer 21

PVC:

Ventricular Foci become irritable because:
- Low oxygen (very sensitive indicator of ischemia)

• Low K+ (hypokelemia)
• Other pathology (mitral valve prolapse, myocarditis)

PVC’s usually have long compensatory pauses because the beat after is strong (long time for ventricles to repolarize, long time for Ca to enter and preload to happen)

Question 22

Explain what the EKG will look like for:

A. Single PVC

B. Bigeminy or Trigeminy

C. Multiforme

Answer 22

Single PVC: pretty common, one weird wide QRS

Bigeminy or Trigeminy: 1 PVC : 1 Normal Beat or

2:1

Multiform: runs of three or more, multiform (different appearances of PVCs)

Question 23

Explain what an R on T is

What will it look like on an EKG?

Answer 23

R on T’s are when a PVC happen during the downstroke of the T wave

The donstroke of the T wave is a vunerable period (relative refractory). If a PVC hits then, it can lead to runs of PVCs (ventricular tachycardia)

Question 24

What is SVT/Paroxysmal Supraventricular Tachycardia?

What does it look like on an EKG?

Answer 24

SVT:

Essentially the heart is being paced faster than normal by something above the ventricles

Atrial tacycardia will have all p waves

Junctional tachycardia will have no p waves

Question 25

Carotid Massage: - Goal: Increase _____ activity to slow sinus firing and conduction through the AV node - Trick ______ into sensing _____ and therefore \_\_\_\_ - Will only fix \_\_\_\_\_

Answer 25

Carotid Massage: - Goal: Increase vagal activity to slow sinus firing and conduction through the AV node - Trick baroreceptors into sensing high BP and decrease sympathetic and increase parasympathetic - Won't fix vtach, only SVT

Question 26

What is Atrial Flutter? What does it look like on an EKG?

Answer 26

Atrial Flutter: SAW TOOTH PATTERN 250-350 bpm Single extremely irritable atrial automaticity focus Back to back identical atrial depolarization Beats are regularly spaced out RE-entry

Question 27

Ventricular Flutter: Explain what it is Explain what it looks like on an EKG

Answer 27

Ventricular Flutter: - 250-350 bpm - Single extremely irritable ventricular automaticity focus - Back to back identical ventricular depolarization (SINE WAVE pattern)

Question 28

Torsades De Pointes: "Twisting of the Point" - Rapid _____ rhythm - Caused by low \_\_\_\_\_ - ______ ventricular pumping - Can degenerate into \_\_\_\_, but often reverts back to sinus rhythm simultaneously What does it look like on an EKG?

Answer 28

Torsades De Pointes: - Rapid ventricular rhythm - Caused by low K, K channel blockers, Long QT syndrome - No effective ventricular pumping - Can degenerate into VFib (and Sudden Cardiac Death) but often reverts to sinus rhythm spontaneously

Question 29

LONG QT SYNDROME: - What is it?

Answer 29

Long QT Syndrome: - Genetic disorder, from mutations in ion channels ( like sodium and potassium channels) - Affects 1 in 3000-5000 people - Lengthening of the vunerable period

Question 30

Fibrillation: - Rapid discharge from \_\_\_\_\_\_\_\_ - Either ____ or _____ foci - Many foci firing, no depolarization spreads far - HR of ____ is hypothetical - Chambers \_\_\_\_\_\_

Answer 30

Fibrillation: - Rapid discharge from many irritable foci - Either atrial foci or ventricular foci - Many foci firing, no depolarization spreads far - Rate of 350-450 is hypothetical, impossible to get a real rate - Chambers do not pump at all

Question 31

Atrial Fib: Explain what it is What does it look like on an EKG What is the big risk with AFib patients

Answer 31

Atrial Fib: Atrial Fibrillation is really fast foci firing in the atria where it kinda jiggles around, never really pumps The EKG has a squiggly baseline with QRS complexes that are not at a regular rhythm: irregularly irregular AFib patients are at a high risk of stroke because the blood pools in the atria and then can coagulate and become clots

Question 32

VFib: Explain what it is What does it look like on an EKG?

Answer 32

VFib: Quivering Ventricles VF is a type of cardiac arrest Death is imminent Requires immediate defibrillation and CPR

Question 33

What is Wolf Parkinson White Syndrome? What does it look like on an EKG?

Answer 33

Wolf Parkinson White Syndrome: A syndrome in which an extra electrical pathway in the heart causes a rapid heartbeat The extra electrical pathway is through the bundle of kent and back to the SA node (after going through his perkinje highway) Common in children Causes a slurred QRS/slow uptake into QRS complex

Question 34

Explain what First Degree AV Block is What does it look like on an EKG?

Answer 34

First Degree AV Block: essentially a slow AV node normally PR interval is about 120-200 msec(3-5 small boxes) longer than that is first degree av block

Question 35

Explain what Mobitz Type I / Wencebach is What does it look like on an EKG

Answer 35

Type of second degree av block pr interval is longer and longer until it drops a beat

Question 36

Explain what mobitz tpe II is

Answer 36

Mobitz Type II is a type of AV block It usually is a problem with the His Perkinje System and not the AV node It is regular intervals of dropped beats

Question 37

Third Degree Block

Answer 37

The P waves and QRS complexes are independent of one another Essentially it's a full AV node block

Question 38

Describe some of the pharmalogical treatments for arrhthmyias

Answer 38