Cardiac Conduction Cycle Flashcards
1
Q
Describe the pathway of the cardiac conduction system.
A
- The sino-atrial (SA) node
- The atrio-ventricular (AV) node
- The bundle of His
- The left and right bundle branches
- The Purkinje fibers
2
Q
The 3 stages of a single heart beat are:
A
- Atrial depolarization
- Ventricular depolarization
- Atrial and ventricular repolarization
3
Q
The PQ segment represents…
A
Atrial contraction and repolarization
4
Q
The QRS segment represents…
A
Ventricular contraction
5
Q
The T wave represents…
A
Ventricular repolarization
6
Q
The ST segment is a…
A
Key indicator for both myocardial ischemia and necrosis if it goes up or down
7
Q
What is Sinus Bradycardia and what does it look like on an EKG strip?
A
- Sinus Bradycardia: HR = < 60
- It is a normal heart tracing, just slower
8
Q
What type of drugs can cause sinus tachycardia?
A
Beta and Calcium Channel blockers
9
Q
What is Sinus Tachycardia and what does it look like on an EKG strip?
A
- Sinus Tachycardia: HR = > 100
- It is a normal heart tracing, just faster
10
Q
Would hypovolemia cause Brady or Tachycardia?
A
Tachycardia – the heart needs to circulate faster to get blood out and BP up
11
Q
What is a Sinus Arrythmia?
A
- Same as Sinus Rhythm, but the rhythm is irregular
- All waves are present, but the P-P interval shifts by more than 10%
12
Q
Possible causes of Sinus Arrythmia?
A
- Respiratory – shifts with inspiration and expiration
- Non-respiratory – for unknown reasons
- Sometimes associated w/ Complete Heart Block
13
Q
How long should the Q-T interval be?
A
- .35-43sec
- 1.5 to just over 2 big squares
14
Q
What is the cause of Atrial Fibrillation and Flutter?
A
Any condition that causes an increase in pressure within the atria can cause AF, but it is mainly linked to enlargement of the left atria (or both) as a result of the increased atrial pressure.
15
Q
What is Atrial Fibrillation?
A
An irregular quivering of the atria as opposed to normal contractions
16
Q
What is the rate of stimulation in atrial fibrillation?
A
Around 600 stimuli/min
17
Q
What does a heart tracing of A-Fib look like?
A
Distinct and irregular R waves with all else being indiscernible and low
18
Q
What does a heart tracing of A-Flutter look like?
A
Sawtooth waves between pronounced R waves
19
Q
What are S/S of A-Fib?
A
- SOB
- Chest Pain
- Both SOB and chest pain are due to lack of O2
- Not always present, but more likely the faster it goes
- Palpitations
20
Q
What are the key points to A-Fib regarding cardiac OP?
A
- Due to rapid contractions of the atria, the ventricles do not have ample time to fill before their contraction leading to a drop in OP to 50% or more
- This will naturally increase symptoms
21
Q
What is the order of TX for A-Fib?
A
- O2 therapy
- Glyceryl trinitrate (GTN)
- Adenosine/Digoxin
- Warfarin/Heparin
- Electrical (DC) Cardioversion
22
Q
Why is Glyceryl trinitrate (GTN) used to treat A-Fib?
A
It a vasodilator commonly used for angina pain as it helps to open up the coronary arteries to increase the blood and oxygen supply to the heart muscle.
23
Q
Why is Adenosine/Digoxin used to treat A-Fib?
A
to slow down the heart and allow the ventricles to work more efficiently
24
Q
Why is Digoxin specifically used to treat A-Fib?
A
- Strengthens myocardial contraction and tells the SA/AV nodes to slow down
- This slowing down often helps the heart re-assert its normal rhythm.
- If not, we move to Cardioversion
25
What is Cardioversion?
the use of drugs or electric shock to reset the HR back to Sinus
26
How does Electrical Cardioversion work?
* There is the delivery of a synchronized electric shock at the point in the conduction cycle where the atria is repolarizing.
* The effect is to literally stop and restart the heart.
* It is hoped that when the heart restarts, the SA node restarts with normal function.
27
Which condition is less @risk for embolization: A-Fib or A-Flutter?
A-Flutter
28
The “Flutter” rate for A-Flutter is around…
150-300/min
29
Describe a Premature Atrial Contraction heart tracing.
* PQRST complex is present in general
* Periodically, the STQ will show as one wave, this is the premature atrial contraction OVER the ST complex.
* This will be followed by a prolonged T to P segment, then a return to PQRST until the next premature contraction
30
When is a De-fib used?
* ONLY USED when heart has STOPPED, will kill the flutter pt
* If person is alive, alert, responsive… DON"T FUCKING DO IT!
* Must be unconscious – completely
31
What two chemicals are used for Chemical cardioversion?
* Adenocord
* Adenosin
32
How is chemical cardioversion administrated?
* If fluids present, take off, need direct access to admin med
* Administer quickly followed by 10-20mL of NS to get it in system
33
What is the PT teaching re: Chemical cardioversion?
* gonna feel some warmth
* heart is going to briefly stop (which can be scary for pt, we see it as a flatline) and then,
* if it works, it will kick back in to sinus.
* Sometimes it doesn't work, if so, its tried again, if not again, then another med is used
34
Describe the heart tracing for a First Degree Heart Block.
* This will be tricky as it looks just like a normal sinus rhythm.
* The only difference is a prolonged P-Q interval
35
What is the intervention for a First Degree Heart Block?
Treat the underlying cause and observe for progression to a more advanced heart block
36
Describe a Second Degree AV Block – Type I (Wenckebach)
* P-Q interval gets progressively longer until there is a QRS complex drop
* Then it resets and does it again
37
What is the Tx for Second Degree AV Block?
Treatment is usually not indicated as this rhythm usually produces no symptoms
38
Describe a Second Degree AV Block – Type II
* PQRST waves all present
* Key characteristic is multiple P waves in a row prior to a QRS complex.
39
What is the Tx for a 2nd degree AV Block -Type II
Artificial pacing
40
Describe a Third Degree (Complete) AV Block
* atrial rate is usually normal; faster than the ventricular rate
* normal with constant P-P intervals, but not "married" to the QRS complexes
* QRS may be normal or widened depending on where the escape pacemaker is located in the conduction system
* It is ultimately an irregular rhythm
41
What is the cause of a 3rd degree heart block?
* digitalis toxicity
* acute infection
* MI and
* degeneration of the conductive tissue.
42
Tx for 3rd degree heart block?
* External pacing and atropine for acute, symptomatic episodes and
* Permanent pacing for chronic complete heart block.
43
Describe a Premature Ventricular Contraction heart tracing
* The P wave is followed by a positively inflected Q wave (now an R wave) rather than negative.
* This is the ventricular contraction
* This will be followed by an abnormally large T wave and subsequent negative inflection, then back to the P wave
44
Describe a V-Tach heart tracing.
* ONLY R waves present
* Just a constant cycle of giant R waves
* all other conduction is masked
45
Common causes of V-Tach?
* CAD
* acute MI
* digitalis toxicity
* CHF
* ventricular aneurysms.
46
Tx for V-Tach?
* Electrical countershock is the intervention of choice if the patient is symptomatic and rapidly deteriorating.
* Some pharmacological interventions include
* amiodarone and
* lidocaine.
47
V-Tach can rapidly progress to…
V-Fib
48
V-Fib results in the absence of…
Cardiac OP
49
Describe a V-Fib heart tracing.
* Looks like a mini V-Tach
* Low conduction scribble line w/ no QRS
50
Tx for V-Fib
Immediate defibrillation and ACLS protocols.
51
Describe A-Systole heart tracing
Flatline
52
A-systole interventions?
* CPR, 100% oxygen,
* IV
* intubation
* transcutaneous pacing
* epinephrine 1.0 mg., IV push, q3-5 minutes
* atropine
53
What is a Sinus Node Dysfunction (SND)
SND refers to abnormalities in sinus node impulse formation and propagation, and includes sinus bradycardia, sinus pause/arrest, and sinoatrial exit block.
54
Although SND may occur at any age, it is primarily a disease of the \_\_\_\_\_.
Elderly
55
What is the Tx for chronic, symptomatic SND?
Pacemaker therapy
56
True or False
Asymptomatic SND Pts do not require pacemaker therapy
True
57
As SND becomes more severe, patients may develop symptoms due to organ _____ and pulse \_\_\_\_\_.
* Hypoperfusion
* Irregularity
58
Traditional pacemakers are used to treat…
slow heart rhythms.
59
Pacemakers regulate the _____ atrium and ventricle to maintain a good heart rate and keep the atrium and ventricle working together.
Right
60
A biventricular pacemaker is a special pacemaker used for cardiac _____ therapy designed to treat a delay in heart ventricle contractions.
Resynchronization
61
The two main types of programming for pacemakers are:
* Demand pacing
* Rate-responsive pacing
62
Explain “demand pacing” pacemaker programming.
* monitors your heart rhythm.
* It only sends electrical pulses to your heart if your heart is beating too slow or if it misses a beat.
63
Explain “Rate-responsive” pacemaker programming.
* Pacemaker monitors your sinus node rate, breathing, blood temperature, and other factors to determine your activity level.
* It will then speed up or slow down your heart rate depending on how active you are.
64
How long should the PR interval be?
* 0.12-0.20 or
* 3-5 small squares
65
How long should the QRS interval be?
0.06-0.12 or
\< than 3 small squares
66
How do you calculate the HR w/ a 6 second strip?
* # of R waves in 6 seconds x10
* Rhythm must be regular
67
How do you calculate an irregular rhythm on a strip?
300 divided by the number of boxes between R waves
68
Characteristics of a 1st degree heart block...
partial block Consistent prolonged PR interval
69
Characteristics of a 2nd degree, type 1 heart block...
* progressive block
* Progressively long PR interval
* Eventual QRS drop and cycle repeats
* “long, long, drop”
70
Characteristics of a 2nd degree, type 2 heart block...
* intermittent block
* No progressive PR
* interval Normal EKG rhythm with occasional QRS drops
* “normal, normal, drop”
71
Characteristics of a 3rd degree heart block...
* complete block
* P waves and QRS waves are not coordinated
* Each will have their own regular, unrelated tempos
72
What type of drugs end in "pril" and what do they do?
* Ace Inhibitors
* Prevents fluid retention
* Reduces blood pressure
73
What type of drugs end in "olol" and what do they do?
* Beta blockers
* Slow heart
* Reduce BP
74
What type of drugs end in "ipine" and what do they do?
* Calcium channel blockers
* Reduce SVR, BP, contractility, conduction
* Diltiazem & Veropamil are also calcium channel blockers
75
What type of drugs end in "ides" and what do they do?
* Diuretics
* Reduces fluid volume
76
What are normal potassium levels?
3.6 to 5.2
